HEXACHLOROCYCLOPENTADIENE

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: 77-47-4; Chemical Formula: C₅Cl₆ .

No previous OSHA limit existed for hexachlorocyclopentadiene. The Agency proposed to establish a 0.01-ppm 8-hour TWA limit for this substances, based on the ACGIH (1986/Ex. 1-3) recommendation; NIOSH (Ex. 8-47, Table N1) concurred with this proposal, and the final rule adds this limit to the Z table. Hexachlorocyclopentadiene is a yellow to amber-colored, non flammable liquid with a pungent odor.

Hexachlorocyclopentadiene has a high order of acute toxicity in laboratory animals. Rabbits, mice, rats, and guinea pigs died from inhaling 89.5 percent of the vapor in air (Treon, Cleveland, and Cappel 1955/Ex. 1-497). In 150 daily exposures of seven hours each, rabbits, rats, and guinea pigs survived concentrations of 0.15 ppm, but a similar exposure was fatal to four of five mice. At approximately twice this concentration, mice, rats, and most rabbits died by or before the 25th exposure, but guinea pigs survived 30 exposures. The hexachlorocyclopentadiene vapors caused tearing, labored respiration, and, at high concentrations, tremors. Treon and associates (1955/Ex. 1-497) observed degenerative changes in the brain, heart, liver, adrenal glands, and kidneys, and pulmonary irritation occurred in all species, even at the lowest concentration of 0.15 ppm. At higher concentrations, pulmonary edema, hyperemia, necrotizing bronchitis, and bronchiolitis were observed (Treon, Cleveland, and Cappel 1955/Ex. 1-497).

In humans, there are few data concerning hexachlorocyclopentadiene’s toxicity. Irritation is known to occur, but the intolerable odor and eye irritation associated with exposure to this substance have discouraged prolonged exposures (McGilvray 1971, as cited in ACGIH 1986/Ex. 1-3, p. 300).

The New Jersey Department of Public Health (Exs. 144, 144A) urged OSHA to establish a PEL for hexachlorocyclopentadiene on the basis of EPA’s IRIS data. The use of this approach is discussed in Section VI.A of the preamble.

The proposed TWA PEL of 0.01 ppm for this severely toxic substance is about 10 times below the level associated with systemic damage and pulmonary irritation in experimental animals. In the absence of any limit on exposure, OSHA finds that employees are at significant risk of intense eye and pulmonary irritation and multiple organ damage; the Agency considers these effects to be material impairments of health and functional capacity. To substantially reduce these risks, OSHA is establishing an 8-hour TWA limit of 0.01 ppm for hexachlorocyclopentadiene.