Dichlorvos -- a 2-year inhalation carcinogenesis study in rats

Area of Science:

• Toxicology
• Environmental Health
• Carcinogenesis

Background:

• Dichlorvos is an organophosphate insecticide.
• Assessing long-term health effects, including carcinogenicity, is crucial for pesticide safety.

Purpose of the Study:

• To evaluate the potential carcinogenicity of dichlorvos vapour.
• To determine the effects of chronic dichlorvos exposure on tumor incidence in rats.

Main Methods:

• A 2-year inhalation study was conducted on 5-week-old Carworth Farm E strain rats.
• Rats were exposed to varying concentrations of dichlorvos vapour (0, 0.05, 0.5, and 5.0 mg/m³).
• Tumor incidence was analyzed using relative risk analysis, alongside assessments of growth, survival, and various physiological parameters.

Main Results:

• No dose-related increase in tumor risk was observed in either male or female rats.
• Growth rates were depressed in treated rats, particularly males, and survival increased at the highest exposure level (5 mg/m³).
• No significant compound-related changes were found in food intake, organ weights, hematology, blood chemistry, or tissue histology, except for cholinesterase activity.

Conclusions:

• The study provides evidence that dichlorvos vapour does not increase tumor incidence in rats.
• These findings support the safety of dichlorvos for its registered insecticidal uses.
• Long-term exposure to dichlorvos at the tested levels did not induce carcinogenic effects in rats.