Risk-Based Environmental Decisions

In August of 1997, the Environmental Protection Agency (EPA) formed an advisory committee to consider how the Agency should respond to the issue of endocrine disruptors in the environment. Such committees are formed under the Federal Advisory Committee Act (FACA), which specifies that government agencies will bring together relevant outside experts to advise them whenever decisions must be reached that involve significant technical issues. The Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) was formed under FACA to advise the Agency on the design of a program to determine which substances in the environment pose a risk to health through endocrine disruption (i.e. disruption of the endocrine system controlling the many hormones produced by the body, and which in turn control processes of development, reproduction and metabolism).

Since risk assessments can involve a large number of steps, including calculations requiring expertise in a wide range of scientific disciplines as well as mathematics and statistics, there is a need to subdivide the process. By doing this, the analyses of data and the calculations are separated into parts that can be handled by individuals with the appropriate expertise, ensuring that these same individuals don’t wander off into parts of the assessment for which they have inadequate training. If separated in the proper way, it even is possible to produce an assessment in which any of the separate parts can be revised without necessarily revising all of the other parts.

Both the regulatory community and water providers (e.g. water utilities) have become increasingly concerned with the possibility of outbreaks of microbes through the water supplies [1]. These outbreaks can occur because microbes are evolving into strains for which there are no existing defenses (including methods to disinfect water), because the public has in general lost track of the devastation caused by microbes historically, and because the therapeutic efficacy of antibiotics may be decreasing due to extensive use. In response to this threat, the EPA, American Water Works Association (representing water providers), public health officials, etc, have banded together to define the risk posed by these new microbes (bacteria, viruses, protozoans, etc) and to improve those areas of risk assessment where knowledge is inadequate to either predict or control the risks.

Radon has provided the risk management community with a difficult example of a pollutant that moves through essentially the entire environment and exposes people through inhalation, ingestion and dermal absorption. It is radioactive, and so presents a threat from the radiation it emits. It is an inert gas, meaning it tends not to react chemically with other materials in the environment and, hence, can move easily through soil, air, etc. It is ubiquitous in the soil beneath homes, diffusing up into the home air, and also enters homes through the drinking water (especially when that water has been drawn from wells that are surrounded by rock).

Regulatory decisions usually are made in the face of considerable uncertainty and debate. Predictions of risk are uncertain. Stakeholder groups come to the debate with different estimates of the risk. There are differences of opinion as to the goals of regulation, how uncertainty is to be incorporated into decisions, or how non-health goals (such as cost) are to be reflected in the choice of policy. While some of these issues require methods and facts mastered by technical experts, many are matters of societal judgment requiring insights into politics, law, ethics, etc.

The Environmental Protection Agency is developing final standards for the allowable concentrations of disinfection by-products (discussed in Chapter 3) in U.S. drinking water supplies. While disinfection is known to lower significantly the risk from microbial infections, epidemiological studies have suggested that there are cancer and other risks from the DBPs [1]. Many other disinfection byproducts, however, remain to be identified and the public health significance of these is unknown. The relatively low concentrations of the various natural and man-made contaminants in existing drinking water, the inability to obtain valid and complete exposure histories for individuals, and the challenge of controlling confounding factors, have made it difficult for epidemiological studies to detect and estimate risks of cancer from the DBPs [1,2]. Still, information on exposure of animals to individual DBPs has allowed the EPA to develop health criteria in drinking water that would result in either no expectation of non-cancer health effects or an acceptable lifetime probability of cancer (see the discussion in Chapter 5).

In this final chapter, we turn to the issue of using risk analysis to not only justify a policy, but to select an optimal strategy for reducing risk. Most pollution control strategies can be characterized as a single-medium, single pollutant, approach. Such an approach begins by dividing the environment into three primary compartments: air, water, and land (soil). Pollution problems then are grouped into three categories: air pollution, water pollution, and solid waste pollution problems. In the single-medium approach, these three categories of problems are managed independently without consideration of their interactions. For example, major air pollution sources may be required to install the best available control technologies (BACT) based purely on consideration of the risk from releases to air; industrial wastewater dischargers may be required to meet best available technology (BAT) effluent limitations based solely on the risk from releases to water; and RCRA (Resource Conservation and Recovery Act) and CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act) impose restrictions on the options for land disposal of solid waste [1-3] based solely on the risk from burial. Similarly, the choice of manufacturing processes and pollution control technologies often reflects concern for a single primary pollutant that dominates current regulatory focus, while a facility may emit literally dozens of chemicals, metals, etc.