PART 11. CHEMICAL CARCINOGENESIS

CHEMICAL CARCINOGENESIS: INTRODUCTORY REMARKS

Leonard Chiazze, Jr. Georgetown University School of Medicine

Washington, D.C. 20007

The growing number of environmentally related cancers suggests that surveil- lance should play a greater role in identifying potential carcinogenic risks among working populations. Although a later session will be devoted to surveillance among high-risk groups, a few comments may be appropriate here. Potential carcinogens are being identified with increasing frequency. The evidence would seem to indicate that this identification comes more as a result of accidental clinical observations than from a systematic surveillance effort. Events leading to the systematic study of vinyl chloride workers is a case in point. It has been suggested that the high risk of this disease for polymerization workers might have gone unnoticed except for observation by a plant physician ( J . W. Lloyd- NIOSH Communication, January 1975). Unfortunately, components of a sur- veillance program are complex, and data acquisition requires a significant organized effort to identify risks early enough for effective action. In order to accomplish this goal, timely information must be available, which will enable one to characterize a working population and its environment, to provide appropriate outcome measures, and to measure effectively the interrelationship among the three.

The usual course of action is to apply classic epidemiologic methods to test hypotheses about risk factors once suspicions have been raised by accidental observations or descriptive studies. Any number of studies have demonstrated clearly that both population and outcome (measured by mortality) can be described retrospectively. Procedures are difficult and time-consuming, but the goals are achievable. Unfortunately, there usually is no way of retrospectively describing the precise working environment. Further, the use of mortality as an outcome measure means that the problem is identified long after it arose and that others will probably be affected before effective preventive measures can be initiated. It is clear, then, that in order for surveillance to be effective in early identification of excess risk, it must include early effects recording as well as continual monitering of the working environment.

Unfortunately, there are serious deficiencies in our capability to provide uni- form, complete, and up-to-date information on effects. Consider the varying levels at which health effects may be measured: (1) death, (2) morbidity (clinical illness), and (3) early abnormality (abnormal lab test). For mortality, there is a national data-acquisition effort. While some information on morbidity and early abnormalities is available, that information is not part of any SYS- tematic occupational health-data system. A cooperative uniform reporting and analysis system could result in early risk identification enabling action, rather than reaction. Such a system would involve a minimum uniform data set for outcomes and exposures and could utilize data from nationally sponsored pro- grams such as those of NCHS and NCI (SEER) that focus on morbidity. Industry records are, of course, the key to any early warning system with the capability of providing a total system of environmental and effects evaluation. It is Iikely that components for reasonably effective surveillance exist currently if properly drawn together.

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