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An overview of regulatory classification systems on carcinogens in the Organization for Economic Cooperation and Development (OECD) countries is presented based on a questionnaire study. Most OECD countries have implemented legislation including classification systems and lists of carcinogens. Basically, there are two types of classifications systems. The major difference between the two is that in one system carcinogens are classified according to the weight of evidence for carcinogenic effects in humans, whereas in the other carcinogens are allocated to various groups according to potency. Even if the classification systems may differ, the substances classified as carcinogens are to a large extent the same. Classification of carcinogens will in many countries require hazard labeling. This labeling, i.e., the limit for labeling of substances and preparations, and risk phrases show considerable similarities, but differ in certain aspects. Several countries have restrictions on sale and/or use of carcinogens. There is a trend toward introducing more mechanistic considerations in the classification of carcinogens.

An analysis of several agencies' risk assessments reveals that the present conservative approach through several stages of estimates of amounts of regulated substances, the exposure levels, and cancer risks often tends to distort the actual final regulation. Changes in this process are desirable and possible and would reduce overestimation of cancer risk assessments. These possible changes are discussed.

In reaching a regulatory decision on the use of pesticides with carcinogenic potential, it is of great importance to investigate the extent of dermal exposure and absorption of a pesticide to users and field workers. By applying this information, along with the appropriate carcinogenicity categorization of a pesticide, a reasonably sound regulatory decision can be derived. Seven pesticides were selected, based on adequacy of tumor data, and were taken through the tumor evaluation system as reported in Part I 1984, Regul. Toxicol. Pharmacol. 4, 355-360). A step-by-step analysis on how a regulatory decision is reached on each pesticide by the EPA and CDFA was discussed.

Pesticides have been used for many years. In earlier times they were a protection against fungi and insect pests. The great increase in the use of pesticides occurred with the development of new organic chemicals following World Wars I and II. In addition to chemicals for the control of fungi and insects, new developments were nematocides, herbicides, rodenticides, avicides, defoliants, wood preservatives, etc. The use of chemicals helped increase productivity, but caused great concern about their effect on human health and safety. On the other hand, chemicals did help tremendously from the standpoint of protecting against diseases that were carried by insects, especially mosquitoes. Adverse publicity has caused great concern about pesticides and this is especially so since our society has undergone great changes from an agricultural society to an industrial society and finally to a communications society. Unfortunately, publicity relating to the use of pesticides has seldom been balanced from the standpoint of the good and the bad. In fact, the communications media has and does usually stress the potential adverse effects of pesticides without reference to the good. This has caused concern on the part of advocates and the average person to the extent that it has placed heavy constraints on agriculture. There is a need for the dissemination of balanced information on the good as well as the bad of pesticides.

Various aspects of regulatory decisions involving the concepts of "unacceptably hazardous" and "acceptably safe" as related to the growing emphasis on the legal terminology of de minimis are outlined. It is concluded that with rare exceptions a proper public policy for risk evaluations is far from implementation.