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Toxicological Risks of Selected Flame-Retardant Chemicals
Boric Acid
In the occupational setting, toxic effects following exposure to boron are generally acute, and include nosebleed, nasal irritation, sore throat, cough, and shortness of breath (IPCS 1998). Garabrant et al. (1984) found an increase in reports of eye irritation, dry mouth, nose or throat irritation, and productive cough in workers in a borax mining and refining plant. Chronic bronchitis, without any abnormal regions on a chest X-ray or impairment of pulmonary function, was also found in the borax plant (Garabrant et al. 1985). In a prospective study of workers exposed to sodium borate dust in a mine and processing plant, Wegman et al. (1994) found increased nasal, eye, and throat irritation, cough, and breathlessness. No long-term effects were found in that study.
Exposure to boric acid 6 hr/d, 5 d/wk had no effect on body weight gain, hematology, blood chemistry, urinalysis, or microscopic analysis in rats (77 mg/m3 for 24 wk; 175 mg/m3 for 12 wk, or 470 mg/m3 for 20 wk) or dogs (57 mg/m3 for 23 wk) (Wilding et al. 1959, as cited in ATSDR 1992).
Immunological Effects
No studies were identified that investigated immunological effects of boric acid following inhalation exposure. Data from three case reports suggest that inhalation exposure to high concentrations of zinc-containing compounds stimulates changes in immune parameters. Farrell (1987) reported that a worker developed hives and angioedema (suggestive of an immediate or delayed IgE response) following exposure to a low dose of zinc oxide fumes. The symptoms reappeared in a challenge test, suggesting a sensitization to zinc compounds. A correlation between exposure to zinc oxide and the proportion of activated helper-, inducer-, suppressor-, and killer-T-cells was observed among 14 welders approximately 20 hr after exposure to zinc oxide (77–153 mg Zn2+/m3) (Blanc et al. 1991, as cited in ATSDR 1994). Ameille et al. (1992) reported elevated levels of lymphocytes in the bronchoalveolar lavage fluid of a smelter worker exposed to unknown concentrations of zinc fumes. Cytokine responses have been observed in bronchoalveolar lavage after inhalation of zinc oxide fumes from welding (Blanc et al. 1993; Kuschner et al. 1995, 1997).
Marrs et al. (1988) did not observe abnormalities in the lymph nodes, thymus, or spleen tissue of female rats, mice, or guinea pigs killed 18 mo after a 20-wk exposure to zinc oxide/hexachloroethane smoke at concentrations as high as 119.3 or 121.7 mg Zn2+/m3 for 1 hr/d, 5 d/wk.
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