What can be learned about exposure from the results of biomonitoring?

As indicated previously, biomonitoring provides a measure of the exposures to natural and synthetic substances in the various environments in which humans live. Until recently, biomonitoring was used mainly in occupational and a limited number of clinical settings. In the workplace, this approach provides information about workers who have received higher than acceptable exposures and thus need to change their environment and/or behaviors. Clinically, biomonitoring can be used in identifying specific individuals with high exposures, e.g., people exposed to large amounts of arsenic. This information can be used in deciding which medical interventions or treatments may be appropriate.

The extensive use of biomonitoring to assess general population exposures to chemicals in the outdoor and indoor environments is much more recent and is designed to accomplish a number of aims. Two of the main goals are to determine: (1) which chemicals are present at high enough levels to leave traces in the human body, and (2) the relative levels of these compounds. Since such biomonitoring has just begun, the early results are most useful for establishing baseline levels of each chemical, against which to compare future monitoring results. Such comparisons can identify trends in exposures and help to assess the success of steps that have been taken to reduce the amounts of particular chemicals in the environment. For example, the success of campaigns to reduce exposures to secondhand smoke can be assessed in this manner.

In addition, population biomonitoring may be helpful in identifying compounds whose levels in the environment have increased to the point that they can be detected in human fluids and tissues. These data often suggest that there are sources of this chemical that have not been identified or that knowledge about the environmental movement of these compounds is faulty. Moreover, the identification of these chemicals may be accompanied by the recognition that data on the possible adverse effects of these compounds is limited. These outcomes are likely to lead to additional research on sources, environmental distribution and toxicity of the newly detected compounds.

Further, if the monitoring is done on sufficiently large and diverse groups of individuals, it may be possible to identify specific sectors of the population that have significantly higher exposures to a particular chemical than does the general populace, e.g., urban dwellers may have higher exposures to components of automobile exhaust. This information, in turn, may help to identify sources of these chemicals and, if the levels are of public health concern, to develop interventions to reduce future levels of these compounds in humans.

Finally, general population monitoring results may be useful in extending the clinical applicability of such data, as they can be used to establish reference levels for a much greater number of chemicals than are currently known. Such reference levels can be used by physicians to assess whether individuals have unusually high exposures to a substance and thus the appropriateness of particular medical interventions or treatments.

In sum, biomonitoring provides exposure information that can be used in a number of ways. These data help in understanding which chemicals are in the environment and the relative levels of each; how these levels change over time, and which sectors of the population may have unusually high exposures to particular compounds. As a result of this understanding, it may be possible to assess the effectiveness of steps taken to reduce exposures, to identify new research that is needed and to help physicians diagnose and treat patients who may have had unusually high exposures to particular substances.