Comparative subchronic studies on 2,4-dichlorophenoxyacetic acid, amine, and ester in rats

Area of Science:

• Environmental toxicology
• Agricultural science
• Mammalian toxicology

Background:

• 2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide.
• Different forms of 2,4-D exist, including 2,4-D acid, 2,4-D dimethylamine salt (DMA), and 2,4-D 2-ethylhexyl ester (2-EHE).
• Understanding the comparative toxicity of these forms is crucial for risk assessment.

Purpose of the Study:

• To evaluate the subchronic toxicity of three representative forms of 2,4-D in rats.
• To determine if different forms of 2,4-D exhibit varying toxicity profiles.
• To establish a no-observed-effect level (NOEL) for subchronic exposure to these 2,4-D forms.

Main Methods:

• Subchronic toxicity studies were conducted on rats using 2,4-D acid, DMA, and 2-EHE.
• Animals were administered doses ranging from 0 to 300 mg/kg/day (acid equivalent basis).
• Key toxicological endpoints, including hematology, clinical chemistry, organ weights, and histopathology, were assessed.

Main Results:

• Treatment-related findings included decreased red cell mass, altered thyroid hormone levels (T3, T4), and reduced gonadal weights.
• Increased weights of the liver, kidney, and thyroid were observed.
• High-dose females exhibited cataracts and retinal degeneration.

Conclusions:

• The subchronic toxicity of 2,4-D acid, DMA, and 2-EHE was found to be comparable in rats.
• A subchronic no-observed-effect level (NOEL) of 15 mg/kg/day was supported for all three forms.
• These findings indicate a low subchronic toxicity potential among representative forms of 2,4-D.