12.8 Environmental health practice
Oxford Textbook of Public Health
Environmental health practice
Lynn R. Goldman
Environmental health assessment
Environmental health policy-making
The ‘players’ in environmental health policy
Environmental health policy principles adopted by governments
Environmental health policy tools
Global environmental health policy issues
Environmental health assurance
Command and control approaches to environmental health management
Environmental health management tools
The right to know and the power of information
International agreements and the emergence of international standards
Environmental health can be best understood within an overall context of health. In 1993, the World Health Organization (WHO) stated: ‘environmental health comprises those aspects of human health, including quality of life, that are determined by physical, chemical, biological, social and psychosocial processes in the environment. It also refers to the theory and practice of assessing, correcting, controlling, and preventing those factors in the environment that can potentially affect adversely the health of present and future generations’ (WHO 1993). Thus, as defined, environmental health encompasses a wide array of determinants that can impact on the health of the individual. A broad overview of environmental health and topics in environmental health science is given in the chapters in Part 8 of this textbook.
This chapter will focus on the practice of environmental health with respect to non-occupational environmental exposures. It will also focus on those aspects of the environment that are largely not under the control of individuals, such as contaminants in food, drinking water, and indoor and outdoor air. It will not cover voluntary exposures like smoking nor will it cover injury prevention and control of radiation hazards, which are covered in other chapters. It also will not cover occupational health; an overview is given in Chapter 8.6.
Many factors modify the relationship between environment and health. The practice of environmental health should take into account the variability in individual responses to the environment. Differences in age, gender, and individual genetic make-up influence both exposure and susceptibility to environmental agents. A challenge in environmental health is the consideration of all age groups, as well as the very ill and the very healthy, in evaluation of hazards. Behaviour is also important and can have a major impact on exposure. In addition, social differences can affect exposure. For example, diets vary greatly across different cultural groups. People who live in poverty may experience multiple environmental threats, dietary inadequacies, and other factors that contribute to increased risk from environmental exposures.
The practice of environmental health is inextricably involved with the prevention of chronic diseases such as cancers, asthma, and birth defects, as well as acute illnesses such as viral gastroenteritis. The general state of knowledge about causation of many chronic diseases is less advanced than for communicable diseases so that while outbreaks or statistical excesses (so-called ‘clusters’) of chronic disease are often attributed by the public to environmental exposures, in many cases the cause is unknown. Thus, practitioners of environmental health are often called upon to address not only known exposures and links to disease but also diseases of unknown aetiology and public concern about the potential for environmental links. How to investigate such issues is covered in Chapter 8.5. In the United States, the Centers for Disease Control (CDC), the National Center for Environmental Health, and the Agency for Toxic Substances and Disease Registries (ATSDR), as well as state and local public health agencies, are often called upon to address such community outbreaks.
From the outset it is important to emphasize that the practice of environmental health may differ greatly in industrialized nations versus countries in transition and developing countries. Certain environmental health problems are much more serious in developing countries; for example, drinking water contamination with micro-organisms and toxic substances is much more prevalent and consequent morbidity and mortality more serious. Indoor and outdoor air pollution are much more impacted by the burning of coal, wood, and other biomass fuel sources for cooking and heating homes. Air is much more polluted because many of the controls and technological changes that have been required in developed countries have not yet been applied. Chemical spills and plant accidents are more common and there are fewer means to protect nearby communities and passers by. Not covered in this chapter but very important worldwide is disaster prevention and management. Worldwide there are large numbers of unnecessary deaths and injuries due to earthquakes, storms, and floods, which are completely preventable with appropriate environmental measures like construction standards for homes and buildings. However, while the priority issues for environmental health management may differ in different countries, the general principles for environmental health practice do not.
In 1965, René Dubos noted that indices of environmental health are ‘expressions of the success or failure experienced by the (human) organism in its efforts to respond adaptively to environmental challenges’ (Dubos 1965). This effort to respond adaptively to environmental challenges becomes ever more complex as the environment is changed by humans at a very rapid pace. Despite the difficulty of adapting to an environment that has been changed dramatically within just a few generations, there is evidence of remarkable success in the twentieth century. The sanitation movement of the 1800s resulted in enormous reductions in mortality due to infectious diseases and marked increases in life expectancy. This has resulted in much of the increase in life expectancy in the United States, from 47 years in 1900 to almost 77 in 1997.
In the last 30 years, stronger environmental laws in the industrialized nations have resulted in cleaner air, safer drinking water, and recovery of some water bodies that in 1970 had unacceptable levels of pollution for fishing and recreation. In the United States, air lead levels are 98 per cent lower than 20 years ago, and from 1976 to 1993, the percentage of children 1 to 5 years old with elevated blood lead levels decreased from 88 per cent to 4 per cent. Reports to the nation’s Toxic Release Inventory indicate that emissions of toxic wastes from American manufacturers decreased nearly 50 per cent between 1988 and 1996. Such successes are indicative of the important role of management of environmental health hazards.
