The city should take care when locating sports fields and allowing construction on or near Hydro corridors - but the city shouldn't go overboard in trying to protect residents from electromagnetic fields, said Toronto's Medical Officer of Health Dr. David McKeown Thursday, July 3.

"It may be better to do your jogging in the hydro corridor than it is not to jog," Dr. McKeown told Toronto's Board of Health as it considered a recommended policy of "prudent avoidance" when it comes to electromagnetic field (EMF) exposure.

"The idea is to minimize the exposure to EMFs so that people get the best benefit from the use of the land with the minimum risk."

The board finally recommended McKeown's strategy - which is literally based on uncertainty about the health effects that EMF exposure has on human health. The International Agency for Research on Cancer has classified the fields as a potential carcinogen because of association with childhood leukemia. But the results are inconclusive.

So the policy would see the city taking low or no-cost actions to reduce the exposure of young children to high EMFs, such as are found in the vicinity of hydro corridors.

But McKeown said that shouldn't include keeping children away from the facilities, if they're the best locally-available recreation spaces available.

It's all a matter of degree.

"The use of those lands provides an important benefit to the city," said McKeown. "They are areas of city activity, cultural activity and urban agriculture uses. The assessment is that the health benefits of those uses outweigh the risks of exposure to EMFs. But there are ways of reducing EMF exposure in a cautionary manner which doesn't impair the use of corridors but provide assurances."

The board also heard from Ward 39 (Scarborough-Agincourt) Councillor Mike Del Grande.

He suggested that the board recommend some form of signage, that would alert potential users of parkland underneath hydro wires of the EMF levels.

"If there is a potential issue with respect to leukemia, then we should have signs posted in those hydro fields indicating what the level of exposure is," Del Grande said. "If I'm walking my dog in the hydro field or somewhere else, I should have a choice based on my having the right to know."

Del Grande also wanted to explore ways to make builders of subdivisions abutting hydro corridors inform potential buyers of the risks.

"I venture to say that nobody knows what the exposure is on homes that back onto hydro fields," he said. "We're saying we have an issue with respect to having facilities near these corridors."

McKeown, however, pointed out that the city wouldn't have the authority to impose restrictions on developers in that way.

The board is, however, asking the city to request developers in such a circumstance to take low- or no-cost mitigation measures.

McKeown said the best way to protect children from exposure is not to simply keep them clear of Hydro corridors - but to generally be aware of issues surrounding EMFs, which are also generated by household appliances, electrical wiring and large electrical facilities such as transformers.

The board did recommend looking at the EMF levels along Commissioner's Street in the eastern waterfront - a major hydro corridor immediately adjacent to industrial properties.