What a bloodbath on Wall St — XOM down 5%, UNH down 5%, DIS down 4%. But the biggest loser this week was DDT.
DDT featured prominently in the recent blog highlighting the ongoing studies by Berkeley’s Barbara Cohn. Despite “wild rhetoric of the environmentalists” (as Norman “Green Revolution” Borlaug put it in 1971), study after study exonerated DDT, culminating in the famous large-scale Long Island Study. In many publications in the scientific literature and the popular press, the Long Island Study repeatedly gave DDT a clean bill of health.
At least until epidemiologists found a way to compare breast cancer rates to childhood exposure.
I got email from indignant DDT defenders. But my point was not so much about DDT (or GMO’s) per se as it was about how hard it is for science to discern long-delayed, distant, and indirect effects on ecosystems and human health. The Long Island Study’s exoneration of DDT didn’t mean much because it was looking at the wrong questions.
But in a study just out in the International Journal of Cancer, we now learn that the Long Island Study didn’t exonerate DDT anyway. Enough time has now passed to allow researchers to now find that levels of blood DDT (or its metabolite DDE) at time of diagnosis partly predicts survival. High levels are correlated with mortality rates, low levels are inversely correlated.
As Parada et al. point out,
This is the first population-based study in the United States to show that DDT may adversely impact survival following breast cancer diagnosis.
And then this dry academic sentence that is actually quite alarming:
Further studies are warranted given the high breast cancer burden and the ubiquity of these chemicals.
DDT. Just a few years ago it was a martyr to ignorant anti-chemical luddites perpetrating a “deadly fantasy” about a modern agricultural technology proven safe by science. Now it not only causes breast cancer in women decades after childhood exposure, but the amount of it in their blood as adults is linked to how long they survive. And this last finding comes from the same study that previously was “very very conclusive” in showing DDT to be safe.