At the same time, there are other trends in environmental health that are more disturbing and indicative of a failure to adapt to a changing environment (McMichael 1993). Globally, the trend for pollution of air and drinking water supplies is upward. In most of the world, population is exerting an enormous pressure on resources and contributing to pollution. Drinking water is under pressure both from pollution and from consumption, and in many parts of the world there are serious shortages of drinkable water. Even in the United States, there are shortages of potable drinking water in many parts of the country. In addition, overfishing and pollution of water bodies is posing an increasing threat to fish harvests. In most of the world there is little control of chemicals and pesticides in commerce and chemical waste disposal, even while development is moving forward at a very rapid pace. Even in developed nations, there are numerous challenges that remain. To a great extent the easiest problems have been addressed, leaving environmental threats that are much more difficult to control and require more participation from a broader range of society. Often the problems that must be faced involve multiple small sources of pollutants rather than a few large and visible ones. Many of these small sources are from sectors, like agriculture and small business, which are less familiar with environmental regulations and often resistant to change. Clearly, they will need to be involved, yet they do not have the resources of large industries to address environmental issues. As vehicle emissions become a larger component of air pollution, land use, transportation planning, and urban sprawl are becoming greater concerns. Furthermore, problems like non-point source pollution engage everyone in society from the farmer to the weekend car mechanic who needs to know how to properly dispose of used motor oil. All of this means that new tools for assessing and managing environmental hazards will be needed in order to continue to achieve gains in environmental health.
In 1988, the American Institute of Medicine published a report, The Future of Public Health, which defined three major functions for the practice of public health practice: assessment, policy development, and assurance (IOM 1988). This chapter will take this approach in describing the practice of environmental health.
Environmental health assessment
The weight-of-evidence approach employed in environmental health inevitably involves a multitude of disciplines. Toxicology is the study of how chemicals and pollutants can be hazardous to humans and other organisms. Environmental epidemiologists study and interpret the distributions and relationships among diseases and exposure in the environment. Exposure assessors and industrial hygienists have expertise in measuring and estimating human exposure to contaminants. Analytical chemical laboratories are important for measuring levels of pollutants whether in human blood and tissues or in environmental samples such as air, food, water, and soil. Statistics and modelling experts contribute an understanding of how to utilize the often immense quantity of data in order to inform decision-making. Many scientific disciplines, ranging from environmental and atmospheric chemistry to hydrogeology, which looks at the dynamics of flow of water in the environment, are needed to understand how pollutants move in the environment and the ultimate fate in terms of exposures to humans and ecosystems. Many fields of engineering are involved—chemical engineers who can design processes to minimize, eliminate, or treat wastes, sanitary engineers who can design treatment systems for wastewater, and so forth. Engineering may play a role not only in the management of environmental hazards but also in the development of standards, as described below.
Generally, the assessment of environmental health threats involves the identification of hazards that may lead to disease states, and measurement or monitoring of exposures or doses to the population. Hazard is a measure of the intrinsic ability of the stressor to cause harm. Dose is the amount of the stressor delivered to the person, organism, or ecosystem.
The principles are those used in the evaluation of epidemiology—the nine Bradford Hill principles—strength of association, consistency, specificity, temporality, biological gradient, biological plausibility, coherence of evidence, experimental evidence, and reasoning by analogy. A strong association between hazard and dose is one where the risk or odds of disease is relatively large. A consistent association is one that is demonstrated in different studies and perhaps using different methods. Specificity is the extent to which the effect is uniquely associated with a disease. For example, vinyl chloride is the only exposure known to cause a rare cancer, angiosarcoma of the liver. Temporality concerns the relationship between time of exposure and time of disease. Some diseases (e.g. cancer) may have long latency periods, as much as 10 or more years. Other diseases are caused by more immediate exposures; for example, pesticide poisoning from carbamates occurs within an hour of exposure. Biological gradient refers to the ability to demonstrate that there is a dose–response between the exposure and the disease. Biological plausibility is the extent to which the association is consistent with what is already known about the response to the exposure and/or the disease. Coherence of evidence concerns the fit between the studies and what else is known that is relevant to the association and experimental evidence is evidence from controlled experiments that is relevant. Reasoning by analogy is the extent to which the observed pattern is similar to known exposure–disease relationships. For example, knowledge about how benzene causes cancer has been helpful in interpreting data for similar compounds, with similar results from animal studies, but which lack the epidemiological information available for benzene.
Hazard identification generally relies on two types of information: data from epidemiological studies, and data from animal testing and other scientific studies of animals. There are many sources of hazard information (Table 1). Environmental epidemiology is defined as ‘the study of the effect on human health of physical, biologic, and chemical factors in the external environment, broadly conceived. By examining specific populations or communities exposed to different ambient environments, it seeks to clarify the relationship between physical, biologic or chemical factors and human health’ (National Research Council 1991).
Table 1 Sources of hazard information
Environmental health surveillance is an important tool for community environmental health; it is defined as the ongoing systematic collection, analysis, and interpretation of data on specific health events affecting a population (Thacker and Stroup 1994). Surveillance of hazards and exposures, as well as diseases, is critical to the practice of environmental health (Wegman 1992). By tracking exposures and diseases we can identify and respond to different kinds of public health problems. Surveillance and monitoring are also essential to the assurance function, i.e. the follow-up to make sure that the treatment for the community is effective (Thacker et al. 1996). Examples of environmental health surveillance include air pollution monitoring, blood lead monitoring, poison centre surveillance for pesticide and chemical ingestions, pesticide illness reports, asthma surveillance, and birth defects registries. All of these are tools for monitoring trends, and identifying opportunities to prevent and control environmental disease and exposures. Another form of surveillance is post-market monitoring for adverse effects. In the United States, there are provisions under both the pesticide and chemicals laws for reporting adverse health (as well as environmental) effects of toxic chemicals to the Environmental Protection Agency (EPA). This can be an important safety mechanism for chemicals approved as a result of animal testing alone since such limited testing cannot detect effects that are expected to occur in a small percentage of the population, especially idiosyncratic effects that are not completely dose dependent.
