Toxicity and degradation of the insecticide monocrotophos

Monocrotophos, commonly named Azodrin or Nuvacron, is an organophosphate insecticide, which in spite of ban is preferred due to its high efficacy against insect pests. With a field application dose of 0.25–1.5 kg ha⁻¹, it has median lethal dose (LD₅₀) of 18–20 mg kg⁻¹ for mammals and half-life of 17–96 days. Monocrotophos uncontrolled application in farming has led to the contamination of surface and groundwater, causing neurotoxicity, genotoxicity, hyperglycaemic and stressogenic effects on different organisms. Being readily soluble in water, it is grouped under class I: highly toxic compounds. Microbes such as Bacillus, Pseudomonas, Aspergillus, Anabaena and Nostoc at 25–37 °C and pH 5.5–8.5 have the ability to utilize monocrotophos as nutrient source and can tolerate up to 500–1200 mg L⁻¹ of monocrotophos, causing its complete or partial degradation to dimethyl phosphate, phosphoric acid, valeric or acetic acid. On the other hand, generation of ·OH radicals by photoactivation of the catalyst such as TiO₂ and ZnO leads to complete mineralization of monocrotophos. Biodegradation followed by photocatalytic degradation would be the most efficient and sustainable approach. This review focuses on toxicity, fate of monocrotophos in the environment and its microbial and photocatalytic degradation.