OSHA's previous exposure limit for furfural was an 8-hour TWA limit of 5 ppm, with a skin notation. The Agency proposed reducing this limit to 2 ppm TWA and retaining the skin notation, based on the ACGIH recommendation; these limits are established in the final rule. Furfural is a colorless, oily liquid that turns rust-colored when exposed to air and light.
An inhalation exposure to 260 ppm of furfural was fatal to rats but not to mice or rabbits. A four-week exposure of dogs to 130 ppm for six hours a day caused liver damage, but no adverse effects were observed at 63 ppm (AIHA 1965, as cited in ACGIH 1986/Ex. 1-3, p. 280).
Bugyi and Lepold (1949/Ex. 1-1077) described numbness of the tongue and oral mucosa, absence of a sense of taste, and labored breathing in workers exposed to furfural (at unspecified levels) in a poorly ventilated facility. Korenman and Resnik (1930, as cited in ACGIH 1986/Ex. 1-3, p. 280) stated that inhalations of from 1.9 to 14 ppm furfural caused headaches, itching throat, and eye irritation; Kuhn (1944/Ex. 1-883) reported that exposure to furfural damages the eyesight in some individuals. NIOSH (1975e/Ex. 1-1183) described widespread eye and respiratory tract irritation in workers at a grinding wheel plant exposed to furfural vapor at levels ranging from 5 to 16 ppm. NIOSH (Ex. 8-47, Table N2; Tr. p. 3-86) did not concur with the proposed limit on the basis of these findings and, in addition, urged the Agency to follow up on a recent NTP assay with regard to a possible carcinogenic response in animals exposed to furfural. OSHA notes that Dunlop and Peters (1953/Ex. 1-1189) report that a 15-year study of furfural use in the synthetic resin industry revealed that this substance is not hazardous to employee health in facilities that are adequately ventilated, and that only occasional individual sensitivity was found. The Agency will carefully monitor the results of the NTP Study, currently in peer review, as well as any other scientific evidence pertaining to the health effects of furfural. NIOSH was the only commenter on this substance in the rulemaking record.
After reviewing the evidence above, OSHA concludes that its former 5-ppm TWA limit is not sufficient to protect workers from eye and respiratory tract irritation; this is evidenced by the NIOSH study (1975e/Ex. 1-1183), in which widespread irritation was reported to occur among workers exposed to 5 to 16 ppm. OSHA considers the eye and respiratory tract irritation caused by exposure to furfural to be material impairment of health. Therefore, to protect workers from eye and respiratory tract irritation, OSHA is revising its limit for furfural to 2 ppm as an 8-hour TWA; this limit is established in today's rule. OSHA is also retaining its skin notation; Sax and Lewis (Dangerous Properties of Industrial Materials, 7th ed., 1989) reported the dermal LD(50) in rabbits to be 620 mg/kg, indicating that furfural penetrates the skin and can cause systemic effects.