n-BUTYL GLYCIDYL

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: 2426-08-6; Chemical Formula: C₄H₉OCH₂CH₂OH

The former OSHA limit for n-butyl glycidyl ether was 50 ppm as an 8-hour TWA. The ACGIH-recommended TLV is 25 ppm; NIOSH has recommended that occupational exposure to n-butyl glycidyl ether not exceed 5.6 ppm as a 15-minute short-term level. The proposed PEL was 25 ppm as an 8-hour TWA, and the final rule promulgates this limit. n-Butyl glycidyl ether is a clear, colorless liquid.

OSHA’s former PEL of 50 ppm, which was adopted from the ACGIH’s 1968 TLV list, was based on a Dow Chemical Company report (cited in ACGIH 1986/Ex. 1-3) that showed that repeated applications of n-butyl glycidyl ether to the skin of humans caused irritation and sensitization; at the time, the ACGIH concluded that a limit of 50 ppm would prevent these irritant responses. Subsequently, the ACGIH reduced the TLV to 25 ppm, noting that the 50-ppm limit was only 13 times lower than the 8-hour LC(50) (670 ppm) reported for this chemical in rats, and that a wider margin of protection was desirable.

The NIOSH limit of 5.6 ppm was recommended in the Institute’s June 1978 criteria document on glycidyl ethers (NIOSH 1978d/Ex. 1-232). This limit was based, in large part, on mutagenic studies conducted in microbial and mammalian test systems, as well as on some evidence for other members of the glycidyl ether family showing that exposure is associated with testicular atrophy and hematopoietic abnormalities in laboratory animals. After publication of its Criteria Document, NIOSH received a confidential report prepared for the Shell Development Company by Anderson et al. (1957, as cited in ACGIH 1986/Ex. 1-3, p. 81), who had conducted a rat inhalation study. In this research, rats were exposed to 38 ppm, 75 ppm, 150 ppm, or 300 ppm n-butyl glycidyl ether for seven hours daily, five days per week for 10 weeks. Atrophic testes were found in 5 of 10 rats exposed to 300 ppm, very small testes were found in 1 of 10 rats exposed to 150 ppm, and patchy atrophy was found in the testes of 1 of 10 rats exposed to 75 ppm. No effects were observed in rats exposed at 38 ppm. Based on this additional evidence, NIOSH reaffirmed its REL for n-butyl glycidyl ether in a current intelligence bulletin (NIOSH 1978p, as cited in ACGIH 1986/Ex. 1-3, p. 81).

The Workers Institute for Safety and Health (WISH) and the AFL-CIO submitted posthearing comments on butyl glycidyl ether (Exs. 116, 194). These commenters opposed OSHA’s proposal to adopt the ACGIH TLV for this substance on the basis of the reproductive study published in a NIOSH CIB (discussed above) which shows testicular atrophy in exposed laboratory animals. According to WISH:

• OSHA’s review of this substance in the proposal attempts to state that the 25 ppm ACGIH level is protective against these reproductive effects because a no-effect level of 38 ppm was observed (Ex. 116).

WISH found this conclusion unjustifiable because of the short exposure period (10 weeks) used in the study establishing the NOEL for reproductive effects and because considerable uncertainty always surrounds no-effect-level studies. In addition, WISH pointed out that “fertility in rats is less sensitive to certain testicular effects than human fertility” and, therefore, that this animal is not the best predictor of human reproductive effects (Ex. 116). In response to these comments, OSHA wishes to clarify that the Agency did not intend to imply in the proposal that the 25-ppm limit would protect against all risk of possible reproductive effects. In fact, the proposal merely noted that 25 ppm was below the no-effect level for reproductive effects in rats. The Agency agrees with WISH that the use of a longer exposure period in the Anderson et al. (1957, as cited in ACGIH 1986/Ex. 1-3, p. 81) reproductive study might have established a lower NOEL.

However, based on the existing evidence for reproductive effects linked to n-butyl glycidyl ether exposure, OSHA concludes that reducing the PEL from 50 ppm to 25 ppm will substantially reduce the significant risk of these reproductive effects and will also protect workers against the irritation and sensitization effects, all of which constitute material health impairment caused by exposure to this chemical. The Agency notes that NIOSH’s REL of 5.6 ppm (15-minute STEL) is based on the result of in vitro testing in both microbial and mammalian systems; extensive extrapolation is required to predict effects in humans on these bases. The final rule establishes a permissible exposure limit of 25 ppm TWA for n-butyl glycidyl ether.