[8] Just half of fenitrothion's minimally effective dose altered the thyroid structure of a freshwater murrel (the snakehead fish).

[9] Cases of non-specific encephalopathy and fatty visceral changes (Reye's syndrome) in children living in the vicinity of fenitrothion-spraying operations invoked the research described latterly in Science,[10] and originally in The Lancet:[11] 2-day-old mice were dosed topically for 11 days with fenitrothion, amongst other substances.

The encephalopathy showed no specific central-nervous system lesion, but death followed a sequence of paralysis and convulsions.

The possible role of exposure to combinations of insecticides in human viral susceptibility requires further attention.Further study showed that the illness was caused not by fenitrothion itself, but combinations which included the surfactants and the solvent (with or without the pesticide) clearly showed that pretreatment with these chemicals markedly increased the viral lethality in the test mice.

[12] In an unusual demonstration of resistance to pesticides, 8% of insects in farm fields were found to carry a symbiotic gut microbe that can metabolize and detoxify fenitrothion; after in-vitro tests showed that the microbe significantly increased the survival of fenitrothion-treated insects.