Phosphorus trichloride

Endpoint summary

Description of key information

Older proprietary studies of toxicity by the oral, dermal and inhalation routes are available.  Supporting published data are also available.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

18 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

592 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

1 260 mg/kg bw

Additional information

Acute oral toxicity

The acute oral LD50 of phosphorus trichloride was found to be 200 mg/kg bw and 540 mg/kg bw in the rat in older proprietary studies comparable to OECD 401 (Terrell, 1977; Lesit & Weigand, 1978). A further published study (Molodkina, 1973) reports an LD50 value of 550 mg/kg bw. However a much lower value of 18.0 mg/kg bw was determined in another study (Randall & Robinson, 1990). The wide variation in acute oral LD50 values may be a consequence of the dose vehicle: vegetable/corn oil was used as a vehicle in the studies of Terrell and Molodkina, however the study of Randall & Robinson did not use a dosing vehicle. The consequent rapid and violent reaction of the test substance in the stomach may therefore potentiallty have caused much greater toxicity.

Acute inhalation toxicity

In a proprietary acute inhlation toxicity study (Cannon, 1977), no deaths (0/10) occurred in rats exposed to a nomimal exposure concentration of 20.29 mg/L. However the study is not considered to be sufficiently reliable in the absence of any analytical data on the exposure concentration. An additonal published study by Molodkina (1973) reported an analytical LC50 of 0.22 mg/L. An additional study (Hollander & Mayer, 1977) reported mortaility in rats exposed for very brief periods. A good quality published study (Weeks et al, 1964) reports analytical LC50 values for 4 -hour exposures of 0.592 mg/l in rats and 0.285 mg/l in guinea pigs.

Acute dermal toxicity

In the acute dermal toxicity study in the rabbit (Imlay, 1977), no deaths occurred at a dose level of 250 mg/kg bw (0/13 animals tested), however the single animal tested at 500 mg/kg bw died. Based on the results of this study, the acute dermal LD50 of the substance is calculated to be between 250 -500 mg/kg bw, but is considered likely to be closer to 500 mg/kg bw. In a further rabbit study, the acute dermal LD50 was calculated to be 1260 mg/kg bw.

Justification for classification or non-classification

Phosphorus trichloride is listed on Annex I of the Dangerous Substances Directive (67/548/EEC) with classification as (R28) 'Very toxic if swallowed' and (R26) 'Very toxic by inhalation'. No change to this classification is proposed on the basis of the available data.

On the basis of the studies reported (dermal LD50 of 1260 mg/kg bw), classification with (R21) 'Harmful in contact with skin' is also proposed.