Tuesday, July 10, 2007

Malathion spraying in Manitoba

I am a bit puzzled that suddenly there are these orders. The West Nile virus mosquitoes have been prevalent before. There are not even any human cases as yet just bird positives. Why now and why no possibility of exclusion zones.
It is not even clear that the spraying works to any degree except in the short term. Although the preponderance of evidence is that small doses are not that harmful to humans what of its effects on other living things such as birds?
There are other methods of controlling mosquitoes. With other policies costs and benefit studies are required. Have they ever been done for this? And how do you quantify the value of a person's right not to be sprayed if they oppose it? If there were very strong community health reasons for spraying perhaps this right should not trump the policy but there is precious little evidence provided that spraying has any proven advantage compared to methods not involving spraying. The government by the way withdraw a grant to a group that was opposed to spraying! I wonder who makes Malathion and if they lobby the government re spraying.

Insecticide fog falls on Brandon for first time in 3 decades
Last Updated: Monday, July 9, 2007 | 3:45 PM CT
CBC News
The City of Brandon fogged its streets with the malathion this weekend for the first time in 30 years, one of several Manitoba communities under provincial orders to kill adult mosquitoes.

The province issued an order for the western Manitoba city to spray the broad-spectrum organophosphate insecticide due to an increasing population of mosquitoes that carry the West Nile virus in the area.

"Our biggest efforts to start the program was sort of the green space where there's a lot of community recreational use, i.e. down by the river corridor area," city spokesman Rick Bailey said. "We concentrated on that area, we did walkways, but in essence we went through the entire city."

Despite not having used the equipment in three decades, Bailey said it went very well. It took four trucks one night to fog the entire city of 40,000.

"We have had concerns from our residents that don't really agree with using, you know, a pesticide to spray for adult mosquitoes, but basically I think staff have done a really good job of notifying [them]," he said. "All in all, I think most understand that, you know, it is a health order and we have to look after the best interests of the whole community."

City officials say they are waiting to hear whether the province will order another round of fogging.

A second application could take place as early as Wednesday, Bailey said.

Elsewhere in the province, the towns of Beausejour, Niverville and Oakbank were to be fogged Monday night, if weather permits.

Winnipeg is carrying out two fogging campaigns: One for "nuisance" mosquitoes, which respects the 100-metre buffer zones around the properties of residents who have opted out of the program, and the other under the ministerial order, which ignores the buffer zones.

Parts of eastern and northwestern Winnipeg were fogged under ministerial order over the weekend, but no further fogging is scheduled under that program for Monday night, according to the city's website.

Under the nuisance program, fogging is scheduled for areas in northeast and central Winnipeg.

However, fogging only takes place when the weather permits: Temperatures must be at least 13 C and there can be no significant wind or rain.

The forecast for southern Manitoba for Monday night calls for high winds and rain, and the mercury is expected to hover around the 13 C mark.

Here are two short pieces on malathion versus mosquitoes. I imagine there are much more thorough analyses if one searched.

Experts split on safety, efficacy

Winnipeg is one of just a few municipalities in Canada that still fog with malathion to kill mosquitoes.

Critics of the city's use of malathion say the insecticide is ineffective and causes health problems. Experts are split on its benefits – and its safety.

Retired entomologist Bill Turnock questions the effectiveness of the city's fogging program. He says officials want to show they're doing something to kill mosquitoes, but fogging with malathion isn't the best way.

"To be effective, the fog droplets have to actually hit an insect," he says. "The delivery systems that we have and the terrain that they're fogging [make] it extremely difficult to get the kind of coverage you need to kill a high percentage of mosquitoes."

Peter Parys, co-ordinator with the city's insect control branch, defends malathion, saying it's difficult to gauge its effectiveness.

"I don't have exact data in terms of how effective it is, but you have to put it in the context of an integrated mosquito-control program," he says. "Fogging is just one component of our program."

• Short-term benefit, long-term risk? •

Family physician Brenda Maxwell is opposed to fogging with malathion. Maxwell is president of the Manitoba College of Family Physicians, but she isn't speaking for the college.

Although she agrees West Nile virus is a problem, Maxwell says there are dangers with pesticides that need consideration.

"We're not looking at the increased number of children with non-Hodgkins lymphoma, the adults with breast and prostate cancers, that may be linked to the pesticide use," she says, adding that the use of pesticides has also been linked to neurological diseases and respiratory problems.

Maxwell says the long-term health risks of malathion may not be worth the short-term benefit of possibly having fewer mosquitoes around for a few days.

"To increase the risk of the whole of society for trying to kill a few adult mosquitoes with a substance which, first of all, over time, doesn't even reduce the mosquito count, seems to be a bit against any kind of intelligent thinking," she says.

Malathion has been used since the 1950s in Canada. Health Canada says the amounts used by the city do not pose a health threat to people. But Maxwell worries about the cumulative effect of all pesticides, which she says could weaken people's immune systems.

• City plans to continue using malathion •

Chemistry professor Norman Hunter agrees that long-term high exposure to any chemical is detrimental, but he plays down the effects of malathion.

"It's designed for killing insects. It interferes with insect metabolism, growth and biochemistry, so it kills adult mosquitoes, for example, which is why it's used here, but it certainly has less of an effect with humans," he says.

"There's a lot more fog in the air from all the car pollution than there is from malathion. I think that malathion is being used so minimally and the amount of times it's being used is so minimal that it shouldn't be a big deal."

Peter Parys with the city's insect control branch, says the city plans to continue using malathion because it's federally approved and is being used appropriately.

Parys says the city is looking into chemical alternatives to malathion.

Last Updated: July 21, 2004

Here is another:

Malathion vs. Mosquitoes:

Every summer, the city of Winnipeg's insect control branch uses a variety of insecticides – both biological and chemical – to control the population of harmful and nuisance insects, such as mosquitoes, cankerworms, elm bark beetles and other bugs.

The city uses malathion to control adult mosquitos. Malathion is an organophosphate insecticide that has been registered for use in Canada since the 1950s.

For mosquito control, malathion is applied by "fogging," using "ultra-low volume" equipment on trucks. The equipment creates a very fine mist of about 60 grams of malathion per hectare.

Besides mosquito control, malathion is also used to control other insects in agricultural settings, such as food or ornamental crops.

• Is it dangerous? •

Malathion is toxic to all insects, including those considered beneficial to humans, such as honeybees. It is also toxic to fish and other aquatic animals. Health Canada's Pest Management Regulatory Agency says the insecticide "displays low toxicity" to birds and mammals.

The chemical degrades rapidly in the environment; officials say it has a half-life of less than one day in soil, which means it takes less than a day for half of a dose to disappear. In the air, its half-life is 1.5 days, on plants about 5.5 days, and in water half a day to 19 days.

Opponents to malathion say the chemical can weaken the immune system and cause cancer, birth defects, intestinal disorders, kidney problems and other health problems.

However, the Pest Management Regulatory Agency (PMRA) recently completed a re-evaluation of public health uses of malathion. It determined the insecticide is still "acceptable for use in controlling adult mosquitoes."

Even for someone who is outside during fogging, the PMRA says, exposure levels would be much lower than those that caused problems in animal tests.

Young animals were more sensitive to the toxic effects of malathion, and the chemical appeared to have adverse effects on the offspring of test animals.

However, the PMRA says the amount of malathion ingested by those animals is far greater than the amount people would be exposed to in fogging situations.

Last Updated: June, 2006

No comments: