Final Notes

At the beginning of the semester, I gave my personal definition of environmental health as "a public health discipline that takes a wholistic approach to work toward an environment in which toxic, infectious, and other potentially dangerous or damaging agents are minimized in a way that promotes a healthy, sustainable ecosystem." We have been asked to revisit our definitions and discuss whether we would change them at all. For my part, I would not, as I feel like my original definition encapsulated my views, and this course has only served to reinforce them.

My view of environmental health has always been that a systems approach is essential. An ecosystem, in that respect, is not terribly different from an individual being. As a healthcare practitioner, I cannot consider my patients' individual problems in isolation. I very often have to consider whether addressing one issue will create or exacerbate problems with other body systems. Medications can have side effects and unintended consequences, and a failure to consider those possible complications can potentially have devastating effects. The same applies when considering the impacts of our actions on the environment.

Although my participation in this course has not been at the level I would have preferred, I have at all times found it interesting and challenging. 

Disasters and Terrorism

In a 2008 training document of the Federal Emergency Management Agency (FEMA) containing definitions of terms used by the agency, nearly 11 full pages were devoted to various definitions and descriptions of what is meant by the term “disaster”.  The first definition offered, though, and the meaning which seems to come up most frequently, in slightly varied forms, is very similar to one that was put forward in our discussions on this topic: “An event that requires resources beyond the capability of a community and requires a multiple agency response”. (PDF link, last visited 1 May 2012)

Disasters are generally broken down into natural vs. manmade events. The 1988 Robert T. Stafford Act defined natural disasters as, “Any hurricane, tornado, storm, flood, high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption, landslide, mudslide, snowstorm, drought, fire, or other catastrophe in any part of the United States which causes, or which may cause, substantial damage or injury to civilian property or persons.“ 

An argument was made in the discussion that a forest fire affecting a million acres but not damaging any manmade structures or causing any deaths wouldn’t be a disaster, but it is not clear under the above definition of natural disaster whether this would be true. If that million acres were commercial timber, then the economic effects might cause the event to be considered a disaster. And having been downwind of large scale forest fires in Québec, I think that an argument could be made that increased morbidity due to heavy smoke cover, even absent any demonstrable increase in mortality, might meet some definition of a disaster.

The scope and severity of a natural disaster is also due, to some extent, to the degree of human development in the location where the disaster occurs. The amount of economic damage done by hurricanes is often due to the degree of real estate development in coastal regions, and Hurricane Katrina would not have had nearly the impact it did on New Orleans had the development of the shipping channels between the city and the Gulf of Mexico not impaired the natural capacity of the Mississippi Delta to absorb the impact of the storm surge. Similarly, landslides and mudslides in places like coastal California or, say, the favelas of Rio de Janeiro would not have nearly the same impact were it not for the amount of human development on high risk hillsides.

Whereas the adverse effects of natural disasters are primarily an effect of their destructive power, manmade disasters tend to have effects which are more toxicological in nature. Well known examples of these are the 1984 Bhopal, India, industrial disaster, the 1986 Chernobyl nuclear disaster, and the 1989 Exxon Valdez oil spill (the 1980s were clearly bad for more than hairstyles). A much more recent one was the Deep Water Horizon oil spill of 2010. Although the oil spills didn’t result in significant loss of human life, they still had considerable negative impact on local ecosystems.

There are also some disasters which have both natural and manmade components. The 1889 Johnstown flood in western Pennsylvania was principally manmade, because it was due to the failure of a faulty dam, but that failure was precipitated by heavy rains which exceeded the dam’s capacity to withstand the force of the water. Similarly, although last year’s Fukushima Daiichi nuclear disaster was precipitated by the earthquake and tsunami, the plant meltdown itself resulted more from a failure of the plant’s designers and management to anticipate and plan for such a contingency, despite the plant’s being sited in one of the most seismically active areas on the planet.

Although Moeller considers terrorism alongside disasters, and although the effects of terrorist acts can certainly be psychologically catastrophic, even if not particularly damaging economically, terroristic activities are distinguishable from disasters by the presence of maleficent intent. The Department of Homeland Security (DHS) defines terrorism as a “premeditated threat or act of violence, against noncombatant persons, property, environmental, or economic targets, to induce fear or to intimidate, coerce or affect a government, the civilian population, or any segment thereof, in furtherance of political, social, ideological, or religious objectives” (see above link). Differences aside, both disasters and terrorism are considered potential public health emergencies, and so there is overlap with regard to strategies to mitigate both.

The first essential step in mitigating either disasters or terrorist activities is the development of an emergency preparedness plan.  The purpose of this is not to deal with the emergent situation itself, but rather to prepare for the eventuality and provide a basic framework for development of a response. Moeller lists five elements of emergency preparedness:

1.       Consider the full spectrum of possible accidents.

2.       Estimate their likelihood of occurrence.

3.       Analyze their potential consequences.

4.       Identify significant structures, systems, and components designed to mitigate the consequences.

5.       Identify a subset of accidents and related scenarios that need to be formally considered.

He also calls for estimates of potential doses to the public, in the case of toxicological events, and a system of review in the event that the plan is called into play, in order to refine and improve the plan for future events.

The emergency response plan, though related, is primarily concerned with the actions to be taken in the event of a disaster or terrorist attack. Moeller distinguishes between national/regional plans, which focus on responsibilities and mobilization procedures for relevant agencies, and local plans, which are more detailed and definitive and include specific countermeasures. He identifies four phases of the response plan – pre-event phase, warning phase, response phase, and recovery phase.

With regard to countermeasures, these are actions which are effective at reducing population exposures, safe, practical, and defined. The most well known countermeasures are evacuation, sheltering, and protective prophylaxis. Additional countermeasures could include those such as boiling or filtering water if there has been contamination of the water supply, or washing produce if contamination is a possibility.

For all of these, communication of plans to relevant parties is essential to proper coordination between response agencies. Also, good communication can help to ensure that the risks to the public are minimized, which is the principal goal of such measures.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Energy Resources and Conservation

 In physics, energy is thought of as either potential – i.e., stored - or kinetic - manifested most often as object movement, heat, or light. When we discuss energy resources, we are generally talking about sources of what Webster’s Student Dictionary of the English Language calls “[t]he motive power essential to modern technology, derived from various natural sources.”

Broadly speaking, energy resources can be divided into nonrenewable and renewable sources. Nonrenewables are finite resources that are generally extracted from the earth. These include petroleum, natural gas, coal, uranium, and lithium used in batteries and power cells. Renewable resources are those such as solar, wind, and biomass power – all of which originate at a basic level from light and heat energy reaching Earth from the sun – hydropower, tidal, and geothermal energy.

It might be tempting to conclude that nonrenewables are inherently more polluting, but this is not necessarily the case. As I pointed out back in the discussion on air quality, cooking and heating with wood or dung is a significant contributor to poor indoor air quality in many developing countries. Large scale hydropower projects like the Aswan High Dam in Egypt and China’s Three Gorges Dam have also been associated with widespread environmental degradation, and smaller dams, such as those which provided a century or more of inexpensive power here in Maine, created significant barriers to natural movement of fish species like the Atlantic salmon. On the other side, nuclear power is generally considered to be among the cleanest sources of electricity, despite the political implications associated with its usage.

That said, the finite nature of nonrenewables has made their acquisition much more costly as demand increases and availability wanes. In some cases, the political costs may be high even when the economic costs are much less so. Natural gas, for instance, is still cheap and abundant, but increasing public outcry over concerns about the hydraulic fracturing process used to extract it certainly appear to be creating some image difficulties for the industry. In the case of nuclear power, the potential for a catastrophic event, however small, is a very frightening prospect for the public, particularly those of us who grew up with images of Three Mile Island and Chernobyl, not to mention last year’s meltdown of the Fukushima Daiichi nuclear plant in Japan after the tsunami.