It is important to recognize that environmental health monitoring is not the same as environmental quality monitoring. In the United States, a review of the available monitoring for environmental quality found that few of the data collected are useful for tracking status and trends in environmental health (Goldman et al. 1992). Although many of these data systems have other important uses for enforcement and administrative purposes as well as for assessment of ecological systems, it is clear that environmental health assessments need to be better informed by information about both exposure and disease rates in populations. There are examples of remarkable successes that have resulted in application of the public health model for surveillance in environmental health. The CDC surveillance of lead levels in children in the United States demonstrated the benefits of the EPA’s phase-out of lead in petrol (gasoline) at a time when this was in doubt and there were efforts to overturn the decision. Despite this and other successes, the capacity for environmental surveillance at the federal, state, and local level is quite limited.
Environmental epidemiology suffers from some limitations. Firstly, it cannot detect risks of concern when there is little variation in exposure across the population. For example, dioxin exposures are difficult to evaluate in the general population because most people have dioxin body burdens within a narrow range. Secondly, epidemiology cannot be applied before approving the introduction into commerce of a chemical, product, or technology. Thirdly, studies of environmental exposures often rely on measurements for the ambient environment as a whole rather than measurements of individual exposures. Such studies are known as ecological studies and they are often the only feasible way to study exposures; air pollution is often studied this way. Generally, the larger the area over which exposures are averaged, the greater are the methodological limitations with these studies. The major limitation of ecologic studies is the ecological fallacy, which in some circumstances can result from making causal inferences based on ecological data (Morgenstern 1982).
Animal toxicity testing allows examination of a wide range of exposures, use of experimental controls to limit the possibility of confounding and premarket prediction of hazards. The principles of toxicology are described in Chapter 8.2. In the practice of environmental health, governments have established regulatory standards or guidelines to ensure that any testing required by the law meets strict standards for quality of the data generated. The international standard that is available, and employed by most industrialized nations, is the set of internationally harmonized guidelines developed by the Organization for Economic Co-operation and Development (OECD). Test guidelines attempt to assay toxic properties of chemicals in a manner that is valid, reproducible, standardized between different laboratories, and is as humane to laboratory animals as possible. In countries, specific requirements for testing vary with the type of substance and the statute under which the substance is covered. In the United States, the most highly tested substances are food-use pesticides, for which numerous health tests are required including tests of acute and chronic toxicity, neurotoxicity tests, cancer bioassays, and multiple generation studies to assess reproductive and developmental toxicity. In addition, there are new requirements for tests of immunotoxicity, developmental neurotoxicity, and endocrine toxicity that are being implemented by the EPA. The OECD is currently developing new and enhanced assays for endocrine disruption for oestrogen, androgen, and thyroid effects. Because most chemicals and pesticides are marketed in many countries, the OECD has also established an agreement for Mutual Acceptance of Data to avoid unnecessary duplication of tests.
Toxicity testing is done under good laboratory practices, standards established by governments to eliminate extraneous factors, such as poor nutrition of animals, sloppy laboratory practices, or unclean environments, which would tend to bias or distort the results of laboratory tests. These practices also include record-keeping requirements that allow intensive peer review of studies to ensure their quality. There is an internationally agreed upon set of good laboratory practice for chemicals adopted by the OECD.
Despite efforts to carry out accurate toxicity tests, these tests have limitations. To be cost-effective and humane, they are designed with as few animals as statistically possible, while dosing animals at high levels. Outcome measures have been refined over the years but may be cruder than the measurements that can be taken in humans; for example, a mouse cannot report a headache. There can be phenomena that occur in the high-dose groups that are not relevant to human risk assessment. Thus, expert judgement is needed to interpret such data and it is important that scientists review all of the evidence before making a judgement. Unfortunately, there is a perception that animal testing is irrelevant. When we have both epidemiological and animal testing data, there is a striking concordance between the two with respect to relevance to risk assessment. Furthermore, most chemicals that have been subjected to high dose testing do not cause cancer, refuting the often made assertion that ‘everything causes cancer if you give a high enough dose’.
Despite the availability of accepted tests and practices to assess hazards, the truth is that we know very little about the chemicals used in commerce worldwide. In the United States a recent evaluation by the EPA found that even among the more than 2800 chemical produced at a total of at least 1 million pounds (about 500 000 kg) per year only one in five have a complete set of screening level hazard information and 40 per cent have none (US EPA 1998a).
Assessment of exposure involves numerous factors. Usually in risk assessment one does not have access to precise measurements of all these exposure attributes, and yet they are all important in being able to calculate an average daily lifetime exposure. It would be useful to know the rate and duration of exposure and the amount absorbed, as well as the body weight. In a laboratory experiment, a toxicologist has almost complete control over these factors.
