Contents Notes |
At a workshop sponsored by the EPA Office of Research and Development in February 1987, thirteen expert panelists discussed research needed to support the development of risk assessment methodologies for tumor promoters. The panelists exchanged current data on promotion, identified data gaps, and formulated general and specific research recommendations. Available data suggest that there are probably at least three stages of carcinogenesis - initiation, promotion and progression - and that there are agents that are associated predominantly with these three stages. The panelists agreed that the mechanism of promotion is not currently understood, and they suggest that there may be several different mechanisms of promotion. Available data suggest that promotion is substantially different from initiation and that traditional risk assessment models for carcinogens are not appropriate for promoters. The panelists agreed that not enough data are currently available to assess the risks of promoters and that substantial research is needed in several areas, including: mechanisms of initiation, promotion and progression; the behavior of promoters in humans, especially epidemiological studies; development and validation of statistical models for initiation/promotion systems; the behavior of promoters in organs other than the skin and the liver; interspecies differences in promotion; expansion of the chemical data base for known and potential promoters; synergism among promoters; and development validation of in vitro screening models for known experiment promoters. |