This report updates a 1981 study ofmortality at three United Kingdom chromate producing factories, and pays special attention to workers engaged after major plant and process changes were completed during 1958-60.

OBJECTIVES. Our objectives were (1) to describe an analysis of the spatial pattern of cancer incidence in Ontario and (2) to discuss the quality of data in the Ontario Cancer Registry with respect to the accuracy of local cancer rates. METHODS. Cancer incidence rates were calculated for 22 cancer sites in 49 counties of Ontario during 1976 to 1986. Capture-recapture methods were used to estimate completeness of case registration, and completeness of residence information was also assessed. Spatial autocorrelation was used in measuring the geographic pattern of incidence rates. Comparisons were also made between sexes and with earlier data from 1966 to 1975. RESULTS. The quality of the geographic data in the registry appeared good, and corrections for incomplete or inaccurate registration had little impact. About one third of the sex-site combinations showed some evidence of spatial patterning in the cancer rate. Particularly strong regional variation was noted for cancers of the stomach, lung, uterus, and prostate. CONCLUSIONS. The analysis revealed a number of cancers with significant spatial patterning of risk. Further work is needed to relate the cancer data to other information on potential life-style and environmental factors.

Summary.-Mortality from stomach cancer was examined over the period on Worksop and 5 other nearby mining towns, and in 4 non-mining towns in Nottinghamshire. For each town, expected numbers of deaths at national rates were adjusted to allow for local/national differences in social-class distribution and number of miners, since mortality is known to be high nationally among miners and miners' wives, and to vary markedly with social class. After adjustment, the stomach-cancer Standardized Mortality Ratios (SMRs) for the aggregate of mining towns were 92 for men and 104 for women. For the non-mining towns equivalent SMRs were 91 and 86, and mortality was markedly low at ages under 65 for both sexes. Mortality in Worksop was not significantly raised, and appeared similar to that elsewhere in the mining towns. This result does not support the earlier finding by others that stomach-cancer mortality in the town was significantly raised, nor the accompanying suggestion of an association with the high nitrate content of the local drinking water via the action of nitrosamines.

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