Chapter 9: Determining Conclusions and Recommendations
- Section 9.1) Determining Conclusions
- (Section 9.2) Determining Recommendations and Developing a Public Health Action Plan (PHAP)
Communicating your conclusions and recommendations (i.e., communicating the bottom-line public health messages) in a clear and concise way is critical. Throughout the public health assessment process, you are synthesizing information that will support and enable you to draw public health conclusions. In addition, you are identifying public health actions that might be needed to eliminate or prevent exposures, or you are identifying critical data gaps.
This chapter describes the process by which you, with the input of the site team, take the findings of exposure and health effects evaluations and draw conclusions regarding the degree of public health hazard, if any, posed by the exposure situations you have studied at a site (Section 9.1). The chapter also describes how to develop recommendations and a "public health action plan" (PHAP) (Section 9.2). An overview of the process is shown in Figure 9-1.
This chapter also describes ATSDR's "conclusion categories" and the criteria for selecting the appropriate category for a particular site. In addition, guidance is provided for developing recommendations and a PHAP that will help ensure that needed follow-up actions are achieved. The chapter also provides tips for the content and wording of conclusions and recommendations.
While this chapter focuses to a great extent on how the health assessor draws and communicates overall conclusions, it cannot be emphasized enough that public health conclusions and recommended public health actions are often made throughout the public health assessment process.
9.1 Determining Conclusions
Based on the results of the exposure and health effects evaluations, the team will characterize the degree of public health hazard at the site based on the following factors:
- The existence of past, current, or potential future exposures to site-specific contaminants (including radionuclides) or physical or safety hazards.
- The susceptibility of the potentially exposed population.
- The likelihood of exposures resulting in adverse health effects.
Based on the available information, you will need to make a statement about the health hazards associated with the site—for completed, and in some instances potential, exposure pathways and the time period of potential concern. In short, you need to determine whether conditions:
- Pose a hazard.
- Pose no hazard.
- Cannot be fully evaluated because critical information is missing.
One of these three choices will apply to all conditions encountered. Once you formulate your conclusions, an ATSDR "conclusion category" is assigned. Section 9.1.1 describes the process for drawing conclusions and for determining the appropriate conclusion category. Section 9.1.2 describes how to present the conclusions in the public health assessment document in a clear and succinct manner.
The analyses conducted throughout the public health assessment process provide the basis for conclusions regarding the level of public health hazard a site or hazardous substance release might pose. The conclusions are dependent on the characteristics and circumstances of exposure (i.e., route, extent, magnitude, and duration). In cases where completed or potential exposure pathways are identified, conclusions should be based on the result of the health effects screening and public health implications analyses.
Within the overall framework of 'hazard,' 'no hazard,' and 'cannot be fully evaluated' (see Figure 9-1), ATSDR has established five distinct descriptive conclusion categories to help ensure a consistent approach in drawing conclusions across sites and to assist the public health assessment team in determining the type of follow-up actions that might be warranted. The conclusion categories also serve as a consistent reporting mechanism of site-specific hazards in ATSDR's Hazardous Substance Database (HazDat).
These five categories are:
- Category 1 Urgent public health hazard
- Category 2 Public health hazard
- Category 3 Indeterminate public health hazard
- Category 4 No apparent public health hazard
- Category 5 No public health hazard
The definitions for each category are presented in Table 9-1. A more extensive description of ATSDR's conclusion categories and the specific criteria that should be used in selecting a category are presented in Appendix H. Appendix H also includes possible follow-up activities associated with each of the categories (see also Section 9.2).
Categories 1 and 2 indicate that conditions are such that there is a reasonable possibility that adverse health effects have occurred or are likely to occur in sufficiently exposed members of the population. Category 4 indicates that adverse health effects are not likely in the population; exposures might be possible, but neither duration nor the degree of exposure is sufficient to result in adverse health effects. Category 5 indicates that no public health hazard exists because no exposure is occurring.
