The limits of regulatory toxicology

The Acceptable Daily Intake (ADI) has been used by regulatory and public health organizations (e.g., the U.S. Food and Drug and Administration, and the World Health Organization) for chemicals for more than 50 years. The ADI concept was also initially employed at the U.S. Environmental Protection Agency at its inception in 1971, although with the adoption of newer terminology, it later became known as the Reference Dose (RfD). It is clear from the literature that both were first devised as instruments of regulatory policy. In the intervening years, it has become common to use language that implies that these standards are statements of scientific fact. Similarly, some of the discretionary or default values that are used to derive regulatory standards are represented as scientific assumptions when in fact they also represent regulatory policy. This confusion impedes both the best use of the available science and informed public participation in policy making. In addition, the misconception of the ADI or the RfD as statements of scientific fact may impede the consideration of alternative means to reduce exposure to chemicals that may be harmful, including regulatory measures that do not involve prescribing a regulatory concentration limit.