Size-Resolved Sulfuric Acid Mist Concentrations At Phosphate Fertilizer Manufacturing Facilities In Florida

Strong inorganic acid mists containing sulfuric acid were identified as a ‘known human carcinogen ’ in a National Toxicology Program (NTP) report where phosphate fertilizer manufacture was listed as one of many occupational exposures to strong acids. To properly assess the occupational exposure to sulfuric acid mists in modern facilities, approved National Institute for Occupational Safety and Health (NIOSH) Method 7903 and a cascade impactor were used for measuring the total sulfuric acid mist concentration and size-resolved sulfuric acid mist concentration, respectively. Sampling was conducted at eight phosphate fertilizer plants and two background sites in Florida and there were 24 sampling sites in these plants. Samples were analyzed by ion chromatography (IC) to quantify the water-soluble ion species. The highest sulfuric acid concentrations by the cascade impactor were obtained at the sulfuric acid pump tank area. When high aerosol mass concentrations (100 mg m3) were observed at this area, the sulfuric acid mists were in the coarse mode. The geometric mean sulfuric acid concentrations (–geometric standard deviation) of PM23 (aerodynamic cut size smaller than 23 mm), PM10 and PM2.5 from the cascade impactor were 41.7 (–5.5), 37.9 (–5.8) and 22.1 (–4.5) mg m3, respectively. The geometric mean (–geometric standard deviation) for total sulfuric aci