All of these considerations have helped to increase interest in renewable resources, but the U.S. energy infrastructure is still largely based around petroleum and coal, and the political will to shift decisively away from these still seems worryingly small. This is almost certainly due, in large part, to the continued political power of the petroleum and coal mining industries. That said, there are some signs of a shift in focus. On my way to work this morning, I happened to hear the following report on Exxon Mobil on public radio (Link, last visited 1 May 2012).

Cullen, et al., looked at the topic of reducing greenhouse gas emissions through reducing the use of polluting energy resources.  They broke total emissions down into four essential elements – GDP, population, demand, and supply substitution (i.e., replacing nonrenewable carbon-based sources with less polluting sources). As discussions of population or wealth reduction are largely untenable, they focused their evaluation on global ability to reduce demand, noting that much of the current discussion focuses instead on supply substitution. Their conclusion is that reducing demand is within the realm of possibility, but faces significant barriers, particularly socio-cultural and economic (Cullen, et al., 2011).

Having grown up through the energy crisis of the 1970s and the era of McMansions and Hummers and having had a grandfather who was concerned about energy and environmental conservation, I’ve long been interested in questions of energy utilization and conservation.  On a personal level, this has led to purchasing a hybrid car for improved gas mileage, switching from an older oil boiler to a high efficiency propane boiler for home heating and hot water, purchasing new windows and using plastic film on older windows in winter to reduce heat losses, setting thermostats lower during the heating months, buying locally-produced foods or growing my own when possible, replacing incandescent light bulbs with compact fluorescents, installing a dual flush mechanism on the toiler for reduced water usage, and generally looking for ways to reduce my carbon footprint.

I have also read a good bit of Sarah Susanka’s “Not So Big” writings (http://www.notsobighouse.com), which focus on lower impact, smaller house design, in large part to reduce energy utilization. More recently, I’ve been reading about the Passivhaus ultra-efficient building standard (http://www.passivehouse-international.org), which is intended to require little to no supplemental energy inputs to meet heating and cooling needs. As I live in a state that is approximately 80% forested and have access to a family-owned woodlot, I’ve also looked into high efficiency masonry heaters as a way of utilizing wood as a primary heating source in a manner that is relatively less polluting, sustainable, and that will reduce our need for petroleum-based heat sources.

The problem with these sorts of measures is that they are costly to institute, particularly when it comes to retrofitting a 300-year-old house, and without significant inputs and incentives from the public sector to help drive these sorts of improvements, it is going to remain a significant challenge for most of the general public to be able to make the sorts of changes that will be necessary to reduce energy demands that will be necessary going forward. As I mentioned before, this is the same conclusion arrived at by Cullen, et al. My feeling is that a comprehensive energy strategy must take these considerations into account and will require both substitution of renewable and non-polluting sources for petroleum-based energy as well as strong measures to drive reductions in demand, such as surcharges to raise the relative costs of inefficient systems and increased incentives to promote utilization of higher efficiency, less polluting systems.

An ideal energy strategy also needs to look closely at transportation infrastructure. I currently have a one hour commute to work, four to five days per week. Although there are a few public transit options in the area, I have looked at both the time and the economic costs associated with using these to make my commute. Instead of a drive that is almost exactly one hour, I would have to drive one-half hour, take a train into the city where I work, take a bus from the train station to a central bus terminal, wait an hour for the connecting bus which gets closest to my workplace, then walk about a half mile from the nearest bus stop to my workplace, on a busy road without sidewalks. This would double the costs of my commute and increase my daily commute time to 6 hours.

One hot button issue in the debate over energy conservation is that of increased nuclear energy utilization. This certainly does carry some promise with regard to reducing greenhouse gas emissions and is a known technology. That said, there are significant political barriers to moving in this direction due to highly publicized disasters such as the ones mentioned above and concerns about the proper storage and disposal of spent fuels. Although the overall risks are considerably lower than those of, say, driving a car every day, the potential for widespread catastrophe in the event of reactor damage is much more worrisome to the general public. Another argument against further nuclear development is that it is a very costly resource to develop and takes economic resources away from the development of renewable resources, such as wind and tidal power.

Overall, it’s hard not to see the outlook for the future as being rather bleak, but this will ultimately depend upon whether the political and social willpower can be found. As outlined above, the potential to head off a global crisis exists. The question is whether we, as a species, will take the necessary actions, or if our efforts will be too little, too late.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Cullen, J.M., Allwood, J.M., and Borgstein, E.H. “Reducing energy demand: what are the practical limits?”. Environmental Science & Technology. 45: 1711-1718. http://dx.doi.org/10.1021/es10264n

Risk Assessment and Management

The U.S. Environmental Protection Agency (EPA)defines risk as “the chance of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor,” with a stressor being “any physical, chemical, or biological entity that can induce an adverse response.” Risk assessment, then, is a scientific process of quantifying and characterizing the nature of health risks to humans or to the environment, and risk management is the process which determines the best methods for protecting public and environmental health from these risks (EPA Risk Assessment website, last visited 30 April 2012).

Following the previous discussion on standards, it is clear that many of the same limitations to the development of adequate standards apply to the risk assessment process. Risks can only be characterized and quantified to the extent that we have scientific data available. As data are often either lacking or limited by available technologies, risk assessment and management are necessarily iterative processes. Moeller uses the nuclear accident at Three Mile Island as an example, as it helped to highlight deficiencies in previous risk assessment methodologies and led to improvements in the process.

There is also considerable overlap between the concepts of standards and risk assessment/risk management. In essence, risk assessment is an integral part of the process of developing standards, as it helps to determine and quantify threshold exposure levels. The development of standards, in turn, is part of the process of risk management, because the standards provide the necessary benchmarks for determining mitigation and enforcement needs.

The EPA lists related, but slightly different, steps for assessing risks to human health vs. to ecological systems. Both begin with what they refer to as the planning and scoping process, which is essentially the preparatory background research needed. For human health risk assessments, the steps are then hazard identification, dose-response assessment, exposure assessment, and risk characterization. In the case of ecological risks, the steps are problem formulation, analysis, and risk characterization.

In either situation, the risk characterization cannot be considered static, as new or ongoing research may reveal previously unrecognized effects, or even the presence of unrecognized confounders which have falsely inflated the apparent risk. In essence, the iterative process is that of the Plan-Do-Check-Act cycle of continuous quality control (ISO website, last visited 30 April 2012).The planning process and the assessment steps previously mentioned correspond to the Plan and Do phases of the cycle, respectively. The Check phase is one of determining how well the risk has been quantified/characterized and what deficiencies exist in the currently available data, and the Act phase is one of determining how to address these deficiencies for the next iteration of the cycle.

Although risk management is also an iterative process, it relies on far more than just the scientific and methodological considerations of risk assessment. Risk management must also take into account the feasibility of control measures, socioeconomic factors and political considerations. Additionally, risk management must factor in the potential impact of alternatives to the risk being considered. For instance, if the exposure of interest is the product or by-product of an industrial process, risk management must also consider the potential risks of pushing industry toward alternate processes, the product or by-products of which may pose equal or greater risks that the primary agent of concern.

Risk management is also not wholly dependent upon the existence of well-characterized or quantified risk. The Precautionary Principle is that of instituting control measures when there is evidence of serious damage to human health or the environment, even though the risk may not yet be well quantified. As the United Nations’ 1992 Rio Declaration stated, “[L]ack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.” This principle is, of course, highly subject to interpretation, and is not an acceptable substitute for a proper risk assessment. It does, however, provide a rational basis for instituting an initial risk management program until an apparent risk can be more accurately assessed.

Because risk management is also an inherently politically-charged process, as well, risk communication is an extremely important component of the process for developing consensus among shareholder groups, including the media, the general public, and policymakers. Although communication needs to be scientifically-based, it should also take into consideration the target audience, as non-technical audiences are likely to lose or misinterpret the intended message when highly technical language is used (FDA website, last visited 30 April 2012).

