Useful as biomonitoring can be, there remain significant challenges to improving its utility. Largely missing are precise assessments of risk that are necessary to determine the health consequences of exposures. In other words, biomonitoring reveals the amount of a chemical in an individual’s body, but such knowledge is largely meaningless unless we know at what level in body fluids or tissues health consequences do and don’t occur. As noted by Dr. David Galbraith in his 2005 presentation to the International Society of Regulatory Toxicology and Pharmacology: “Our vastly improved abilities to detect have often outstripped our abilities to detect meaning.
Biomonitoring can improve risk assessments by enabling researchers to couple direct observations of physical symptoms or effects with measurements of chemical uptake. But establishing the correct relationship is no easy task.* Biomonitoring data only reflect the amount of a chemical in the body at the time of testing, which may differ from the original exposure. “One sample reading could represent exposure from yesterday, last week, or 30 years ago,” Dr. Galbraith has observed.
Moreover, health consequences, if any, may result either from the original exposure or from the presence of the compound in the body over time. Nor is the source of exposure always apparent, further complicating the interpretation of biomonitoring results.
Uncertainties also arise when exposure measurements approach the minimum levels that can be detected, or when the test for detecting a particular chemical is complex or unproven. Chemical levels may also vary depending on the type of tissue or body fluid tested. In addition, there may be questions about which form of a compound (or combination of forms) is most appropriate to measure.
These challenges were recently documented by a committee of the National Academy of Sciences, which concluded that, “The ability to generate new biomonitoring data often exceeds the ability to evaluate whether and how a chemical measured in an individual or population may cause a health risk or to evaluate its sources and pathways for exposure.” The NAS committee’s findings and recommendations are summarized in Graphic 2.
Graphic 2: Summary of NAS Conclusions
|There has not been a coordinated or consistent strategy for selecting chemicals for testing.||Set priorities for biomonitoring based on health risk and the potential for exposure.|
|The ability to detect chemicals has outpaced the ability to interpret health risks accurately.||Undertake epidemiologic and toxicological exposure assessments for use in biomonitoring.|
|The results of biomonitoring are not communicated appropriately or effectively to the public.||Create strategies for reporting biomonitoring results in an accurate and objective manner.|
|Biomonitoring studies present ethical issues related to informed consent, the interpretation and communication of results, and follow-up with subjects.||Biomonitoring studies must consider ethics and individuals’ rights in the development, implementation and reporting of results.|
Source: National Research Council, “Human Biomonitoring for Environmental Chemicals,” 2006.
* Many regulations are based on risk assessments calculated from workplace exposures. However, workplace studies often suffer methodological flaws.