Current environmental and public health regulations are largely based on a theoretical calculation of risk associated with human exposure to chemicals in air emissions, water discharges, soil contamination and consumer products. That is, risks of exposures are based on the concentrations of chemicals in the environment, rather than actually in our bodies. Biomonitoring offers the opportunity to analyze the relationship between chemicals in the environment and actual bodily uptake.
Most regulations rely heavily on animal research to estimate potential human health effects. Such studies typically involve exposing rats and mice to chemicals at constant levels every day (often for a lifetime and at concentrations that are substantially above real-world exposures). But the relationship between the level of exposure to a chemical and the amount that ends up in fluids and tissues is complex; to extrapolate from animals to humans is even more so. As noted by Michael Kamrin, a professor emeritus of toxicology at Michigan State University, “[U]nless adequate toxicokinetics* data are available, it is very difficult to compare the dietary levels used in laboratory experiments to fluid and/ or tissue levels measured in biomonitoring studies.” Thus, toxicologists are taking steps to better understand how chemical exposures equate to blood or tissue concentrations, which will help to make biomonitoring data more meaningful.
Biomonitoring involves measuring actual levels of exposure within the body, which can help to make risk assessments far more accurate. In the case of phthalates,† for example, the CDC’s biomonitoring is helping researchers differentiate among the various sources of exposure and determine how environmental exposures translate into actual body concentrations. As noted by Dr. James Pirkle, deputy director for science at the CDC’s National Center for Environmental Health: “[I]t has helped us clarify some understanding about the relative exposure that are, say, in cosmetics and personal care products compared to, say, phthalates that are in soft vinyl plastic products like in toys or in vinyl tubing or things like this. … [T]here is much greater detail … separating out those different kinds of sources and how those sources relate to different levels in people.”
* Toxicokinetics is the study of the relationship between exposure to a chemical compound and the compound’s toxicity. Toxicokinetics data are not available for many chemical compounds.
† Phthalates are a family of chemical substances with a variety of applications, but they are commonly used to make vinyl soft and flexible.