NITROGLYCERIN

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: 55-63-0; Chemical Formula: CH₂NO₃CHNO₃CH₂NO₃

The former OSHA PELs for ethylene glycol dinitrate (EGDN) and nitroglycerin (NG) were ceilings of 0.2 ppm which were equivalent to 1 mg/m³ and 2 mg/m³, respectively, both with skin notations. The proposed PELs for these substances were 20 minute STELs of 0.1 mg/m³, (0.02 and 0.01 ppm, respectively) and NIOSH (Ex. 8-47, Table N1) supported the proposal (which was based on NIOSH’s recommended limits). The ACGIH (1986/Ex. 1-3) has established a TLV-TWA of 0.05 ppm (0.3 mg/m³) for EGDN and a TLV-TWA of 0.05 ppm (0.5 mg/m³) for NG, both with skin notations. In the final rule, OSHA is establishing 15-minute STELs of 0.1 mg/m³ for EGDN and NG and retaining the skin notations for these substances. EGDN is a yellowish, oily, explosive liquid, and NG is a pale yellow, viscous liquid.

Most occupational exposures to EGDN actually involve mixtures of EGDN and NG. Because EGDN is 160 times more volatile than nitroglycerin and most of the mixtures of these two substances used in industry consist of 60 to 80 percent EGDN, the adverse effects associated with the inhalation of the vapors from such mixtures can be attributed primarily to EGDN.

Trainor and Jones (1966/Ex. 1-107) reported that exposure to EGDN:NG at a level of 0.7 mg/m³ for 25 minutes was sufficient to produce decreased blood pressure and a slight headache in humans. These authors also reported that workers at a munitions plant developed headaches when exposed to EGDN:NG concentrations between 0.1 and 0.53 mg/m³ (0.36 mg/m³ average). Morikawa, Muraki, Ikoma et al. (1967/Ex. 1-55) found that workers in an explosives plant exposed to low concentrations of EGDN:NG (0.066 ppm (approximately 0.5 mg/m³) was the highest average level) had a much higher incidence of abnormal pulse waves than did controls (143 out of 1,271 versus 0 out of 175). Abnormal pulse waves often indicate a clinically significant defect in the functioning of the heart and/or circulatory system (Braunwald 1978/Ex. 1-1001).

In its criteria document for NG and EGDN, NIOSH (1978h/Ex. 1-234) refers to a report of a dynamite worker who died when exposed to EGDN:NG concentrations between 0.3 and 1.4 mg/m³, as well as to another report of two workers who died suddenly following exposure to EGDN:NG at concentrations ranging from 1.7 to 2.7 mg/m³. NIOSH (1978h/Ex. 1-234) observed that skin absorption may have contributed significantly to the exposures causing these deaths.

OSHA received several comments on EGDN and NG (Exs. 3-661, 8-66, 121, 190, and 154). These commenters raised two issues: the technological and economic feasibility of the proposed limits, and the strength of the evidence and significance of the adverse effects associated with exposure to EGDN and NG.

In regard to the issue of technological and economic feasibility, which was raised by ICI Americas, Inc. (Ex. 154) and the Institute of Makers of Explosives (IME) (Ex. 121), OSHA has reviewed the record and has concluded that explosive manufacturers will be able to meet these limits through a combination of equipment improvements and respiratory protection. OSHA believes that, if compliance cannot be achieved via engineering controls and/or process improvements, air-supplied respirators with quick-release couplings could be used to achieve the final rule’s limits. The Agency’s reasoning is discussed in detail in the Technological Feasibility section of the preamble (Section VII).

On the second point addressed by commenters, the meaning of the health effects observed to occur in connection with exposure to EGDN:NG, the IME states that:

• [T]he NIOSH Criteria Document relied upon in the… [proposal] was based on outdated and irrelevant information. Its findings are based on exposure conditions and data that, because of industry-initiated improvements, was not reflective of the improved conditions in NG/EGDN-manufacturing plants…in 1978, and is not reflective of the greatly improved conditions prevailing in plants at the present time….industry hygiene programs…[have] eliminated the bulk of…workplace exposure[s] (Ex. 190, p. 4).

According to the IME, OSHA’s proposal did not “identify any significant health risk” of EGDN:NG exposure at the former PEL; the IME asserts that “headaches are transitory phenomena which pose no significant health risk” (Ex. 190, p. 5).

OSHA does not share the IME’s view of the significance of chemically induced headaches. The Agency believes that such headaches impair performance, cause pain and suffering, affect the safety of the victim and his or her co-workers, and contribute to absenteeism. In the case of EGDN:NG-induced headaches, however, headaches have a greater meaning: they are an early warning of vasodilation, an indicator of systemic toxicity. OSHA also finds the report of an EGDN:NG-induced death in an explosives manufacturing facility both convincing and troubling. The Agency continues to be persuaded by the evidence in the Trainor and Jones (1966/Ex. 1-107) study, the NIOSH criteria document (1978h/Ex. 1-234), and the Morikawa, Muraki, Ikoma et al. (1967/Ex. 1-55) study that the health effects associated with exposure to very low levels of EGDN:NG (i.e., in the range of 0.1 to 1.4 mg/m³) are acute, may occur after brief exposures, and have been shown to be lethal.

According to NIOSH (Ex. 150, Comments on EGDN:NG), the 15-minute 0.1 mg/m³ limits being established in the final rule will protect against “angina pectoris, other signs and symptoms of cardiac ischemia or heart damage, and against sudden death…since all of these…seem to be related to compensatory vasoconstriction induced by repeated exposure to NG or EGDN” (Ex. 150). NIOSH also reports that a preliminary study of mortality resulting from heart disease and other causes among NG workers by Reeve, Bloom, Rinsky, and Smith (1983a and 1983b, as cited in Ex. 150) suggests an association between NG exposure and cardiovascular disease mortality; at the facilities where this increase in cardiovascular disease occurred, exposures were being maintained near or below 0.02 ppm (0.2 mg/m³) (Ex. 150).

Hypotension and headache have been observed in populations exposed to EGDN:NG at levels below 0.5 mg/m³ for brief periods (25 minutes), and fatalities have occurred after EGDN:NG exposures at concentrations between 0.3 and 1.4 mg/m³, in one instance, and between 1.7 and 2.7 mg/m³, in another. OSHA’s former standard was 1.0 mg/m³; since worker deaths have occurred at or near this level, OSHA is establishing short-term limits for EGDN and NG of 0.1 mg/m³ and retaining the skin notations for these substances in the final rule. OSHA concludes that these limits are necessary to prevent fatalities and to protect against the significant risks of vasodilation and cardiac effects associated with exposures to EGDN:NG in the workplace. The Agency has determined that the cardiovascular effects caused by EGDN:NG represent material impairments of health. Because EGDN:NG is readily absorbed through the skin and can produce systemic effects by this exposure route (Tr. pp. 9-149 to 9-150), OSHA is retaining the skin notations for both substances.