Comparison of observed radiological abnormalities in the heavy clay industry with risks predicted by exposure-response relationships from high-potency quartz exposures ata Scottish colliery

There is increasing pressure in the UK and elsewhere to tighten the regulation of workers’ exposures to airborne silica. This is largely driven by results from industries where exposures to respirable silica have led to rapid and in some cases severe development of disease. However, it has been demonstrated that risks from respirable silica vary greatly across industries, and precautions that are appropriate in one industry may be over-protective in another. In risk assessments in the UK, quantification of risks has relied heavily on results from an IOM study of Scottish coalworkers, which allow predictions of risk of radiographic abnormalities from estimates of individuals’ cumulative exposures to respirable quartz. These contrast with data from an IOM epidemiological study of heavy clay workers, for whom we hold both exposure estimates and radiographic results. In the present study, the prediction equations from the coalworkers��� study have been applied to the exposures of the heavy clay workers, with and without an allowance for a possible 15-year latency period for development of abnormalities following exposure. All the results predict levels of abnormality greatly in excess of the few cases observed. This lends support for the proposition that the quartz exposures in the two industries are of quite different potencies. Further investigation of health risks in the heavy clay industry may require follow-up of workers seen in the epidemiological study. “”