Pesticide Impacts on
Human Health

"Precautionary Principle"

by Joel Tickner
The Networker
The Newsletter of the Science and Environmental Health Net
May, 1997 - Volume 2, #4

During the past twenty-five years, government agencies in the United States have used decision-making instruments to assess, control, and prevent the environmental and public health effects associated with synthetic chemicals. These instruments, including cost-benefit analysis, epidemiology, and risk assessment, have been used to make risk-based decisions. While these instruments have been used successfully to control certain hazards, the incidence of environmentally and occupationally related disease in humans remains significant.

Current environmental decision-making processes suffer from several constraints, which limit our ability to identify, anticipate, and prevent potential harm to human health and the environment. Decisions to take action to limit hazardous substances are often made only in response to the scientific establishment of a causal link between a substance and a specific harm. Proving cause takes extensive time and resources. Among the difficulties in proving cause are:

  1. Limitations in scientific knowledge. The capacity to identify and prevent potential harmful environmental effects is limited by the present state of scientific knowledge.

    Scientific knowledge is especially limited in understanding the variability and effects of pollution on ecosystems. The ability of science to identify a threshold for effects or an assimilative capacity for an ecosystem is limited by deficiencies in data; lack of knowledge about processes in humans and nature; the effects of chemical mixtures and other stressors; variation in exposure; and the time lag between exposure and effects (Gee, 1994). Waiting for convincing human evidence can pose high human health and ecological costs.

  2. Problems of statistical power. Regulatory programs often fail to consider statistical power in decision making. Statistical power describes in mathematical terms the probability of an experiment or monitoring program actually detecting an effect where one exists (McGonigle, et al., 1994). This lack of attention to statistical power leads to experimental approaches that minimize the probability of incorrectly concluding that there is an effect when one does not exist, termed a type I error. This type of error would lead an agency to erroneously impose regulation.

    However, this focus on minimizing type I errors necessarily increases the probability of type II errors, concluding that there is no effect when one actually exists. A type II error would lead to a failure to prevent an adverse effect. Thus, experiments that fail to find an effect may erroneously conclude the null hypothesis, that no adverse effect exists, when the experimental design lacks sufficient statistical power to identify an effect in the first place. This problem raises a fundamental question with regard to experimental methods: Is absence of evidence of harm the same as evidence of absence? Safe application of a threshold for adverse effects relies on an ability to prove the null hypothesis, a no effect level for those effects.

  3. Low-level adverse effects. Evidence regarding the effects of several classes of chemical compounds at low levels of exposure is slowly evolving. For example, dioxins, a highly studied class of compounds, cause adverse effects in the range of parts per quadrillion (U.S. EPA, 1994). Evidence regarding the endocrine disrupting ability of certain synthetic compounds has shown that even very low level exposures, during certain periods of development, can cause wide ranging reproductive and developmental effects (Colborn and Clement, 1992). Contrary to the expected pattern, research has shown that some of these effects occur at low levels of exposure and not at high levels (Colborn, Dumanoski and Myers, 1996). Low level adverse effects pose several difficulties: Monitoring and control of industrial emissions at very low exposure levels is technically difficult and subject to wide uncertainties. If adverse effects are being observed at very low levels of exposure, there is reason to believe that similar effects may occur at even lower (but still unmeasurable) levels of exposure.

  4. Difficulties in addressing cumulative effects. Traditional decision making strategies have focused on single chemical, single medium effects, when, in reality, humans and ecosystems are exposed to a wide variety of physical and chemical stressors. The way we monitor exposure and effects fails to consider the cumulative effects of multiple physical and chemical stressors, leading to underestimates of potential adverse effects.

  5. Financial and resource limitations. More than 70,000 chemicals are currently used in commerce, while only several hundred are regulated worldwide, and less than 10% have been adequately tested for effects on humans and the environment. The costs and time associated with chemical testing and environmental monitoring (e.g., identifying or disproving adverse effects) inhibit the comprehensive evaluation of all hazards prior to commercializing a chemical or approving an activity. These costs have, in part, led to a decision-making and policy emphasis on quantification of hazards rather than fundamental prevention.

    These limitations in current decision-making techniques lead to the question: How can preventive policies to protect human health and the environment be developed in the face of significant scientific uncertainty regarding cause-effect relationships or the extent of potential damage?

The Precautionary Approach

Given the limitations of science to address emerging environmental problems, such as endocrine disruption, there is a significant need for the development of new public policy approaches to anticipate and prevent harm to human health and the environment. The question of what society should do in the face of uncertainty regarding cause and effect relationships is necessarily a question of public policy, not science.

