The need to clean up polluted air and water has long caught public attention. But we tend to take the purity of our food-producing soils for granted.
That's a dangerous mistake. A slow buildup of toxic metals is quietly ruining farmland in many parts of the world.
There are no culprits to fine or wayward industries to discipline. Toxic metal pollution is a consumer-driven problem. It typifies a new kind of environmental challenge.
Take cadmium, for example. It's one of the worst soil poisons. It is a trace contaminant in phosphorus. It enters soil as part of phosphate fertilizer. There's so little cadmium in the fertilizer that it had not been a concern until recently as massive amounts of fertilizer have been used to meet the world's rising food demand.
This is a case where the new field of industrial ecology can shed valuable insight. As explained by one of its practitioners -- William Stigliani of the University of Northern Iowa at Cedar Rapids -- this science tackles chemical pollution by taking ''a holistic approach.'' Instead of concentrating on polluting industries, it looks at how the chemicals cycle throughout the economy and how they behave in the environment. It is equipped to handle situations, such as metal contamination, where pollution sources include users of chemicals as well as the producers of the chemical-containing products.
Professor Stigliani is part of a team assembled by the International Institute for Applied Systems Analysis in Laxenburg, Austria. This is a research organization supported by 17 nations, including the United States. Discussing the team's work during the recent annual meeting of the American Association for the Advancement of Science in Atlanta, Stigliani explained that it has focused on the Rhine Basin in Europe. The aim is to use this region as a test bed to develop methods for assessing consumer-driven pollution that can be used worldwide.
Rhine Basin countries have cut industry-driven pollution to 1/10th what it was 20 years ago, Stigliani said. He added that ''one thing that ... was very very clear from our analysis is that the share of heavy metals [pollution] has shifted ... from industrial point sources to diffuse sources [related to] consumption.'' It's those diffuse consumer sources that have to be dealt with now.
Cadmium, for example, is also a contaminant in zinc ore. Zinc producers sell the cadmium to manufacturers who use it in plastics, paint pigments, as coatings on steel, and in those handy rechargeable nickel-cadmium batteries. The cadmium gets into the environment from the way consumers use these products and eventually dispose of them.
This kind of pollution will be harder to curb than the effluents of factories. If governments banned cadmium-containing products, the poisonous metal would then be a waste product for zinc refiners. It would shift disposal from the consumer landfill to the industrial landfill. It would be better, Stigliani suggested, for manufacturers to design the products for recycling or safe disposal.
Soil contamination from cadmium-containing fertilizer will be even harder to deal with. Restricting fertilizer use in food-rich countries might be feasible. But it would be difficult for food-short nations with burgeoning populations. Taking contaminated land out of production won't solve the long-term problem.
The new industrial ecologists like Stigliani don't have ready answers for such problems. What they do have is an analytical method for understanding the complexities of consumer-driven pollution. It can show the fallacies of seemingly sensible measures such as trying to curb cadmium pollution simply by banning cadmium-based products. And it can highlight unsuspected pollution such as cadmium contamination from fertilizers.
This is a way to clearly define the problems. And that often is the first step in finding solutions.