|1: Urgent Public Health Hazard||Applies to sites that have certain physical hazards or evidence of short-term (less than 1 year), site-related exposure to hazardous substances that could result in adverse health effects and require quickintervention to stop people from being exposed.|
|2: Public Health Hazard||Applies to sites that have certain physical hazards or evidence of chronic (more than 1 year), site-related exposure to hazardous substances that could result in adverse health effects.|
|3: Indeterminate Public Health Hazard||Applies to sites where critical information is lacking (missing or has not yet been gathered) to support a judgment regarding the level of public health hazard.|
|4: No Apparent Public Health Hazard||Applies to sites where exposure to site-related chemicals might have occurred in the past or is still occurring, but the exposures are not at levels likely to cause adverse health effects.|
|5: No Public Health Hazard||Applies to sites where no exposure to site-related hazardous substances exists.|
Determining the appropriate hazard category requires professional judgment. You need to decide what category best describes site conditions. A category is assigned after considering site-specific exposure potential, health effects information, and community health concerns. As discussed in earlier chapters, you must consider and integrate the total body of information available for the site when assessing public health hazards and, ultimately, in selecting the appropriate conclusion category. To reiterate, these include:
- Presence of completed or potential exposure pathways.
- On-site and off-site environmental contaminant concentrations.
- Potential for multiple source exposures.
- Contaminant interactions.
- Presence of potentially exposed populations, including sensitive or highly susceptible populations.
- Opportunities for acute or chronic exposures.
- Nature of toxic effects associated with site contaminants and the conditions of exposure associated with these toxic effects.
- Community-specific health outcome data.
- Community health concerns.
- Presence of physical hazards.
Throughout the public health assessment process, you must determine whether critical data are available and sufficient to support a public health conclusion. If critical data are found to be missing, you will need to consider recommending actions that might help fill those data gaps (see Section 9.2).
As repeated throughout this manual, sites are unique. Professional judgment is therefore needed in deciding how best to present the conclusions and assign a conclusion category(ies). It is rare that an entire site would be found to pose the same level of public health hazard. You should therefore generally focus on those exposure pathways and locations that pose a hazard. In doing so, you will assign conclusion categories to the exposure pathways that pose a hazard and the populations impacted. When site conditions have varied over time, it may be appropriate to assign a separate conclusion category for past, current, and future exposure conditions. For example, indicate that before municipal water was made available to the community the groundwater pathway posed a past public health hazard for those individuals drinking water from private wells within ½ mile south of a particular site. You would then note that current and future pathways pose no public health hazard because the potential for exposure to contaminants in groundwater was eliminated with the municipal water hook-up.
Sometimes for administrative purposes (e.g., HazDat reporting), a single conclusion category is selected for an entire site based on the completed exposure pathway that poses the highest degree of hazard. For example, if exposures to site-related contaminants via air and soil are shown to pose no public health hazards, but exposures to detected levels of contaminants in water do pose health hazards, then the site is categorized as posing a "public health hazard." In this example, it is critical, however, to also clearly describe the conclusions and absence of hazards for the air and soil pathways.
Instances often arise in which actual or potential exposures are identified but no health hazards are determined to exist (i.e., Category 4—No Apparent Public Health Hazard). For example, an estimated exposure doses might exceed a health guideline or a regulatory action level, but your integrated analysis might indicate that adverse health effects are not likely because of site-specific exposure conditions and substance-specific properties. Take, for example, a site where the maximum exposure point concentration of a particular metal exceeds an ATSDR comparison value by a factor of 10. Upon closer examination and integration of site-specific exposure and health effects data, you may determine that harmful exposures are not occurring based on the following:
- An analysis of the temporal and spatial distribution of the data reveals that assuming exposure at the maximum detected concentration overestimates likely exposures.
- Limited bioavailability of the metal greatly reduces exposure potential.
- In light of the above, estimated doses are determined to be several orders of magnitude lower than adverse effect levels seen in the relevant scientific literature.
Such a scenario might cause confusion, however, in cases where EPA or another regulatory agency is proposing or taking measures to reduce exposures by cleaning up the site (e.g., soil removal or groundwater treatment) based solely on a comparison to screening or comparison values. In such cases, you will need to offer perspective as to why detected concentrations that exceed regulatory levels of concern might not be a public health concern. Reiterate that comparison values and regulatory action levels are not indicators of adverse effects but are generally used as levels considered amply safe when setting cleanup goals (see Chapter 7 and Chapter 8). Explain why prudent public health practice calls for reducing exposures even when the assessment does not indicate that health hazards exist. For example:
Data needed to draw conclusions might not always be available. In some cases, additional data might be required to confirm or further support the decision made. It is important to carefully examine the criticality of missing data. When concluding that more data are needed to support a conclusion, determine whether the needed data can be obtained and, if so, obtained in a timely manner. In some cases, the data might never be available (e.g., past exposure data) so you will need to use the best available data (e.g., more recent sampling data or modeled data) to evaluate potential hazards and draw conclusions.
