Water contamination
According to the US EPA, imidacloprid, has the potential to leach to ground water. In addition, high solubility and mobility are concerns for transport to surface water by dissolved runoff.
The half life (the amount of time required for half of an applied pesticide to break down or move away from the test site) of imidacloprid in water was much greater than 31 days at pH 5, 7, and 9.
Its ability to move through soil has been tested, along with other widespread water contaminants and it was found to be the quickest. Nevertheless, the EPA did not classify imidacloprid as a restricted use product, probably for economic reasons.