Tar acids, methylphenol fraction

Endpoint summary

Description of key information

Most critical values of cresols:
oral: LD50 rat 121mg/kg bw (o-cresol)
dermal: LD50 rat 301mg/kg bw (p-cresol)
inhalation: LC50 rat >710mg/m³ (m-cresol and p-cresol)

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Dose descriptor:

LD50

Value:

121 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Dose descriptor:

LC50

Value:

710 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion

Dose descriptor:

LD50

Value:

301 mg/kg bw

Additional information

Acute oral toxicity:

The most critical value for cresols was reported in the study performed with o-cresol where the oral LD50 of undiluted o-cresol in rats was determined to be 121 mg/kg bw. Following oral application the LD50 in rats was 242 mg/kg bw for undiluted m-cresol and 207 mg/kg bw for p-cresol. In all 3 studies 5 rats per dose were treated and mortalities occurred in all except the low dose groups. The observed signs of intoxication for all cresols included hypoactivity, tremors, lacrimation, dyspnoea, hemorrhagic rhinitis, convulsions and prostration observed within 4 hours post dosing. (Ind Bio-test Lab Inc 1969).

 

Acute dermal toxicity:

The LD50 of p-cresol for acute dermal exposure was the most critical of the cresols with 301 mg/kg bw. The other cresols revealed LD50s of 1380 mg/kg bw (o-cresol) and 2050 mg/kg bw (m-cresol). All studies were performed by Bio-test Lab Inc (1969) on 5 rabbits that received 4 doses of the cresols respectively. The animals were observed for 14 days post exposure and mortality and clinical signs were reported. Mortalities occurred in all dose groups between 215 mg/kg bw (1 out of 5) and 3160 mg/kg bw (5/5). Clinical signs included hypoactivity, tremor, convulsion, salivation, dyspnoea, prostration and additionally the treated skin showed severe erythema and burns in the high dose groups.

 

Acute inhalation toxicity:

An acute inhalation study was performed similar to OECD guideline 403 with p-cresol (Ind Bio-test Lab Inc 1969). 6 rats were exposed to 710 mg/m³ for 1 hr at room temperature and observed for clinical signs or mortality up to 14 days post exposure. Gross necropsy was performed at the end of the observation period. The same study was performed with m-cresol where additional information about the airflow of 10.0 Lpm was reported. The exposure of male rats for 1 hour to 710 mg/m³ m-cresol or p-cresol led to no mortalities or any clinical signs. These studies where chosen for the most critical LC50 of cresols because of their higher reliability in comparison to the other performed study with o-cresol. 6 male rats were exposed to 1220 mg o-cresol/m³ and observations for clinical signs, mortality and gross autopsy were reported. Generalized inactivity and lacrimation were observed at the first 15-30 minutes of treatment with recovery at treatment day.

Justification for classification or non-classification

Cresols have to be classified according to:

DSD: oral: T, R25: Toxic if swallowed; dermal: T, R24: Toxic in contact with skin

CLP: oral category 3, H301: Toxic if swallowed; dermal category 3, H311: Toxic in contact with skin