Lead is dangerous particularly to children It can cause learning disabilities and lower IQ. New testing by CBC Marketplace reveals that lead in drinking water remains a problem for many Canadian families.

Ewan and Phoebe Ross who live in Hamilton, Ontario, drink only bottled water now since the city called their mother. "We received a phone call that we ought not to drink the water because we had a level that was three times the allowable level for lead."

Wendy Leigh Bell had the old water pipes into her house replaced. Towns and cities across the country have spent hundreds of millions of dollars replacing old pipes to reduce lead leaching into drinking water. Some cities add chemicals to reduce lead levels. But has it worked?

Marketplace tested tap water in 50 homes across the country. Half were built before 1970, the other half 1970. Fifteen had lead levels above the maximum allowable limit. The water in one home was 250 times that limit.

The test used water taken from the tap as soon as the tap was opened. That's how the British and Americans test for lead.

But he Canadian guideline recommends letting the water run for three minutes before taking a sample.

In all but two of the homes the lead level dropped below the allowable limit.

"If you do all your sampling after a three to five minute flush, you are greatly underestimating the average concentration of lead in the water," says Dr. Richard Mass a chemist at the University of North Carolina.

But Health Canada says the Canadian testing method is just as accurate. "Our philosophy as stated is to try to see what the average amount of lead is in the water a person consumes," said Health Canada's David Green.

Health Canada advises you to run your tap water before you drink it. To be safe you can let the water run or use a filter that removes lead. Boiling doesn't work.