First world estimate of metal pollution.

First world estimate of metal pollution

Nearly every major industry releases one or more trace metals into the environment. Ore smelting spews arsenic and lead into the atmosphere. Urban wastes and coal ash disposal lace soils with zinc, copper and mercury. Power plants and smelters taint rivers, lakes and seas with selenium, cadmium and nickel. But unlike organic pollutants, these metals are not biodegradable; they stay in the ecosystem, building up to what can become toxic levels.

In the May 12 NATURE, two researchers present the first quantitative worldwide estimate of the annual industrial input of 16 trace metals into the air, soil and water. "On a global basis there are tremendous quantities of toxic metals released into the environment," says Jerome O. Nriagu, an environmental geochemist at Canada's National Water Research Institute in Burlington, Ontario. He compiled the figures for 1984 emissions with atmospheric chemist Jozef M. Pacyna of the Norwegian Institute for Air Pollution Research in Lillestrom. The researchers conclude the toxicity of the trace metals released each year now exceeds that of all radioactive and organic pollutants combined, assuming toxicity is measured as the amount of water that would be required to dilute pollutant concentrations to levels safe for drinking.

This study "illustrates pretty clearly that human activities are significantly altering the cycling of many heavy metals in the environment on a global scale, and not just in New York City or in your local sewage treatment plant," comments atmospheric chemist Robert A. Duce at the University of Rhode Island in Narragansett.

Nriagu and Pacyna's results are consistent with measurements of several trace metals made by Duce and his coworkers in remote regions of the Pacific Ocean. "We are definitely seeing the impact [of metal emissions] thousands of miles away from the sources," Duce says. "But the problem is what does it mean? Is it causing a problem? I don't think we have the answer to that."

Nriagu, however, says the accumulation of toxic metals in the human food chain is accelerating. He believes the world may be facing a "silent epidemic of environmental metal poisoning."

The NATURE paper expands upon atmospheric emission estimates of five metals Nriagu compiled in 1975. It is the first study to look at world metal inputs into soils and water, and as such helps scientists see how metals move between air, soil and water. The researchers note that contamination of freshwater in Europe, North America and Asia may be much more severe than generally realized and that in some parts of Japan and Europe, metal levels in soils have overwhelmed the environment's natural ability to cleanse itself.

Happily, not all of the news is bad. According to Nriagu, atmospheric levels of lead, zinc, cadmium and copper dropped between 1975 and 1984. Lead emissions will continue to fall, he says, mostly because of U.S., Canadian and European controls on leaded gasoline. still, he adds, while the global numbers are encouraging, the problem is simply shifting from developed nations to the developing countries, which have no controls on lead and other metals.