OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: 7783-41-7; Chemical Formula: OF2
The former PEL for oxygen difluoride was 0.05 ppm as an 8-hour TWA. The ACGIH has established a limit of 0.05 ppm as a ceiling value. The revision of the TLV for oxygen difluoride from an 8-hour TWA to a ceiling value reflects the general position of the ACGIH that ceiling TLVs are more appropriate for chemicals that cause acute but not chronic health effects. OSHA proposed a permissible exposure limit of 0.05 ppm ceiling for oxygen difluoride. NIOSH (Ex. 8-47, Table N1) concurred with the selection of this limit, and it is established in the final rule. Oxygen difluoride is an unstable, colorless gas with a foul odor.
Oxygen difluoride is a substance having extremely high acute toxicity; it is an acute irritant and causes fatal pulmonary edema and hemorrhage in animals exposed to 0.5 ppm for a few hours (ACGIH 1986/Ex. 1-3). A single exposure to 0.1 ppm also had an effect on the lungs, as evidenced by development in animals of a tolerance to the acute effects of this substance after an isolated exposure. Animals acutely exposed to oxygen difluoride have also exhibited gross changes in the kidneys and internal genitalia (LaBelle, Metcalf, Suter, and Smith 1945, as cited in ACGIH 1986/Ex. 1-3, p. 452; Lester and Adams 1965/Ex. 1-963). Only NIOSH commented on this substance.
Because of the extreme acute toxicity of this compound and the effects noted at 0.1 ppm, the former TWA-PEL of 0.05 ppm was not sufficiently protective of workers; this former limit would still permit the brief periods of high exposure that have been associated with severe lung damage, which the Agency has determined represents a material impairment of health. Therefore, to reduce the significant risk of acute lung damage associated with brief excursion exposures to oxygen difluoride, OSHA is establishing a ceiling limit of 0.05 ppm for this substance.
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