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Executive Summary
The Agency for Toxic Substances and Disease Registry (ATSDR) convened a seven-member panel to review and discuss the current state of the science related to hair analysis, specifically its use in assessing environmental exposures. ATSDR invited a cross section of scientific experts in the fields of hair analysis, toxicology, and medicine to participate in 1½ days of discussions on a variety of topics, including analytical methods, factors affecting the interpretation of analytical results, toxicologic considerations, and data gaps/research needs. The meeting was held June 12 and 13, 2001, in Atlanta, Georgia.
Background
ATSDR convened this panel in response to (1) a growing number of inquiries from community members looking for assistance in interpreting hair analysis results and (2) agency interest in learning more about the utility of hair analysis in evaluating exposures and health effects at hazardous waste sites. The agency hopes to use the input received from this effort to develop guidance for agency health assessors on the use and interpretation of hair analysis data.
The general questions that ATSDR seeks to answer include:
This summary report presents the findings of the
panel discussions. Central discussion points are highlighted below.
Overview Of Discussions
Panelists engaged in a series of discussions to address ATSDR's questions, pointing to several limitations—having to do with the current state of the knowledge—on the usefulness of hair analysis in assessments of environmental exposures. Discussions focused primarily on metals and trace elements in scalp hair. Panelists considered the distinct differences between using hair analysis to identify exposures (Is the substance reaching people? Does a competed pathway exist?) and using it to predict, diagnose, or treat disease (What do hair concentrations tell us about the likelihood of harmful health effects?). Panelists noted that the latter is where the largest data gaps exist.
Although they were not required to reach consensus, the panelists did agree on the following summary statement related to the overall usefulness of hair analysis in evaluating environmental exposures:
For most substances, insufficient data currently exist that would allow the prediction of a health effect from the concentration of the substance in hair. The presence of a substance in hair may indicate exposure (both internal and external), but does not necessarily indicate the source of exposure.
For what substances do reliable hair analysis methods exist?
The group agreed that laboratory methods exist to measure the levels of some environmental contaminants in hair, but procedures need to be standardized to help ensure more accurate and reliable results (this includes ensuring that samples are collected by a trained person and establishing consistent sampling protocols, washing protocols, quality control/quality assurance procedures, etc.). Further, the panel agreed that testing should be targeted to the specific element of interest.
When is it appropriate/inappropriate to consider hair analysis in assessing human exposures to environmental contamination?
In general, panelists agreed that, before determining the appropriateness of hair analysis as an assessment tool, assessors should consider the following:
The panelists agreed that a relationship between contaminant concentrations in hair and any kind of measurable outcome have only been established for methyl mercury (e.g., the relation between maternal hair levels and observed developmental neurological abnormalities in offspring) and to a limited extent for arsenic (e.g., segmental analysis for forensic analysis), provided external contamination can be ruled out. There may be unique forensic settings for other substances.
The group also indicated the need to evaluate, on a substance-
and exposure-specific basis, the extent to which hair analysis may
be more advantageous than other biological sampling, such as blood
or urine analysis.
What data gaps exist that limit the interpretation and use of hair analysis in the assessment of environmental contaminants?
The group identified several factors that limit the interpretation of even the most accurate, reliable, and reproducible laboratory results. These include:
In moving forward, the panelists encouraged the standardization of sampling protocols and identified possible research areas. Before hair analysis can be considered a valid tool for any particular substance, research is needed to establish better reference ranges, gain a better understanding of hair biology and pharmacokinetics, further explore possible dose-response relationships, establish whether and when hair may serve as a better measure or predictor of disease than other biological samples (e.g., blood or urine), and learn more about organic compounds in hair.
Future ATSDR Activities
ATSDR plans to evaluate all the input received during the panel deliberations and generate a report on lessons learned from the panel discussions. In addition, the agency anticipates that the following activities will help all of ATSDR's divisions as well as professionals in the community.