An example of a situation in which good risk communication was likely important in shaping policy was the passage in Maine last year of a ban on the sale in the state of reusable food containers made with plastics containing bisphenol A (BPA). BPA is used to harden some plastics by increasing crosslinking between polymer chains and is also used in the lining of food cans and in some types of paper. Although it has been known to possess some estrogenic properties since 1936, BPA was grandfathered in as an existing chemical under the 1976 Toxic Substances Control Act and industries were allowed to continue using it without safety testing (Flint, et al., 2012).

Although BPA does not bioaccumulate at a level that reaches the EPA’s threshold for concern, several studies have documented detrimental effects in some wildlife species at levels of contamination which are known to occur in the environment. These include the brown trout, which is an important game fish in the state. Additionally, there is growing evidence that it may increase infertility risks in women and may increase the risk of estrogen-responsive tumors, such as meningioma (Ehrlich, et al., 2012, and Duan, et al., 2012). Although this represents only a tiny fraction of the available data, the governor stated at a press conference that he didn’t see that there was any greater risk than women growing “little beards”.

Given that the governor’s party controls both branches of the state legislature and the fact that both branches voted overwhelmingly in favor of the ban, it is clear that the potential risks of BPA were communicated to them sufficiently to garner broad bipartisan support for the measure. Of course, there still remains the question of whether the ban will a) adequately reduce levels of BPA contamination, and b) avoid increasing levels of other, potentially more damaging, substitutes for BPA remains to be seen. With ongoing iteration of the assessment and management processes, though, and with good risk communication, there is at least some hope that these risks can be mitigated.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Flint, S., et al. “Bisphenol A exposure, effects, and policy: a wildlife perspective”. Journal of Environmental Management. 104(2012): 19-34. doi: 10.1016/j.jenvman.2012.03.021

Ehrlich, S., et al. “Urinary bisphenol A concentrations and implantation failure among women undergoing in vitro fertilization”. Environmental Health Perspectives. E-pub, http://dx.doi.org/10.1289/ehp.1104307

Duan, B., et al. “The relationship between urinary bisphenol A levels and meningioma in Chinese adults”. International Journal of Clinical Oncology. E-pub, doi: 10.1007/s10147-012-0408-6

Occupational and Environmental Standards

In his chapter on occupational, population, and environmental standards, Moeller starts by defining primary, secondary, and tertiary standards. Primary standards are threshold levels of exposure to chemical or physical agents, such as noise levels, that are designed to minimize the risk of human disease. Secondary standards are threshold levels of exposure designed to minimize damage to the environment or elements of human civilization, such as agricultural crops or manmade structures, or to meet aesthetic concerns, such as drinking water appearance and taste. Tertiary standards are derived standards intended to ensure that the primary levels are not exceeded.  Moeller points out that secondary standards are often more restrictive than primary standards, since some agents are undesirable even at levels that are below those known to have negative health impacts in humans.

One of the earliest exposures for which standards was developed was ionizing radiation, as its deleterious effects were recognized relatively early on in radionuclide research and utilization. Early standards were not formalized until the formation, in 1928, of the International X-Ray and Radium Protection Committee (now the International Commission on Radiological Protection, or ICRP) and the U.S. Advisory Committee on X-Ray and Radium Protection (now the National Council on Radiation Protection & Measurements, or NCRP).

Early standards were based on concerns about potential hereditary damage, derived from research done in Drosophila flies. From about 1960, though, standards were changed to reflect epidemiological studies conducted on survivors of the atomic bomb explosions in Hiroshima and Nagasaki, Japan. Those studies demonstrated no significant hereditary effects, but rather the effects of acute radiation poisoning and chronic health effects of exposure, particularly an increased incidence of leukemia.

Early EPA primary standards focused on the concept of the “maximally exposed individual”, with the idea that no member of the public should exceed such limits. Because such a hypothetical individual was difficult to identify, this evolved to the concept of the “reasonably maximally exposed individual” (RMEI), meaning the focus of limits was shifted toward critical groups of individuals with highest temporospatial risks of exposure -  eg., due to occupation, location, or lifestyle. By setting limits for such individuals, exposures should be kept below threshold for average members of the public.

Moeller lists eight criteria for establishing and applying standards:

1.       Understand the conditions for application of the standard and whether it is to be a primary or secondary standard.

2.       Identify what is to be protected – humans, wildlife, agricultural crops, buildings, etc.

3.       Review all possible pathways of exposure.

4.       Review applicable human epidemiological data.

5.       Review available data on negative impacts to nonhuman animals, plants, and the ecology.

6.       Establish a schedule for completing studies to fill in gaps in knowledge.

7.       Evaluate existing standards and their source.

8.       Develop guidelines for application and enforcement of the standard, including the limitations and uncertainties inherent in the standard.

The limitations of standards, of course, are manifold, and Moeller also lists several of these:

1.       The evaluated endpoint, usually a form of cancer, may have multiple causes, which can confound analysis of effects.

2.       There is very little dose-response data developed expressly for the purpose of developing standards, so much has to be extrapolated from other studies.

3.       Dose-incidence relationships are often poorly defined and can be complicated by differing risks for different routes of exposure.

4.       Standards often don’t account for differences between population groups – e.g., weight, size, diet, lifestyle, etc.

5.       There is often little or no coordination between standard-setting agencies, such as OSHA and EPA.

6.       Standards may not apply to all potential sources of exposure.

7.       Standards are generally set for a specific route of exposure and don’t take into account the cumulative effects of exposure via multiple routes.

8.       Sound epidemiological data for the effects of exposure may be lacking.

9.       The risks associated with a particular exposure may not be quantified.

10.   Few standards exist for the protection of the natural environment, property, or aesthetic concerns.

11.   Standards focused on maximal acute exposure may miss the effects of low level, chronic exposures, or biological effects may not occur in either a direct linear fashion or according the minimum threshold concept of effect – i.e., different effects may occur with different levels of exposure.

The two broad strategies for enforcing standards are a “top-down” and a “bottom -up” approach. In the first case, an upper bound is set and the limit reduced from that to a reasonably achievable level based on site-specific considerations. With the bottom-up approach, a relatively stringent lower level is set and then adjusted upward if needed due to feasibility or cost limitations. In theory, either approach should tend toward achieving a middle ground, but it’s not clear whether one or the other would be more subject to purely political considerations.  Because different agencies use different approaches, too, it is possible for incompatible or contradictory standards to exist.

Moeller suggests that there should be greater harmonization between federal agencies, in order to develop more uniform standards. At the federal level, I think this is a very desirable aim, as it should ultimately reduce bureaucratization. My sense, though, is that the current climate is one of minimal communication and coordination between agencies. Further, trying to coordinate standards at an international level is exceedingly difficult, and a uniform standard may not be desirable if it fails to take into consideration culture or region-specific differences.

That said, there are possibilities in this regard. The United Nations Framework Convention on Climate Change (http://unfccc.int/), despite contentions among nations, was able to institute the Kyoto Protocol, which set standards for greenhouse gas reductions for signatory nations. This has not, of course, been a completely successful effort, as Canada pulled out of the treaty and the United States Congress has never ratified the agreement, but it is an example of a widespread multinational effort at developing some uniformity of standards.

A smaller, but still very notable example, of multinational efforts at developing uniform standards is the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (http://www.ich.org/). This is a joint partnership between regulatory agencies in the U.S., the European Union, and Japan, as well as pharmaceutical industry, to develop more uniform standards for the drug approval process. This effort helps to streamline bureaucratic processes, but also has the advantage for industry of making the drug approval process more efficient, as testing for approval doesn’t have to be repeated multiple times to meet widely varied standards.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Electromagnetic Radiation

Electromagnetic radiation comes from both naturally-occurring and manmade sources and is generally classified as either ionizing or nonionizing, depending upon the amount of energy carried by the radiation’s wave particles, or photons. The energy level is directly proportional to and often expressed using the oscillation frequency of the photons. Ionizing radiation is that occurring in the high energy ranges – e.g., gamma rays, ultraviolet light, x-rays - which is capable of stripping electrons from atoms struck by the photons. The energy transferred in this reaction can cause cellular damage or other harmful changes in chemical or biological structures.

