Types of Sampling Data

This section describes the types of information you will look at to get a basic understanding of the site. It explains where to find these data and key questions to ask as you begin selecting data to use in the PHA process.

An important component of the PHA process is evaluating the usability and quality of environmental and biological sampling data.

Environmental sampling data indicate contaminant levels in various environmental media. These media may include water (e.g., groundwater, surface water, tap water), soil, air, and plants and animals (also called biota). For some sites, biological sampling data (e.g., blood, urine) collected from community members also might be available to evaluate exposures.

ATSDR typically relies on other agencies’ sampling data that are collected for many reasons, so the data ATSDR uses are not always specifically collected for the PHA process. For example, sampling data may be collected to

study background contamination levels,
evaluate efficacy of remediation projects,
support an ecological risk assessment,
inform an academic research project, and
characterize the presence of physical hazards, like combustible gases or explosives.

Key Questions to Ask When Selecting Data

When considering the appropriate data to use, consider the following:

Are the available data of sufficient quality and quantity to conduct the PHA process?
Are the sampling data representative of site and environmental conditions in exposure units, at the point of exposure, and for the timeframe of exposure?
If data gaps are identified, how should they be filled?
For what purpose was each sampling data set collected? If samples were not collected specifically to inform the public health assessment process, can they still be used for that purpose?

Health assessors must understand the underlying reasons why sampling data were collected before using them for the PHA process. That is because data used in the PHA process should fulfill a specific need (i.e., characterizing contamination levels in exposure units for completed and potential exposure pathways) — and this need does not always align with the objectives of the available sampling programs.

Note: This e-manual covers the topic of evaluating exposure pathways after this section on selecting sampling data. But during the PHA process, health assessors often consider exposure pathways first and then evaluate sampling data based on their understanding of the completed and potential pathways.

This does not mean that data collected for other reasons cannot be used in the PHA process. Rather, health assessors must understand why data were collected and what they represent before using them to evaluate environmental exposures. Health assessors should never blindly use sampling data just because they are available. This concept is very important and is discussed in greater detail in other parts of this section.

Health assessors are not expected to be experts in every environmental science discipline. When reviewing a highly technical sampling data set or an unfamiliar subject matter – or even for a second opinion on a data interpretation – health assessors should confer with ATSDR SMEs or the ADS Group.

Sources of Sampling Data

A logical starting point for gathering sampling data for the PHA process is to check with EPA and the state or tribal environmental agency. However, many other parties have provided ATSDR with sampling data over the years. These include other government agencies (federal, tribal, state, and local), site owners and their consultants, universities, non-profit organizations, and community members. The health assessor must gather all available sampling data that may inform the PHA process.

For some sites, other sources of sampling data are those that ATSDR collects during an exposure investigation (EI) [PDF – 1,034 KB]. Health assessors can recommend that ATSDR conduct EIs to fill gaps in the available sampling data. ATSDR EIs can include environmental sampling and/or biological sampling.

ATSDR conducts EIs when no sampling data are available to verify human exposure to contaminants, but exposure is suspected. The agency also conducts EIs in cases where the available data are too limited to reach conclusions. EI results are site-specific and applicable only to the sampling locations or investigation participants (i.e., they cannot be generalized to other areas, individuals, or populations). Results are used to identify a site’s appropriate follow-up public health actions. If you think an EI is warranted for a site, be sure to read ATSDR’s criteria for deciding whether conducting an EI is appropriate (see these criteria in ATSDR’s PHAT EI Mini-Module [PDF – 1,034 KB]).

The ultimate question you should ask is, will additional environmental or biological sampling help public health professionals, environmental risk managers, and other decision makers determine whether interventions are required to minimize or eliminate human exposure? If so, confer with ATSDR’s EI Group or other experts to explore the feasibility of performing an EI at your site.

Sampling data will provide health assessors direct measurements of contamination levels in the environment or in community members. Another input that health assessors should consider is modeled data, which estimate contamination levels. Issues to consider for these types of data are discussed in the modeled data section.