Chapter 1: Introduction

The Agency for Toxic Substances and Disease Registry (ATSDR) determines public health implications associated with hazardous waste sites and other environmental releases. This work supports ongoing site investigations conducted by other agencies, addresses community health concerns, and results in recommendations for preventing harmful exposures and conducting additional scientific study. ATSDR has developed a methodology for evaluating the public health implications of exposures to environmental contamination—the public health assessment process.

ATSDR has written this manual to provide guidance to new and experienced health assessors when performing the variety of tasks associated with the public health assessment process. The manual presents specific approaches, methods, and resources that can be used to:

  • Evaluate environmental exposures associated with a hazardous waste site.
  • Assess the potential for adverse health effects resulting from environmental exposures at a site.
  • Recommend sound public health actions based on the scientific evaluation of health and environmental data.
  • Involve communities near a site and respond to their health concerns.
  • Organize and write a public health assessment document to convey the findings of the assessment.

To provide a foundation for this document, this introductory chapter discusses:

  • Why ATSDR conducts public health assessments (Section 1.1).
  • The key elements of the public health assessment process (Section 1.2).
  • The overall purpose and goal of this guidance manual (Section 1.3).
  • How the manual is organized (Section 1.4).

1.1 ATSDR’s Mandate and Mission

Congress established ATSDR in 1980 under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as the Superfund law. This law set up a fund to identify and clean up our country’s hazardous waste sites. The U.S. Environmental Protection Agency (EPA) and individual states regulate the investigation and cleanup of site-related contamination. Under the Superfund law, ATSDR is charged with assessing the presence and nature of health hazards to communities living near Superfund sites, helping prevent or reduce harmful exposures, and expanding the knowledge base about the health effects that result from exposure to hazardous substances.

In 1984, amendments to the Resource Conservation and Recovery Act of 1976 (RCRA)—which provides for the management of hazardous waste storage, treatment, and disposal facilities—authorized ATSDR to conduct public health assessments at these sites when requested by EPA, states, tribes, or individuals. ATSDR was also authorized to assist EPA in determining which substances should be regulated and the levels at which substances may pose a threat to human health. The passage of the Superfund Amendments and Reauthorization Act of 1986 (SARA) broadened ATSDR’s responsibilities in the areas of public health assessments, establishment and maintenance of toxicologic databases, information dissemination, and medical education. ATSDR also conducts public health assessments when petitioned by concerned community members, physicians, state or federal agencies, or tribal governments.

CERCLA, as amended by SARA (104 [i][6][f]), requires that, at a minimum, ATSDR consider the following factors when evaluating the public health impact (or risk) associated with site exposures:

  • The nature and extent of contamination at a site.
  • The demographics (size and susceptibility) of the site population.
  • The exposure pathways that may exist at a site (to what extent people contact site contaminants).
  • Health effects and disease-related data associated with the observed levels of exposure.

Since its inception, ATSDR has continued to improve its approach to evaluating public health hazards in light of evolving science. The agency has refined its mission and goals to practice the best science and meet the needs of site communities. ATSDR’s current mission and goals are reflected in the box below.

ATSDR’s MissionTo serve the public by using the best science, taking responsive public health actions, and providing trusted health information to prevent harmful exposures and disease related to toxic substances.

ATSDR’s Goals

  • Evaluate human health risks from toxic sites and releases and recommend timely, responsive public health actions.
  • Ascertain the relationship between exposure to toxic substances and disease.
  • Develop and provide reliable, understandable information for affected communities and tribes and for other stakeholders.
  • Build and enhance effective partnerships.
  • Foster a quality work environment at ATSDR.

1.2 The Public Health Assessment Process

ATSDR has developed a method to evaluate the public health implications of exposures to environmental contamination. This method is called the public health assessment process. The public health assessment process serves as a mechanism for identifying appropriate public health actions for particular communities. The process may be triggered by a site’s listing on the National Priorities List or a specific request (or petition) from a community member or another government agency. The purpose of the process is to find out whether people have been, are being, or may be exposed to hazardous substances and, if so, whether that exposure is harmful, or potentially harmful, and should therefore be stopped or reduced. The process also serves as a mechanism through which the agency responds to specific community health concerns related to hazardous waste sites. Figure 1-1 illustrates the process, which is briefly summarized below.

