The Environmental Protection Agency (EPA) just named the first five substances it will fast-track towards risk evaluation.

The substances are on the EPA’s radar due to indications that they may be persistent, bioaccumulative, and toxic. PBTs, as such a group of chemicals are called, don’t break down easily, and thus may be retained in the environment or in the bodies of organisms.

An example of one such PBT is mercury. Aquatic microbes convert mercury into a compound called methylmercury which fish ingest but don’t excrete. Generally, fish-eaters like sharks, swordfish, and marlin have higher concentrations of mercury in their bodies because they take up methylmercury from the surrounding water, as well as in their diets. This process of gradual buildup is called bioaccumulation.

Unlike fish, humans are able to excrete mercury. Unless you consume several hundred servings of high-mercury fish each day, you won’t experience any negative effects. This is a classic example of our favorite mantra, “the dose makes the poison.” Mercury poisoning and Minamata disease, a condition which results from persistent exposure to the heavy metal, are truly dangerous. But the level of mercury that an average person comes into contact with on a given day is several hundred thousandths of a percent less than the level which would cause damage. (Unless you’re eating fish from Minamata Bay circa 1956, of course).

This gets back to our original point of the EPA fast tracking the group of five PBTs for risk evaluation. A proper evaluation of risk must examine what level of a given substance regular people are exposed to, and federal law even mandates that consideration be paid to vulnerable groups, such as pregnant women and workers who handle such substances on a daily basis.

Under the new Frank R. Lautenberg Chemical Safety for the 21st Century Act (LCSA), the EPA was granted more authority to take action on unreasonably dangerous chemicals. If an evaluation reveals that the intended use of one of the chemicals introduces an unreasonable risk, the agency can impose an appropriate course of action including labeling requirements, use restrictions, phase-outs, or bans.

We have yet to see how the EPA will conduct its assessment, but we certainly hope that each chemical evaluated under LCSA is given an appropriate consideration of actual risk.