[A survey on workers' individual exposure to crystalline silica in the building industry]

The wide-spread presence of silica in nature and the variety of materials containing it cause crystalline silica exposure of workers in various industrial activities. Moreover crystalline silica is classified as carcinogenic to humans (Group 1) by IARC, in relation to its possible lung carcinogenicity.

The purpose of this paper was to assess respirable particles and crystalline silica exposure of workers in a number of some building sites located in the area of a Local Health Unit in the Umbria region. The study examined differences in four types of building sites: "construction of new buildings", "renovation of old buildings", "road construction" and "transport of aggregates by loaders in crushing plants". According to the strategy suggested by European Standard EN 689/1997, personal air samples were collected during work in jobs characterized by elevated amounts of widespread dust.

Analysis of data showed that levels of exposure to crystalline silica were lower than the limits recommended by ACGIH/2010 in almost all samples except one. The percentages of crystalline silica in respirable particles were in the range 0.4%-21%. Crystalline silica exposure levels were different in the various jobs and comparison between the mean values of exposure levels in each one showed statistically significant differences (p < 0.01, variance analysis). Work with the highest exposure to crystalline silica were: brick cutting, plaster brushing, "Serena stone" cutting, as they use tools operating at high speed and often in dry conditions (grinder, power drill, pneumatic hammer), producing low-size airborne particles (respirable fraction). During work in these jobs levels of worker exposure to crystalline silica showed high variability, so that it was impossible to establish if in the medium-long term, they were lower than the Threshold Limit Values with a set probabilistic certainty (OTL test, confidence level 95%). In the remaining jobs the assessment of occupational exposures to crystalline silica showed a low probability of exceeding the Threshold Limit Values.