Health Care Providers
Analysis of Hair Samples :
How do hair sampling results relate to environmental exposures?
In growing numbers, community members who are concerned about environmental exposures are having hair samples
analyzed for chemical contamination and asking public health agencies to interpret the testing results. As a result, public
health officials need to understand the science of hair sampling results. This fact sheet gives basic information on the
strengths and limitations of human hair analysis. Overall, although hair analysis has some potential advantages over
other biological sampling techniques, the Agency for Toxic Substances and
Disease Registry (ATSDR) considers that the limitations associated with hair
analysis currently far outweigh the strengths of this sampling tool.
ATSDR believes many scientific
This fact sheet applies only to the use of hair analysis for assessing environ-
issues need to be resolved before
mental exposures, and does not address other applications of hair analysis
hair analysis can become a useful
techniques, such as use of hair analysis in forensics or in testing for illegal
tool to understand environmental
exposures. Although hair analysis
may answer some questions about
environmental exposure to a few
What are the strengths and limitations of
substances, hair analysis often
hair sampling and analytical methods?
raises more questions than they
answer. With very few exceptions,
A reported strength of hair sampling is that it is less invasive than other
hair analysis results provide no
biological sampling methods, such as collecting blood samples. However,
insights as to whether an individual
sampling and analysis of hair samples suffer from many limitations; most
will develop health effects.
notably, standard procedures have not been published for collecting, wash-
ing, and analyzing hair samples. Consequently, many questions regarding
appropriate sampling and analytical procedures remain unanswered.
For instance, no consensus has emerged among scientists about the extent to which different cutting tools introduce
contaminants into hair samples, about the part of the scalp from which hair samples should be collected, and about the
influence of washing techniques. Further, scientists have not developed approaches for using hair analysis to character-
ize exposures for most organic compounds, in part because questions remain on what metabolites to look for in the hair.
Hair analysis has been performed for a limited number of substances of environmental concern, primarily metals and
selected organo-metallic compounds (like methyl mercury). Overall, standard sampling and analytical methods need to
be developed before hair analysis can become an accurate and precise technique.
How well do hair analysis results characterize exposure?
If a substance is detected in a hair sample, the one defensible conclusion that can be drawn is that the individual was
exposed to the substance at some time when the hair strands were growing. Three key limitations prevent further
interpretation of most hair analysis results:
Hair analysis results cannot pinpoint the sources of chemical contaminants that were detected. For instance, hair
analysis results typically cannot distinguish substances that have deposited onto hair (perhaps from hair care products or
dusts) from substances that might have distributed into hair following an environmental exposure, such as ingestion of
contaminated drinking water. In other words, hair analysis generally cannot differentiate internal from external exposure.
Further, because many substances commonly detected in hair are also found in our diets and in occupational settings, it
is often impossible to determine whether, or to what extent, environmental exposures contributed to a measured con-
centration. In short, a detection generally will not tell you how, when, or where the individual was exposed.