Nonionizing radiation, on the other hand, is that which occurs in lower energy ranges – generally from the lower end of the ultraviolet spectrum on down. Although generally thought of as safer, there are in some ways more questions surrounding the biological effects of nonionizing forms of radiation. Although we may know a great deal about the benefits and potential dangers of infrared radiation (i.e., heat), we are still learning about the effects of electric and magnetic fields.

Our understanding of ionizing radiation, which led to our understanding of atomic structure, dates back to the late 19^th century. Early experiments led to an understanding of natural sources of radiation, such as uranium and radium, as well as our ability to produce radiation via a high charge electrical field, such as is done today with diagnostic x-ray equipment.

And although there are benefits to be gained from the utilization of ionizing radiation – nuclear fission to produce electricity, x-rays for medical diagnosis, radioisotope therapy for some forms of cancers, etc. – there are also potentially harmful biological effects. When electrons are stripped from atoms within a living cell, the remaining anion is highly reactive and can trigger a series of chemical reactions which damage cellular structures and function. While some of this damage can be repaired, damage to DNA can result in cellular death or can result in changes that lead, sometimes several years later, to the development of cancer.

For this reason, exposures to manmade sources of radiation are typically tightly regulated. Within my own work setting, our x-ray and CT rooms are required to be lead-lined to prevent transmission of x-rays through walls. Personnel are required to wear lead-lined personal protective gear to limit exposure when we must be present in the room for imaging (which is most of the time when taking x-rays), and all staff who use the equipment must wear radiation dosimetry badges, so that our monthly and cumulative doses can be monitored.

Natural sources of ionizing radiation are somewhat more difficult to control and monitor. We are all bombarded with cosmic rays constantly, as these high energy rays can pass readily through buildings. People who fly frequently in commercial jets are exposed to even higher levels, since there is less attenuation by the atmosphere at higher altitudes. Here in New England, the large concentration of granitic deposits are also a terrestrial source for ionizing radiation, as they contain numerous radioactive isotopes, including uranium.

One of the by-products of radioactive decay in granitic substrates is radon gas, which can accumulate in basements with dirt floors (such as my own). Because radon is heavier than air and because it decays rapidly to a solid radionuclide, it can accumulate in the lungs and act as a source of long-term exposure, which can increase the risk of lung cancer. Because Maine has a fairly shallow soil layer overlying largely granitic rock, much of the state is classified as Zone 1 for radon exposure potential by the EPA, which means exposures here are among the highest (http://www.epa.gov/radon/zonemap.html).

Of course, we are almost all constantly exposed now to mandmade nonionizing radiation. Most houses are replete with electronic devices, such as computers, stereos, microwave ovens, televisions, etc. – all of which produce magnetic fields. Most Americans now own cell phones, many use Bluetooth devices to communicate through their phones, and cell towers are continuing to pop up all over the country to expand network coverage. All of these things increase ambient nonionizing radiation levels.

Cell phones, in particular, have been a source of considerable controversy in the last several years, at least since Hardell, et al. (1999) first posited a possible link between cell phone usage and brain tumors. The most recent report on the Interphone Study conducted by the International Commission for Non-Ionizing Radiation Protection Standing Committee on Epidemiology, however, found no association between cell phone usage and an increase in glioma or meningioma occurrence at this time. Although the authors did report some limitations with the study, they noted that the heaviest users were actually more likely to overestimate past usage, which would tend to bias findings toward a positive association (Swerdlow, et al., 2011). Additionally, these findings do not preclude the possibility that an association might become apparent in another 5 to 10 years or longer.

Perhaps the take-home message should be: Don’t be afraid to use your cell phone, but try to turn it off and walk away from time to time.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Hardell, L., et al. “Use of cellular telephones and the risk for brain tumours: A case-control study”. International Journal of Oncology. 15(1): 113-116. 1999.

Swerdlow, A.J., et al. “Mobile phones, brain tumors, and the Interphone Study: Where are we now?”. Environmental Health Perspectives. 119(11): 1534-1538. 2011.

Insects and Other Animals

As a veterinarian, a large area of my professional training and focus is in zoonotic disease, not only with regard to animal-to-human transmission but occasionally concerning the reverse, as well. Viruses will often mutate and jump from one species to another; bacteria are notoriously promiscuous and readily exchange DNA that will allow them to propagate more rapidly, often at the expense of host health; and parasites, though often more host-specific, can occasionally infect multiple species or can cause serious disease when they find their way into aberrant hosts.

Some animals can be very useful to humans, such as honeybees and other crop pollinators. Others are nuisance species and can cause serious damage to food crops, either by causing physical damage or by spreading viral or fungal plant pathogens.  Conversely, human activities can be damaging to animal populations, from habitat destruction to overuse of nonselective pesticides.

Because this topic covers such an enormous scope, I am going to focus primarily on areas in which I have particular knowledge and interest. First and foremost of these is rabies, which is one of the oldest recognized zoonoses. For the entirety of my career as a practicing veterinarian, I have lived and worked in rabies-endemic regions, principally the Atlantic seaboard states. The virus is primarily maintained in wildlife reservoirs and incidence fluctuates on a fairly regular cycle, as host populations wax and wane.

Because the disease is one of the earliest for which a vaccine was developed, vaccine programs are well recognized as the most efficacious means of prevention and standard protocols are well established. All fifty US states require vaccination of domestic pets, and approved vaccine products exist for livestock species, as well. As a result, human deaths from the disease are extremely low in the US, as well as in other countries which have adopted mandatory animal vaccination programs (i.e., essentially all developed nations). 

Worldwide, however, over 55,000 people are estimated to die each year from the disease, with the largest numbers of deaths occurring in Africa and in the Indian subcontinent (http://www.rabiescontrol.net).

In the US, the majority of human cases over the last couple of decades have been strains of the virus associated with bats. Mistakenly identified by Moeller as rodents (they are chiropterans), bats are a very important group of species ecologically, both as pollinators and seed dispersers and as consumers of insect pests. That said, they are also capable of finding their way into human dwellings through very small openings, and their bites are often not recognized, due to their small sharp teeth and the potential for victims to be bitten while they are sleeping or otherwise unaware of the bat’s presence (http://www.cdc.gov/rabies/bats/index.html).

Living in northern New England, tickborne disease are also a significant concern, especially Lyme disease, caused by the spirochete Borrelia burgdorferi. Lyme disease is not spread by direct transmission between affected species, but primarily by the tick species Ixodes scapularis. In clinical practice, I see the disease and identify the tick vector extremely frequently. There are some differences between the clinical syndromes in dogs and humans, but both can potentially experience polyarthritis, fever, and neuropathies. In dogs, we occasionally see immune-mediated damage to the kidneys, which generally carries a very poor prognosis. And although the organism is treatable, it is not considered to be a curable disease and recrudescence is possible.

When I lived in North Carolina, ticks were vectors for Rocky Mountain Spotted Fever, babesiosis, ehrlichiosis, anaplasmosis, and numerous other diseases. A study published one of my colleagues at NC State in 1999 showed high levels of coinfection in both dogs and humans at one kennel in the eastern part of the state (Kordick, et al., 1999).

Mosquitoes are also an important vector for disease spread. Worldwide, malaria is probably the most well-known mosquito-borne disease. Many other disease, including dengue fever and yellow fever, are also transmitted by mosquito species. In the late 1990s to early 2000s in the eastern US, mosquitoes were the vector for West Nile virus infection, which had spread to North America via migratory birds. Although the virus is host-adapted and rarely causes serious disease in definitive host species, in aberrant hosts, such as corvid birds and humans, it can potentially cause serious neurologic disease and even death.