Direct measurements of exposure to the human population are almost never available to decision-makers. It is recognized that such direct measurements, in combination with better information about environmental sources and levels, would be a vast improvement over the current methods for modeling and estimating exposure. In the United States the National Health Assessment and Nutrition Examination Survey (NHANES) has conducted some population monitoring of exposures, but, other than for lead, there are no national data available for trends.
As a practical matter, actual exposure measurements are often replaced by defaults. At the EPA, the policy is to assess a reasonable high-end exposure, i.e. an exposure at the upper 90th or 95th percentile. However, summation of numerous high-end exposures can greatly overestimate exposure. Exposure to pesticides in food is a good example of this. If one adds up the upper 90th percentile bound for all foods, a theoretical individual eats 5000 cal/day, not exactly a reasonable high-end estimate of exposure. If there are data on distributions of food consumption and on pesticide levels in the food, it is possible to use probabilistic modelling, which incorporates those distributions for all foods to compute the distribution of exposure to pesticide residues in the food. Most frequently, this is done using Monte Carlo modelling techniques, not only for pesticide residues on food but also for other aggregate exposure situations. Monte Carlo and other probabilistic modelling techniques simulate the distributions of individual combinations of multiple exposures, to produce a theoretical distribution of an aggregate exposure to the population.
Currently, there is no process under way for international harmonization of exposure assessment. This is probably because of the large differences (cultural, dietary, climatic, etc.) which can lead to differences in exposures for different countries. For example, there is more consumption of drinking water in a hot equatorial climate, and there is more consumption of marine mammals among traditional societies in the Arctic.
A number of tools are used for integrating and summarizing information about environmental health hazards. Environmental health relies extensively on the use of risk assessment to evaluate environmental stressors. Use of risk assessment allows us to extrapolate either between human populations or from laboratory animals to humans. It involves weighing all the evidence in order to develop estimates of the risks to populations who may be exposed. The current practice of risk assessment in environmental health is largely based on a set of principles developed by the National Academy of Sciences in 1983. Risk is a function of hazard and dose. Four steps in risk assessment have been delineated: hazard identification, dose–response evaluation, exposure assessment, and risk characterization (National Research Council 1983). These are described in detail in Chapter 8.8. Some aspects of hazard and exposure assessment are addressed above. The section below discusses some aspects of dose–response evaluation and risk characterization that are important to the practice of environmental health.
As described in Chapter 8.8, the practice of dose–response assessment differs significantly between a carcinogen and a non-carcinogen. Cancer assessment is one of the most established areas of risk assessment. There are several authoritative bodies, all of which conduct cancer risk assessment in a similar fashion. On the international level, there is the International Agency for Research in Cancer (IARC), which publishes monographs on assessments of individual carcinogens. There are many bodies in the United States, but the most important is the National Toxicology Program, which reviews the evidence and lists substances likely to be carcinogenic in its Biennial Report on Carcinogens.
Hazard assessments for cancer are done in a roughly similar fashion worldwide. At the hazard assessment phase, all studies relevant to the assessment of cancer are reviewed. If there is definitive human evidence of cancer causation, all of these bodies rate the chemical as a human carcinogen. A substance can also be rated as a human carcinogen when the human evidence alone does not prove a causal relationship, but the weight of the evidence is convincing. (This is a change from the past, when only human data could be used to make this judgement.) When there is strong evidence, but not probative, of carcinogenicity to humans, the substance is considered to be a ‘probable’ human carcinogen. Most systems then have a category for ‘possible’ carcinogens, those with weaker evidence and non-carcinogens, chemicals that despite testing show no evidence for carcinogenicity.
At the dose–response assessment phase, the default assumption is that the dose–response curve is linear at low doses and starts at zero. This means that we assume that for every additional exposure there is additional cancer risk. In other words, we generally assume that if 20 out of 100 people exposed at 1 part per 1000 in air will get cancer, the risk for an exposure to a much lower level of 1 part per million would be 200 cancers for every 1 million people exposed. This relationship is assumed unless there is compelling evidence for a different dose–response relationship at low doses.
There are many mechanisms for carcinogenicity and it is believed that not all of these mechanisms have linear dose–response relationships at low doses. However, there are rigorous criteria for accepting arguments to depart from the low-dose linear model, and most carcinogens are still considered to have linearity at low doses. Whether from human or from animal data, the dose–response curve is modelled using statistical techniques that extrapolate from the higher doses in the occupational or laboratory setting to the lower doses that are often of concern in environmental settings. Because of the uncertainties in extrapolating from high to low doses, and to account for the variability in the general human population, the dose–response curve is plotted with 95 percentile confidence limits and the upper 95th percentile bound is generally used for risk assessment. This estimate is combined with the exposure assessment to give a probabilistic estimate of risk, for example 10–3, 10–5, or 10–6.
There are alternatives to the risk assessment approach for regulation of carcinogens. One is the so-called Delaney Clause in the United States Federal Food, Drug and Cosmetics Act which applies, in part, to the regulation of cancer risks from pesticides in food. On the basis of a hazard identification alone (carcinogenicity in animals), it sets a standard of no allowable residues of that pesticide in processed food. Later scientific developments—in the form of increasingly sensitive methods in analytical chemistry, tools for quantitative risk assessment, and new understandings of cancer mechanisms—eventually led Congress to change its policy and remove pesticides from governance by the Delaney Clause. However, in the United States, the Delaney Clause still applies to food additives and colourants that are intentionally added to the food supply. Similarly, in the European Union pesticides that are both mutagens and carcinogens are not allowed in groundwater at levels above 1 ppm regardless of the level of risk.
