Toxicology

Whenever a group of citizens becomes concerned about the toxicity of a chemical substance, they typically want immediate answers to the following questions:

• Is this chemical harmful?
• At what level of exposure is this chemical harmful?
• What are the symptoms of exposure to this chemical?

Unfortunately, from the point of view of the toxicologist, the answers to these questions are seldom simple. This problem is compounded by the fact that most chemicals of unknown toxicity did not exist until at most a few decades ago, so data for long-term exposure may not exist.

Even when the question is as apparently straightforward, such as "Is such-and-such a chemical harmful?", the answer will seldom be as simple as, "Yes, in amounts exceeding 16 parts per million." This is because a complete scientific answer must take into account other factors such as the age of the individual exposed, the duration of exposure, and whether other environmental pollutants are present that could interact with and magnify the substance's toxicity. In the same way, workplace guidelines for adults who spend an eight-hour day in a factory may be difficult to apply to a residential setting where children and homemakers spend most of their time.

Because modern science and technology developed many of the chemicals scientists are now evaluating for toxicity, it is perhaps not surprising that many laypersons have grown skeptical about the ability of scientists to identify toxic materials. Because toxicologists report their findings in the form of statistics and probabilities, separate government agencies have been known to issue conflicting regulations governing exposure to substances based on different interpretations of the same data.