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: 117-81-7; Chemical Formula: C24H38O4

OSHA formerly had a limit of 5 mg/m3 TWA for di-sec-octyl phthalate. The ACGIH has a TLV-TWA of 5 mg/m3 and a TLV-STEL of 10 mg/m3, and these are the limits that were proposed. In the final rule, OSHA is retaining the 8-hour TWA limit of 5 mg/m3 and adding a 15-minute STEL of 10 mg/m3 for this light-colored, viscous, odorless, combustible liquid.

Di-sec-octyl phthalate (DEHP) is not acutely toxic in small laboratory animals via the oral route. The oral LD(5)0 reported for mice is 26.3 g/kg; for rats, it is 33.8 g/kg (Krauskopf et al. 1973/Ex. 1-495). No skin irritation or sensitization potential has been demonstrated in either animals or humans, and the lethal dermal dose in rabbits is about 25 ml/kg (Singh, Lawrence, and Autian 1972/Ex. 1-436). Shaffer, Carpenter, and Smyth (1945/Ex. 1-369) and Lawrence (unpublished data, as cited in ACGIH 1986/Ex. 1-3, p. 223) have reported deaths in rats and chronic diffuse inflammation of the lung in mice exposed to DEHP at unspecified levels.

Long-term dietary toxicity studies in rats, guinea pigs, and dogs have established a no-effect dose level of about 60 mg/kg/day, and no carcinogenic or histologic abnormalities were observed at this level (Gesler 1973/Ex. 1-481). Higher doses were associated with growth retardation and increased liver and kidney weights but not histologic abnormalities. Metabolic studies have demonstrated that laboratory animals do not appreciably metabolize DEHP (Dillingham and Autian 1973/ Ex. 1-477). Teratogenicity studies in pregnant rats indicated that fertility is unaffected at doses of 0.1, 0.2, or 0.33 percent of the acute intraperitoneal LD(50) dose for rats, although slight effects on embryonic and fetal development were observed in these animals; skeletal deformities were the most common teratogenic effects observed (Dillingham and Autian 1973/Ex. 1-477). Mutagenic effects were observed at intravenous doses of one-third, one-half, and two-thirds of the acute LD(50); these effects are consistent with DEHP’s ability to produce dominant lethal mutations (Dillingham and Autian 1973/Ex. 1-477).

A study of workers exposed to a mixture of the vapors of diethyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate reported that exposures to 1 to 6 ppm caused no peripheral polyneuritis (Raleigh, as cited in ACGIH 1986/Ex. 1-3, p. 223). However, Russian investigators examined male and female workers exposed to between 1.7 and 66 mg/m3 of various combinations of airborne phthalates (including butyl phthalate, higher aryl phthalates, dioctyl phthalate and others) and noted complaints of pain, numbness, and spasms in the upper and lower extremities after six to seven years of exposure. Polyneuritis was observed in 32 percent of the workers studied, and 78 percent of these workers showed depression of vestibular receptors (Milkov, Aldyreva, Popova et al. 1973/Ex. 1-646).

OSHA received a comment from the Chemical Manufacturers Association Phthalate Esters Program Panel (Ex. 3-900). Although the Panel did not oppose the proposed PEL for di-sec-octyl phthalate, it objected to this substance’s categorization as a neuropathic agent on the grounds that (1) confounding exposures to tricresyl phosphate and vinyl chloride, which are known neurotoxicants, occurred in the study referenced in the NPRM; and (2) other studies (in humans or animals) have not substantiated that this substance is neuropathic:

  • Including [di-sec-octyl phthalate] in this category of compounds [i.e., neuropathic agents] is not justified and could lead to improper labeling of the material or unwarranted regulations, and restrictions on the use of the material based on unfounded conclusions (Ex. 3-900, p.1).

In response to this comment, OSHA notes that the classification scheme used in the preamble to the proposed and final rules is not intended to have regulatory implications. As explained earlier in the preamble, OSHA is using this scheme simply to facilitate generic rulemaking; the various categories reflect the health endpoint used by the ACGIH or NIOSH as the point of reference in setting a limit. Most of the substances included in this rulemaking produce multiple health effects and could be classified in more than a single health effects category. Di-sec-octyl phthalate is no exception, and exposure to this substance has been associated with liver damage, testicular injury, and teratogenic and carcinogenic effects in experimental animals, as well as with possible neuropathic effects.

Another commenter, Lawrence H. Hecker of Abbott Laboratories, feels that the STEL for di-sec-octyl phthalate is unwarranted (Ex. 3-678, p. 8). OSHA disagrees with Dr. Hecker and finds that, for substances posing serious health hazards, such as those associated with di-sec-octyl phthalate exposure, the STEL further protects workers from the significant adverse effects that could occur in the short-term excursions above the TWA limit permitted in the absence of a STEL.

NIOSH concurs in OSHA’s selection of limits for di-sec-octyl phthalate but believes it should be designated as a potential occupational carcinogen (Ex. 8-47, Table N6A). On the other hand, the Chemical Manufacturers Association’s (Ex. 140) analysis of the evidence for DEHP’s carcinogenicity led the CMA to conclude that this substance is not a carcinogen. OSHA is aware of di-sec-octyl phthalate’s carcinogenic effects in experimental animals and notes that IARC has determined that sufficient evidence exists to designate it as an animal-positive carcinogen. However, adequate data are not available to evaluate the risk of cancer to humans. The Agency will continue to monitor the scientific evidence for di-sec-octyl phthalate and will re-evaluate this substance in the future if such evidence suggests that this is appropriate.

In the final rule, OSHA is retaining the 8-hour PEL of 5 mg/m3 and adding a 15-minute STEL of 10 mg/m3 for di-sec-octyl phthalate. The Agency concludes that these limits together will protect workers from the significant risks of neuropathic, hepatic, and other systemic injuries, which constitute material health impairments and are associated with exposure to this substance.