Toxicology of haloacetonitriles

Haloacetonitriles are by-products of water chlorination and may form in vivo from the reaction of residual chlorine with endogenous compounds such as amino acids. Dibromoacetonitrile (DBAN) was negative in selected mutagenic assays; dichloroacetonitrile (DCAN) was mutagenic in S. typhimurium, but not in S. cerevisiae. Both DBAN and DCAN may be carcinogenic. There is a paucity of basic toxicological data for these compounds. The studies described were conducted to determine the acute, subacute, and subchronic toxicity of DBAN and DCAN. The acute oral LD50 values (mg/kg) in mice and rats are: DBAN, mice: 289 (M), 303 (F); DBAN, rats: 245 (M), 361 (F); DCAN, mice: 270 (M), 279 (F); DCAN, rats: 339 (M), 330 (F). Death was preceded by slowed respiration, depressed activity, prostration, and coma. There were no apparent compound-related gross pathological effects. DBAN (in corn oil) was administered by gavage to male and female CD rats for 14 or 90 days at levels of 23, 45, 90, and 180 mg/kg/day or 6, 23, and 45 mg/kg/day, respectively. Mortality was 100% at 180 mg/kg and 40% (M) and 20% (F) at 90 mg/kg/day. Compound-related mortality was 10% (M) and 5% (F) at 45 mg/kg and 0% (M) and 10% (F) at 23 mg/kg during the 90-day study. No consistent, significant, adverse compound-related effects on any of the parameters evaluated were evident. Possible target organs might be spleen, thymus, and liver. The no-observed adverse-effect level (NOAEL) for 14 days was 45 mg/kg/day and for 90 days was 23 mg/kg/day. DCAN (in corn oil) was administered by gavage to male and female CD rats for 14 or 90 days at levels of 12, 23, 45, and 90 mg/kg/day or 8, 33, and 65 mg/kg/day, respectively. There were no deaths during the 14-day study. Compound-related mortality was 50% (M) and 25% (F) at 65 mg/kg, 10% (M) and 5% (F) at 33 mg/kg, and 5% (M) and 0% (F) at 8 mg/kg during the 90-day study. Body weights were significantly lower at 90 and 65 mg/kg/day; weight and ratios of spleen and gonads and cholesterol levels were significantly lower at 90 mg/kg/day. No consistent, significant adverse compound-related effects on any of the parameters evaluated were evident. The NOAEL for 14 days was 45 mg/kg/day and for 90 days was 8 mg/kg/day.