Friday, July 16, 2010


While browsing the Environmental Health News website today, I came across an article about a mosquito-spraying program in Winnipeg. Apparently the city is using a chemical called malathion to destroy the local mosquito population. Residents who are concerned about the toxicity of the insecticide are allowed to opt out of the program, which under current city policy creates a 100m buffer zone around a given home. But not for long: a city councillor has urged the municipal government to recommend that the provincial government shrink the size of these no-spray zones. The issue is that when enough residents opt out of the program in one area, entire city blocks go unfogged, mosquitoes abound, and we all lose five-millionths of a litre of blood.

Before mentioning a few issues I have with this program, let's remind ourselves what the perpetrators look like:

I found this image on the website of a family naturist park, accompanying some information about their mosquito and black fly population control methods. Now, we all know that the internet contains a lot of misleading information, so I've chosen my source carefully. I can't help but believe that this group of people, who frequently let their entire bodies come into contact with nature and generally tend to respect the environment, needs an effective but also non-poisonous method of pest control. They're using a biological agent called Bti, which is sprayed onto mosquito breeding sites in spring (and can also be used in spot-treatments of standing water later in the year). After years of widespread use in Canada and the US, this bacterium is pretty much conclusively only toxic to mosquito and black fly larvae, so it's perfectly harmless to us and our beloved pets, and to boot, it biodegrades within a few days. Sounds awesome!

So what do we know about this Malathion character in the other corner of the ring? For one thing, as the article mentions, the US Department of Agriculture suspects it is carcinogenic, but unfortunately doesn't have enough evidence to prove this is the case. I don't know about you, but when research tells me that smoking is linked to lung cancer, but it can't be proven directly, that's enough to make me avoid cigarettes. And that fact sheet I hyperlinked to above, the one published by Health Canada and found on Winnipeg's official city website? It talks of malathion not posing a health concern, but then goes on to list nine ways to reduce exposure to the chemical! Scary!

To make matters worse, this insecticide is what's known as an "adulticide" because it kills off the bugs once they've matured to adulthood (as opposed to Bti, which is toxic only to larvae). An undesirable consequence of using adulticides is that they tend to be sprayed over large areas, affecting more than just mosquitoes along the way. Malathion is highly toxic to bees and fish, and while humans don't necessarily care about the other populations of insects that are wiped out by this chemical, other animals, like birds, suffer when their source of food disappears. (Also, losing bees spells trouble for us, seeing as they are pollinators that we depend on to grow food. More on that in another post.)

Lastly, I am always concerned about the use of insecticides because of their tendency to encourage the development of resistance in the very pests we use them against. Eventually, we are going to run out of chemicals that mosquitoes are still susceptible to but that don't also kill everything else, including us in the meantime. It sounds like Bti is good alternative. A better one would be to make use of mosquitoes' natural predators, like dragonflies.

So, while we wait for the research to be conducted and new legislation to pass, we can work on other things, like fighting against the use of malathion and its cousin insecticides and planting gardens that dragonflies would thrive in. Easier yet is avoiding the outdoors at dusk! Don't forget those citronella candles...

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