2: Unleaded petrol
In the early 1920s, chemists added lead to petrol to help vehicle engines run more smoothly. Though it was a known toxin, the risk to health was considered minimal. Decades later, with increasing numbers of vehicles on the road, the dangers became apparent. Engines emit fine lead particles that contaminate soil and can be inhaled and ingested by people. Children are especially vulnerable to lead poisoning, giving rise to such health problems as diminishing IQ, organ damage and hearing loss. In the 1970s, the USA began restricting the amount of lead allowed in fuel, finally banning it in 1996 with the Clean Air Act. Other counties rapidly followed. Elevated blood lead levels in children went from 88 per cent of children in the 1970s to 1 per cent in 2006. Now, only a few countries still use leaded fuel, and UNEP is aiming for global eradication of leaded petrol by 2013.