Abstract |
Two previous studies (1969-1971 and 1969-1974 study periods) examined the relationship between cancer incidence and chrysotile asbestos ingested through drinking water in the San Francisco-Oakland Standard Metropolitan Statistical Area (SMSA). Population density, an important covariable in the relationship between cancer and environmental agents, was not included in the analyses of these studies. The present work determines the effect of this covariable on the results of the second San Francisco-Oakland SMSA study. The conclusion of the reanalysis was that population density was distributed across the San Francisco-Oakland SMSA in such a way that it had little effect on the observation of a relationship between ingested asbestos and cancer. |