Toxicology and carcinogenesis studies of diethylamine (CAS No. 109-89-7) in F344/N rats and B6C3F1 mice (inhalation studies).

UNLABELLED

Diethylamine is used mainly as a chemical intermediate to produce the corrosion inhibitor N,N-diethylethanolamine and a lesser amount is used to produce pesticides and insect repellants and in rubber processing. Diethylamine was nominated for study by the National Institute of Environmental Health Sciences based upon its high production volume and ubiquitous natural occurrence in trace amounts and because of the lack of chronic toxicity and carcinogenicity data on the chemical. Male and female F344/N rats and B6C3F1 mice were exposed to diethylamine (approximately 99.9% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in bacterial mutagenicity tester strains and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study. The mean body weights of 250 and 500 ppm males and females and 125 ppm males were significantly less than those of the chamber controls. Clinical findings included lethargy, nasal/eye discharge, abnormal breathing, thinness, eye abnormalities, and discolored urine. The thymus weights of males exposed to 125 ppm or greater and females exposed to 500 ppm were significantly less than those of the chamber controls. Focal eye lesions were noted at necropsy in four males and three females exposed to 500 ppm and one male exposed to 250 ppm. Crusty noses were observed in most 500 ppm males and females and in two 250 ppm males. Suppurative inflammation, necrosis of the turbinates (except in one 125 ppm female), and squamous metaplasia of the respiratory epithelium of the nose were present in all rats exposed to 125 ppm or greater. Ulcer of the respiratory epithelium and atrophy of the olfactory epithelium occurred in all rats exposed to 250 or 500 ppm, and ulcer of the nasopharyngeal duct was present in all 500 ppm rats. Suppurative inflammation of the cornea was present in most rats exposed to 500 ppm. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. Two males and three females exposed to 500 ppm died during the first week of the study. The mean body weights of males and females exposed to 125 ppm or greater were significantly less than those of the chamber controls. Males and females exposed to 250 or 500 ppm lost weight during the study. Lethargy, abnormal breathing, and thinness were observed in most mice exposed to 250 or 500 ppm. Eye irritation and discharge, nasal discharge, and low fecal and urine output were noted in 500 ppm mice. Thymus weights of 250 and 500 ppm males and 125 ppm or greater females were significantly less than those of the chamber controls. Suppurative inflammation of the nose occurred in all males exposed to 250 or 500 ppm and all females exposed to 125 ppm or greater, and most males exposed to 125 ppm. Turbinate necrosis occurred in all exposed mice except one 31 ppm female. Squamous metaplasia of the respiratory epithelium and olfactory epithelial atrophy were seen in mice exposed to 125 ppm or greater. In the lung, the incidence of minimal chronic active inflammation of mainstem bronchi was significantly increased in 500 ppm males. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. There were significant exposure concentration-related decreases in sperm motility in 32, 62, and 125 ppm males; there were no significant differences in the lengths of estrous cycles between chamber control and exposed groups of females. Exposure-related nasal lesions were seen primarily in rats exposed to 62 or 125 ppm. These lesions included turbinate necrosis, suppurative inflammation, respiratory epithelial hyperplasia, squamous metaplasia of the respiratory epithelium, and olfactory epithelial atrophy. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. The mean body weights of 125 ppm males and females were significantly less than those of the chamber controls. There were significant exposure concentration-related decreases in sperm motility in males exposed to 32, 62, or 125 ppm; the estrous cycle of 125 ppm females was significantly longer than that of the chamber controls but only by half a day. Histopathologic changes were noted primarily in the nasal cavity and involved both the respiratory and olfactory epithelium of males and females principally in the 62 or 125 ppm groups. These lesions included suppurative inflammation, squamous metaplasia of the respiratory epithelium, olfactory epithelial atrophy, and necrosis of the turbinates. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, or 125 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of rats was similar to that of the chamber control groups. Mean body weights of males and females exposed to 125 ppm were less than those of the chamber controls after week 57. Increased incidences of eye abnormality occurred in exposed males and females. A spectrum of nonneoplastic lesions was observed in the respiratory and olfactory epithelium of the nose in exposed rats. The lesions included suppurative inflammation, ulceration of the respiratory epithelium, hyaline droplet accumulation in the glands of the respiratory epithelium, necrosis of the turbinates, squamous metaplasia of the respiratory epithelium, hyperplasia of the respiratory epithelium, atrophy of the olfactory epithelium, hyaline droplet accumulation in the respiratory and olfactory epithelium, basal cell hyperplasia of the olfactory epithelium, respiratory metaplasia of the olfactory epithelium, and goblet cell hyperplasia. The incidence of chronic inflammation of the pleura was significantly increased in 125 ppm females. The incidences of histiocytic cellular infiltration of the alveolus of the lung were significantly increased in all exposed groups of females and the incidence of chronic inflammation was significantly increased in 125 ppm females. In 125 ppm males, the incidence of suppurative inflammation of the cornea was significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to diethylamine vapor at concentrations of 0, 16, 31, or 62.5 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of mice was similar to that of the chamber control groups. Mean body weights of males and females were similar to those of the chamber controls. Eye abnormality was observed in greater incidence in exposed groups of males than in the chamber controls, and torso/ventral ulcer/abscess was observed in six 62.5 ppm males compared to none in the chamber controls. A similar spectrum of nonneoplastic lesions was seen in the nose of exposed mice as was seen in rats.

GENETIC TOXICOLOGY

Diethylamine was not mutagenic in either of two independent bacterial mutagenicity assays, each conducted with and without exogenous metabolic activation enzymes. Bacterial strains tested included Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 and Escherichia coli strain WP2 uvrA/pKM101. In addition to the negative results in the two bacterial assays, no significant increases in the frequencies of micronucleated erythrocytes were seen in peripheral blood of male or female B6C3F1 mice from the 3-month study.

CONCLUSIONS

Under the conditions of these 2-year inhalation studies, there was no evidence of carcinogenic activity of diethylamine in male or female F344/N rats exposed to 31, 62.5, or 125 ppm. There was no evidence of carcinogenic activity of diethylamine in male or female B6C3F1 mice exposed to 16, 31, or 62.5 ppm. Exposure to diethylamine resulted in increased incidences of nonneoplastic lesions of the nose in male and female rats and mice, of the cornea in male rats, and of the pleura and lung in female rats.