Non-cancer risk assessment generally involves use of the reference dose or acceptable daily intake approach. The process of establishing such regulatory levels is described in Chapter 8.8. It is important for decision-makers to understand that a reference dose is a dose considered safe with a margin of uncertainty rather than a bright line for toxicity. A chronic reference dose is an estimate of a daily exposure to a population, which, over a 70-year lifespan, is likely to have no significant deleterious effects (Barnes and Dourson 1988). An acute reference dose considers a one-day exposure only. Generally, the reference dose for an acute exposure may be much higher than the reference dose for a chronic exposure but this is very much dependent on the nature of the chemical and effects under study.
Children and other susceptible populations pose a special challenge for assessment of environmental hazards. Children are not just small adults. They develop very rapidly in the first few years of life, their diets vary from those of adults, and they require more caloric intake, oxygen, and water for their body weights than adults. Children’s metabolism changes over the first few years of life, affecting how their systems handle pharmaceuticals and toxic substances. Normal childhood behaviour includes intense exploration of the environment and hand-to-mouth activities that can lead to increased exposures to contaminants in soil and around the home. Children lack judgement and thus cannot avoid exposures unless adults ensure that their environments are safe (Rogan 1995).
These differences between children and adults influence toxicity and exposure assessments for children, as well as options for risk management. A National Research Council (NRC) committee in its 1993 report Pesticides in the Diets of Infants and Children concluded that the toxicity of, and exposures to, pesticides are frequently different for children and adults. It found that, despite a wealth of scientific information to warrant addressing risks to children, the EPA rarely did so in making regulatory decisions about pesticides. The committee advised the EPA to incorporate information about dietary exposures to children in risk assessments, and augment pesticide testing with new assessments of neurotoxicity, developmental toxicity, endocrine effects, immunotoxicity, and developmental neurotoxicity. It recommended that the EPA include cumulative risks from pesticides that act via a common mechanism of action and aggregate risks from non-food exposures when developing a tolerance for a pesticide. Since that time there has been a major undertaking by government to incorporate these recommendations into federal management of the use of pesticides (National Research Council 1993).
There are many other vulnerable populations as well, many of whom are not in the workplace. Those who live in poverty are very vulnerable because of the potential to multiple exposures, poorer diets, and lack of access to medical care (IOM 1999). For example, children who are relatively deficient in iron or calcium absorb more lead per gram of intake than children who have adequate nutrition. The elderly population may be particularly susceptible to some environmental exposures and may have slower elimination of many toxicants. Those who have chronic illnesses are often more susceptible as well. For example, people who have HIV or are immunosuppressed as a result of cancer therapy are much more at risk for serious infections from pathogens in drinking water or food. Pregnant women are at risk not only from the perspective of exposure of the developing child but also because of altered physiology and metabolism of many toxic agents. For women, menopause may be another time of vulnerability. For example, there is evidence that at the time of menopause BLLs increase because of liberation of stored lead from bones.
It is easy to conclude that the process of dose–response assessment has become ever more complex given considerations of the increasing sophistication in understanding of mechanisms of toxicity as well as increased appreciation that there are some in the population that are more vulnerable. This is creating challenges for practitioners in environmental health in developing a language that can be used and understood by stakeholders as well as decision-makers to achieve the public involvement and transparency that are so important in environmental health practice.
Risk characterization is the final step of the risk assessment process. No additional scientific information is added during this phase, which involves estimating the magnitude of the public health or environmental problem. Much judgement is needed in appropriate selection of populations and exposure levels for analysis. In addition, it is important that relevant statistical and biological uncertainties are made clear at this stage. This part of the risk assessment process is the largest nexus between risk assessment and risk managers, and it is important that risk managers receive a complete set of information to guide decisions. This is where the very complex interactions between scientists, decision-makers, and the public occur, and yet where some of the most difficult communication issues occur as well.
The International Program for Chemical Safety, which is a collaborative effort between the WHO, the United Nations Environment Program (UNEP), the International Labor Organization (ILO), and the Food and Agriculture Organization (FAO), publishes Environmental Health Criteria documents which are intended to serve as international characterizations of risk for substances. In addition, there is information available in the ILO Chemical Safety Cards, in the WHO–FAO pesticide assessments and in summary form on UNEP’s Global Information Network. Many nations make risk assessments widely available via the internet and other means but it is important to emphasize that the exposure assessment may differ between countries, as mentioned above.
Environmental health policy-making
Environmentally induced diseases and injuries are almost completely preventable, using pollution prevention, product design, engineering controls, personal protection, and education. So much of environmental health practice falls outside the realm of traditional medicine because the focus is generally on primary prevention, preventing exposures before the development of disease. At the same time, other interventions flow directly from a physician encounter that diagnoses the health problem and forms a connection between that problem and an environmental exposure (for example, childhood lead poisoning, pesticide poisoning, and asthma exacerbation by air pollution). As with occupational disease, single or small numbers of diagnosed cases can be sentinels for more widespread population exposures and disease. However, environmental health requires a broad range of disciplinary approaches and the application of engineering, sanitation, public health nursing, education and communication, epidemiology, toxicology, statistics, laboratory, administration, enforcement, and legal expertise as well as the expertise of public health generalists and physicians. Therefore this is a complex web of scientific expertise and information and much of the science of environmental policy-making involves the task of weaving together information from many disciplines to define problems and develop alternative approaches to solving them (Gordon 1997).
