A finalised review has been issued by the EPA describing the scientific basis for the human health hazard and dose-response assessments of inhaled Libby amphibole asbestos (LAA) in connection with IRIS (the Integrated Risk Information System database, available via http://www.epa.gov/iris/index.html).

An inhalation reference concentration (RfC) of 9 x 10-5 fibres/cm3 of air was calculated, based on localised pleural thickening (associated with decreased lung function) in exposed workers. (The RfC is an estimate of a continuous inhalation exposure that is likely to be without an appreciable risk of non-cancer deleterious effects to humans, including sensitive subgroups, exposed throughout their lives.)

Under the EPA guidelines for carcinogen risk assessment, LAA is also “carcinogenic to humans” following inhalation exposure based on convincing evidence of a causal association between exposure to LAA fibres and increased lung cancer and mesothelioma mortality. An inhalation unit risk (IUR) value of 0.17 per fibre/cm3 was proposed [so exposure to about 6 x 10-5 fibres/cm3 would be associated with an additional lifetime cancer risk of 1 in 100,000].

US Environmental Protection Agency (EPA). National Center for Environmental Assessment (NCEA). Toxicological review of Libby amphibole asbestos in support of summary information on the Integrated Risk Information System (IRIS). (Note: This document is an assessment of the noncancer and cancer health effects associated with the inhalation route of exposure only.) Final review (dated December 2014), EPA/635/R-11/002F. http://www.epa.gov/iris/toxreviews/1026tr.pdf

 

The above items were taken from the January/February 2015 issue of Toxicology and Regulatory News which is sent automatically to members of bibra (click here)

 

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