Air quality correlates of chronic disease mortality: Harris County, Texas 1969--1971.

Air quality correlates of chronic disease mortality in 180 census tracts of Harris County, Texas, were studied using 3 years mortality for 1969--1971. This study was designed to test with a different data base the universality of several study results which have reported significant correlations between heart disease and air pollutants. Air quality data (suspended particulates, benzene solubles, sulfur dioxide, and metals associated with particulates: copper, mercury, manganese, lead, nickel, zinc, chromium, and cadmium) were related to both sex and age adjusted crude death rates, and cause-specific death rates for age cohorts for 7 categories of heart disease, and pneumonia, asthma, cancer, tuberculosis, and accident deaths. The results of the study were in agreement with the findings of the other researchers who used national data. Suspended particulates and cadmium concentrations were found to be correlated (r=.38, .36; P less than .001) with ischemic heart disease (IHD). Many other significant correlations are reported but are not cause-specific. Socio-economic indicators were also correlated with IHD, thus confounding the issue. Further work is planned using more sophisticated statistical techniques to disentangle the relative contribution of each of these highly intercorrelated factors. No causality can be assigned at this stage, although this study, with the other cited, points to possible risk factors for IHD which need further evaluation.