Age-adjusted, sex- and race-specific 1969-1971 cancer incidence ratios for the 722 census tracts of the San Francisco-Oakland Standard Metropolitan Statistical Area were compared with measured chysotile asbestos counts in tract drinking waters. The water supplies serving the area have varying contact with naturally occurring serpentine. The t test for multiple regression coefficients and the t test for correlation coefficients showed significant (p less than 0.01) relationships between chrysotile asbestos content of tract drinking water and white male lung, white female gall bladder and pancreas, and peritoneal cancers in both sexes. Of weaker significance (0.01 less than or equal to 0.05) were female esophagus, pleura and kidney, as well as stomach cancers in both sexes. These associations appeared to be independent of income, education, asbestos occupation, marital status, country of origin and mobility.

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PCA and factor analysis assist in the identification of the interrelationships of multiple variables, all acting simultaneously. Multivariate methods handle large volumes of data resulting from the interactions of multiple variables and identify principal components or factors that link some of the variables and that unlink others. There are as many components or factors identified as there are variables studied. The information provided by the factors is not identical; the first factors reflect links of a greater strength and influence on the context than do the last factors. The graphic, three-dimensional representation of the principal components helps to provide a better understanding of the interrelations among variables. These relationships can be extrapolated qualitatively to generate postulates or to reveal trends, making multivariate techniques useful hypothesis-generating tools.These analyses can be useful for comparing new antimicrobial agents with existing ones. Microbiological activity influences the interest in a new antimicrobial agent in its early development stages. In the present study, multivariate analysis techniques were used to investigate the interrelationships of * Corresponding author. Mailing address: Clinical Investigation