Although syndromically similar, the western, eastern, and Venezuelan equine encephalitis viruses (WEE, EEE, and VEE, respectively), are genetically unrelated viruses which are also transmitted from birds to aberrant mammalian hosts via mosquito vectors. As their names suggest, they can cause neurologic disease similar to West Nile and can be fatal. My husband and I own alpacas, and the farm where most of our animals were boarding was one of several in southeast New Hampshire affected by an outbreak of EEE in the summer of 2005 (Nolen-Watson, et al., 2007). During that same period, a total of eleven human cases were identified in Massachusetts and New Hampshire, four of whom died from the disease (MMWR, 2006).

Clearly, control of vector and other pest species is important in managing these problems, but achieving this is not always straightforward. For some insect species, release of sterile males can help reduce population numbers, but given the short life cycle of most insect species, this requires sustained effort for long-term impact. The use of pesticides is problematic because of the risk of damaging non-target species – either beneficial insects or species higher up the food chain, such as occurred with DDT. In the case of rodent species, physical traps are not always humane or effective and poisonous baits can be consumed by non-target species – I frequently see rodenticide poisonings in pets.

That said, the challenges are not insurmountable. In malaria-endemic regions, selective spraying of DDT and increased use of mosquito netting has helped to impact the disease, which remains incurable. In agricultural settings, increased of integrated pest management strategies, such as promotion of predatory insect species, has helped to reduce the use of harmful pesticides. As long as we exist as part of the Earth’s ecosphere, though, we will have to continue finding a balance between our impact on other species and their impact on us.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Kordick, S.K., et al. “Coinfection with multiple tick-borne pathogens in a walker hound kennel in North Carolina”. Journal of Clinical Microbiology. 37(8): 2631-2638. 1999.

Nolen-Watson, R., et al. “Eastern equine encephalitis in 9 South American camelids”. Journal of Veterinary Internal Medicine. 21(4): 846-852. 2007.

MMWR. “Eastern equine encephalitis – New Hampshire and Massachusetts, August-September, 2005”. 55(25): 697-700. 30 Jun 2006.

Solid Waste

In 1976, Congress passed the Resource Conservation and Recovery Act (RCRA), which defined solid waste as follows:

“[A]ny garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including solid, liquid, semisolid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations and from community activities.”

This act specifically excluded solids from sewage or industrial wastewater discharges, which were discussed as part of the liquid wastes journal entry.  A subsequent amendment to the act, though, also set a definition for hazardous waste, which is any solid waste or combination of wastes which may:

“(1) cause, or significantly contribute, to an increase in mortality, or an increase in serious irreversible or incapacitating illness; or (2) pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed.”

To address the matter of hazardous waste, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in 1980, which has become more commonly known as Superfund. This act established regulations regarding the management of closed and abandoned hazardous waste sites, made parties responsible for hazardous waste releases at the sites liable, and established a trust fund for cleanup of sites when no responsible party could be identified.

In 1995, around 24,500 of the identified Superfund sites were designated as low priority and subsequently fell under the management of the Brownfields Development Initiative, which was created in 2002. This initiative provided government incentives for cleanup and redevelopment of these sites for public, private, or commercial usage.

Radioactive waste, such as spent nuclear fuels and some medical waste, is another category of solid waste, and mixed waste is, as the name suggests, a combination of two or more types of solid waste. And aside from the categorical considerations, solid waste management can be complicated by the fact that it encompasses items ranging in size from gum wrappers to retired airliners.

Management of hazardous wastes often involves some form of treatment "designed to change the physical, chemical, or biological character or composition" in such a way as to render the waste either nonhazardous or less hazardous and make it safer to store or dispose of. Methods of hazardous waste treatment include incineration, heat treatment (useful with volatile solvents), solidification into glass- or sand-like particles, chemical treatments to neutralize or degrade toxins, and biological treatments which use microbes to help break down or convert toxins into less hazardous forms.

Radioactive wastes are managed according to their potential level of hazard. Low level wastes, such as radioactive materials from healthcare or research facilities, pose a relatively lower risk and are generally managed by storage in earth-covered concrete bunkers with mechanisms designed to prevent leaching into surrounding soils. Uranium mill tailings are a particular high volume form of low level waste that are stabilized in situ by the Army Corps of Engineers. High level wastes, such as spent nuclear fuel rods or decommissioned armaments, pose a much higher health and environmental risk, and so the goal for managing these products is deep underground storage, though political considerations have made this challenging here in the US.

One particularly troublesome solid waste category over the past few decades is that of electronics. As computers and mobile phones have become increasingly commonplace, but with a relatively limited life span, it has become increasingly apparent that this portion of the waste stream will have to be addressed, especially given the fact that electronic devices typically contain numerous heavy metals and plastics which can have a significant negative environmental impact in quantity. Considering that an estimated 100,000 personal computers enter the waste stream daily, the need to deal with this problem is rapidly gaining urgency.

 And, of course, one major component of electronic devices is a major problem in its own right. To quote the movie The Graduate, “One word: plastics”.  In recent years, a great deal of media attention has been given to the “Great Pacific Garbage Patch”, an accumulation of plastic debris in the North Pacific Gyre. As documented in the video below, the effects on wildlife can be devastating, both due to mechanical injury, such as strangulation or bowel obstruction, and to toxicity caused by the propensity of plastics to adsorb chemicals, especially persistent organic chemicals such as dioxins and PCBs.

With regard to municipal wastes, landfills are the most common form of disposal. Because household wastes do contain some level of hazardous substances, landfills are regulated by the EPA under the 1984 RCRA amendments. They cannot be located in floodplains, on wetlands, near airports, or in areas subject to damage from disruptive geological events, such as landslides or earthquakes. They must be designed to prevent groundwater contamination, including clay and impermeable synthetic liners and leachate collection and treatment systems. Wastes must be covered daily to prevent spread of disease by or to vermin and wildlife, and access must be restricted to prevent unauthorized dumping. Monitoring systems must be in place to detect groundwater contamination or other problems, and lastly, operators must maintain monitoring systems for 30 years after a landfill is decommissioned.

Other methods for dealing with municipal wastes are surface impoundments, which are storage facilities that are generally ineffective and not adequately secure, and waste piles, which are non-containerized and which are primarily used for temporary storage. Some solids, such as sludge from municipal wastewater treatment facilities are managed by spreading them on the soil surface or working them into the soil. In this case, soil microbes complete the breakdown of waste components. Underground injection wells, into which waste is injected under high pressure, are only used in the US in certain exempt oil and gas wells.

Given the finite space available for landfills and the consumption demands of an ever-growing population, the demand for recycling has been growing, though many challenges still exist. The largest hurdle is, perhaps, developing a cultural imperative to recycle at all levels, from the individual to the municipal to the state and national levels. If we are to avoid ending up literally living on a junk heap, though, it’s a hurdle we will have to leap.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Liquid Wastes

The management of liquid wastes is, in some ways, tied in closely with drinking water quality. As I already discussed in that section, agricultural and other liquid wastes can enter into surface and groundwater sources for drinking water, as can pathogens from inadequate or improper management of human and animal wastes. The subject of liquid waste management, however, is much broader than just the safety of the water we drink and is crucial to the health of entire ecosystems.

The first federal law in the US to address surface water quality was the Water Pollution Control Act of 1948. This was expanded in 1956, and in 1965, Congress passed the Water Quality Act, which provided for assistance to states to meet specific water quality standards. That law was updated in 1972 and 1987, and 1977 saw the passage of the Clean Water Act, which provided for the development of technical programs and permitting processes to limit and mitigate water pollution.

