Malathion sprayed across Winnipeg may not have met certain guidelines

WINNIPEG — It’s been widely sprayed across Winnipeg, but now a new analysis of city owned malathion batches shows some did not meet World Health Organization (WHO) guidelines.

The City of Winnipeg sent samples from two batches of its mosquito fighting chemical to a lab for analysis.

READ MORE: City to begin fogging Sunday; Health Canada approves Winnipeg’s malathion supply

Isomalathion is an impurity found in some batches of malathion and can be significantly more toxic to humans than malathion.

Those levels can increase in the chemical over time or if it is exposed to heat by being stored improperly.

The City of Winnipeg’s supply of malathion was years old with some of its product dating back more than a decade.

An analysis of lab test results, done by Elias Consulting, show that a batch of malathion from 2007 obtained from the province does not meet WHO guidelines because of elevated levels of isomalathion. Concentration levels of the toxic compound must not exceed 0.4 per cent in any batch of malathion.

One test done from that batch came back with isomalathion levels of 1.3 per cent.

The report states the 2007 batch has “excessive isomalathion levels and the toxicity could be 2-4 times the level” of the WHO guidelines.

“For the public, this would be the equivalent of applying compliant malathion at up to four times the concentration,” the report states.

Tweet This Click to share quote on Twitter: "For the public, this would be the equivalent of applying compliant malathion at up to four times the concentration," the report states.

However, both the city and independent experts who spoke to Global News said there is no reason to be concerned and it poses no health risk.

“There is really no reason for concern,” said Ken Nawolsky, the superintendent of insect control. “After talking to the consultant, it’s not an unreasonable risk to the public. In terms of the threshold we are 50 pe rcent lower than the acute exposure.”

A statement that was echoed in the report which states that even at a concentration of four times the acceptable rate of compliance, the levels still fall below the acceptable exposure guidelines set by the Acute Exposure Guideline Levels for Hazardous Substances (AEGL).

RELATED: ‘They’re strong biters’: Mosquitoes with painful bite hatching early

In June, the city used its old stock of malathion from 2003 to fog the city. Shortly after, Health Canada told the city to stop using the remainder of its chemicals because they were too old.

The city bought 670-litres of the chemical from Saskatchewan in 2003 at a cost of $12,600, however, the label states it shouldn’t be used after one year.

READ MORE: Winnipeg will not be using malathion to fog mosquitoes until further notice

None of that stock was tested for isomalathion levels, but according to the lab analysis, “it should be assumed” that had it been tested isomalathion toxicity levels would also likely have been higher than the allowable limit.

“We only had 670L so less than half the city would have been applied with that product,” said Nawolsky. “It stated in the report that the risks are definitely acceptable to the general public.”

Tweet This Click to share quote on Twitter: "We only had 670L so less than half the city would have been applied with that product," said Nawolsky. "It stated in the report that the risks are definitely acceptable to the general public."

The city told Global News the level of degradation would be minimal and the results would likely be very similar to what was found with the 2007.

Experts said they do not believe there would be any risk to the average person’s health based on those results.

The city said it is already in discussions with the province of Manitoba to return the expired, unusable stock and possibly to get a refund.

It also said now, more than ever, it is pushing to to get the environmentally-friendly alternative, DeltaGard, approved for use in Canada.

“Both the province, the City of Winnipeg and Manitoba Conservation are all working very hard to get that product expedited into Canada for next season,” he said.”