Malathion sprayed in Winnipeg may not have met guidelines

Malathion sprayed acrossWinnipeg in June may not have met World Health Organization (WHO) guidelines, according to an analysis of lab results.

The City ofWinnipeg sent samples from two of its batches of the mosquito-killing insecticideto a lab for analysis after a CBC I-Team story revealed the city's supply had been stored too long to be incompliance with federal rules.

• Health Canada tells Winnipeg it can't fog with years-old malathion

Toxic isomalathionlevels can increase in the chemical with time or when exposed to heat. The City of Winnipeg'ssupply wasyears-old with some product dating back 13 years.

An analysis of labtest results revealed thata 2,000-litrebatch of malathion from 2007obtained from the province does not meet WHO guidelines because of elevated levels of isomalathion.Thecut off forisomalathionconcentrations in any givenmalathionbatchis 0.4 per cent.

The analysis reportby Elias Consulting notes that the 2007 batch has "excessive isomalathion levels and the toxicity could be 2-4 times the level" of theWHO guildelines.

"For the public, this would be the equivalent of applyingcompliant malathion at up to four times the concentration," the report notes.

None of the 2007 product has been used according to the city, but earlier this summer the city depleted its supply of an even older batch ofmalathion dating back to 2003. None of the 2003 stock had been tested for isomalathion levels, but according to the lab analysis, "it should be assumed" that had itbeen tested isomalathion toxicity levels would also likely have been higher than the allowable limit.

The city says based on the report, "public exposure to isomalathion would likely be below the Acute Exposure Guideline Levels for Hazardous Substances (AEGL) and would not present an unacceptable risk to the public or to workers."

The city says it iscurrently in discussions with the province to return the unusable2007malathion.

The city's 2009 batch of malathion did meetWHO and AEGL standards. The city has restarted its fogging program with that product.

• Fogging to resume as 2009 city insecticide stock gets passing grade

Even though federal rules state malathion cannot be stored longer than one year, Health Canada's Pest Management Regulatory Agency will allow the city to fog with older product so long as it is tested for toxic isomalathion by an accredited lab.