Determination of Noncancer Chronic Reference Exposure Levels

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Abstract

AMMONIA (Anhydrous ammonia; aqueous ammonia) Inhalation reference exposure level 100 m mg/m 3 (U.S. EPA-RfC) This document summarizes the evaluation of non-Critical effect(s) Hazard index target(s) cancer health effects by U.S. EPA for the RfC. Pulmonary function tests or subjective symptomatology in workers Respiratory system II. Description Colorless liquid Molecular formula NH 3 Molecular weight 17.03 g/mol Density 0.6818 g/cm 3 @ 20°C Boiling point-33.5° C Vapor pressure 6460 mm Hg @ 25°C Solubility Soluble in water, alcohol, and ether Conversion factor 1 ppm = 0.71 mg/m 3 III. Major Uses or Sources This strongly alkaline chemical is widely used in industry as a feed stock for nitrogen-based chemicals such as fertilizers, plastics and explosives (ATSDR, 1990). IV. Effects of Human Exposures Comparisons were made between 52 workers and 31 control subjects for pulmonary function and eye, skin and respiratory symptomatology (Holness et al., 1989). The pulmonary function tests included FVC (forced vital capacity – the total amount of air the subject can expel during a forced expiration), FEV 1 (forced expiratory volume in one second), FEF 50 (forced expiratory flow rate at 50% of the FVC) and FEF 75 (forced expiratory flow rate at 75% of the FVC). Age, height, and pack-years smoked were treated as covariates for the comparisons. The workers were exposed on average for 12.2 years to mean (time-weighted average) ammonia concentrations of 9.2 ppm (6.4 mg/m 3), while controls were exposed to 0.3 ppm (0.21 mg/m 3). No differences in any endpoints were reported between the exposed and control groups.

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