Scope of the Committee's Effort
In this century, incineration has been used widely to reduce the volume of municipal-solid waste and produce electric energy or steam, to reduce the volume and potential infectious nature of contaminated medical waste, and to reduce the potential toxicity and volume of hazardous chemical and biological waste. Although various forms of incineration are widely used for waste management, pollution control, or energy recovery, there has been increased public debate in the last several decades over the expected benefits mentioned above and the potential risk to human health that might result from the emission of pollutants generated by the incineration process.
Unfortunately, there have been only a few studies of human populations that investigated the attribution of certain adverse health effects to particular incinerators. Most studies were unable to detect any effects. Those studies, of which the committee is aware that did report finding health effects, had shortcomings and failed to provide convincing evidence. Therefore, those reported effects are still open to many other possible explanations (see Chapter 5).
Debate over the expected benefits and the potential health risk of waste incineration has led to substantial polarization of opinions with respect to regulatory decisions about incineration facilities. This report, by the Committee on Health Effects of Waste Incineration, of the National Research Council's Board on Environmental Studies and Toxicology, addresses scientific and technical aspects of the design and operation of facilities that burn waste, releases of pollutants from such facilities and transport through the environment, possible human health effects of exposure to those pollutants in the environment, and relevant regulatory and sociological considerations. For this report, “incinera
tion” is a general term that refers to the process of burning waste through the use of incinerators, industrial boilers, or furnaces, kilns, or other facilities.
CHARGE TO THE COMMITTEE
The committee was specifically asked to assess relationships between various aspects of waste combustion and estimates of human health risk. The committee was asked to consider, to the extent practicable, the following issues for the combustion of hazardous, nonhazardous, and hospital wastes:
Relationships between human health risk estimates and various design, siting, and operating conditions at waste-combustion facilities, including incinerators, cement kilns, industrial furnaces, and industrial boilers.
Operating practices at combustion facilities and expectations regarding technology and the release of hazardous substances.
Appropriate methods for assessing the siting, design, and operation of combustion facilities.
Appropriate health-based performance criteria for demonstrating that a combustion facility meets and maintains agreed upon health-risk tolerance levels.
Types of scientific, technical, and other information that should be provided to government officials, industry managers, and the general public to help them understand and weigh the risks associated with waste combustion and its alternatives including innovative ways of oxidizing waste.
Public perceptions of waste combustion and their bases.
It is important to note that the committee was not asked to assess the magnitude of health risks associated with individual waste-incineration facilities. Also, the committee was not asked to develop its own health-risk tolerance levels for incineration facilities.
The committee formed to address this charge was composed of persons with expertise in incineration technology, emission characterization, transformations and fate of environmental pollutants, exposure and dose characterization, public health, health risk assessment, sociology, risk perception and risk communication, and law. Biographical information on the members is provided in Appendix A.
COMMITTEE'S APPROACH TO ITS CHARGE
In developing an approach to its task, the committee received oral and written testimony from interested or affected citizens; community activists; industry representatives; environmental advocates; professional scientists and engineers; and local, state, and federal government officials. The committee also gathered and considered relevant available information.
The committee focused on three types of waste streams for which incineration has been used as an option for waste management: municipal solid wastes, hazardous wastes, and medical wastes. The committee structured its efforts by using an emission-to-receptor framework that is a modification of the risk assessment frameworks presented by NRC (1983, 1994). The committee's framework included consideration of the following components:
Emission characteristics and various factors that could affect emissions resulting from waste-incineration facilities.
Transformation and fate of certain emitted contaminants in various environmental media (i.e., air, water, and soil).
Contributions of incineration to environmental concentrations of contaminants.
Human populations that might be exposed to contaminants of concern, and the pathways through which exposure can occur.
Health responses that might be expected from exposures to contaminants of concern.
Characterization of relationships between waste incineration and health risks.
Other aspects of the committee's study that are not explicitly included in the emission-receptor framework are public perceptions of waste combustion and their bases, sociological considerations of incineration facility siting, and communication of information for understanding and weighing the risks associated with waste combustion.
The committee did not consider the potential health effects on organisms other than humans. In addition, the committee did not consider incineration of waste streams consisting solely of sewage sludge, wood wastes, radioactive waste, or industrial waste that is considered nonhazardous. 1 It is possible, however, that some of those types of waste are fed to a facility that incinerates municipal solid waste.
The committee also did not address, to any great degree, the effects of waste-management activities, such as waste recycling or reuse, except for how such practices might affect the characteristics of waste streams fed to an incineration facility and the resulting emissions to the environment. The committee focused its attention on wastes that have reached an incineration facility—not on the collection, storage, or transportation of wastes to a facility and not on transportation of residual ash away from a facility. However, if one were to perform
Various aspects related to the use of incineration for destroying the U.S. stockpile of extremely hazardous chemical agents and munitions have been addressed by another NRC committee (see NRC 1999a and related reports cited therein).
a comparative assessment of the total environmental impacts of waste incineration as a management option, the above-mentioned considerations should be included.
Despite past efforts to characterize the potential health risks at numerous individual existing and proposed incineration sites, the committee has carried out this study with rather sparse information on the relationship between human exposure to pollutants released to the environment through waste incineration and the occurrence of health effects because such information is generally unknown. One reason, for example, for the lack of information is that few epidemiologic studies have been conducted to investigate exposures to incineration emissions and their human health consequences. Although the committee was not asked to and did not attempt to perform its own epidemiologic studies or risk assessments at individual waste-incineration facilities, the committee used available data on human and animal exposures to specific substances to examine the implications for incinerator sites of dose-response projections (see Chapter 5).
The committee conducted this study with the understanding that society faces the challenge of choosing among various waste-management alternatives. Although a comparative health risk assessment of alternatives for managing waste streams was not part of its charge, the committee conducted this study with the intent of informing the public debate over appropriate uses of waste incineration.
ORGANIZATION OF THE REPORT
The emission-receptor framework, described earlier, was used to develop and organize the chapters of this report. The six components of the charge to the committee are addressed within these chapters. Chapter 2 presents an overview of waste generation, waste stream composition, and waste-management activities that affect the characteristics of waste fed into incineration facilities. Chapter 3 discusses various incineration processes used to burn waste, characteristics of emissions of certain contaminants, operating practices and design options most likely to affect emissions, and expectations regarding the technology and release of hazardous contaminants from incineration facilities. Chapter 4 discusses the environmental transport and fate of pollutants once they have left an incineration facility, and considers the contribution of incineration to ambient concentrations of such pollutants.
Chapter 5 examines the techniques used to evaluate the potential for health effects from incineration, and discusses some of the results obtained with those techniques. It also relates human health risk estimates to issues discussed in Chapter 3 and Chapter 4 with respect to various design and operating conditions at waste-combustion facilities. In addition, Chapter 5 identifies important considerations for developing health-based performance criteria to demonstrate that a combustion facility meets and maintains agreed-upon health-risk tolerance levels.
Chapter 6 discusses the regulations that affect waste incineration in the United States. Chapter 7 discusses important social issues, including public perceptions of waste combustion and their bases. The chapter also discusses risk communication about incineration. Chapter 8 addresses important uncertainties involved in assessing possible relationships between exposure to environmental concentrations of pollutants released from waste-incineration facilities and occurrences of human health effects.
Chapter 3, Chapter 4, Chapter 5, Chapter 6, Chapter 7 through Chapter 8 provide conclusions and recommendations regarding appropriate methods for assessing the siting, design, and operation of combustion facilities. They also identify various types of scientific, technical, and other information that should be provided to decisionmakers and other interested or affected parties to help them understand and weigh the risks associated with waste combustion.