VERNON HOUK, Centers for Disease Control
National Institute of Occupational Safety and Health
Two years ago dioxin seemed poised to clear its name. Scientists concluded that the chemical acts through a special mechanism: it attaches to a receptor–a lock for which dioxin is the key-in living cells. The dioxin-receptor pair goes to the cell nucleus, where it gloms onto DNA and helps trigger a cascade of nasty effects. Under this theory, industry claimed, there might be a safe level of dioxin: one that doesn’t fill enough receptors to change DNA.
But research last year at the National Institute of Environmental Health Sciences threw into doubt the idea that dioxin must attach to a minimum number of receptors to cause harm. And according to EPA draft reports obtained by NEWSWEEK, dioxin may affect the central nervous and immune systems-increasing susceptibility to infections and tumors-independent of receptors. Other studies, says deFur, find that if a pregnant animal is exposed once to dioxin, her offspring’s reproductive system can be damaged.
If EPA decides that dioxin isn’t so bad, paper mills could avoid the steep cost of reducing dioxin emissions (dioxin forms when chlorine used for bleaching combines with lignin in wood pulp) and lawsuits seeking billions of dollars in damages from paper and chemical firms could flame out. It will be at least a year before EPA finishes its analysis. Even then the verdict will likely be equivocal. As usual, society will have to decide whether to err on the side of caution or risk finding out too late that dioxin is as dangerous as originally thought.
