There was no previous OSHA limit for vinyl acetate. OSHA proposed establishing a 10-ppm TWA and a 20-ppm STEL for this substance, based on the ACGIH recommendation, and the final rule establishes these limits. Vinyl acetate is a volatile liquid that polymerizes in light to a colorless, transparent mass and usually contains an inhibitor, such as hydroquinone.
The basis for the proposed limits is an epidemiologic report by Deese and Joyner (1969/Ex. 1-412) describing 15 years of industrial experience with vinyl acetate production. These authors reported that vinyl acetate is not a significant irritant at exposure levels of 5 to 10 ppm but causes cough and hoarseness at around 22 ppm. They also found no evidence of adverse chronic effects resulting from exposure to 5 to 10 ppm, as determined from medical records and examinations. While conducting air sampling for the study, the primary author (Deese) experienced hoarseness at concentrations of 4.2 to 5.7 ppm, and eye irritation at 5.7 to 6.8 ppm. Three chemical operators and one technician did not report any subjective responses at these levels. The ACGIH (1986/Ex. 1-3, p. 621) also cited a personal communication from the Mellon Institute (1968) stating that vinyl acetate concentrations of less than 5 ppm are detectable by odor, although some individuals may detect the odor at concentrations of 0.5 ppm (Mellon Institute 1968, as cited by ACGIH 1986/Ex. 1-3, p. 621).
NIOSH (1978i, as cited in ACGIH 1986/Ex. 1-3, p. 621) reviewed these data and concluded that the recommended exposure limit be designed to protect even the most sensitive individuals from sensory irritant effects. Since the lowest level reported to cause upper respiratory tract irritation was 4.2 ppm (Deese and Joyner 1969/Ex. 1-412), NIOSH recommended that workplace exposures not exceed 4 ppm measured over a 15-minute period. In its prehearing submission (Ex. 8-47, Table N2), NIOSH continued to recommend its earlier limit.
The NIOSH REL of 4 ppm (ceiling) relies on a report concerning the experience of a single individual; in contrast, the limits being established today are based on a 15-year epidemiology study that suggests that a 10-ppm TWA and a 20-ppm STEL will provide protection against the risk of irritation associated with exposure to vinyl acetate at higher levels. OSHA considers the irritation caused by exposure to vinyl acetate a material impairment of health. Therefore, the Agency is promulgating this 8-hour TWA and STEL combination as the revised limits for vinyl acetate.