2,3-dichlorobuta-1,3-diene

Endpoint summary

Description of key information

There are no standard studies on the repeated dose toxicity of 2,3 dichloro-1,3 butadiene following oral or dermal exposures. No effects attributed to 2,3 dichloro-1,3 butadiene were observed in a sub-acute repeated dose inhalation study in which rats were exposed to vapours at 0.4 mg/l. In a one-generation, repeated dose inhalation exposures to 2,3 dichloro-1,3 butadiene at 0, 1, 5 or 50 ppm, A NOEL of 5 ppm (25 mg/m3) was reported based on observations of decreased body weight, weight gain and food consumption parameters and degeneration of the nasal olfactory epithelium at 50 ppm. 

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEC

25 mg/m³

Study duration:

subchronic

Species:

rat

Additional information

There are no standard studies on the repeated dose toxicity of 2,3 dichloro-1,3 butadiene following oral or dermal exposures.

No effects attributable to 2,3 dichloro-1,3 butadiene were observed in a sub-acute repeated dose inhalation study, in which 10 male Crl:Cd rats were exposed to vapours at a concentrations of 0.4 mg/l for 6 hours/day, 5 days/week for 2 weeks (control rats were simultaneously exposed to air only). No effects on clinical parameters or microscopic changes were observed in treated rats. Although liver mitotic parameters were slightly increased following the 10th exposure, levels were normal following 14 days of recovery. The significance of this change is not clear since no other morphologic alterations were observed. The mean relative liver weights of treated rats were significantly higher that controls after the 10th exposure but were normal after 14 days of recovery. Treated rats had significantly lower body weights than controls during the exposure period, but showed a normal rate of weight gain during recovery. The relative testing weights of test rats were significantly higher than that of controls after 14 days recovery. In the absence of any microscopic changes, the relevance of this weight change is questionable

The sub-chronic repeated dose inhalation toxicity of 2,3 dichloro-1,3 butadiene was investigated in a one-generation fertility and early embryonic developmental study in which groups of Crl:CD®(SD)IGS BR rats (24/sex/concentration) were exposed by whole body inhalation to vapours at 0, 1, 5, or 50 ppm. Rats were exposed for 6 hours/day during premating (8 weeks; 5 days/week), during cohabitation of mating pairs (up to 2 weeks, 7 days/week), and then post-cohabitation for males and nonpregnant females (approximately 7 days, 7 days/week). The pregnant dams were exposed from conception to implantation (days 0-7 of gestation). In parental rats, no treatment-related effects were observed on mortality, clinical parameters, oestrous cycle and sperm parameters, mating, precoital interval and fertility, gross observations and organ weights. Treatment-related effects evident at 50 ppm were decreased body weight and weight gain, food consumption and efficiency and degeneration of the nasal olfactory epithelium.

The no-observed-effect level (NOEL) for the sub-chronic repeated dose inhalation toxicity of 2,3 dichloro-1,3 butadiene in rats was reported as 5 ppm (25 mg/m3) based on observations of reduced body weight, bodyweight gain and food consumption parameters and degeneration of the nasal olfactory epithelial toxicity at 50 ppm.

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: nose

Justification for classification or non-classification

There is insufficient evidence to classify 2,3 dichloro-1,3 butadiene for repeated dose toxicity