Monitoring Our Chemical Bodies

By Jody A. Roberts

In 2007 the U.S. Centers for Disease Control and Prevention (CDC) will release its fourth “National Report on Human Exposure to Environmental Chemicals” containing information on the presence of synthetic and industrial chemicals in the bodies of the nation’s populace. This is one of more than a dozen human biomonitoring studies that the U.S. government has initiated in recent years. The release of the CDC report provokes eagerness and anxiety. It adds to the proliferation of information about how we, as complex chemical beings, interact with chemicals in the world around us. However, uncertainty continues to confound how this information can and ought to be used to understand the intimate links between our bodies and our environment. Each new biomonitoring report challenges those in related fields to communicate its results more effectively to colleagues, policy makers, and exposed communities.

Biomonitoring in this context is a tool for assessing human exposure to chemicals by measuring the chemicals in human specimens, such as blood or urine. The result of this analysis, or the mixture of synthetic chemicals found in a given person, is referred to as the individual’s body burden. Human biomonitoring can be used to track exposure to chemicals, compare exposure rates among geographically separate groups, and gauge the effectiveness of regulatory measures designed to limit exposure. In some cases direct analysis of a chemical is not possible, and researchers must develop ways to identify and measure the metabolites of that chemical, known as a chemical biomarker. While analytical chemists and others in the biomonitoring field have developed increasingly sensitive methods to detect the presence of more and more chemicals, the search for chemical metabolites and other biomarkers presents a serious and ongoing challenge to the heightened use and effectiveness of human biomonitoring studies.

As the science of human biomonitoring has made testing more reliable (if not quite standardized), the number and variety of tests being conducted by various organizations has increased. Several agencies of the U.S. government conduct biomonitoring surveys; California recently announced it would begin its own tests; Canadian legislators are discussing the creation of a nationwide study; and the European Union is considering implementing regular biomonitoring studies. Such nongovernmental organizations as the Environmental Working Group and Commonweal also use biomonitoring to draw attention to human exposure to synthetic chemicals.

While new technologies are now available, human biomonitoring studies and analytical methods have been a key component of the occupational health field for more than a century. Beginning in the late 19th century, workers were routinely monitored for lead exposure, but the nature of those studies differs from that of current studies. In the case of lead and other occupational health hazards a clear and obvious danger gave rise to the monitoring techniques. Monitoring was a means for measuring the exposure and effectiveness of safety protocol, which translated into specific and tangible solutions for adapting a somewhat controllable environment—the workplace. With the advent of human biomonitoring as an extension of public health initiatives, defining such concepts as “environment” and “hazard” becomes more problematic.

Those seeking to deduce health information from new studies find it difficult to decipher the results. For lead there is information on exposure levels dating back several decades; new studies confirm that overall blood lead levels, though still alarmingly high in some locations, have declined since federal regulations banned lead use in automobile fuel and household items. But when a new test detects the presence of a previously undetectable chemical, there is no context in which to place the results. Without background or baseline information, it is almost impossible to determine whether an exposure level is normal, abnormal, or excessive.

This uncertainty makes it difficult to communicate the results of biomonitoring studies to interested parties. Most studies include caveats that proof of a targeted chemical’s presence does not signify proof of its harm, but the chance remains that policy makers or affected communities will interpret results in their own way, taking what they want from ambiguous tables and graphs.

In its recent report on human biomonitoring the National Research Council highlighted communication as one of the major problems facing scientific and regulatory communities. This dilemma exists in part because the science required to understand the implications of the presence of synthetic chemicals in the human body has not kept pace with the science that allows its detection. Perhaps nowhere is this more evident than in studies related to the effects of endocrine-disrupting chemicals.

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