If you determine that insufficient data exist to draw a conclusion, clearly indicate this in the public health assessment document. In addition, recommend additional actions when possible (see Section 9.2) and/or state that a definitive conclusion cannot be drawn due to the absence of critical data.
Not all data gaps are data needs. Before recommending sampling or further investigation, carefully assess and distinguish what would be good to know versus what is needed to draw a public health conclusion, as well as issues that the community needs to know or that it might reasonably expect to be addressed. Provide as much perspective as possible using available data.
Conclusion categories are required in all site-specific public health assessment products assessing the public health implications of exposure pathways or site conditions (e.g., PHAs, public health consultations [PHCs]). If you are solely providing comments, technical assistance, or general scientific information as part of a public health-related activity, a conclusion category is not necessary. Specific instances where you will not need a conclusion category include:
- Presenting comments on a site-related document (e.g., a remedial investigation/feasibility study, a work plan, or other similar documents).
- Providing technical assistance in determining contaminants to test, detection limits, monitoring levels, or other similar assistance.
- Providing general information on hazardous substances, diseases, or issues that are not directly related to a specific site.
The Conclusion section of the public health assessment document should present a definitive statement about the health threat, if any, posed by a site. Key issues should be highlighted. When possible, you should clearly state what is known and unknown by exposure pathway. When stating conclusions, present a clear narrative statement regarding the likelihood of adverse health effects under site-specific conditions. The health decision needs to be supported by a clear "story."
Specifically, the following should be explicitly and unambiguously stated:
- Potential health effects from exposure to site contaminants (past, current, future) by exposure pathway. Also indicate any pathways eliminated from the evaluation due to the absence of exposure.
- Responses to predominant community health concerns.
- Results of health outcome data evaluations.
- The effect that missing or insufficient information has on the analyses and conclusions.
All conclusion statements should be succinct and not repeat large portions of statements presented in the Discussion section. The first conclusion should emphasize the main thrust of the public health assessment and address the key issues presented in the Purpose and Health Issues section. Subsequent conclusions should follow the main points from the Discussion section. In most cases, it is advisable to present conclusions in order of public health priority or importance. Conclusion statements must be fully consistent with information presented in the public health assessment document and should not introduce any new information.
Conclusion categories must be presented in proper context. You must clearly describe the basis of the selected conclusion category(ies). As mentioned above, ATSDR designed its conclusion categories to help assessors consistently formulate conclusions. You should therefore understand and follow the criteria set forth for selecting a conclusion category. When communicating conclusions, however, it is of utmost importance to clearly describe the essential message of the public health assessment in plain language, both in terms of what is and is not known, before presenting the specific conclusion category. For example, the essential message of ATSDR's "no apparent" category is that no hazard exists although some exposure might be occurring. In such a case, a statement such as the following is appropriate:
Such wording provides a definitive statement regarding hazard and clearly indicates the ATSDR category for HazDat.
All conclusions must be supported by information presented in the Discussion section. Limit the use of the conclusion categories to the Summary and Conclusion sections of the document. The Discussion section, for example, should not include the phrase "no apparent" health hazards.
The language and tone used in presenting conclusions should be sensitive and explanatory, especially when presenting conclusions related to community concerns (see Chapter 4).
9.2 Determining Recommendations and Developing a Public Health Action Plan (PHAP)
After reaching conclusions about a site, you may recommend that actions be taken to protect public health. PHA recommendations should emphasize prevention of releases and prevention of exposure and any precautions required to ensure that public health is protected. Because ATSDR is an advisory agency and not a risk management agency, your recommendations may identify actions that other entities (e.g., site owners, state health or environmental agencies, as well as divisions within ATSDR) will need to take to implement the recommendations. As the health assessor or team leader you should work with the members of your team in determining the most appropriate recommendations. The criteria described in this section should guide your decisions.
In general, your recommendations are made to identify:
- Practical ways to stop, reduce, or prevent exposure (Section 9.2.1).
- Activities to further characterize the site and possible exposure (Section 9.2.2).
- Health activities that are service- or research-oriented (e.g., medical monitoring, health education, health studies/health surveillance, substance-specific research) (Section 9.2.3).
