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NIOSH Testimony on the Occupational Safety and Health Administration Proposed Rule: Occupational Exposure to Benzene, Part 2, by J. D. Millar, March 1986.

NIOSH 1986 Mar:10 pages
This testimony concerned data contained in a study dealing with mortality in the chemical industry as a result of exposure to benzene (71432) causing increased incidences of lymphatic and hematopoietic cancer. NIOSH took the position that exposure to peak concentrations of benzene at less than 25 parts per million (ppm) was associated with a relative risk of 3.38 for these diseases. It was not specified whether these peak exposures occurred alone or as part of an otherwise constant exposure pattern. The relative risk was still well above 1.0. Two other cases classified in the continuous exposure group had spent most of their work time in intermittent exposure jobs and only a modest amount of time in continuously exposed jobs. The absence of a dose/rate effect was not a particularly surprising finding to NIOSH, and was not considered to discount the need for a limit on short term exposures. Cumulative dose was important and the ability of benzene to accumulate in the body must be carefully examined. Once inside the body, benzene is not uniformly distributed, but concentrates in the bone marrow of experimental animals where it can be metabolized. Benzene metabolites can covalently bind to bone marrow DNA and inhibit RNA synthesis. Single exposures to benzene at low doses have produced increased in the numbers of micronuclei and sister chromatid exchanges in rats. Benzene metabolites have been shown to produce an increased frequency of sister chromatid exchanges in cultured human lymphocytes. Responses to additional specific questions concerning NIOSH's view of benzene research were provided.
NIOSH-Author; NIOSH-Testimony; Millar-J-D; Laboratory-animals; Benzene-poisoning; Cancer-rates; Mortality-rates; Epidemiology; Risk-analysis; Leukemogenesis; Hematopoietic-system; Carcinogens;
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NIOSH, 10 pages
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division