Human Biomonitoring of Environmental Chemicals
The Issue
A key tool used to measure our exposure to chemicals in the environment is called “human biomonitoring.” The data from human biomonitoring is an increasingly important part of understanding exposure and managing the health risk posed by chemicals.
Background
Biomonitoring is the measurement of a chemical, the products it makes after it has broken down, or the products that might result from interactions in the body. These measurements are usually taken in blood and urine and sometimes in other tissues such as hair, saliva and breast milk.
It is difficult to predict levels of chemical substances in people using estimates or measurements of chemicals in air, soil, water, food or commercial products. This is because we have to make assumptions about personal habits and lifestyles, and make assumptions about how the chemical substances are absorbed, distributed, used and eliminated from the body. Biomonitoring decreases these uncertainties and will help to make sound decisions about the health of Canadians.
How human biomonitoring studies are conducted
A human biomonitoring study involves several steps. First, a decision is made on the design of the study which includes its objectives, the population in which the study will be carried out, and which chemicals to measure. This decision involves statistical considerations (e.g. having a sufficient number of subjects to meet the study objectives); the biologic relevance of the chemicals and availability of laboratory methods to measure them; and ethical aspects to ensure the appropriate treatment of study participants, their personal information and their results.
The second step is the actual conduct of the study. This involves enrolling volunteers; obtaining their consent to participate; collecting relevant questionnaire information; collecting their tissue and/or fluid specimens followed by the laboratory analysis.
The third step is the statistical analysis of data, the interpretation of study results, and the preparation of study reports. The final step is the communication of results to individual study participants, to policy-makers and agencies, and to the media and the public.
Studying Populations
Biomonitoring studies may involve the general population or sub-populations (e.g. women of child-bearing age, children or specific ethnic populations) and they may be done as small exploratory investigations, studies of occupational groups, and in clinical studies.
Whether or not the results of a certain biomonitoring effort can be applied to a larger group of people depends mostly on the source of the population data. In other words, if the information comes from a random selection in a clearly defined population, and the level of participation is high, then the results can usually be applied to a larger population group.
What Human Biomonitoring Studies Tell Us
Large national or regional-scale biomonitoring surveys can help monitor our exposure to chemical substances, and help us determine if the exposure is changing over time. An example of such a study is the U.S Centers for Disease Control(CDC) National Report on Human Exposure to Environmental Chemicals;  http://www.cdc.gov/exposurereport/ .It measure a wide range of environmental chemicals in the civilian population every two years and has tracked the large decline in blood lead in children as result of the use of unleaded gasoline.
Biomonitoring studies that focus on sub-populations can help establish exposure levels for that particular group in comparison to the broader population. This kind of information is more specific, and may not be available from larger-scale studies.
Biomonitoring is also used in studies, known as epidemiological studies, examining the cause and effect relationships between exposure to environmental chemicals and health problems.
Using Human Biomonitoring Data
Human biomonitoring data can be used by government, researchers and health practitioners in a wide variety of ways:
- To establish baseline levels of chemicals in Canadians and detect trends in exposure over time and by geographical region.
- To identify populations that might have higher levels of specific substances, and who are at higher risk of adverse health effects.
- To measure the number of people who have elevated levels of substances that are known to be toxic.
- To examine the relationship between the amount of exposure (i.e. the dose) and health effects.
- To identify substances that were not thought to be a concern or to accumulate in people.
- To set priorities and take action to protect the public’s health, including priorities for research on human health effects.
- To assess the effectiveness of public health and environmental actions intended to reduce exposures and health risks of Canadians to specific chemicals.
Limitations
While human biomonitoring is an important tool, there are certain limitations in its use. Because of advances in laboratory technologies, our ability to measure chemicals and generate biomonitoring data has, in many cases, exceeded our ability to interpret what the data mean to health. More work needs to be done to assess the sources of exposure and to evaluate the toxicological and health impacts of environmental chemicals. This will help in using biomonitoring data more effectively in managing the health risk of chemicals. This will lead to better understanding and communication of biomonitoring study results. A further challenge is that not all chemical substances lend themselves to biomonitoring techniques, and other ways may be needed to estimate human exposure.
Health Canada’s Role
Health Canada’s role is one of fostering biomonitoring surveys and studies, science and research. This includes the development of new chemical measurements and analytical methodologies and investigating the possible adverse health effects that may result from exposure to environmental chemicals.
In addition, Health Canada has a leadership role in producing and disseminating national biomonitoring data, identifying new priority substances for future studies, contributing to international monitoring efforts, and facilitating cooperation with other organizations with an interest in biomonitoring.
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