Sir — In his book Pandora's Poison: On Chlorine, Health and a New Environmental Strategy, recently reviewed by Terry Collins (Nature 406, 17 –18; 2000), Joe Thornton advocates a broad policy that would require industry to phase out chlorine-based technologies in favour of cleaner alternatives. He says we must do away with a regulatory system that looks at one chemical at a time, and replace it with a precautionary approach that addresses major classes of chemicals and industrial processes.
Considering all organochlorines, from essential non-toxic PVC to the very toxic 2,3,7,8-TCDD (dioxin), as one class to be discarded is as non-scientific as saying that all reptiles and birds are dangerous because some snakes are venomous.
There is no scientific basis for regulating all hydrocarbons — from non-toxic polyethylene (PE) to very toxic polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene — as one class. Nor is there any scientific basis for regulating nitrogen-containing organics, from nylon to nitro-PAHs (the most powerful mutagens ever found , contained in diesel motor exhaust). Such a broad-based precautionary principle would mean that chlorine, nitrogen and every other organic material would be banned.
Chlorine is a very reactive element, making reactions possible that otherwise would be very difficult to perform without much more energy or more pollution. Chlorine is used in chains of processes: it is first used to make the building blocks for polyurethane and the remaining HCl is used to make PVC. That halves the energy needed to make chlorine for both. Without chlorine, the amount of (toxic) waste from polyurethane manufacturing would be much higher.
Thornton has been quoted in the online Environment News Service ( http://ens.lycos.com/ens/jun2000/2000L-06-08-06.html) as warning that levels of dioxin in the environment can only increase, as long as organochlorines are produced. He claims that there is no safe way to dispose of them: “once they're in you, there's no way to get them out”.
This is a clear untruth. In every Western country the levels of DDT/DDE, PCBs and dioxins in the environment and in animals and humans have fallen or are falling rapidly since these industrial products and by-products have been banned or restricted. PCB levels in North Sea fish are now half what they were ten years ago. The dioxin content of Belgian mothers' milk has gone down by 30% in five years — mainly because of the stringent measures that were imposed on incinerators — during a period when chlorine and PVC production, use and incineration were higher than ever before.
“Like the Romans, who sipped from lead cups, ran drinking water through lead pipes, and bathed in lead basins, we have built our house of poison unaware of the consequences,” Thornton says.
But unlike the Romans , who were likely to die by the age of 40 either from lead poisoning or as a result of infections, today's Westerners reach 80 years and older. In my view, this is not least thanks to drinking chlorinated water run through PVC pipes, swimming in chlorinated pools, eating food sealed in PVC-wrap foil, sleeping on mattresses made using chlorine and taking medicines of which 80% are made with the help of chlorine.