A cross-sectional study of 788 male employees of an aluminum production company examined the relationship of radiographic abnormalities to smoking and dust exposure from the mining and refining of bauxite to alumina. Among the aluminas produced were low temperature range transitional forms. The present analyses were limited to nonsmokers and current smokers. Two National Institute of Occupational Safety and Health (NIOSH)-certified "B" readers interpreted the radiographs. The predominant radiographic abnormalities noted were scanty, small, irregular opacities in the lower zones of profusion 0/1 to 1/1. Rounded opacities were rare. Among nonsmokers with low dust exposures, the prevalence of opacities greater than or equal to 1/0 showed no trend with increasing age and duration of exposure, suggesting no relationship between age and prevalence of opacities of Category 1 or more in this cohort (p greater than 0.10). Nonsmokers who had accumulated higher dust exposures showed a trend of increasing prevalence of opacities with increasing duration, suggesting an effect of occupational exposure at higher cumulative exposure levels (p less than 0.05). In most exposure categories, smokers exceeded nonsmokers in their prevalence of opacities greater than or equal to 1/0; the overall prevalence among smokers being 12 and 11% according to Readers A and B, respectively, compared with 4% in nonsmokers (p less than 0.01). In conclusion, 7 to 8% of aluminum workers in this cohort had radiographic findings of scanty, small, irregular opacities, the prevalence of which was increased among smokers (p less than 0.01). There was a moderate increase in the prevalence of opacities with increasing tenure in nonsmokers with high cumulative exposures (p less than 0.05).

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Present confusion that equates the presence of a biological effect with a deleterious implication ignores several concepts. To believe that a single molecule's presence in a cell implies a definite potential for deleterious effect disregards stochastic considerations. To believe that such molecules cause an undesirable effect disregards the presence of multiplicity of interferring substances. Such thinking also does not take into account the fact that the dose of a foreign atom may be related to the probability of its interacting with an available active site, or that similar probability governs the answers to the question of whether interactions will occur at discrete topographical loci upon a structural or functional molecule (or on a possible precursor). While the construction of stochastically sound model is remote, the reasonableness of the hierachy of cellular element concentrations as these relate to metabolic function suggests that a threshold for biological activity exists within a cell at 10(4) atoms. The cellular organism operates within a quantitative rate limit that transcends any statements having only qualitative bases. Thus concepts concerning encroachments on response capabilities over a lifespan are inadequate descriptors of biological activity in the absence of quantitative qualifiers.

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