Recommendations for actions needed to protect the health of those living or working on or near the site will vary from site to site. Depending on the site-specific situation, both short- and long-term public health needs should be considered. Short-term recommendations may include supplying bottled water or conducting an emergency removal action. Recommendations to meet long-term public health protection needs include those related to institutional controls for restricting site access, deed restrictions on land use, and continuous environmental monitoring for specified periods.
In addition to stating recommendations, Public Health Action Plans (PHAPs) are included in all PHAs(1). Your PHAP will outline actions or activities that have already been taken to protect public health, activities that are currently underway, and activities that will be conducted in the future. PHAPs are also included in some health consultations, depending upon site conditions and community interest. That is, your PHA must include a plan that clearly describes the implementation and timing of the recommended public health action(s). Actions described in the PHAP might vary from health investigations in the community near the site to environmental characterization activities to better identify populations at risk of exposure.
For a site that poses an urgent public health hazard, ATSDR may respond by quickly issuing a public health advisory to EPA. Appropriate state, tribal, and local entities are also notified, and ATSDR works with them and others to ensure the public is protected. A health advisory should be considered whenever chemical contamination or physical hazards associated with a site necessitate an expeditious response to protect public health. The health advisory recommends measures to be taken to reduce exposures and to eliminate or substantially mitigate the public health hazard(s) (see Appendix H for health advisory-related public health actions). A health advisory should be issued as soon as possible after the health assessor has determined that an urgent public health hazard exists—that is, it does not have to and should not wait until the public health assessment process is completed. For more information see ATSDR's Web site at: http://www.atsdr.cdc.gov/hac/index.html.
As shown in Table 9-2 and detailed in Appendix H, the type of action(s) recommended by ATSDR is dependent on the site's conclusion category and corresponds directly to the specific conclusion(s) drawn about a site. The type of actions typically recommended and the factors you should consider when developing and presenting recommendations are described in the following subsections.
|Conclusion Category||Type of Action|
|Category 1: Urgent public health hazard||Measures to immediately stop or reduce exposures (e.g., provide alternative drinking water). The PHA should describe actions already taken and those planned.*|
|Category 2: Public health hazard||Measures to reduce or prevent chronic exposures. The PHA should describe actions already taken and those planned.*|
|Category 3: Indeterminate hazard||Measures to fill critical data gaps so that a public health call is possible. The PHA should describe needed actions.*|
|Category 4: No apparent public health hazard||No action(s) may be necessary. Depending on the level of community concern and site issues, some of the same actions taken for Categories 1 and 2 should be considered.*|
|Category 5: No public health hazard||No actions are likely.|
* See also Appendix H
Actions that prevent or reduce exposures should be recommended when a public health assessment identifies current exposures to contaminant levels associated with adverse health effects. You may recommend that removal or remedial measures be taken to eliminate any current exposures or to prevent potential future exposure.
Recommended actions may include:
- Removing physical hazards (e.g., unsafe structures, unexploded ordnance).
- Informing affected populations of contamination or exposure.
- Establishing institutional controls on land use.
- Restricting public use of or access to a site.
- Restricting use of drinking water supplies and/or providing alternate water supplies.
- Establishing measures to restrict contaminant migration.
- Remediating contaminant sources.
- Establishing safety plans and monitoring during removal actions/remediation.
- Evacuating or temporarily relocating populations.
At times, site information is not available or is insufficient and cannot be used to adequately characterize site environmental conditions, the type and extent of contamination, and locations of populations that might be exposed to site-related contamination. In cases where data critical to your public health conclusion are missing, brief explicit recommendations should be made outlining the information required and why it is critical. Working with other stakeholders, identify the data needed, where it should be collected, who should collect it, and who should receive and evaluate the data.
Recommended actions may include:
- Conducting additional or continued environmental monitoring
- Conducting private well or public water system surveys
- Conducting surface water use surveys
- Conducting plant or animal consumption surveys
- Conducting land use surveys
- Further characterizing demographics of potentially affected populations
- Characterizing human activities on or near the site
- Characterizing contaminant source(s)
- Characterizing explosion potential
- Characterizing hydrogeology
- Characterizing radionuclide activity
If efforts to obtain the data in a timely manner are unsuccessful, start the collection process as described, and complete the PHA using the information you do have. When critical data become available, you can then use it to update the PHA, to write an addendum to the PHA, or to release a PHC that incorporates your new understanding of the site.
