Toronto Globe and Mail
4 February 2003

Mercury a global problem, UN says. Pollutant may already have caused learning problems and impaired nervous systems in millions of children worldwide

Martin Mittelstaedt, Environment Reporter

The world's environment is being contaminated by alarming amounts of mercury, a devastating nerve poison that is building up in many fish species and among people who consume them, says a new report from the United Nations.

The UN report expressed concern that mercury exposure could be causing brain damage in humans, particularly among infants who are most susceptible to mental impairments from the heavy metal.

It also concluded that mercury is a "major threat" to the world's fishing industry, an important component of the food supply and the main way people are exposed to the pollutant.

"The available data indicate that mercury is present all over the globe, especially in fish, in concentrations that adversely affect human beings and wildlife," the report concluded.

It said predatory aquatic animals higher up on the food chain -- pike, king mackerel, walleye, and large tuna, as well as seals and toothed whales --have the highest mercury levels. It said canned tuna is generally made from smaller fish, and has lower levels of the metal.

The international body said millions of children may already be suffering ailments -- ranging from learning difficulties to impaired nervous systems-- due to dietary mercury.

The biggest source of mercury emissions is from coal-burning power plants and waste incinerators, which together account for about 70 per cent of man-made emissions, according to the report, which was released yesterday.

But the UN said people are also being exposed through the amalgam used to repair dental cavities, mining activities where mercury is used to extract gold, some vaccines, drugs, and even some contact lens solutions.

Although mercury discharges in some countries are declining -- the UN cited Canada's cut to six tonnes a year from 30 tonnes between 1990 and 2000 --emissions remain high and are growing in Asia because of increased energy usage as countries there industrialize.

Once emitted into the atmosphere, mercury knows no boundaries, and can move thousands of kilometres on air currents to other continents, where it is deposited in precipitation and then enters the aquatic food chain.

Even though Canada has cut its pollution, half the mercury falling on North America comes from outside the continent, according to the report.

As an element, mercury can't be destroyed, and concentrations continue to build up in the environment.

Human activity has tripled the level of mercury in the environment, according to the report.

The report "shows that the global environmental threat to humans and wildlife has not receded despite reductions in mercury discharges, particularly in developed countries," said Klaus Toepher, executive director of the UN's environment program.

The study was requested by UN members and is being presented this week to an environment ministers meeting of the global body.

It will be used to recommend steps to reduce emissions.

Mercury emissions by continent

The following numbers are estimates of global atmospheric mercury releases in 1995 (in tonnes/year).