As more Americans move to get rid of old personal computers, the nation may face a significant environmental problem. PCs contain traces of toxic chemicals such as mercury, and one survey found that old computer monitors are one of the largest sources of lead in landfills. A report released this month by the National Safety Council estimates that only 11 percent of the PCs that became obsolete in 1998 were recycled, and only 3 percent resold or donated. Recycling is difficult and often unprofitable, and many charities and schools don’t want donations of old computers unless they have Pentium chips. By 2002, 3.4 million more PCs will go obsolete than will be shipped by manufacturers. Suggested solutions include designing PCs to be updated and recycled.