provide substantial information on risk (Asp et al., 1994; Bueno de Mesquita et al., 1993).

Cancer incidence during the first ten years after exposure to TCDD was investigated in the Seveso cohort (Bertazzi et al., 1993). There were no cases of renal cancer diagnosed in Zones A or B, the most heavily exposed areas. Based on ten cases of renal cancer in men in Zone R, the least exposed area, the relative risk was 0.9 (CI 0.4-1.7). Based on seven cases of renal cancer in women in Zone R, the relative risk was 1.2 (0.5-2.7).

A PMR study examining causes of death among veterans on the state of Michigan's Vietnam-era Bonus list was recently reported (Visintainer et al., 1995). This study compared 3,364 Vietnam veterans with 5,229 age-matched veterans who served elsewhere. Based on 21 cases of renal cancer among Vietnam veterans, the PMR was 1.4 (0.9-2.2).

Summary

The studies reviewed since the publication of VAO indicate marginally positive results. They are not, however, significant enough to suggest any change in the committee's view that there is inadequate or insufficient evidence to determine whether an association exists between exposure to herbicides and renal cancer.

Conclusions

There is inadequate or insufficient evidence to determine whether an association exists between exposure to the herbicides (2,4-D, 2,4,5-T and its contaminant, TCDD; cacodylic acid; and picloram) and renal cancer. The evidence regarding association is drawn from occupational and other studies in which subjects were exposed to a variety of herbicides and herbicide components.

Bladder Cancer

Summary of VAO

For bladder cancer, Fingerhut et al. (1991) found a small excess in mortality in their study of chemical production workers exposed to TCDD. In the total cohort of 5,172 workers, there was an SMR of 1.6 (CI 0.7-3.0), based on nine cases. In workers with at least one year of employment and 20 years latency, there were four cases (SMR = 1.9, CI 0.5-4.8). Other studies of bladder cancer have produced inconclusive results. Occupational studies include studies of chemical production workers in the United States and other countries (Moses et al., 1984; Suskind and Hertzberg, 1984; Bond et al., 1988; Zober et al., 1990; Saracci et al., 1991), agricultural and forestry workers (Burmeister, 1981;



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