Last month's talks to mitigate global warming may have flopped (Science, 3 November, p. 920), but this week brought some consolation to those concerned about the planet's environmental health: the first-ever global agreement to abolish a class of dangerous industrial chemicals. The treaty, finalized by representatives of 122 countries meeting in Johannesburg, South Africa, also spells out a process to put more chemicals on the black list.
The treaty on persistent organic pollutants, or POPs, as they're known, will ban or phase out 12 pesticides and other chemicals that are still used in many developing countries. These "dirty dozen" are highly toxic and don't break down easily, which means they accumulate in body fat. Concern about the toxicity of POPs "goes all the way back to Rachel Carson's" warning about DDT and eggshell thinning in birds, notes reproductive toxicologist Louis Guillette of the University of Florida, Gainesville.
The POPs treaty, organized by the United Nations Environment Program over the past 2 years, will ban eight of these pesticides immediately once the treaty has been ratified by 50 countries. Two industrial byproducts on the list, dioxins and furans, will be reduced right away and eliminated "where feasible," for example, by clamping down on open trash burning. PCBs, used in electric transformers mainly in Russia, will be allowed until 2025 as long as equipment is maintained to prevent leaks.
Treaty negotiators made an exception for DDT used to control malaria after a small group of malaria experts argued that there was no effective substitute. Roger Bates of Africa Fighting Malaria, a loose coalition of DDT supporters in South Africa, says that banning DDT now would be like "crossing a street with heavy traffic to avoid a crack in the pavement."
One major sticking point was laying out the rules for adding more chemicals to the list. European countries and environmentalists argued for incorporation of the "precautionary approach," which says that it may be necessary to take action even when the scientific evidence is incomplete. But U.S. officials worried that would ignore risk analysis, which bans chemicals only if enough data show they're dangerous. In the end, delegates compromised by explaining that precaution would be "an integral part of--and not separate from--the overall scientific process," according to a statement from U.S. State Department negotiator Brooks Yeager.