For example, with a site where no groundwater sampling data are available or they are of insufficient quality or quantity, you might state:
ATSDR has evaluated regional groundwater flow patterns (site-specific potentiometric maps are not available) and determined that it is possible that on-site groundwater may flow towards off-site private drinking water wells. The discovery of groundwater contamination at the site is recent and therefore, no groundwater sampling data are available to date. As such, ATSDR cannot make any public health conclusions about possible exposure to contaminants in drinking water.
EPA has signed an administrative order with the site owners who will be collecting on-site groundwater samples during the summer of this year, under EPA oversight. ATSDR will evaluate the sample results to complete the pathway evaluation. Additional efforts to conduct private well sampling for homes located within ½ mile south of the site later in the year are being undertaken by the county health department. ATSDR will also review these data once available.
Depending on the degree of exposure or hazard identified, coupled with the overall level of community health concern, various follow-up health activities may be considered. Recommendations will stem from your site-specific public health conclusions and include activities aimed at further evaluating the health status of the site community or educating the community and other stakeholders about the health effects (physical and psychological) related to the site.
Recommended actions may include:
- Conducting biologic tests for exposure or changes in body function
- Conducting health education
- Performing health studies or health surveillance
- Conducting substance-specific research
Table 9-3 provides a description of various types of health activities and highlights the factors that need to be considered in making a decision about their appropriateness. No specific formula exists for determining which, if any, of these activities should be recommended. However, the questions in the table can help guide site-specific decisions.
The site team should consider the criteria presented in Table 9-3 in consultation with the appropriate technical experts and/or the agency divisions or other stakeholders ultimately responsible for implementing the activity. This is often accomplished during the course of the public health assessment process. For example, no recommendation to conduct a health study should be made as a matter of course without conferring with an epidemiologist and the Division of Health Studies to assess the feasibility and appropriateness of such a study. The team also will determine who will conduct the recommended actions (e.g., health education specialists, local health departments, area physicians) and coordinate with the appropriate groups. For example, if the assessment reveals the need to educate local physicians, the health educators on the team would need to become involved and might ultimately provide the needed education.
Biologic Monitoring The measurement of a substance, its metabolite, or another marker of exposure in human body fluids or tissues to confirm human exposure to a hazardous substance.
Biomedical Testing Testing of persons to find out whether a change in a body function might have occurred because of exposure to a hazardous substance.
Community Health Education Programs designed with a community to help it know about health risks and how to reduce these risks.
Community Stress Education Community education designed to help community members better cope with the stresses of potential environmental contaminant exposure.
Health Professional Education Information for doctors, nurses, or other health care providers about environmental exposures and their prevention, substance-specific risks, community health warning signs, and/or special diagnostic techniques for detecting possible site-related illnesses.
Case Study A medical or epidemiologic evaluation of one person or a small group of people to gather information about specific health conditions and past exposures.
Cluster Investigation A review of an unusual number, real or perceived, of health events (for example, reports of cancer) grouped together in time and location. Cluster investigations are designed to confirm case reports; determine whether they represent an unusual disease occurrence; and, if possible, explore possible causes and contributing environmental factors.
Epidemiologic Study A study of the distribution and determinants of disease or health status in a population; the study of the occurrence and causes of health effects in humans.
Health Investigation The collection and evaluation of information about the health of community residents. This information is used to describe or count the occurrence of a disease, symptom, or clinical measure and to evaluate the possible association between the occurrence and exposure to hazardous substances.
Health Statistics Review The analysis of existing health information (i.e., from death certificates, birth defects registries, and cancer registries) to determine if there is excess disease in a specific population, geographic area, and time period. A health statistics review is a descriptive epidemiologic study.
Public Health Surveillance
|Substance-specific Applied Research
A program designed to fill important data needs for specific hazardous substances.
DHEP: Division of Health Education and Promotion
DHS: Division of Health Studies
DT: Division of Toxicology
EICB: Exposure Investigations and Consultation Branch
As discussed above, when developing recommendations you should focus on identifying measures that will prevent or eliminate exposures to harmful levels of hazardous substances or provide a means for obtaining more information to improve your assessment of possible public health hazards. You are not required to determine what specific action is needed or exactly how it should be implemented to reach your objective, but you should work closely with other divisions within ATSDR and other entities that might ultimately be responsible for implementing the recommended actions (e.g., other federal, state, or local agencies; tribes; the community; private parties).
