Deborah Cory-Slechta, Ph.D.
University of Rochester
An NIEHS-funded study in mice revealed that when inhaled, the pesticide paraquat can enter the brain. The researchers also found that, in male mice only, paraquat exposure impaired sense of smell, an early sign of Parkinson’s and other neurodegenerative diseases. Inhalation represents realistic route of pesticide exposure for farmers but is often overlooked in basic animal research and risk assessments, according to the authors.
The researchers exposed adult male and female mice to paraquat aerosols in a whole-body inhalation chamber for four weeks. They measured paraquat concentrations in various brain regions, the lungs, and kidneys. Using an olfactory discrimination assay, they assessed how exposure affected the sense of smell.
Paraquat was detected in four regions of the brain as well the lungs and kidney. Levels in the olfactory bulb were substantially higher than in any other brain region, consistent with inhalation exposure through the olfactory system. Paraquat levels in all tissues returned to control values within four weeks of the end of exposure. Exposed male mice had a persistent impaired sense of smell compared to controls. Exposure did not affect sense of smell in female mice. According to the authors, results highlight the importance of considering route of exposure to determine safety estimates for neurotoxic pesticides.
Citation: Anderson T, Merrill AK, Eckard ML, Marvin E, Conrad K, Welle K, Oberdorster G, Sobolewski M, Cory-Slechta DA. 2020. Paraquat inhalation, a translationally relevant route of exposure: disposition to the brain and male-specific olfactory impairment in mice. Toxicol Sci; doi:10.1093/toxsci/kfaa183 [Online 29 Dec 2020].