Winnipeg, a city addicted to fogging
A short-lived scare about malathion reveals the depth of our love for airborne pesticides
The drug in question is malathion, the pesticide the city's been using to kill adult mosquitoes for decades. Though Winnipeg has been preparing to kick the habit for nearly 10 years, it's not ready to move on to a purportedly less dangerous replacement chemical.
The methadone in this analogy is deltamethrin, a synthetic pesticide modelled after natural pest-controlling molecules called pyrethrins, which are found in chrysanthemum flowers.
While the science isn't unanimous, there's a belief deltamethrin is less harmful to the environment.
While malathion may not have much of an effect on people — it's merely a probable carcinogen, in the eyes of the World Health Organization — the chemical is a conclusive killer of unsexy but important invertebrates such as amphipods, which are small crustaceans that play an important role in freshwater food chains.
Winnipeg, the only major Canadian city to use malathion, hopes to switch to deltamethrin as soon as Health Canada's Pest Management Regulatory Agency says it's OK to do so.
But since that hasn't happened, there was a freakout on Friday, when the city learned it wasn't allowed to consume it's remaining stash of malathion.
The bad news came from CBC Manitoba's I-Team, which learned the product label had been changed to prevent the use of the chemical if it was stored more than one year.
That's problematic for a couple of reasons. For starters, malathion's manufacturer doesn't make the stuff every year. Secondly, malathion consumers such as the City of Winnipeg and the Province of Manitoba routinely sit on their stockpiles
The city only fogs for nuisance mosquitoes — that is, species that are not known to transit diseases to people — when an arbitrary, council-approved measure of annoyingness is met. That happens when the overall mosquito trap count in the city is above 25 for two consecutive days and at least one quadrant of the city has an average trap count above 100. That does not happen every year.
The province only uses its stash of malathion when the presence of West Nile virus is detected in enough mosquitoes and birds to declare a public-health threat. That too does not happen every year.
Nonetheless, both the city and the province like to have malathion on hand in the event they need a chemical fix. Without a pesticide to kill mosquitoes, the only method they have to kill nuisance species such as Aedes vexans or the West Nile-carrying Culex tarsalis is vigorous slapping.
Happily for both levels of government, Ottawa did not leave them in the lurch. Within hours of the CBC report, Ottawa informed Manitoba it's probably cool to use its stash of malathion, purchased way back in 2008. All the province has to do is send samples of its malathion to a lab in Ontario and hope the tests don't detect the presence of dangerous impurities that may result when the chemical starts to break down.
A few hours later, Winnipeg received the same conditional OK about its own stashes of malathion, purchased in 2007 and 2009. This is more contentious, given that the city once purchased surplus malathion from a Saskatchewan seller who noted the product came in leaky containers.
Still, because there is no immediate need to fog in Winnipeg to combat the nuisance of mosquitoes or a public health threat, the day-long scare did not affect fogging operations in any way.
What it did was highlight how reliant the city is upon the use of pesticides to kill adult mosquitoes on a psychological basis.
Simply put, nuisance-mosquito fogging does very little to control mosquito populations. While the weather is the main factor that determines whether large numbers of blood-sucking insects can emerge in Winnipeg, the real reason they largely are not present every day from Easter to Thanksgiving is the city engages in aggressive larviciding.
Every spring and often all summer, Winnipeg's insect control branch spills pesticides into bodies of standing water to kill mosquito larvae. This is the only effective way to keep mosquito numbers down.
Fogging for adult mosquitoes only makes skeeters disappear for a couple of days. This is why scientists consider the practice entirely cosmetic.
Politically popular pesticides
Knowing this, you have to wonder why Winnipeg bothers to engage in nuisance-mosquito fogging at all. The answer is simple: residents would freak out if the city suddenly stopped spraying.
Generations of politicians have learned this lesson. In 2004, former mayor Sam Katz's first campaign pledge was to reduce mosquito numbers in Winnipeg. He even held up a placard, showing a mosquito with a red line across it.
Would-be mayor Gord Steeves, the former St. Vital councillor, wanted to reduce fogging buffer zones, even though that was impossible, given the way malathion is sprayed.
Current Mayor Brian Bowman also knows the end of fogging would amount to political suicide.
"I think most Winnipeggers expect we are going to do nuisance-mosquito fogging. I'd like to see us using an agent other than malathion and that's why we're taking concrete steps to move to DeltaGard and we're waiting for federal approvals to use that agent," Bowman said on Friday, referring to the commercial name for deltamethrin.
"Malathion, as you know, has been a controversial agent in Winnipeg and in other municipalities that have been using it and I'd like to see us get out of malathion."
It's not like Winnipeg has a choice: Malathion is going the way of DDT, Bud Lite Lime and other noxious substances.
The city does have a choice, however, when it comes to nuisance fogging. Just don't expect any mayor or council to place environmental concerns above the desire for Winnipeggers to sit in their back yards without reaching for mosquito spray during our brief summers.
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