2,4-dichlorophenol

Endpoint summary

Description of key information

The SIDS dossier reports a number of acute oral toxicity studies. The lowest acute oral LD50 reported is 1276 mg/kg bw. This value is taken as the oral toxicity end point as it was the lowest and so most conservative value. 
In addition an acute dermal study is reported and referenced herein since it relates to skin corrosivity. The LD50 is reported to be 780 mg/kg/bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

1 276 mg/kg bw

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

780 mg/kg bw

Additional information

Annex VII of Regulation (EC) No 1907/2006 in section 8.5 states the study/ies do(es) not generally need to be conducted if the substance is classified as corrosive to the skin. This is reiterated in section R.7.4.2 of the ECHA Guidance on information requirements and chemical safety assessment, Chapter R.7a : Endpoint specific guidance.

Therefore, this endpoint is not required for a substance classified as corrosive to skin. However, since a number of LD50 acute oral toxicity studies are publicly available they have been reported here. The lowest credible acute oral LD50 reported was 1276 mg/kg bw, attracting a DSD classification of 'Harmful if swallowed' (R22) and a CLP classification of 'Acute toxicity 4' (H302) .

The endpoints presented are summarised in the table below:-

LD50 mg/kg	IUCLID Endpoint
1276	001
2830	002
580	003
1630	004
3670 (Males)	005
4500 (Females)	005
1630 (Males and Females)	006
>2400 - <2800 (Females)	WIL-22001

In addition, an acute dermal study is reported in the SIDS dossier. The requirement to perform an acute dermal toxicity study is listed in Annex VIII of Regulation (EC) No 1907/2006. Therefore it is not required. However, given that the most likely route of any exposure to this substance would be through skin contact in either manufacture or use it is prudent to include this study reference. The SIDS dossier assigns a validity of 1 (valid without restrictions) to this study which was conducted according to OECD guideline 402. The study was performed with the substance in molten form in order to bear closest resemblance to any potential human exposure by accidental spillage. In male rats the minimum lethal dose was 300 mg/kg/bw. 4/5 deaths were observed at the high dose level of 2000 mg/kg in males and females. A slight decrease in motor activity was noted from 200 mg/kg which was no longer present 24 hours after application. However as the dose increased (300 mg/kg to 1400 mg/kg) a marked decrease in motor activity was observed and respiratory impairment was noted. These signs were still present up to 6 and 9 days respectively after treatment. At 2000 mg/kg, coma, soft faeces and blood-like colouration in urine were observed. Locally, at all doses, marked to severe irritation resulting in skin necrosis was noted after removal of the patch, which was hardly reversible within 2 weeks.

 

Justification for classification or non-classification

The substance is classified as in Annex I to 67/548/EEC as :-

Toxic, T, R24 - Toxic in contact with skin, R22 - Harmful if swallowed, R34

and in Annex VI (Table 3.1) of CLP-Regulation (EC no 1272/2008 as :-

Acute Toxicity 4,              H302 - Harmful if swallowed

Acute Toxicity 3               H311 - Toxic in contact with skin

Skin Corr IB                     H314 - Causes severe skin burns and eye damage

Analysis of data summarised here supports this classification.