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Description of key information

Three acute toxicity studies are available for each of the oral, dermal and inhalative route of exposure.
Following studies were selected as key studies:
The acute oral toxicity of triclosan was tested in a rat study according to the US FIFRA §81-1 test guideline which in principle was similar to the OECD TG 401 (Product Safety Labs 2800).
The acute dermal toxicity of triclosan was tested in rabbit according to the method described by Noakes & Anderson (1969), which was in general compliance with OECD 402 (Ciba-Geigy Ltd 800761).
The LD50 obtained from these two studies were as follows:
Acute oral toxicity (rat): LD50 LD50 > 5000 mg/kg bw (both sexes)
Acute dermal toxicity (rabbit): LD50 > 6000 mg/kg bw (both sexes)
The acute inhalation needed to be discarded because on unadequate test system since triclosan was dissolved into ethanol for aerosolization and this is not a representative exposure system for human hazard assessement because triclosan is a solid, powdered substance. Exposures during manufacturing or formulation activity would be a dust, if any, and not to a fully respirable aerosol of triclosan in ethanol. Thus, the study is considered as not reliable for hazard assessment and classification.
Nevertheless and for information only, this acute inhalation toxicity (rat, 4 h exposure) resulted in LC50 = 0.436 mg a.i./L air (both sexes).

Key value for chemical safety assessment

Additional information

Acute oral toxicity:

5000 mg triclosan/kg bw was administered to ten healthy rats (Product Safety Labs 2800). The animals were observed for signs of gross toxicity and mortality at least once daily for 14 days. Bodyweights were recorded just prior to administration, on Day 7 and 14 (termination) or after death. Necropsies were performed on all animals. One female died on day 3 of the study. All animals exhibited clinical signs including diarrhoea, soft faeces, ano-genital staining, and hunched posture, lethargy, abdominal distension, piloerection, ocular discharge and/or irregular respiration. Most survivors recovered from the above clinical signs by day 7 and gained weight over the 14-day observation period. Gross necropsy of the decedent revealed discoloration of the lungs and gastro intestinal tract and injection of the blood vessels of the gastro-intestinal tract. Gross necropsy findings at terminal sacrifice were generally unremarkable. Thus, The acute oral LD50 of triclosan in the rat is greater than 5000 mg/kg bw.

 

Acute dermal toxicity:

Triclosan was dermally applied to groups of each three male and female NZW rabbits (Ciba-Geigy Ltd 800761). Rabbits were exposed via the shave dorsum to doses of 1000 or 6000 mg/kg bw for 24 h under semi-occlusive conditions. Animals were observed for up to 21 days for mortality and clinical signs. One male of the 6000 mg/kg group died on day 8 post exposure. Compound-related clinical signs in the 1000 and 6000 mg/kg bw dose groups included: sedation, dyspnoea, exophthalmos, ruffled fur, and curved body position. In addition, ataxia was noted in the 6000 mg/kg group only. The animals of the control group failed to show any toxic symptoms. The acute percutaneous LD50 of triclosan in the rabbit is greater than 6000 mg/kg bw.

 

Acute inhalation toxicity:

Rats were exposed nose-only for 4 hours to triclosan aerosol generated by injecting a 50 % suspension of triclosan in ethanol 94% + 1% cyclohexane a rate of 6, 12, 18, 18 mL/hr into an air stream that was discharged into the exposure chamber at a rate of 10 litres/min (Ciba-Geigy 800760).The triclosan concentration of the aerosol and its particle size distribution in the vicinity of the animals was monitored at regular intervals throughout the aerosol exposure.The test concentrations were 124, 466, 513 and 678 mg/m3 (measured), corresponding to 0.124, 0.466, 0.513 and 0.678 mg/L air. The test series comprised 6 groups including 4 treated groups and 2 controls, a sham and an ethanol control group. After a 4 hour inhalation exposure the rats were returned to their cages and were observed during a period of 14 days for clinical signs and mortality; body weight was assessed. At the end of the observation period, the surviving animals were sacrificed for the purpose of necropsy.

Particle size distribution analysis of the chamber airborne particles showed that >90 % were smaller than 7 µm in diameter, indicating that the aerosol was respirable. For the males, mortality in the triclosan-treated groups was 20, 60, 70 and 100% in the 0.124, 0.466, 0.513 and 0.678 mg/L group, respectively. For the females, mortality in the triclosan-treated groups was 0, 30, 30 and 70% in the exposure groups, respectively. No mortality occurred in the two control groups.  Thus, there was an apparent sex difference in the toxicity of the test material. All deaths occurred during the 4 hour- exposure period, with the exception of one male of 0.513 mg/L exposure group that died on day 6. Necropsy of dead and sacrificed treated animals revealed some cases of discolored areas in the body (no further specified) in each group exposed to the test material. Necropsy of the control animals of both the sham and the ethanol control groups revealed no abnormalities. Thus, for acute inhalation exposure to triclosan aerosol, the following LC50 estimates were reported:

Males: 0.286 mg/L air

Females: 0.603 mg/L air

Both sexes: 0.436 mg/Lair

Thus, the results of the present study indicate that triclosan in ethanol as an aerosol is toxic when inhaled. However and despite of the result, the study was discarded since triclosan was dissolved into ethanol for aerosolization; this is not a representative exposure system for human hazard assessement because triclosan is a solid, powdered substance. Exposures during manufacturing or formulation activity would be a dust, if any, and not to a fully respirable aerosol of triclosan in ethanol. Thus, the study is considered as not reliable for hazard assessment and classification.

Justification for classification or non-classification

Triclosan is listed in Annex I and according to the EU Directive 67/548/EEC, the substance is not classified for acute toxicity.

According to the Annex VI of the CLP regulation, there is no need for classification of triclosan for the acute oral, dermal and inhalation routes of exposure.