The ‘players’ in environmental health policy
Who makes environmental health policy? Nearly everyone at some level is involved with decisions related to the environment and health. At all levels, decisions about the planning of towns and cities, road building, and economic development all have an impact on environmental health. Much of the time, the policy-makers may not be aware of the environmental health implications of these decisions. Yet there is a need for more input of public health assessment data into such decision-making processes at all levels. For example, health experts are rarely engaged in discussions about transportation planning in the United States. Involvement of ‘stakeholders’, those with a stake in the outcome of decision-making, is important in environmental health policy-making. In a sense, since everyone wants to be able to breathe clean air, drink safe drinking water, and eat healthful food, all are stakeholders in environmental policy-making. Much of the art of environmental health practice is in not only informing but also involving stakeholders in all stages of the decision-making process, from problem definition through selection of alternative solutions to the problem (Omenn 1997). It also involves no small amount of political will to see solutions through, since by its very nature environmental health protection inevitably involves costs to taxpayers, or to industry, or to both. At the same time, environmental health practice usually creates winners as well as losers, and planning for transition from more to less polluting activities is at the heart of environmental health policy-making at its best.
Environmental health policy principles adopted by governments
In 1992, more than 100 nations signed the United Nations Commission on Environment and Development (UNCED) Treaty that formally adopted the goal of sustainable development and 27 principles of sustainable development (Table 2). Chief among these is Principle 1, which states: ‘Human beings are at the center of concerns for sustainable development. They are entitled to a healthy and productive life in harmony with nature.’ Principle 2 is also very fundamental: it describes a ‘sovereign right’ of states ‘to exploit their own resources pursuant to their own environmental and developmental policies, and the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction’ (UN 1992).
Table 2 UNCED principles of sustainable development most relevant to environmental health
The precautionary principle is another UNCED principle for environmental policy-making. As governments agreed in 1992: ‘In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation’ (UN 1992). For example, DDT was banned in the United States long before its precise mechanisms of action had been described by scientists.
Another important principle, adopted in many nations, is the principle of ‘the polluter pays’. This means in essence that those who profit from pollution should pay the price for cleaning it up. More recently, this has evolved into the concept of economic instruments such as pollutant trading systems which employ market forces to shift the societal cost of pollution to the polluter, in order to bring down overall levels of pollution.
Environmental health policy tools
A number of tools are used in risk policy-making. Many environmental standards are based in whole or in part on best available technology, such as the air toxics Maximum Achievable Control Technology (MACT) standards under the American Clean Air Act and similar Best Available Technology standards in many European countries. Technology standards can be combined with risk-based standards. For example, for hazardous air pollutants the EPA was directed by Congress to regulate using MACT standards and then to assess the ‘residual risks’ and tighten the regulations if necessary.
Pollution prevention is another important principle of environmental policy; the rungs of the pollution prevention ladder go from the most preferable strategy, reduction of pollution at the source (source reduction), to waste minimization, reuse, recycling, emissions controls, and, least preferably, clean-up. It is generally less expensive to reduce pollution at the source and thus avoid costs of emissions controls and environmental cleanup.
In some cases an economic analysis of costs or feasibility in developing standards is an important driver in decision-making. Economic analyses can play a number of roles including assessing costs and benefits of an action (so-called cost–benefit analysis) weighing the relative cost-effectiveness of alternative solutions to a problem and identification of economic inequities in impact that can inform decision-making.
Pollution and its consequences are not distributed equally in society, and thus it is important to consider environmental justice issues in assessment of hazard (IOM 1999). Unfortunately, in the past there was a failure to do so, accounting for concentrations of polluting industries, sources of air pollution, and waste disposal operations in certain low-income and minority communities. In addition, there are higher rates of many diseases in poor and minority communities in the United States and elsewhere, lending support to the notion of differential exposure and risk.
Another important tool at a community level is an ecosystem-based approach or a community-based approach to environmental protection. In the United States, under the Clean Air Act, it has long been recognized that, for many communities, it would not be possible to meet standards unless management is undertaken for an entire air shed. This approach is now being adopted for the protection of large and complex watersheds both within countries and internationally. Increasingly it is recognized that non-point sources of pollution to air and water—i.e. sources that are diffuse rather than from large industrial incinerator stacks and water disposal outfalls—are important. Ecosystem-based approaches are more effective than individual permitting activities in controlling such sources. In the United States, of increasing concern is agricultural runoff from confined animal feeding operations, which can release harmful pathogens and nutrients to aquatic environments. The nutrients in turn have been associated with blooms of harmful organisms like Pfiesteria. Only watershed-based management schemes can address this kind of pollution.
Global environmental health policy issues
The threats of large-scale changes to the global environment, such as destruction of the tropospheric ozone layer and global climate change, are encouraging nations to co-operate on environmental policy issues. For example, air pollutants can persist and travel long distances, creating environmental damage. Hazardous wastes can be transported across borders and into nations with little or no capacity to handle them. Pollution to large water bodies like the Great Lakes or the Baltic Ocean can affect the quantity and quality of food available to neighbouring nations. Clearly when pollutants cross boundaries environmental decision-making must occur on an international basis. Agreements such as the United States–Canada joint agreement for the Great Lakes are beginning to govern how we manage resources that are shared by many nations (US EPA 1997).