Several policy analysts confronted with this problem have proposed a concept called the "precautionary principle" or the "precautionary approach" (Cameron and Abouchar, 1991 and Dethlefsen, 1993). At the center of the precautionary principle is the concept of taking anticipatory action in the absence of complete proof of harm, particularly when there is scientific uncertainty about causal links (Jackson, 1993). The precautionary principle states that decision-makers should act in advance of scientific certainty to prevent harm to humans and the environment (O'Riordan and Jordan, 1995). It addresses many of the limitations of current decision-making methods, such as type II errors, problems of cumulative effects, and limitations of science. Precautionary approaches are goal oriented, lending themselves to technology innovation, pollution prevention, and facility planning.

The precautionary approach evolved as a response to the environmental and human health impacts caused by the rapid industrial growth following World War II and the weaknesses of early pollution control legislation. It is relatively new to environmental decision-making, having emerged during the early 1970s in West Germany -- "vorsorgeprinzip" in German (Von Moltke, 1988). At the core of early conceptions of this principle was the belief that society should seek to avoid environmental damage by careful forward planning, blocking the flow of potentially harmful activities (O'Riordan and Jordan, 1995). The vorsorgeprinzip developed into a fundamental principle of German environmental law and has been invoked to justify the implementation of vigorous policies to tackle acid rain, global warming and North Sea pollution.

The precautionary principle has since flourished in international statements of policy; conventions dealing with high-stakes, low scientific certainty environmental concerns; and national strategies for sustainable development (Dethlefsen, 1993, O'Riordan and Jordan, 1995). It has gained international acceptance as a guiding principle for environmental decision-making.

The precautionary principle was first introduced in 1984 at the First International Conference on Protection of the North Sea. Following this conference, the principle was integrated into numerous international conventions and agreements including the Maastricht Treaty, the Barcelona Convention, and the Global Climate Change Convention. It has been implicitly incorporated into several environmental laws in the U.S., such as the Pollution Prevention Act of 1990. The U.S.-Canadian International Joint Commission has called for a phase-out of persistent organic chemicals in the Great Lakes ecosystem based on weight-of evidence criteria. The criteria state that action should be taken to prevent environmental damage when evidence from several studies taken together indicate actual or potential environmental harm.

While the precautionary principle is growing in acceptance, it lacks a specific, widely recognized definition. With few exceptions, the principle remains only a concept, provides few guidelines for policy makers, and fails to constitute a rigorous analytical framework. Although several frameworks for integrating the principle into environmental decision making have been proposed (Cameron and Abouchar, 1991, Stijkel and Reijnders, 1995, and Mee, 1995), with the exception of Germany, no comprehensive, systematic structure for precautionary decision-making has been applied on a national or international level. One expert on the development of the precautionary principle has identified four questions which need to be answered in order to develop a common understanding of this concept (Gundling, 1982). These are:

  1. What is the specific content of the principle of precautionary action?;
  2. What are the functions of the principle of precautionary action?;
  3. Does the principle of precautionary action require specific instruments or regulations, and if yes, what are these?; and
  4. What are the conceptual and other limitations of the principle of precautionary action?

Lack of a generally accepted formulation and criteria to guide its implementation has limited the wide-spread use of the precautionary principle in environmental decision-making and in some instances has led to heated debate and controversy. As such, there is a clear need to establish an institutional framework for the precautionary approach. This framework would need to introduce a common definition for the precautionary principle as well as establish a set of criteria for precautionary decision-making. Conceptually, the precautionary approach to decision-making would consist of the following elements:

  1. A goal-setting, guiding principle of precaution in the face of scientific uncertainty;
  2. Tools for decision-making in the face of uncertainty (e.g., decision making criteria); and
  3. methods to carry out precaution-based decisions such as pollution prevention, phase-outs, and flexible assurance bonding.

A precautionary principle decision-making tool must be developed based upon this policy framework. Preliminary research into the precautionary principle has found that rather than being a quantitative tool, potentially limited by a lack of data, uncertainties, and assumptions, the precautionary decision-making protocol must establish qualitative criteria for decision-making.

Thus, the protocol must consist of methodological guidelines for weighing scientific evidence and qualitative decision-making criteria that will instruct policy makers on how to proceed when dealing with limited or uncertain scientific evidence. It would consist of a two part decision tree analysis: (1) one section for decision-making based on potential hazards which already exist; and (2) a second part for decision-making regarding the introduction of new chemicals, products, and activities with potential impacts. Precaution would serve as a default decision if clear evidence of harm or safety were absent.

