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Health Canada said Wednesday it wants to phase out a controversial pesticide that's come under increasing scrutiny because of its possible role in the decline of the bee population. But the new federal phaseout is being done because of the risk to aquatic insects, not pollinators.

Health Canada said in a news release that the current use of the pesticide imidacloprid is "not sustainable" and that the levels found in waterways and aquatic environments "are harmful to aquatic insects" including mayflies and midges, important food sources for fish, birds and other living things.

Imidacloprid is a neonicotinoid, a popular class of pesticides used to protect against insects. Imidacloprid is absorbed by the plant, protecting it as a whole. There is no evidence to suggest the pesticide poses a risk to human health, according to Health Canada.

The phaseout would apply to trees, greenhouse uses of the pesticide, commercial seed treatment, outdoor agricultural uses and turf. It would not apply to use of the pesticide in and around homes or buildings, injections directly into tree trunks or use of the pesticide in flea, tick and lice treatments in cats and dogs.

The decision was made after department officials completed a re-evaluation of imidacloprid, which found the risks to aquatic insects to be unacceptably high. The assessment also found that birds and small mammals who feed on seeds treated with imidacloprid may also be at risk. In light of the evidence, the government has decided to launch reviews of two other popular neonicotinoids, called clothianidin and thiamethoxam.

Health Canada's Pest Management Regulatory Agency is also conducting a separate assessment of what role those three neonicotinoids are playing in the decline of bees. Earlier this year, Health Canada published a preliminary assessment of imidacloprid that found the pesticide did not pose a significant risk to pollinators. The final assessment of the three pesticides is expected to be published next year.

In the case of imidacloprid, the government is proposing a three- to five-year phaseout plan, with the longer timeframe being used to accommodate those who can't find suitable alternatives to imidacloprid.

Faisal Moola, director general for Ontario and Northern Canada with the David Suzuki Foundation, said news of the phaseout is welcome. But he questioned the need for such a long lead time before the proposed changes take effect, especially considering that other jurisdictions, such as Ontario, have already moved forward with regulations to reduce imidacloprid. A ban on the chemical is already in place in the European Union.

Moola said he is "baffled" the government hasn't taken more action to restrict these pesticides to help protect pollinators, as so much research has shown they pose a risk to bees.

On its website, Health Canada acknowledges reports of bee deaths linked to exposure to dust from corn and soy seeds treated with neonicotinoids. But new planting rules adopted in 2014 helped reduce bee deaths from pesticide exposure by up to 80 per cent, the department says.

The proposed changes are open to a 90-day consultation period. Health Canada said it would consider "potential alternative mitigation strategies that would achieve the same outcomes in a similar time frame."

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