Another international issue in environmental policy is the emergence of a global economy together with a global trading system that is more open than in the past. Although trading agreements have recognized past environmental agreements there is always the possibility of trade taking precedence over future environmental actions. Environmental policy-making must take into account not only national economic interests but international ones as well, while upholding the sovereign right of nations to establish their own health and environmental standards as agreed in UNCED.
Environmental health assurance
Environmental health assurance is a complex process that involves a multitude of players. In most nations, there are a number of governmental entities that carry out the process of providing environmental health protection. Generally there is a national environmental ministry that carries out most national environmental regulatory responsibilities. In the United States, this function is divided between the Department of the Interior and the EPA, but this is the exception rather than the rule. There are separate regulatory authorities for food safety that are either located in the health or agriculture ministry or, in the case of the United States, both. In addition, in many nations, the health or labour ministry also has some responsibility in the area of management of chemicals. There may be separate radiation safety and consumer products agencies as well. There may also be a justice agency (in the United States, this is the Department of Justice), with additional enforcement responsibilities.
In addition to agencies with direct responsibility for environmental health, there are many others who may become involved because of how regulations affect economic interests in society. Thus in the United States, the Departments of Energy, Commerce, Defense, Management and Budget, Small Business, and others all become involved where their interests may be affected by regulations. Therefore at a national level, assurance of environmental health involves a complex web and much of the practice of environmental health involves learning how to co-ordinate and work effectively within this kind of complex environment.
In most nations, environmental regulation is delegated to state and local government levels. For example, municipal waste disposal is primarily a state and local function in the United States. At a local level in the United States, environmental assurance primarily is in the hands of environmental health divisions within local health agencies. However, there are many other players, including those as diverse as environmental agencies, fire departments, and agriculture departments. Whereas activities at a national level may focus on assuring that there is a minimum standard for clean air, drinking water, and food, on a local level there are different responsibilities, such as inspection of food preparation establishments, rat control, sanitation services, spill clean-ups, lead poisoning prevention, and so on.
In the United States, in between the federal and local levels are state departments of environment and health who often administer yet another layer of standards established by state legislatures. Often states are delegated by the federal government to assure the compliance with federal standards as well (Gordon 1997). What is often missing at all levels is the function of monitoring the health of the public and the link between the practice of environmental health and real health improvements.
Command and control approaches to environmental health management
In most of the world, much environmental health assurance is via a command and control approach that involves the development and enforcement of laws, regulations, and standards. For example, there may be rules against leaking septic tanks or creating cross-connections between water and sewer lines in cities. In addition, for chemicals and pesticides there are licensing functions like new chemicals approvals and pesticide registrations. Environmental impact assessments allow the review of proposed projects to ensure compliance with environmental standards prior to the commitment of resources for new development and construction. Permitting of facilities for air emissions, water discharges, and waste disposal are essential to controlling point sources of pollution as is a strong environmental enforcement presence. Generally enforcement is targeted to specific goals—hopefully goals that are informed by priorities for protection of health and ecosystems. The first line of responsibility for enforcement is usually with local and state health and environmental agencies.
Environmental health management tools
There are a number of tools that are used in risk management. Environmental engineering has played a very important role in identifying alternative methods for pollution prevention and control.
Pollution prevention is an important tool for environmental management as well as for policy. Increasingly it is understood that trying to address environmental problems one medium at a time can result in just moving pollutants from water to air to land to water, without a net reduction in risk. So-called multimedia approaches look at all of the impacts of decisions. Pollution prevention can also be an important driver for decision-making. Changes that involve source reduction often occur over a longer production lifecycle than more incremental changes. In the United States pollution prevention is used in both regulatory and also voluntary approaches to environmental assurance. An example of the latter is the Design for Environment programme conducted in the United States by the EPA, which works with sectors in the economy to identify alternative means of production. For example, they established, with the American Chemical Society, a Presidential Award called the Green Chemistry Challenge, a contest in which companies and universities compete to be recognized for innovative new chemistries that reduce waste and are safer for health and the environment.
Environmental monitoring is also an important tool for evaluating the success of efforts and for targeting future regulatory and enforcement actions. Monitoring can involve reporting by regulated entities or actual sampling and analysis of pollutants in the air, water, food, and so on. Such monitoring can be enforcement driven or at random to reflect population exposure. While important for environmental health assurance, environmental monitoring that is directly relevant to human health can feed back into the assessment process and inform future environmental health practice.