As you work through possible recommendations, keep the following questions in mind:
- What feasible, reasonable action is needed?
- Who will implement the action? Have you received their buy-in/commitment to implement the action?
- When will the action begin? Is the time frame reasonable?
- What are the desired outcomes and what population will the action affect?
- What is the impact or health consequence of not implementing the action?
- When will the agency reevaluate the site or actions?
Table 9-4 presents a worksheet that can used in formulating recommendations and in developing a PHAP. The worksheet is completed to illustrate considerations under scenario for which biomonitoring has been recommended.
Thinking about your recommendations and the PHAP in this way and communicating with those entities who will ultimately be responsible for implementing the recommendations throughout the assessment process will help ensure that actions can and, hopefully, will be implemented. It will help ensure that objectives are reasonable; the recommendation is achievable; and, ideally, that buy-in or commitment is received from the party responsible for implementing the recommendation. The PHAP generally does not contain actions not agreed upon by other entities responsible for their implementation.
|Action||Objective(s)||Desired Outcome(s)||Issues That
|Who Will Implement? (Name/entity, address, telephone number, e-mail)||Commitment Received
|Time Line for Completion|
|Collect blood samples to test for lead exposure (for children ages 6 months to 7 years)||Identify and test all at-risk children (will capture current exposure status only; will not identify past or potential future exposures)||Determine if and to what extent children are being exposed to lead||If exposure is occurring, how can it be reduced or eliminated?
If exposure is occurring, can the site be distinguished as the source rather than other sources (e.g., lead paint in homes)?
If no exposure is found, will that change the site conclusion category?
|Local health department in cooperation with ATSDR||Yes, with laboratory assistance provided by ATSDR||Summer (time during which greatest soil exposures expected)|
All public health assessment documents should include a separate section listing recommendations. Recommendations should be active, concise, parallel, and consistent with the summary and conclusions. All recommendations must correlate with conclusions presented in the Conclusion section. You may have conclusions that do not result in recommendations, but you cannot have a recommendation without a conclusion. Note that ATSDR records all site-specific recommendations in HazDat.
Every recommendation should state the urgency with which or the time frame in which the recommendation needs to be addressed. This measure of urgency will indicate the gravity of the attendant conclusion and establish priorities for responding to the recommendation. Recommendations that do not have a time frame for completion might be interpreted as having a low priority.
Clearly state the needed action. For added clarity, you can list the recommended action(s) as bullets, and begin each recommended action with a verb (e.g., monitor, restrict, inform). As with the Conclusion section, the Recommendation section needs to be concise and pertinent to the focus of the assessment.
The PHAP section needs to clearly delineate completed, ongoing, and/or planned actions designed to mitigate or prevent adverse human health effects resulting from exposure to hazardous substances that might be associated with a particular site. It should parallel the recommendations and explicitly state actions already taken to eliminate or prevent public health hazards, as well as the specific plan in place to further investigate or eliminate remaining public health concerns, as detailed below. Clearly indicate the entity (federal, state, local, or tribal agency; community or private party) that has agreed to or should have the responsibility of implementing the recommendation. The PHAP should include the:
- Actions undertaken. Indicate public health actions undertaken to respond to recommendations outlined in the public health assessment. For example, if EPA had previously recommended a private well survey be conducted, that information should be provided in this subsection. The actions might have been carried out by one of the various agencies involved, including ATSDR, EPA, state, local, and tribal health and environmental departments. For sites at which ATSDR has been previously involved, also include past public health efforts and activities in the site community.
- Actions under way or planned. Delineate public health actions that are being or will be carried out by ATSDR and other agencies involved with the site other than ATSDR based on the recommendations presented in the public health assessment. Again, identify the entity that will undertake the activities outlined in a specific recommendation and indicate when, if possible, the activities will take place.
Table 9-5 presents examples of conclusions and recommendations, including a PHAP, meeting the above-stated criteria.
|Public Health Action Plan|
Actions under way
ATSDR. 1994. National exposure registry policies and procedures manual (revised). Atlanta: US Department of Health and Human Services.
ATSDR. 1996. Guidance for ATSDR health studies. Atlanta: US Department of Health and Human Services. April 1996.Top of Page
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