By Janet Raloff
From Chicago, at the EPA Emerging Pollutants Workshop
The standard test to evaluate whether metal-laden products are hazardous fails to flag high concentrations of lead in some discarded electronics equipment, new studies show.
“It was a surprise,” says Timothy Townsend of the University of Florida in Gainesville. On the other hand, the data are consistent with findings by others for certain metal-foundry wastes, he says.
Under the acidic conditions in many landfills, electronic gadgetry can leach lead and other toxic metals. To test an object’s potential to leach metal, federal guidelines require that it be crushed into pieces smaller than 1 cubic centimeter and soaked for 18 hours in a vinegar-strength acid bath. Products that leach at least 5 milligrams of any toxic metal per liter of solution must be designated as hazardous waste when discarded. That usually requires keeping them out of municipal landfills.
When Townsend’s team conducted this standard test on seven shredded computer central-processing units (CPUs), none leached enough lead to be deemed hazardous. However, when the group tested dismantled but unshredded CPUs, 9 of 10 failed the acid test. Nine of 30 cathode ray tubes from color computer monitors passed the standard shredded-parts test even though separate tests have shown that most of these tubes contain huge amounts of lead (SN: 11/4/00, p. 303).
Why didn’t the standard test find hazardous amounts of lead in these computer parts? Townsend says it appears to be the products’ steel content, which, when shredded, alters the acid bath’s chemistry so that it pulls less lead from the shredded parts.
Laptop computers contain much less lead than cathode ray tubes do. Nevertheless, six of eight shredded laptops failed the standard test, as did all eight samples of dismantled but unshredded laptops. The laptops’ low steel content had little effect on the acid bath, says Townsend. Results for cell phones were similar to those for the laptops.
Townsend concludes that for steel-laden electronics, a direct measurement of lead content may be more reliable than the standard leaching test for determining whether the products, when thrown away, should be designated as hazardous waste.
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