The public health assessment process involves the evaluation of multiple data sets. These include available environmental data, exposure data, health effects data (toxicologic, epidemiologic, medical, and health outcome data), and community health concerns. Starting early in the assessment process, ATSDR begins to gather relevant scientific data to support the assessment. ATSDR also needs to learn what people in the area know about a site and site-related exposures and what concerns they may have about its impact on their health. Therefore, ATSDR actively gathers information and comments from the people who live or work near the site, including area residents, civic leaders, health professionals, and community groups. Throughout the public health assessment process, the agency communicates with the public about the purpose, approach, and results of its public health activities.

Figure 1-1. Basic Components of the Public Health Assessment Process
The public health assessment process involves two primary scientific evaluations—the exposure evaluation and the health effects evaluation.

Exposure Evaluation: Exposure assessment is the hallmark of the public health assessment process. ATSDR scientists review environmental data to see how much contamination is at a site, where it is, and how people might come into contact with it. Generally, ATSDR does not collect its own environmental sampling data but reviews information provided by federal and state government agencies and/or their contractors, potentially responsible parties, and the public. When adequate environmental or exposure information is not available to evaluate exposure, ATSDR will indicate what further environmental sampling may be needed and may collect environmental and biologic samples when appropriate.

Health Effects Evaluation: If the exposure evaluation shows that people have or could come into contact with hazardous substances, ATSDR scientists evaluate whether this contact may result in harmful effects. ATSDR uses existing scientific information, which can include the results of medical, toxicologic, and epidemiologic studies and data collected in disease registries, to determine what health effects may result from exposures. ATSDR recognizes that children, because of their behavior, size and growing bodies, may be particularly vulnerable to site-related exposures. Developing fetuses also may be more vulnerable to such exposures. Thus, the impact to children is considered first when evaluating the health threat to a community. The health impacts to other potentially high-risk groups within the community (such as the elderly, the chronically ill, and people who may have higher exposure potential) also receive special attention during the evaluation.

The public health assessment process is iterative and dynamic and may lead to a variety of products or outcomes. The findings may be communicated in public health assessment or public health consultation documents, or an issued public health advisory (if there is an urgent health threat). All of these products serve as an aid for developing public health actions. The audience for such items often includes environmental and public health agencies, communities, and ATSDR itself.

In addition to products developed by the agency, there are other possible outcomes of the public health assessment process. During the course of the process, ATSDR may identify the need to prevent or better define exposures or illnesses in a particular community. ATSDR’s response to such a need might include follow-up health actions such as, initiating an exposure investigation (to better define site exposures), recommending a health study (to identify elevated illness or disease rates in a site community), or working with the community to implement a health education program. ATSDR may also provide technical assistance to other agencies in response to their requests.

The public health assessment process enables ATSDR to prioritize and identify additional steps needed to answer public health questions. The science of environmental health is still developing, and sometimes information on the health effects of certain substances is not available. When this is the case and certain questions cannot be answered, ATSDR will suggest what further research studies and/or health education services are needed.

Public health assessments are conducted by agency health assessors, often supported by a multi-disciplinary team of scientists, health communication specialists, health educators, and/or medical professionals. ATSDR solicits and evaluates information from local, state, tribal, and other federal agencies; parties responsible for operating or cleaning up a particular site; and the community. All of these stakeholders play an integral role in the public health assessment process. ATSDR promotes a team approach to ensure that information used in the assessment is accurate and up-to-date and that community concerns are identified and addressed, and to foster cooperative efforts in implementing recommendations and public health activities.

Chapter 2 of this guidance manual provides a more in-depth description of the various elements and products of the public health assessment process.

1.3 Purpose of This Guidance Manual

This manual is intended to serve primarily as a “how to” guide for the new health assessor and other site team members, and a reference and resource for the more experienced health assessor. For this reason, the “you” used throughout the guide refers to the health assessor. The manual may also be helpful to the public and other end users of ATSDR products.

