The pesticide methyl bromide destroys ozone and causes convulsions, neuromuscular and cognitive problems -- even death -- in farm workers and others directly exposed to it. It also causes unknown damage to children who attend schools near fields where the pesticide is used, and equally uknown damage to people who eat foods grown with the pesticide. The U.S. has signed an international treaty banning all but the most critical uses by 2005, yet the government is working hard to allow exemptions that keep the poison in use indefinitely.