In part, these laws have provided federal funds for construction and maintenance of municipal wastewater treatment plants. The Pollution Prevention Act of 1990 further established a policy of preventing discharge of pollutants at the source wherever possible, and the 2000 Wet Weather Water Quality Act focused on preventing and minimizing the effects of sewer overflow in storm events.

There are different paradigms for classifying liquid wastes. One of these is the degradable-nondegradable classification scheme. Degradable wastes include not only domestic sewage but also organic industrial wastes. Nondegradable wastes are generally inorganic constituents of liquid waste, such as salts and heavy metals. There are also persistent environmental toxins, such as organochlorines (DDT, PCBs, etc.), which fit into neither category neatly, as they degrade extremely slowly.

Because of the difficulties of easy categorization and the potential for liquid wastes to contain both degradable and non-degradable components, the more commonly used paradigm is that of point source vs. non-point source wastes.  The Environmental Protection Agency defines point source wastes as follows:

“Any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock concentrated animal feeding operation (CAFO), landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged. This term does not include return flows from irrigated agriculture or agricultural stormwater runoff.” (http://cfpub.epa.gov/npdes/glossary.cfm?program_id=0#P, accessed 31 March 2012)

Non-point source wastes are, as the name suggests, any wastes not fitting within the definition of “point source” wastes.

This paradigm is more useful because it provides a better framework for designing mitigation and prevention strategies. Point source wastes can often be addressed more effectively than non-point sources with prevention strategies, such as improved processes to minimize primary waste by-products. Additionally, treatment strategies can be more easily targeted to the specific waste stream.  Municipal sewage, for instance, goes through a series of primary, secondary, and tertiary treatment steps to remove suspended solids, aerate and oxidize remaining organic matter, and additional treatments to render the effluent safe for drinking or to release into surface waters. Industrial wastes, similarly, can be put through a series of steps to remove particulates physically; to extract, neutralize, or replace noxious substances through chemical means; and/or to break down organic pollutants through biological processes.

During my time at NC State, one point source that was a frequent topic of conversation within my department was waste lagoons from feeder hog operations. North Carolina is one of the top pork-producing states in the US, and the majority of the feeder operations, a type of CAFO, are located in the Eastern half of the state, which is largely flat coastal plain and more susceptible to flooding. Moeller cites overflow from the lagoons during heavy spring rains in 2009, but I was living in the state in 1999 when a large portion of that area was flooded by rains from Hurricane Floyd. Tabochow, et al. (2001), documented the effects of the flooding of hog lagoons and of municipal wastewater facilities on nitrogen and phosphorus levels in the Neuse River Basin as a result of the hurricane.

Prior to Hurricane Floyd, much of our discussion was on the potential consequences of trying to decommission the hog lagoons. They are constructed with a clay lining, which remains more or less impermeable so long as the lagoon is filled. If the lagoons were to be drained, however, the clay liner would likely dry and crack, providing an entry point for accumulated nitrogen and phosphorus to leach into the water table. The Neuse River drains into the Pamlico Sound, which is the largest lagoon on the East coast and an ecologically sensitive area.

Eutrophication of the waters in this area was and is a significant environmental concern because of the potential damage to shellfish and fishing stocks by algal blooms. JoAnn Burkholder is an aquatic researcher at NC State who has done extensive research on the effects of eutrophication in this area, and a 2004 article suggests that long-term leaching as described above and non-point source runoff may actually be more damaging in this regard than large flooding events such as were seen with Floyd, as the latter resulted in massive flushing and dilution of nutrients and didn’t result in algal blooms or any apparent long-term damage to commercial fisheries (Burkholder, et al., 2004).

A greater concern from the standpoint of water quality degradation is non-point source waste. Because this can come from numerous and difficult-to-trace sources – lawn and agricultural fertilizers, urban runoff, etc. – it is a much more insidious and difficult to control problem. In addition to eutrophication, runoff from paved surfaces, such as parking lots and highways, can carry petroleum distillates, salts, and heavy metals into surface waters and pavement can exacerbate erosion by reducing surface porosity and displacing organic matter and root systems that would otherwise help absorb rainwater.

One strategy that has been of particular interest in mitigation of non-point source, and some point source, wastes is that of constructed wetlands, which are intended to provide a buffer zone between runoff areas and flowing surface waters, as well as a potential sink for nitrogen, phosphorus, metals, and other pollutants. With respect to point source wastes, this strategy has been explored with some success for managing landfill leachate systems (Nivala, et al., 2007; Białowiec, et al., 2012).

A 2011 study looking at constructed wetlands for removal of pesticides from agricultural runoff, though, suggests that under certain conditions, accumulation of the pollutants could occur which might be problematic (Budd, et al., 2011). Further concerns about this approach are the ultimate fate of pollutants like mercury, which can be converted from its inorganic form to highly toxic methyl mercury by bacterial activity in wetlands, though prevention at the source is likely the most effective strategy for minimizing this risk.

Another consideration is the management of biosolids derived from the wastewater treatment process. Sewage sludge is sometimes managed by spreading it on agricultural fields, but there are concerns about the potential for the contamination of food crops by pathogenic bacteria, as well as the potential for heavy metals which are discharged into sewage systems to similarly be redistributed into the food chain. Also, this process takes waste from a point source and transfers it into a non-point source situation, which then makes mitigation more challenging. Animal manure from agricultural activities is also often handled in this manner, with much the same concerns.

Clearly this is a complex issue and this discussion does little more than scratch the surface, but hopefully this gives at least a glimpse into the topic.

REFERENCES

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Tabochow, R.M., Peirce, J.J., & Essiger, C. “Hurricane-loaded soil: effects on nitric oxide emissions from soil”. Journal of Environmental Quality. 30:1904-1910. 2001.

Burkholder, J., et al. “Comparative impacts of two major hurricane seasons on the Neuse River and western Pamlico Sound ecosystems”. Proceedings of the National Academy of Sciences. 101(25): 9291-9296. doi: 10.1073/pnas.0306842101

Nivala, J., et al. “Treatment of landfill leachate using an aerated, horizontal subsurface-flow constructed wetland”. Science of the Total Environment. 380: 19-27. 2007. doi: 10.1016/j.scittotenv.2006.12.030

Białowiec, A., et al. “Nitrogen removal from landfill leachate in constructed wetlands with reed and willow: redox potential in the root zone”.  Journal of Environmental Management. 97: 22-27. 2012. doi: 10.1016/j.jenvman.2011.11.014

Budd, R., et al. “Removal mechanisms and fate of insecticides in constructed wetlands”. Chemosphere. 83(11): 1581-1587. 2011. doi: 10.1016/j.chemosphere.2011.01.012 

The Workplace

Associations between occupations and specific diseases have been recognized for many centuries, from lead exposure among metallurgists, to pneumoconiosis, or “black lung”, among coal miners, to scrotal cancer among chimney sweeps in Victorian England. These associations have sometimes even found their way into the English lexicon, as with the phrase “mad as a hatter”, which evokes the neurological signs and dementia once seen in hatmakers from chronic exposure to the mercury used to cure animal pelts.

Despite the long-standing recognition of occupational risks, though, government agencies, at least in the US, have often been reluctant to institute safety standards.  Workers compensation laws to provide recompense for on-the-job injuries, for instance, were not in place in all states until 1948. The first law protecting non-federal employees, the Federal Coal Mine Health and Safety Act, wasn’t enacted by Congress until 1969, and the Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) weren’t created until the 1970 Occupational Safety and Health Act.

The Toxic Substances Control Acts of 1976 and 2000 set in place rules requiring employers to inform employees about potential hazardous exposures in the workplace, and the Pollution Prevention Act of 1990 established a policy of reducing pollutant levels at the source, also reducing occupational exposures. All of the above have had a positive impact on reducing and mitigating workplace-related injuries and disease, though the institution of certain safety standards has, perhaps unsurprisingly, not been without controversy (Heyden and Pratt, 1980).

