The Computer Take Back Coalition report ranks computer companies by their use of hazardous materials, reporting of recycling and toxics data; worker safety; and willingness to recycle old machines.

"The genius of the high-tech revolution has been the ability to build newer and faster and cheaper computers every 18 months," said Ted Smith, executive director of the Silicon Valley Toxics Coalition, one of the groups in the coalition that released the report. In 1999, 24 million computers in the United States became obsolete, according to data from the National Safety. If the machines are dumped or burned, they threaten to release lead, mercury, cadmium and other toxic metals.

Both Europe and Japan require all computer makers to take back old machines for free. And indeed, Japanese companies such as Canon, Sony, Fujitsu and Toshiba scored the highest environmental grades in the report.