A recent report in JAMA Internal Medicine has elicited great interest from clinicians, endocrinologists, and toxicologists. The key finding was that 3-phenoxybenzoic acid, the main metabolite of numerous pyrethroid insecticides, increased risk of all-cause mortality and specifically, cardiovascular mortality in a US adult population. This finding was surprising because pyrethroids have low mammalian toxicity compared with organophosphates, which pyrethroids largely replaced in the 1980s.
Pyrethroids are synthetic insecticides based on natural pyrethrins, representing 30 per cent of the pesticide market. Pyrethroids inhibit insect voltage-gated sodium channels, thus, mammalians may also be susceptible.
The general population is exposed to pyrethroid residues through food, water or floor dust. Experimental and epidemiological data suggest pyrethroids may disrupt endocrine pathways and interfere with hormones, especially during pregnancy and early childhood. Anomalies that could be related to pyrethroid residues have been reported for thyroid hormones (FT3, T3, T4 and TSH) and sex hormones (FSH and LH).
Moreover, various pyrethroids are formulated in combination with piperonyl butoxide, which is also suspected of neurotoxicity. The main metabolite of numerous pyrethroid insecticides, 3-phenoxybenzoic acid, may increase the risk of mortality, the report found.