Applying Precautionary Principle Decision-making to a Current Environmental Decision-making Problem

Several recent environmental problems provide unique opportunities for applying the precautionary principle. These include: Endocrine disrupting chemicals and persistent organic pollutants (POPs). For example, endocrine disruption poses a serious challenge to traditional decision-making instruments as wide-ranging, often subtle, adverse effects have been linked to low-level exposures and under diverse circumstances. As dose-response for endocrine disrupting chemicals does not appear to be linear, one can assume that the traditional risk assessment paradigm will not adequately protect public health under these circumstances. This problem necessitates a new approach that can address potential impacts, with limited scientific knowledge, across environmental media and agency programs. The precautionary principle framework could be used to develop a general decision-making strategy for the introduction of, and limitations to, potential endocrine disrupting chemicals.

Conclusions

In recent years, government agencies have been struggling with the limitations of current environmental assessment and decision-making approaches, such as risk assessment. The limitations of these scientific approaches become even more evident in the face of new environmental challenges such as endocrine disrupting chemicals and persistent organic pollutants. Scientific knowledge regarding the potential impacts of these classes of chemicals on human health and the environment is extremely limited. Scientific proof of cause-effect relationships (and their extent) between these classes of chemicals and adverse human health outcomes may be several years or decades away and may never be established due to limitations in experimental design and the complexity of natural ecosystems. However, waiting for more evidence may be disastrous and span generations.

The precautionary principle provides a new approach to weighing scientific evidence and making decisions in the face of uncertainty. As

such, the precautionary principle can provide the basis of a policy framework and decision making tool to allow agency policy makers and scientists to deal with current and future environmental challenges. It will help to streamline environmental decision-making, providing a mechanism to address decision-making barriers posed by uncertainty.

The precautionary principle lends itself to pollution prevention approaches and multi-stakeholder, participatory decision-making, central to the agencies' and the public health community's missions. It provides a model to advance the development of new policies and technologies designed to prevent pollution, and environmental damage, at the source.

Given the complexity of current environmental health problems, the paucity of information and subsequent uncertainty about cause-effect relations, and slow pace of government testing and decision-making, the precautionary principle can provide the foundations for policies and decision-making criteria to expedite prevention-oriented public health strategies.

References Cited 1) Cameron, J. and Abouchar, J. 1991. The precautionary principle: a fundamental principle of law and policy for the protection of the global environment. Boston College International and comparative law review 14: 1-27.

2) Colborn, T. and C. Clement, eds. 1992. Chemically Induced Alterations in Sexual and Functional Development: The Wildlife-Human Connection. Princeton: Princeton Scientific Publishing

3) Colborn, T., et. al. 1996. Our Stolen Future. New York: Dutton Books

4) Department of Environment of the United Kingdom. 1988. Ministerial Declaration. Second International Conference on Protection of the North Sea. London.

5) Dethlefsen, V., et al. 1993. The Precautionary Principle: Towards Anticipatory Environmental Management. In Jackson, T., ed. Clean Production Strategies. New York: Lewis Publishers.

6) Gee, D. 1995. Approaches to Scientific Uncertainty. Conference on Transport Policy and Urban Health, London School of Hygiene and Tropical Medicine, 4-7 April.

7) Gundling, L. 1990. Status in International Law of the Principle of Precautionary Action. International Journal of Estuarine and Coastal Law 5:23-30.

8) MGonigle, R.M., et. al. 1994. Taking Uncertainty Seriously: From Permissive Regulation to Preventive Design in Environmental Decision making. Osgoode Hall Law Journal 32:99-169.

9) Mee, L. 1995. Scientific Methods and the Precautionary Principle. In Freestone, D. and E. Hey eds., The Precautionary Principle and International Law. Boston: Klewer Law International.

10) O'Riordan, T. and A. Jordan. 1995. The Precautionary Principle in Contemporary Environmental Politics. Environmental Values 4:191-212.

11) Stijkel, A. and L. Reijnders 1995 Implementation of the Precautionary Principle in Standards for the Workplace. Occupational and Environmental Medicine 52:304-312.

12) U.S. Environmental Protection Agency (EPA). 1994. Health Assessment Document for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Vol. II, Epidemiology/Human Data and Vol. III Risk Characterization. Washington, DC: Office of Research and Development, U.S. EPA. Document number EPA/600/BP-92/001c.

13) Von Moltke, K. 1988. The Vororgeprinzip in West German Environmental Policy. In Royal Commission on Environmental Pollution, Twelfth Report: Best Practical Environmental Option. Cmnd 310. London: HMSO.

Joel Tickner Work Environment Program, Univ. of MA Lowell