Development of an exposure matrix for respirable crystalline silica in the British pottery industry

Processes associated with occupational exposure to respirable crystalline silica in the British pottery industry were investigated to develop estimates of worker exposures from 1930 to 1995. Information was derived from more than 1300 air samples, published literature and unpublished reports of dust control innovations and process changes. A matrix was developed specifically to support a mortality study of 5115 pottery workers in North Staffordshire, UK. Matrix values range from 2 micrograms/m3 for pottery support activities performed in the 1990s to 800 micrograms/m3 for firing activities in the 1930s. Although exposure estimates within decade varied, median concentrations for all process categories displayed an overall trend towards progressive reduction in exposure during the 65 year span. Potential methods to validate the matrix as well as sources of error are discussed.