Although these measures have had a great impact on workplace safety, with deaths per 100,000 workers decreased by 60% between 1990 and 2005, there were still 4 million disabling occupational injuries and work-related illnesses in 2007, resulting in 75 million person-days of lost productivity. Additionally, this may not be an adequate reflection of the true cost of workplace-related illness, since data may be incomplete or incorrect, the long-term effects of occupational exposures may occur with sufficient delay that they are not recognized as being work-related, or exact relationships between occupational exposure and disease may not be adequately understood.

Certainly everyone within the US work force now has some acquaintance with workplace safety regulations. Manufacturing workers are required to wear clothing to minimize risk of getting caught in machinery or protective headgear, eyewear, earplugs or covering, or face masks/respirators as their situation demands. Office workers have standards of ergonomic design to help protect them against repetitive strain injuries. Agricultural equipment has built-in safety mechanisms to help reduce the risk of serious injury or death in farm workers. Chemical workers have personal protective equipment or work with ventilator equipment to minimize dermal and respiratory exposures.

As a clinical healthcare worker, I work with disinfectants and chemicals which can have hazardous effects, sharps which can both cause physical injury and potentially transmit toxic biological or chemical agents. I work frequently with ionizing radiation and have to use lead-lined apron, thyroid shield, and gloves when doing so. While as a veterinarian I don’t have the same level of risk and require the same degree of personal protective equipment that a practitioner working with human patients might have, I still have to be mindful of possible zoonotic exposures and take steps to minimize those risks. I also have to remain mindful that my patients have the potential to inflict significant physical injuries through bites or scratches and can transmit infectious biologic agents.

Additionally, the clinic must maintain material safety data sheets (MSDS) on all chemicals and products used in the clinic. An injury report log is also maintained for any workplace-related injuries or exposures employees may sustain, and all personnel are required to attend training session to make sure everyone is aware of information available, proper personal protective equipment usage, exposure first aid and mitigation, and appropriate measures to take in the event of an exposure, injury, or other emergency situation.

Although these measures are all OSHA-mandated and appropriate to the type of work that is done in our facility, some more general public health measures can also have a positive effect on workplace environments. Since about 1995, a number of municipalities, states, and even countries have instituted bans on smoking in public indoor spaces in order to reduce exposure of both employees and of the general public to secondhand smoke. Studies looking at bar employees and other hospitality workers in many of these localities have found significant decreases in reported symptoms of irritation from smoke exposure; significant decreases in salivary levels of cotinine, a marker for tobacco smoke exposure; and, in studies where it has been evaluated, significant improvements in pulmonary function (Eisner, Smith, & Blanc, 1998; Farrelly, et al., 2005; and Goodman, et al., 2007).

References

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Heyden, S., and Pratt, P. “Exposure to cotton dust and respiratory disease: textile workers, “brown lung”, and lung cancer”. Journal of the American Medical Association. 1980 Oct 17; 244(16):1797-1798. doi:10.1001/jama.1980.03310160013014

Eisner, M.D., Smith, A. K., and Blanc, P.D. “Bartenders’ respiratory health after establishment of smoke-free bars and taverns”.  Journal of the American Medical Association. 1998 Dec 9; 280(22):1909-1914.

Farrelly, M.C., et al. “Changes in hospitality workers’ exposure to secondhand smoke following the implementation of New York’s smoke-free law”. Tobacco Control. 2005 Aug; 14(4):236-241. doi: 10.1136/tc.2004.008839.

Goodman, P., et al. “Effects of the Irish smoking ban on respiratory health of bar workers and air quality in Dublin pubs”. American Journal of Respiratory & Critical Care Medicine. 2007 Apr 15; 175(8):840-845. doi: 10.1164/rccm.200608-1085OC.

Air Quality, Indoor and Out

As with all other areas of environmental concern, the issue of air quality is multifactorial and complex. Broadly speaking, we can break this topic down into outdoor, or ambient, air quality and indoor air quality, though these two categories aren’t necessarily mutually exclusive and the underlying physiological considerations are essentially the same.

Pollutants can enter the respiratory tract either in gaseous form or as airborne, generally microscopic, particulates. Gases that dissolve readily in water, generally those with highly polar molecules, are predominantly absorbed in the upper airways, while less soluble gases pass to the lower airways and alveoli. Ozone is a well known example of the latter case, and increased atmospheric concentrations are known to trigger asthma attacks because of the irritation it causes in the lower airways. Formaldehyde is an example of the former that is commonly used in construction materials and is a known carcinogen.

In the case of airborne particulates, size is the primary determinant of effect. Particles of 5 or more microns in diameter are typically removed by the nose, which effectively filters them out. Particles between 2.5 to 5 microns can generally be inhaled but will deposit in the upper respiratory tract, where they will generally be cleared by the mucociliary apparatus. Particles in the sub-2.5 micron (PM_2.5) range have come under increased scrutiny in recent years, because these are sufficiently small to pass all the way to the alveoli. Also, because they have a relatively much greater surface area to volume ratio, they are thought to serve as a vehicle for depositing adherent chemical contaminants in the lower airways.

Last Fall, I met Dr. Héctor Olvera, a research assistant professor in environmental engineering at the University of Texas at El Paso, whose research is currently focused on the health effects of PM_2.5 particles from diesel exhaust. Although these smaller particles can theoretically remain suspended in air longer, they tend to aggregate into larger particles fairly quickly, their health effects tend to be seen only within a very small radius, generally less than 200m, from the point of emission (personal communication).

For this reason, his current focus is on the corridor around the El Paso-Ciudad Juárez border crossing, which experiences very high levels of diesel traffic and which has residential areas directly abutting the highway. In a previous study of the El Paso area, polycyclic aromatic hydrocarbons (PAHs) - known sources of cellular damage and oxidative stress, which can act as asthma triggers - were found to comprise a larger proportion of total particulate mass in PM_2.5 samples compared to PM_10-2.5 samples (Lauer, et al., 2009).

Here in New England, a significant air quality concern comes from upwind emissions from both industrial point sources, such as coal-fired power plants, and non-point source, or mobile, emissions, such as those produced by traffic in large urban areas.  These produce carbon monoxide (mobile), sulfur dioxide (point source), and nitrogen oxide (both), which serve as precursors to the development of ozone, and the origins of these precursor molecules can be as far away as the Ohio or Mississippi River valleys. Particularly in the spring and summer, when prevailing winds are out of the southwest, this leads to disproportionately high levels of ozone relative to local anthropogenic production (Yu, et al., 2006).

Another topical air quality concern in this region of the country is that of residential wood burning as a source of home heating, which can affect both indoor and outdoor air quality. As Maine is a rural and heavily-forested state, wood fire has been a traditional renewable source of home heating, and it has seen a resurgence in popularity – in the form of woodstoves, masonry heaters, and wood-fired boilers - as home heating oil prices have climbed in recent years. Although the EPA has some guidance toward minimizing air quality concerns on their web (http://www.epa.gov/airquality/community/details/i-woodstoves.html), I could find no quantitative research evaluating the impacts of this shift.

With regard to air quality, there are certainly numerous potential concerns, from cigarette smoke exposures to off-gassing from construction materials, as mentioned above, but a major concern at the global level is that of particulate and carbon monoxide exposures from fires, used both for cooking and for heating. While cooking fires in the developed world are principally natural gas or propane and heating is done with woodstoves, boilers, or other relatively efficient and safe combustion chambers, numerous areas of the developing world still rely on open fires for these purposes.

Balakrishnan conducted studies on particulate exposures from cooking fires in Tamil Nadu (Balakrishnan, et al., 2002) and Andhra Pradesh (Balakrishnan, et al., 2004) states in India and found very similar patterns of exposure in both studies, with women responsible for household cooking having the highest levels of exposure and with a gradient of exposure levels from indoor kitchens without partition to indoor kitchens with partition to walled-in outdoor kitchens to open outdoor kitchens.  Additionally, exposure levels were significantly higher when dung or wood was used as fuel vs. kerosene or gas.

