Application for the Reassessment of a Hazardous Substance under ...

19 SPECIFIC TARGET ORGAN TOXICITY 6.9 (SINGLE DOSE – INHALATION)HSNO Classification: Specific target organ toxicity (Single dose – inhalation)– 6.9AKEY STUDY:• Type of study:• Species:• Strain:• Sex/Numbers:• Test Material:Acute Inhalation Toxicity, LC 50 (4hours, head-only);vapour/aerosol;Rat;Wistar (Bor:WISW);5 (vapour) or 10 (aerosol)/sex/group;Dichlorvos (98.7 % pure, batch no. 809 436 388, lot no.3379);• Dose levels: Vapour: 342 mg/m 3 (nominal), 116 mg/m 3 (analysed) for 4hours;Aerosol: 230-1926 mg/m 3 for 4 hours;• Endpoint: Mortality (LC 50 );• Remarks:For the vapour experiment, 5 animals/sex were exposed for4 hours to a nominal concentration of 342 mg/m 3 (theanalysed concentration was 116 mg/m 3 , the maximumachievable as vapour). All animals showed adverse signsincluding bristling and ungroomed coat, reduced motilityand high gait but there were no deaths. No effects onweight gain were observed during the 14-day observationperiod and autopsy revealed no treatment-related grosseffects.A lethal vapour concentration could not be generated(maximum concentration was 116 mg/m 3 ); LC 50 > 116mg/m 3 (0.116 mg/L).In the aerosol experiment, 10 animals/sex were exposed tonominal air concentrations of 1500 - 15000 μL/m 3 (230-1926 mg/m 3 ) for 4 hours, with the particle mass mediandiameter ranging from 2.8 to 6.4 μm.Adverse signs, evident immediately after exposure (i.e.when rats were removed from tubes) were severe muscletremors and weakness, convulsions, recumbence on side,ataxia, apathy and dyspnoea. More persistent signsincluded ungroomed coat, bristling fur and high gait. AllDichlorvos reassessment – application Page 229 of 436