Recent studies have found evidence of neonicotinoids, a farm pesticide, in Iowa drinking water. As the Washington Post reports, some hold this insecticide responsible for a decrease in the bee population after a study linked it to the death of local bees. Now, neonicotinoids are showing up in water samples across the country, including in samples of Iowa City tap water.
The pesticide was present in tap water samples in a University of Iowa and taps in Iowa City. Concentrations of the neurotoxin found were small--only "0.24 to 57.3 nanograms per liter." This measurement is parts per trillion, but the finding itself is not clear how much exposure to neonicotinoids is safe for human consumption. There is currently no recommendation from the Environmental Protection Agency about how much of the pesticide is acceptable in tap water. Neonicotinoids are often fatal to insect nervous systems, but they do not easily work on a mammal's brain in the same way.
A review of studies concerning exposure to neonicotinoids published by National Institutes of Health found only "low rates of adverse health effects" for those with acute exposure. More studies are required to know how neonicotinoids affect the health of humans who regularly are exposed to the chemicals, especially in a work environment. While 19 forestry employees were studied and no adverse effects were found, that is not a significant sample size. General population studies of chronic exposure did have some association between negative health outcomes, such as memory loss and tremors, but further research is needed to bolster these findings.