McMaster University

McMaster University

Study quiets alarm over lead

The Hamilton Spectator
Teri Pecoskie
September 26, 2011

Despite alarming initial reports, a public health study has found less than 1 per cent of children six-and-under in the lower city have potentially damaging levels of lead in their blood.

The study, which will be presented to the board of health Monday, indicated that six of 643 children tested — or 0.9 per cent — had capillary blood lead levels at or above the Health Canada guidance value, or the value at which follow up actions may be considered to reduce exposure.

These results contrast with initial figures from public health reported by The Spectator in 2008 which indicated that 20 per cent of the first group of children tested had enough lead in their blood to cause permanent developmental damage.

Mayor Bob Bratina, who advocated for the $250,000 study in his former post as Ward 2 councillor, called it "one of the most important reports we've had."

It's an issue that "never went away," he said. "Once council sees the report they'll understand that it was a really good investigation of the subject ... it's about the whole spectrum of the presence of lead."

Bratina said he wouldn't comment further until council members received the report and had a chance to review the findings.

The study found the geometric mean of blood lead levels in children was 0.107 micromoles per litre. This is consistent with a U.S. study which found that, although American kids have a slightly lower blood lead level overall, the same proportion of children is at or above that Health Canada warning threshold of 0.48 micromoles per litre — 10 micrograms per decilitre (one-tenth of a litre). There is little comparable Canadian data on blood lead levels beyond this new Hamilton study.

In 2008 researchers studied children in the area bordered by the Escarpment, Highway 403, Parkdale Avenue and Hamilton Harbour.

The blood samples were collected from children who had lived within the study area for at least three months. Those who registered blood lead levels at or above the conservative study threshold of 0.19 micromoles per litre — 96 children within the lower city — were asked to return for additional blood testing.

Researchers also collected tap water, soil and dust samples at nearly 200 households, and concluded that the levels of lead in those environmental samples were strong predictors of high lead levels in children. Air samples were taken, but the authors couldn't draw a conclusive link between the data and elevated blood lead levels.

The report, a dense 121-page document, found slight differences based on the child's sex and neighbourhood. Boys and those living near the foot of Queen Street and the area south of the rail line between Wentworth Street and Gage Avenue were slightly more likely to register levels at or above the study's standard for additional blood testing.

The authors also acknowledge several limitations with the study. For instance, fewer than half of the sought after sample of 1,300 children responded and participants were more likely to live in the study area's southwest corner, away from the less affluent core and industrial zones.

Balmoral Avenue residents Keith and Bonnie Smith said they're still trying to figure out why their four-year-old son Cameron — one of the first children tested in the study — was found with elevated levels of lead in his blood. They say subsequent environmental tests didn't reveal anything abnormal at their home that could be responsible for the spike, and despite the study's findings, they continue to worry about his long-term health.

"It doesn't make sense why he has that in his blood, there's no reason for it," said dad Keith, who had yet to read the report. The couple agreed that additional testing and more information about blood lead levels would go a long way to quell their fears.

Dr. Shobha Wahi, an associate clinical professor in pediatrics at McMaster who assessed some of the children in the study, agreed that the city should continue investigating the issue.

"I think they maybe need to screen further, because it's the only study we have for kids under seven," she said. "That group probably needs to have a longer term follow up to see what happened."

The report recommends the city continue its low interest loan program and free inspection of lead water service lines. It also recommends an environmental awareness program and that the province be petitioned to provide funding for on-tap water filters in low-income households — although it's mum on the issue of a potential followup study.

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