Parents of children battling head lice are being urged to avoid over-the-counter treatments that contain a pesticide outlawed for agricultural use in dozen of countries -- including Canada -- because of its adverse effects on humans and the water supply.

While a number of lice shampoos don't contain lindane, store shelves across the country are still stocked with brands that employ the controversial chemical.

Lindane-based pharmaceuticals may represent the extreme when it comes to killing lice, but environmental activists say parents are often so disturbed by the thought of their kids harbouring bugs, and the stigma of becoming infected, that they adopt an "eradicate at any cost" stance.

"I don't really think that people comprehend alternative substances are effective and we're more or less dousing our children in pesticides" when using lindane, said Kevin Mercer of the group Riversides, which advocates on water quality issues.

"Using lindane to kill head lice is like using a sledgehammer to kill an ant."

While several environmental groups have called for a ban on lindane-based pharmaceuticals, Health Canada still allows for its use in lice and scabies treatments, even though its use as an agricultural pesticide has been banned.

The Canadian Paediatric Society is reviewing its position on lindane products and currently recommends that they not be used on infants and children under 17. The society advises that products that contain pyrethrin or permethrin, instead of lindane, are considered safe.

California banned lindane products in 2002 amid concerns the chemical was showing up in wastewater and because lindane-based medications were generating reports of skin irritation, dizziness, headaches and, in some extreme cases, convulsions and death.

California estimated that a single treatment of a lindane-based product that was washed down the drain was impacting 22 million litres of water and bringing contamination above the limit of 19 parts per trillion.

A few years after the ban was implemented, officials said lindane levels had become nearly undetectable in the water supply and there was no notable increase in lice or scabies outbreaks.

Several U.S. states in the Great Lakes basin are now considering a similar ban, but the Ontario government and Health Canada say they're not overly concerned about the impacts of lindane-based shampoos.

There is evidence that shampoos are causing some levels of lindane to show up in municipal wastewater effluent testing but "it is uncommon and would have minimal impact to the environment," said John Steele, a spokesman for Ontario's Ministry of the Environment.

"Work has shown that lindane is essentially not a concern and in fact, over 90 to 95 per cent of the samples were non-detect," he said.

"Historically, we have studied the environmental effects of the use of lindane and we have reviewed monitoring data that showed that concentrations of lindane were generally not detected in sediments or (in bacteria, plant or animal life) in the Great Lakes."

Health Canada conducted a safety evaluation for lindane and found the risks associated with occasional and short-duration exposure to head lice and scabies products were less serious than when the chemical was used as an agricultural pesticide.

In 1995, the U.S. Food and Drug Administration said lindane-based products should be used only after other alternatives had failed and currently warns the public that if they are used, they should only be used once.

"Patients are at risk for serious neurologic adverse events, and even death, particularly with early re-treatment," states the warning, which adds that it's not known when it's considered safe to administer a second dose.

Canada should be following the lead of other countries and banning lindane, particularly since Health Canada's adverse reaction database includes more than three dozen cases since 1971 that are linked to lindane, including two deaths, Mercer said.

"It's one of those things that we will wonder once we have banned lindane why the heck we didn't do it sooner, because it's just so obvious," he said.