The right to know and the power of information
Community right to know is a powerful driver for reducing pollution. It was first introduced at a national level in the United States with passage of the 1986 Emergency Preparedness and Community Right to Know Act and establishment of the Toxic Release Inventory (TRI), which initially required the manufacturing industry to report releases of some 300 chemicals to the public. In the rest of the world such reporting systems are called Pollutant Release and Transfer Registries. Like the material safety data sheets in workplaces, community right to know is designed to empower citizens to make informed decisions either as individuals or as a community. Community right to know is a powerful tool not only to inform citizens but also workers within plants as well as plant and corporate managers. In the United States, the TRI helped industry recognize that it often was more cost-effective to prevent the pollution by better managing the flows of materials into, in, and through facilities. In the United States the TRI was also the basis for a voluntary pollution reduction programme in which industry reduced TRI emissions of several toxic air contaminants by 33 per cent by 1992 and 50 per cent by 1995, giving rise to the name ’30/50′ for the programme, from the TRI baseline year of 1988. Overall industry met this target, and those enrolled in the 33/50 programme did so a year early. In 1996, the EPA reported an overall reduction of 45.6 per cent of all TRI releases for ‘base’ facilities and chemicals for a total of 2.4 billion pounds of chemicals released in the environment or transferred for disposal (US EPA 1998b).
Availability of information online is increasing the availability of information generally. A challenge for environmental health professionals will be keeping up with the available information, and helping communities and individuals sift through it to understand what is important and relevant for their communities and how to place it into perspective. Keeping up with and understanding these information sources is a critical part of environmental health practice. Industry has long been concerned that provision of information is damaging to competitiveness. There are other concerns that information can be easily taken out of context and misunderstood by communities. Clearly, while there is an appropriate balance between providing information and other concerns, right to know has proven to be a useful tool for environmental health protection. Since it is here to stay, an important role of environmental health practitioners is to promote the right to understand as well as the right to know, i.e. to provide the context for information so that communities can understand it as well as acquiring it.
Another powerful force in assuring environmental health is the private right of action. This varies with the legal system in place but in the United States the tort liability system sometimes has been a powerful driver towards the prevention of exposures to environmental pollutants. In some instances, American environmental statutes give the public the right to sue the EPA to enforce standards (called ‘citizen suits’ provisions). Completely unique in the United States is California’s Proposition 65, which combined the right to know and the citizen suit approach. Briefly, companies must label products (a) if they may cause more than a one in 100 000 lifetime cancer risk, or (b) if they may cause reproductive toxicity and have exposures at levels greater than 1000 times the level where no effects are seen (the ‘no observed effect level’). Citizens can sue the companies if they fail to provide such warning. Proposition 65 has prompted numerous product reformulations inspired by a desire to avoid having to use the label.
Environmental education also plays an important role in the management of environmental hazards. In the United States, hazards like radon gas in homes and environmental tobacco smoke have largely been managed, on a federal level, by providing education to the public. Environmental educators can also play an important role in helping to translate complex hazard and prevention information so that it is better understood by the public.
International agreements and the emergence of international standards
A number of international organizations are responsible for aspects of environmental health practice (Table 3). This is also a complex web of activity. Already mentioned are the roles of international organizations in the assessment and policy-making functions of environmental health practice. There are global and regional agreements to prevent climate change, control emission of ozone-depleting chemicals (Montreal Protocol), and decrease acid rain. There are chemical agreements on prior informed consent for import of certain toxic chemicals (UNEP 1998) and persistent pollutants (Long-Range Transport of Atmospheric Pollutants Persistent Organic Pollutants Protocol) (UN ECE 1998). In 2001, countries agreed to create a global agreement on persistent organic pollutants. Activity to agree upon a voluntary global system for classification and labelling of chemicals in commerce is also under way.
Table 3 International organizations involved in environmental protection
The Kyoto Climate Change Treaty was negotiated in 1998, and efforts are now under way for countries to begin to ratify and implement that agreement. In the United States, there continues to be debate about the urgency of addressing global climate change as a concern. There has been a gradual and subtle increase in the Earth’s temperature over the last century, caused by the increased levels of greenhouse gases, especially carbon dioxide, in the atmosphere. These gases act as an insulating blanket, reflecting back the heat of the sun in the same way that the glass of a greenhouse works. Warming of the Earth is predicted to have a number of adverse consequences. Firstly, many scientists believe that the climate is already more erratic than historically, increasing the likelihood of regional flooding, drought, and severe storm episodes. Secondly, as the polar ice caps melt, low-lying areas will be inundated. There is already some scientific evidence that this process is beginning to occur. The ultimate result would be flooding, with many coastal and low-lying areas becoming uninhabitable or requiring elaborate dikes and drainage systems. Thirdly, the ecosystem will not be able to adapt readily to a rapid shift in climate. This could result in the spread of vectors of infectious disease, poor health, death of forests and other ecosystems, disruption of agriculture in many areas, and concomitant effects on the health of other species and humans due to the spread of infectious disease and disruption of habitat and food supplies.
In some areas international standards are beginning to emerge. For the purpose of environmental health assurance the most important role these agencies play is in establishing either international treaties (UNEP) or agreements (some of a voluntary nature) that are beginning to form the foundation for global environmental health standards. However, it is important to emphasize that all environmental agreements in existence recognize the sovereign right and responsibility of nations to set their own standards and tend to get involved only with transboundary issues such as movement of pollutants, trade in hazardous goods, and trade in hazardous wastes. Another example is the voluntary system for harmonization of classification and labelling for industrial chemicals led by the ILO. In recognition of the widespread commerce in chemicals and the need for protection in transport, the workplace, and consumer products, nations have agreed to a voluntary system for hazard classification of chemicals and are working towards an agreement for standard labels. Implementation by nations will require several years but will be important for public health protection and right to know internationally.
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