It's bad for kids' brains. Really bad. And Kevin Drum says we could largely solve the problem for relatively little money. And check out this lead-related anecdote:

Lead was banned from gasoline during the 1980s. The job was done by the Reagan Administration. Vice President George H.W. Bush and his "regulatory reform" task force had proposed loosening lead limits, but a brilliant analysis spearheaded by my friend Joel Schwartz (then at the EPA, now at the Harvard School of Public Health) managed to turn the proposal around; even the folks at OMB couldn't deny the data when they had their noses rubbed in them. Such deference to fact would be unthinkable today

Astonishing, but true isn't? One couldn't imagine a policy argument on the merits of any sort convincing the Bush administration of anything. If the gasoline companies wanted something not to happen, it wouldn't happen.