OTTAWA -- The federal government is moving to phase out a common neonicotinoid insecticide after finding that it accumulates in waterways and harms aquatic insects.

Health Canada has announced a 90-day public consultation period on imidacloprid, which is used on everything from cereals, grains, pulses and oilseeds to forestry woodlots and flea infestations on pets.

Neonicotinoids as a class of pesticides have come under heavy scrutiny in recent years for their potential impact on bee populations.

A study by Health Canada found that measurements of imidacloprid in surface water have been found as high as 11.9 parts per billion, while levels above 0.041 parts per billion are a considered to be of scientific concern.

The government is proposing to phase out all agricultural usage and most other outdoor uses of imidacloprid over a period of three to five years.

Ontario's provincial government moved to restrict the use of imidacloprid last year, as have some European countries.

"Based on currently available information, the continued high volume use of imidacloprid in agricultural areas is not sustainable," Health Canada said Wednesday.

The Health Canada study of imidacloprid has also prompted the federal department to begin "special reviews" of two other common neonicotinoids, clothianidin and thiamethoxam.

"Health Canada is taking the findings of the re-evaluation of this pesticide seriously, and is taking action to further protect the environment," Health Minister Jane Philpott said in a release.

The advocacy group Environmental Defence, which has been pushing for a ban on neonicotinoids, lauded the government's decision but said the proposed three- to five-year phase-out period is too long.

"As neonic pesticides are soluble in water, they run off into local waterways and damage insect populations at previously unknown levels," spokeswoman Maggie MacDonald said in a release.

"These devastating findings are in addition to the mounting scientific evidence on how imidacloprid and other neonic pesticides harm the health of bees in disastrous ways."

Health Canada noted Wednesday that incidents of bee kills during the neonicotinoid treatment of corn and soybean crops have fallen 80 per cent since new mitigation measures were imposed in 2014.

However, the department's own 2014 review of neonicotinoid pesticides also found that "scientific research shows long-term effects on pollinators can result from sub-lethal exposure levels. Sub-lethal exposure levels are lower levels of exposure that do not result in immediate mortality."