title: Noncancer inhalation toxicology of crystalline silica: exposure-response assessment.
abstract: Silicosis from inhalation of silica has long been recognized as an occupational hazard. Concern has arisen regarding the potential risk of silicosis from ambient silica (primarily quartz dust). This presentation reviews available data regarding ambient silica levels and estimates of the risk of silicosis at low exposure levels as they relate to the current U.S. Environmental Protection Agency National Ambient Air Quality Standards (NAAQS) for particulate matter. Current data indicate that for individuals not compromised by other respiratory ailments and for ambient environments expected to sustain 10% or less silica fraction in particulate matter with a mean aerodynamic diameter of < or = 10 microns (PM10), maintenance of the 50 micrograms/m3 annual NAAQS for PM10 is adequate to protect against fibrotic effects from ambient silica exposures. Issues such as the large divergence of risk estimates within the occupational setting (particularly at high cumulative exposures) and factors to consider for extrapolating risk in an occupational setting to risk from ambient exposure are discussed.
authors.affiliation: National Center for Environmental Assessment, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA. gift.jeff@epamail.epa.gov
authors.forename: J S
authors.initials: JS
authors.lastname: Gift
authors.forename: R A
authors.initials: RA
authors.lastname: Faust
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D000818:Animals; D004195:Disease Models, Animal; D004781:Environmental Exposure / Q000009:adverse effects / Q000592:standards; D006801:Humans; D016015:Logistic Models; D008452:Maximum Allowable Concentration; D016273:Occupational Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D011658:Pulmonary Fibrosis / Q000453:epidemiology / Q000209:etiology*; D011791:Quartz / Q000009:adverse effects; D018570:Risk Assessment; D012822:Silicon Dioxide / Q000009:adverse effects*; D012829:Silicosis / Q000453:epidemiology; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D011791:Quartz; D012822:Silicon Dioxide