The LED bulbs sold as safe and eco-friendly can contain high levels of lead, arsenic, and other hazardous substances, a new University of California, Irvine (UCI) study showed –- the same bulbs widely used in headlights, traffic lights, even holiday lights. The toxic material could increase the risk of cancer, kidney disease, and other illnesses, although the risks are more long-term than immediate; a single exposure to a broken bulb is unlikely to cause illness. I wouldn’t worry about an immediate release of vapor, said a UCI public health and social ecology professor, the principal investigator and an author of the study. But still, when these residues hang around the house, if not cleaned up properly they could constitute an eventual danger. The lights should be treated as hazardous materials, and should not be disposed of in regular landfill trash, he said, because of the risk of the materials leaching into soil and groundwater.