ABSTRACT
Exposure to silica is still widespread. Some high-income countries have reduced exposure (Gerhardsson, 2002) and virtually eliminated the silica-associated diseases shown in Table 18.1, but silica is ubiquitous in the earth’s crust and has a large number of industrial applications; consequently, silica inhalation occurs globally in many
occupations. It is estimated that 1,026,000 workers in the USA in 2013 were exposed to silica at or above 25 µg/ m3 of air-a stringent but frequently cited workplace standard-and that approximately half of them had exposures above 100 µg/m3 (OSHA, 2013)—a common standard, but one that is too high to prevent silicaassociated diseases (HSE, 2005). In poorer countries, many millions are exposed, constituting approximately
11.5 million in India (Jindal, 2013) and over 2 million in Brazil (WHO, 2007). China is thought to have the largest number of people with silicosis, with 6000 new cases reported annually (Leung et al., 2012). Even with intensied prevention efforts, because of the large numbers currently exposed and the long latency of most of the conditions, silica-related diseases will present to practitioners for decades to come, albeit relatively rarely in many high-income countries.