A somewhat similar study conducted in the Guatemalan highlands found lower indoor carbon monoxide and particulate levels in households using an improved wood-burning stove vs. open wood fires or even gas or mixed fuel sources. The improved stove design vents exhaust to the outside and generally produces a much more efficient burn, though the study did not assess the potential effects on outdoor air quality (Bruce, et al., 2004). The prospect of introducing culturally-appropriate improvements in cooking technology in developing regions, though, has some promising potential to bring about significant improvements in air quality and health.

References

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

Lauer, F.T., et al. “Temporal-spatial analysis of U.S.-Mexico border environmental fine and coarse PM air sample extract activity in human bronchial epithelial cells”. Toxicology and Applied Pharmacology. 2009 Jul 1; 238(1):1-10. doi: 10.1016/j.taap.2009.04.021.

Yu, S., et al. “Performance and diagnostic evaluation of ozone predictions by the ETA-Community Multiscale Air Quality Forecast System during the 2002 New England Air Quality Study”. Journal of Air & Waste Management. 2006 Oct; 56(10):1459-1471.

Balakrishnan, K., et al. “Daily average exposures to respirable particulate matter from combustion of biomass fuels in rural households of southern India”. Environmental Health Perspectives. 2002 Nov; 110(11):1069-1075.

Balakrishnan, K., et al. “Exposure assessment for respirable particulates associated with household fuel use in rural districts of Andhra Pradesh, India”. Journal of Exposure Analysis & Environmental Epidemiology. 2004 May Supplement; 14:S14-S25. doi: 10.1038/sj.jea.7500354.

Bruce, N., et al. “Impact of improved stoves, house construction and child location on levels of indoor air pollution exposure in young Guatemalan children”. Journal of Exposure Analysis & Environmental Epidemiology. 2004 May Supplement; 14:S26-S33. 

Food

As with water, food is essential for survival, and its availability, preservation, and preparation are all important considerations for public health practitioners. Historically, food shortages, often the result of climatic changes, have apparently been a major factor in both epidemics of infectious diseases and in social unrest and armed conflict (McMichael, 2012). Famine has also resulted in large scale human migrations, such as in the Irish Potato Famine of the 19^th century.

Although famine and food shortages continue to be a significant concern in parts of the developing world – contributing to the civil war and unrest in Somalia and to high rates of farmer suicides in India in recent years – there has been growing concern in the US over the issues of both rising levels of obesity and “food deserts”, which are defined as “area[s]…with limited access to affordable and nutritious food, particularly such an area composed of predominantly lower income neighborhoods and communities” (CDC).

The two issues are thought to be at least partly related, as lack of access to supermarkets or farmers’ markets generally means limited availability of affordable fresh produce and other healthy foods. Additionally, there has been considerable controversy regarding the role of heavy marketing of snack foods, beverages and fast foods in a shift away from a healthier, more balanced diet. Although this focus has, to an extent, triggered some increased media interest in homegrown foods and home canning, this also raises concerns about proper preservation of foods in order to prevent growth of contaminants such as Clostridium botulinum, the etiologic agent of botulism, or other bacterial pathogens.

As a veterinarian, much of my public health training has centered on maintaining and ensuring the safety of animal-based foods. Salmonella serovars are often associated with infected poultry products, including eggs; E.coli, especially the O157:H7 strain, have been associated with numerous cases of contaminated beef; and Listeria monocytogenes has been an important pathogen in outbreaks involving processed meats. And although the rate of foodborne illness hasn’t increased significantly in the past 30 years, these organisms continue to be of significant importance. The economic costs of these and other foodborne diseases are estimated at $10 to $83 billion per year in the US alone (Nyachuba, 2010).

One of the factors in the development of large foodborne illness outbreaks in the US has been the dominance of large-scale factory farming. Although it has allowed for overall greater efficiencies in food production, it has also enabled contamination to occur on a larger scale with much wider distribution. This is not to suggest that the problem is unidimensional, however.

In the case of swine production, for example, while conventional factory farming has been associated with widespread presence of multi-drug resistant strains of Salmonella (Gebreyes, et al., 2000), a study comparing the conventional factory-farmed pigs to outdoor-raised, antibiotic-free pigs found the outdoor-farmed pigs had higher levels of seropositivity to Salmonella, Toxoplasma, and even Trichinella, which had largely been eradicated as a public health concern in the US (Gebreyes, et al., 2008).

In a global economy, tracing the origin of contaminated foods can sometimes be a great challenge with significant economic ramifications. In the 2011 outbreak of E. coli O104:H4 in Germany and France, for instance, cucumbers from Spain were initially implicated as the likely source, resulting in considerable market upheaval. Ultimately, however, molecular epidemiologists determined that the source of infection was seed sprouts that had been shipped to a German distributor from Egypt in 2009. That distributor supplied seeds to the sprout farm found to be the point source of the outbreak in Germany, as well as to a British company which repackaged the seeds and sold some in France, which were the source of a smaller outbreak there. (Grad, et al. 2012)

With regard to plant-based foods, a concern that garners a good bit of media attention is that of pesticide residues on fresh fruits and vegetables, with a growing push from consumers for locally produced and organic foods. A newly published review of available data, however, indicates that imported fruits and vegetables actually tend to have lower prevalence of pesticide residues than conventional domestically-grown produce. Additionally, organically-grown produce is not necessarily free of residues, though residue prevalence and levels are generally much lower. That said, the residues present in conventional domestic produce were still generally measured at levels below those established by the EPA for chronic exposure (Winter, 2012).

The development of improved technologies to identify contaminants, though, promises to be an important area of focus to address the issue of global movement of foods. Had the above European outbreak occurred 20 years earlier, the source could have been much more challenging to identify and the outbreak much more widespread. Tools currently in development, such as an electronic “nose” to detect traces of toxins or pathogens before they enter the human food chain, may also go a long way to improving food safety. (Eifler, et al. 2011)

References

Moeller, D.W. Environmental Health, Fourth Edition. Harvard University Press. 2011.

McMichael, A.J. “Insights from past millennia into climatic impacts on human health and survival”. Proceedings of the National Academy of Sciences. 2012 Feb 6. doi: 10.1073/pnas.1120177109.

Centers for Disease Control and Prevention. Healthier Food Retail: Beginning the Assessment Process in Your State or Community. http://www.cdc.gov/obesity/downloads/HFRassessment.pdf

Nyachuba, D.G. “Foodborne illness: is it on the rise?”. Nutrition Reviews. 2010 May; 68(5):257-269. doi: 10.1111/j.1753-4887.2010.00286.x

Gebreyes, W.A., et al. “Antimicrobial resistance of Salmonella isolates from swine”. Journal of Clinical Microbiology. 2000 Dec; 38(12): 4633-4636.

Gebreyes, W.A., et al. “Seroprevalence of Trichinella, Toxoplasma, and Salmonella in antimicrobial-free and conventional swine production systems”. Foodborne Pathogens and Disease. 2008 Apr; 5(2):199-203. doi: 10.1089/fpd.2007.0071.

Grad, Y.H., et al. “Genomic epidemiology of the Escherichia coli O104:H4 outbreaks in Europe, 2011”. Proceedings of the National Academy of Sciences. 2012 Feb 21; 109(8): 3065-3070. doi: 10.1073/pnas.1121491109.

Winter, C.K. “Pesticide residues in imported, organic, and suspect fruits and vegetables”. Journal of Agricultural and Food Chemistry. ePub 2012 Feb 15. doi: 10.1021/jf205131q.

Eifler, J., et al. “Differential detection of potentially hazardous Fusarium species in wheat grains by an electronic nose”. PLoS One . 2011 Jun; 6(6): e21026. doi: 10.1371/journal.pone.0021026.