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About HEDS
Human Exposure Database System- What Is HEDS?
- What Is a Human Exposure Study?
- Who Might Use HEDS?
- What Is Included in HEDS?
- How to Use HEDS
- What Is Metadata?
- Data Use Restrictions -- Read Carefully Before Using!!!
- Protecting Your Privacy
- Disclaimer
- Feedback/Questions
HEDS is the Human Exposure Database System. It is a product of the Human Exposure and Atmospheric Sciences Division (HEASD) of the National Exposure Research Laboratory (NERL) which is a component of EPA's Office of Research and Development (ORD).
HEDS is a web-enabled data repository for human exposure studies. Its mission is to provide data sets, documents, and metadata for human exposure studies that can be easily accessed and understood by a diverse set of users. Although data are provided about human exposure, we strive to protect the confidentiality of all study participants. HEDS operates in conjunction with the Environmental Information Management System (EIMS), ORD's metadata repository. HEDS provides only data and accompanying documentation from research studies; it does not provide interpretations. It allows a user to download documents for review or data sets for analysis on their own computer system.
What Is a Human Exposure Study?
Human exposure studies are designed either to describe the level and extent of human exposure to various pollutant sources or to map the relationships between a person's environment and the impact of pollutant sources from that environment. For each study, there is a defined population of interest. It may be the population at hand that is easily accessible for the study, or it may be a broader population from which the study selects a representative sample that may be extrapolated to the larger population. These studies will likely have a survey of the population, whether households, persons, or buildings. (Further references to participants will be generic references to the members or constituents of the population actually being studied.) This survey may be purely demographic in nature, or it can be composed of several questionnaires, each addressing different information about the population.
Some studies may not involve the taking of physical samples. An example of a simple study without samples would be an activity pattern study. This type of study includes only demographic and activity pattern information for each study participant.
Some studies may include taking physical samples from the participants and their environment. Results from the analyses of these samples are then used with the questionnaire responses to assess potential relationships and subsequently to make predictions about potential causes and effects. Studies with physical samples will have data which relate the samples to the participants and will include parameters that describe the sample and/or are important to interpreting the analytical results from the sample.
Studies that include samples will also have analytical result information. These results may be divided into groups by type of sample matrix (e.g., dust, soil, air, water) and category of target analytes (e.g., metals, VOCs, pesticides). Describing the results requires information that relates the results to the sample (e.g., sample id, lab id, participant id), characteristics of the sample (e.g., matrix, location of sample, related field parameters), and characteristics of the result (e.g., analytical method, detection limit, quality flag).
In these studies it will also be common for quality assurance (QA) data to be tracked. QA data might come from samples that are blanks, spikes, or replicates. QA data will use formats similar to those for the non-QA data with the addition of parameters specific to the type of QA sample.
Below is an example of a study with samples. It is based on the National Human Exposure and Assessment Study (NHEXAS)--Phase I Arizona which contained the following types of questionnaires and samples.
Questionnaires:
- Descriptive--general characteristics of living quarters, makeup of the household, and general characteristics of household members
- Baseline--detailed information on the characteristics of the sampled individuals and their housing, and the frequency of activities over a longer time frame relative to their persistence in environmental or biological media
- Technician Walk Through--information on the physical characteristics of the house, and identification and inventory of pollutant sources present
- Follow-up--information on relatively infrequent activities during the sampling period to explain variation in the sample or results
- Time Diary and Activity--detailed time and location information and activity patterns
- 24-hour Dietary Diary--information on actual daily consumption patterns for a participant for use in estimating dietary exposures
Field Data (examples):
- Floor Dust Samples--House
- Soil Samples--House Foundation and Yard
- Sentinel Air Samples--House
- Surface Samples--House
- Food Diet Samples--Participant
- Vacuum Dust Samples--House
- Blood Samples--Participant
Analytical Results (examples):
- Metals in Air
- VOCs in Water
- Pesticides and PAHs in Dust
QA Results (examples):
- Metals--Spikes
- VOCs--Replicates
- Metals--Blanks
HEDS is available to everyone and is for anyone interested in the subject of human beings exposure to pollutants in the course of their daily lives. It was primarily developed to distribute data from human exposure studies to the community of scientists, especially those who perform human exposure and risk assessments and who develop exposure models.
The information available through HEDS is organized by study. Information for each study will include data sets, data set metadata, documents, and metadata. Studies will be added to HEDS over time. The current contents of HEDS can be found by clicking the HEDS Studies link on the HEDS Home Page navigation bar. New additions are described in What's New.
The information in HEDS is organized as a set of studies each containing data sets, documents, and metadata. There are two documents available for learning how to use HEDS. One document is for First Time Users and provides a step-by-step approach for learning the basic functions in HEDS. The other document is a Reference which describes the functions and file formats available through HEDS.
Metadata are data about data which in this case can include data sets, documents, and studies. That is, metadata is information that helps a user understand the context, contents, and limitations of the data or document. Metadata in HEDS is provided at two levels. General information for each HEDS study, data set, and document is included in EPA's Environmental Information System (EIMS) and can be accessed directly from the ORD-HEDS collection in EIMS or through links in HEDS. Metadata describing the contents of each data set, in the form of a data dictionary and code set, are also provided through HEDS. The HEDS Reference document describes both types of metadata in more detail.
Data Use Restrictions -- Read Carefully Before Using!!!
The EPA does all it can to ensure the identity of individual survey participants cannot be disclosed. All direct identifiers, as well as any characteristics that might lead to identifications, are omitted from the data. Any intentional identification or disclosure of a person or establishment violates the assurances of confidentiality given to the providers of the information. Therefore, users will (1) use the data in this study for statistical reporting and analysis only; (2) make no use of the identity of any person or establishment discovered inadvertently and will advise the HEDS Administrator of any such discovery; (3) will not link this data with individually identifiable data from other EPA or non-EPA data.
By using the data you signify your agreement to comply with the above-stated statutorily based requirements.
The EPA believes in your right to privacy. HEDS and EIMS use cookies in a very limited manner. No additional personal information is required to use HEDS. Feedback and questions about HEDS are handled through the options described in Contact Us.
No information that you provide to the EPA through HEDS will be shared with any other Federal, state, or local government agencies or non-government organizations by the EPA. Any information you provide to EPA will be kept confidential and will only be used to support your request for information from HEDS or EPA. The information will not be given or sold to anyone for their use in soliciting or marketing.
While the EPA diligently attempts to protect your personal information, it cannot completely ensure or warrant the security of any information transmitted to us.
No liability is accepted by the U.S. EPA for any errors or omissions in the results included in the data sets, associated information, and/or documentation. EPA is also not responsible for data analysis results or projections obtained from using, nor the consequences which may result from decisions based on using, the data analysis derived from these files. The user is responsible for the accuracy of their analysis and for validating the applicability of the data results for their intended purposes.
The amount of data available in many of the studies is large and complex, and familiarity with data file manipulation and analysis is required. EPA does not have the resources to perform analyses, check results, debug programs, or do literature review for your work. Thorough review of the documentation on the planning of a study, analytic guidelines, and individual data sets available through HEDS and EIMS should resolve most questions. If you still have questions after careful review of the documentation, please Contact Us. Please review the Data Use Restrictions and your agreement to comply with these restrictions in using the data.
The data for each study are the result of a sampling design specific to the population under study. Thus the data may or may not be representative of subsets of this study's population or of other populations. Each study was designed to test certain hypotheses, and this may limit its applicability for other purposes. When using the data from a study, it is important to consider the percentage of non-responses or non-detects in the data as an indicator of its usefulness for other purposes.
To provide comments or questions about HEDS, please Contact Us.