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National Research Council (US) Committee on Acute Exposure Guideline Levels. Eighteenth Interim Report of the Committee onAcute Exposure Guideline Levels. Washington (DC): National Academies Press (US); 2010.
Eighteenth Interim Report of the Committee onAcute Exposure Guideline Levels.
Show detailsAt its meeting held on June 15-18, 2010, the committee reviewed the AEGL TSD on nitric acid. A presentation on the TSD was made by Gary Diamond, of Syracuse Research Corporation. The following is excerpted from the Executive Summary of the TSD:
Nitric acid is a highly corrosive, strongly oxidizing acid…. For derivation of the AEGL values, both human and animal data were utilized. For AEGL-1 a concentration of 0.53 ppm was adopted for all time points…. The derived AEGL-1 value is above the odor threshold which provides a warning of exposure before an individual could experience notable discomfort…. AEGL-2 and -3 values were based on a lethality study in rats. The point of departure is a NOAEL for AEGL-2 effects and would not be escape impairing; higher concentrations resulted in more severe clinical signs including partially closed eyes and lung noise…. AEGL-3 was based on an estimated LC01 calculated by a log-probit analysis from the lethality study in rats.”
Specific Comments
AEGL-1
The committee recommends an uncertainty factor of 10 for intraspecies differences, because nitric acid exhibits a wide range of responses from healthy or asthmatic individuals and the Sackner and Ford (1981) study used healthy individuals.
AEGL-2
The transient body-weight loss used to derive AEGL-2 values is not an appropriate end point for this guideline level. The study reported partially closed eyes, a borderline AEGL-2 effect, and gasping at the next highest test concentration of 1,600 ppm, an AEGL-2 effect. Thus, the committee recommends a POD of 1,600 ppm for derivation of the AEGL-2 values for nitric acid.
AEGL-3
The committee approved the derivation of the AEGL-3 values for nitric acid.
Other Comments
References to red fuming nitric acid (RFNA) should be removed and inserted into the TSD on oxides of nitrogen.
Nitric acid may exist in the following airborne forms: gas, vapor, mist, fume, and aerosol. The TSD should point out that mist will probably be scrubbed in the mouth or nasal passages, gas and vapor in the upper respiratory tract, and fume and aerosol in the alveolar region.
Page 9, lines 13-23: This case report involves the contact of nitric acid and zinc. Consideration should be given to the reaction of these compounds. Did the authors attribute the effects to only nitric acid? Because the reference was published in 1905, consideration should be given to deleting it.
Page 10, lines 15-21: This case report involved exposure to what was probably nitrogen monoxide (see TSD, page 11, line 37), so the committee recommends removing this reference because it does not involve exposure to nitric acid.
Page 13, line 19: Because all the studies involved exposures to nitric acid fumes, justification should be provided to apply these studies to the vapor and mist forms.
Page 15, lines 5-23: This study compared the toxicities of nitrogen dioxide, RFNA, and white fuming nitric acid (WFNA). Nitric acid produces a white fume, and RFNA (also known as IRFNA-inhibited red fuming nitric acid) produces a red fume, which is due to the nitrogen dioxide. It is likely that there are two different agents for WFNA and RFNA. As noted above, it would be appropriate to remove discussion of RFNA from this TSD.
Page 19, lines 21-28: Why was the Goldstein reference not discussed in Section 3 (Animal Toxicity Data)?
Comment Reference
- Sackner, M.A., and D. Ford. 1981. Effects of breathing nitrate aerosols in high concentrations for 10 minutes on pulmonary function of normal and asthmatic adults, and preliminary results in normals exposed to nitric acid fumes. Am. Rev. Respir. Dis. 123(4):151.
- NITRIC ACID - Eighteenth Interim Report of the Committee onAcute Exposure Guidel...NITRIC ACID - Eighteenth Interim Report of the Committee onAcute Exposure Guideline Levels
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