The Natural Resources Defense Council has got mercury on its mind. They write, “Mercury Poisons Our Children’s Brains” explaining:
Mercury is a potent neurotoxin that, like lead, especially threatens the brains and nervous systems of fetuses and young children. A number of neurological diseases and problems are linked to mercury exposure, including learning and attention disabilities — which are a growing problem — and mental retardation. Mercury also might be linked to the recent increase in autism, Parkinson’s disease and Alzheimer’s disease…one in every 12 women of childbearing age has mercury in her blood above the EPA “safe” level…Toxic mercury emissions from power plants put 300,000 newborns each year at risk for neurological impairment.”
Frightening isn’t it? Lets take a closer look before sending the NRDC a check. How was the EPA’s safe-level arrived at? There are three major studies of mercury and neurological impairment in children due to consumption of contaminated fish. One study found no effect, one was ambiguous, the last found some mild impairment (You would never notice the impairment on an individual level and can detect it only in a large sample. Not to be ignored if it exists, but we are not talking about Downs children). To be on the safe side, the EPA focused on the one study that found an effect. Within that one study there was some uncertainty about how much mercury caused a problem so the EPA took that study’s lower bound (the lower bound of the 95 confidence interval for the statisticians in the audience.) Finally, to really be on the safe side, they divided the lower bound by ten!
Now notice how the charlatans at the NRDC twist a number of true facts to make a big lie. It is true that mercury can cause neurological impairment and it is true that 8% of women have blood mercury greater than the EPA safe level but you would never learn from the NRDC that the EPA safe level is more than ten times smaller than levels that have ever been found to cause mild impairment and that even the existence of such impairment is open to question. Throw in a few warnings about how learning disabilities are a “growing problem” and, for all the readers who don’t have children, don’t forget to mention the “recent increase” in Parkinson’s and Alzheimers and you have a perfect example of advertising masquerading as science. (Ever notice how many public interest groups sound like used car salesmen? Sale! Sale! Sale! Buy now before its too late!)
The NRDC wants emission levels cut by 90% in three years, an approach that would cost billions of dollars. The Bush administration wants to cut levels by 30% over the same time period, which would have a marginal cost of virtually nothing because of other regulations scheduled to take effect in anycase, and by 70% over a somewhat longer time frame. Naturally, the NRDC thinks this is evil. This time, I agree with the administration.