The word “toxic” is typically used in everyday conversation to mean something that readily could cause harm. Something “nontoxic” suggests that it will not cause harm.
Some groups have suggested that we need to get rid of all “toxic” chemicals and replace them with “nontoxic” ones. This suggestion does not recognize the simple truth that all chemicals—whether man-made or naturally occurring—can produce toxic effects above a certain level of exposure.
In assessing the potential for harm, however, regulatory scientists assess the “risk” associated with a substance by considering both the potential hazard that exposure to a substance presents and the degree to which people may be exposed to the substance.
- Risk is the possibility of a harmful event arising from exposure to a chemical or physical agent under specific conditions.
- Exposure describes both the amount of, and the frequency with which, a chemical substance reaches a person, a group of people, or the environment.
- Hazard refers to the inherent properties of a substance that make it capable of causing harm to human health or the environment.
One way scientists assess potential hazard is to expose laboratory animals, usually rodents, to the substance. A typical method is to give rodents very large doses of a substance over various periods of time. Rodents and people are different in many important ways. Giving rodents large doses over various time periods is not the ideal way to test for human effects of small doses. But it does offer clues and can point out areas for further research.
Regulatory agencies take a conservative approach in establishing safe levels of exposure to chemicals. They combine the results of the animal experiments with other available information to estimate an exposure level below which no harmful effects are expected. The agencies then incorporate a margin of safety by dividing this exposure level generally by uncertainty or safety factors of one hundred (100) or one thousand (1,000), or more. The safety factor incorporates the degree of uncertainty associated with the animal results and a level of protection for sensitive individuals, including children.
In the case of phthalates, biomonitoring reports from the U.S. Centers for Disease Control and Prevention (CDC)—found on the human exposure and biomonitoring page—indicate that exposure levels to the general population are considered far below reference doses and other similar safety levels set by the Environmental Protection Agency (EPA) and other US and European authorities.
You can find more information on how a hazard begins to pose a risk in this information sheet prepared by the American Chemistry Council.