The public health assessment guidance manual provides guidance on how to effectively obtain, compile, and interpret environmental health data, and how to put that information into meaningful perspective. It presents the methods and tools health assessors can use to answer the critical question: Are exposures occurring and, if so, are they likely to result in adverse health effects under site-specific conditions? Specifically, it presents approaches to help you understand whether, and to what extent, people are being exposed to site-related chemical or radioactive contamination, as well as the extent to which physical hazards pose a threat.

The manual also repeatedly encourages cooperative efforts among multi-disciplinary teams in evaluating data and drawing public health conclusions and establishing and maintaining good two-way communication with the community. Each chapter provides tips and/or examples on how to effectively communicate scientific information, significant findings, and other information gained through the evaluation process.

The guidance is prescriptive where possible but also presents flexible evaluation tools and approaches that will enable you to address unique circumstances that may be encountered at individual sites. It cannot be emphasized enough that each site is different. Therefore, not all of the elements of the public health assessment process described in this manual apply to all sites. The resources you will need and your level of evaluation will vary. Some sites are more complex and may require extensive data gathering and evaluation of multiple substances and exposure pathways. Others may require only a focused review of a single pathway with little contamination.

Professional judgment, as noted throughout this manual, plays an important role in guiding public health assessments. However, the application of the approaches described in this manual, the use of multi-disciplinary teams, and internal and external review of all public health assessment documents foster the development of consistent, scientifically-defensible products and outcomes.

This manual is just one of many resources available to health assessors, but should serve as a foundation from which to build your assessments. Experience and consultation with peers also will be invaluable in conducting your assessments.

1.4 Organization of the Guidance Manual

This manual is organized as shown below. An overview of the public health assessment process is presented first (Chapter 2 ). Guidance on how to collect pertinent data (Chapter 3) and how to involve and effectively communicate with the community (Chapter 4) is presented next (both of these activities are performed throughout the public health assessment process). Guidance on the components of the two primary scientific evaluations in a public health assessment—the exposure evaluation and the health effects evaluation—is provided in Chapters 5–8. Lastly, guidance on how to draw conclusions and make recommendations is presented in Chapter 9. Each chapter guides the health assessor through the process being discussed, then offers suggestions for presenting public health assessment information and writing a public health assessment document. Supplemental guidance and additional examples are provided in the appendices.


Chapter 2 (Public Health Assessment Overview) highlights the various components of the public health assessment process. It provides the information needed to understand the overall process: why it exists, how an assessment is conducted, and how the findings are communicated. It also explains the distinct difference between ATSDR’s public health assessment process and the quantitative “risk assessment” process used by regulatory agencies.

Data Collection and Involving the Community

Chapter 3 (Obtaining Site Information) describes the sources and types of information generally needed to support public health assessments, answer public health questions, and prepare public health assessment documents.

Chapter 4 (Involving and Communicating With the Community) focuses on how to involve a site community in the public health assessment process and describes effective ways to communicate public health conclusions, including responses specific to health concerns expressed by the community.

Exposure Evaluation

Chapter 5 (Evaluating Environmental Contamination) describes how to evaluate whether available environmental data are of sufficient quality to evaluate exposures and whether the data adequately characterize the spatial and temporal extent of environmental contamination.

Chapter 6 (Evaluating Exposure Pathways) explains the criteria used for determining whether people are being exposed to site-related contaminants and understanding who is being exposed, for how long, and under what conditions. Gaining this knowledge will drive your health effects evaluation.

Health Effects Evaluation

Chapter 7 (Screening Analysis) describes screening methods used to evaluate which site-specific exposure pathways and detected substances need to be studied further. The chapter introduces the basis for and use of ATSDR health-based comparison values and other appropriate screening values. It also describes how to estimate site-specific exposure doses.

Chapter 8 (In-depth Analysis) explains when and how ATSDR performs more in-depth evaluations for the pathways and substances identified in the screening analysis as requiring further evaluation. Specifically, this chapter describes how health assessors integrate and weigh exposure, toxicologic, epidemiologic, health outcome, and medical data when evaluating implications of exposures.

Conclusions and Recommendations

Chapter 9 (Determining Conclusions and Recommendations) describes the criteria used to draw public health conclusions, make recommendations, and outline specific public health actions that may have occurred, may be in progress, or may be planned.

In addition, several appendices are included to supplement chapter-specific guidance.

Page last reviewed: November 30, 2005