Poisons have long shelf lives

Almost three decades after Canada banned lead from household paints and started regulating its use in gasoline, we’re still feeling the effects of lead’s former prominent role in commercial products and industry.

Lead poisoning causes anemia and brain and nervous-system damage. A recent study suggests that low-level exposure to lead also causes high blood pressure, hardening of the arteries and coronary heart disease.

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The study, led by Simon Fraser University researcher Bruce Lanphear, indicates that exposure to historical lead might have contributed to more than 250,000 middle-aged and older people dying prematurely from heart attack and other cardiovascular disease in the U.S.

The study followed participants for almost 20 years, and found that people with high lead levels in their blood — at least 6.7 micrograms per decilitre of blood — were 37 per cent likelier to die early from any cause, 70 per cent likelier to die from cardiovascular issues and twice as likely to die from coronary heart disease than people with low levels of lead. However, even lower levels of blood lead (one to five micrograms per deciliter of blood) seemed to have negative effects.

Those most affected were aged 44 and older. Being older, these people would have had the most opportunities to be exposed to lead when they were young and lead was more abundantly used, as well as since lead was banned.

Exposure occurs when a person comes into contact with lead that has remained in the environment from long-ago use in fuel, paint and plumbing, as well as ongoing exposures from foods, emissions from industrial sources and contamination from lead-smelting sites and lead batteries.

Although the study followed American patients, the results would apply here, too. Canada’s history of lead use parallels that of the U.S.

Lead once was added to gasoline to prevent engine damage due to the auto-ignition of gasoline — or knocking. Since 1990, Canada has regulated the concentration of lead in gasoline produced, imported and sold in the country, with the result that lead in gasoline has virtually disappeared. Today, 99.8 per cent of gasoline used in Canada is lead-free.

One exemption is aircraft fuel — something to ponder when you’re stuck in cattle class while travelling by air and the smell of engine exhaust wafts through the air vents during takeoff and landing.

The same federal regulations banned use of lead in household paint. However, any building constructed before 1990 could and likely does contain lead paint.

Before 1990, vehicle emissions were the largest source of airborne lead particulates in Canada. The controls on lead significantly decreased airborne concentrations, leading to reduced uptake by Canadians.

But those emissions particulates had to go somewhere. Some would have been breathed in by people and animals. Some would have settled onto our gardens, orchards and farms. Some would have drifted on prevailing breezes to the farms and orchards of the Fraser Valley. Some would have rained down on the sea.

The lead produced by the region’s industries would also have found its way into the ground and water around us.

A recent Ocean Wise study of pollutants in B.C.’s coastal waters shows, for example, that Victoria’s Inner Harbour is one of the province’s most contaminated waterways. Among the PCBs, dioxins, mercury and other long-banned chemicals that lace the harbour’s sediments, lead figures prominently. Lead levels in both sediment and mussels collected from the harbour are among the highest of all 55 sites sampled.

These pollutants tell of a time when our picturesque harbour served as a centre for heavy industry.

Just as the mid-1990s global ban on ozone-depleting chlorofluorocarbons stopped the flow of new CFCs into the atmosphere, Canada’s 1990 ban on lead limited new amounts of the metal entering our environment. However, while governments in Canada consider bans and limits on other chemicals and products — including antibacterial agent and pesticide triclosan, anti-cancer drug and dioxin-related pesticide mitotane, plastic microbeads and single-use plastic bags — we need to remember one thing:

Ending the use of lead, pesticides, PCBs or plastic microbeads and bags doesn’t make the substances disappear. We’ll be dealing with their legacies for years to come.

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