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.
Sell.
fieldquestions 
Due to a shortage of pyrethrum, DDT was first used widely by the Allies in WWII to control typhus, malaria and dengue fever. I wonder if any formal safety assessments were made prior to use. I can imagine governments not worrying too much about cancer at the time. One can even see why farmers back from the war might look on DDT as a boon and embrace it enthusiastically.
Though first synthesized in Switzerland, DDT was investigated as insecticide in German in 1929, as part of an effort to find safer insecticides. In comparison with the arsenic-based pesticides that preceded it (and their very clear risks to human health), I think it was an improvement. Modern pesticides developed since then represent still further improvements.
The Nazi War on Cancer describes what inspired the development of newer pesticides:
The situation with the French wine blight 60 years earlier is also illustrative of where we are today. There were two camps: the “chemists” who fought the blight with pesticides, and the “wood merchants” who grafted French varieties onto resistant American rootstock (the original frankenfoods?) I suspect the outcome of this competition today will look the same in 50 years.
Monsanto is developing RNAi spray technology for pests like the potato beetle. The modern chemists are those organic farmers who will continue to use copper and sulfur pesticides indefinitely, rejecting this more precise type of pesticide because of philosophical objections to biotechnology (identified by the USDA NOP as concerns about the sanctity of species boundaries).
Sorry, that should be “first synthesized in Austria”. The person who obtained the first patent on DDT also won a Nobel prize for it:
http://www.nobelprize.org/nobel_prizes/medicine/laureates/1948/muller-bio.html
Monsanto’s RNAi spray is untested and may or may not ever be sold publicly. Why are you so sure it will be (yet another) savior for industrial ag? Cheerleaders such as yourself need to think deeply about what the “pesticide treadmill” is and why it’s in industry’s best interest to keep it running…
Whether it is Monsanto’s spray or another application by another company, what I look forward to is the paradigm shift that allows for targeting unique genetic sequences with a molecule that is otherwise “just RNA” and consumed all the time (the ultimate GRAS material). You either have the matching genes that can be silenced, or you don’t. We won’t worry about bioaccumulation or unknown carcinogenic risks because the residual will never approximate even a tiny fraction of the natural load.
Maybe it won’t pan out. I did edit some of my overly long comment on the challenges of delivery. For both agriculture and medicine we need stable, long-lived chemicals for efficacy. But that stability becomes a liability once the primary benefit is obtained. Ecologists want short-lived, quick degrading chemicals. The problem of pharmaceuticals in wastewater is substantial and I see few other fixes for it on the horizon. If our medicines and pesticides can match unique gene sequences in just the target species, maybe long-lasting is less problem on a couple counts. For medicine, GE phages are likely to biodegrade like any other RNA in the sewage. With RNAi sprays, the challenge is keeping enough on the plant to ensure the pest consumes a lethal dose. So as always, adjuvants or other encapsulation is needed to withstand some rain and UV exposure. Pesticide solutions that require repeat application are losers (and so plants that express the insecticide have an obvious advantage).
Both precision agriculture and precision medicine promise to at least slow down the pesticide/antibiotic treadmills, in some cases even reverse the latter. The idea that we can immunize bacteria against antibiotic resistance is especially a tantalizing and welcome advancement. There are trials showing that glyphosate resistance can also be overcome with RNAi.
I’m rooting for these kind of solutions not because I love industrial ag, but because it’s the biggest impact by surface area on earth, and I want to constrain its growth. I like E.O. Wilson’s latest call for dedicating “half the earth” to wilderness, with continent-spanning biodiversity parks. Achieving that means maximizing productivity on land already under production and reducing pressure (both population/consumption).
Maximizing production per unit area has no necessary relationship with setting aside land. Maximizing per unit labor tends to increase land expansion. (http://www.cifor.org/publications/pdf_files/books/bangelsen0101e0.pdf). Smaller farms tend to produce more per unit area (http://www.sciencedirect.com/science/article/pii/S0305750X09001168 ; http://www.levyinstitute.org/pubs/wp_551.pdf; see further refs. at Note 9 here: http://www.sciencedirect.com/science/article/pii/S0305750X15001217#fn9). See fundamental research in land expansion such as this one: http://bioscience.oxfordjournals.org/content/52/2/143.full ; and the pressures from moving consumption to urban areas here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3720032/ ; http://www.nature.com/ngeo/journal/v3/n3/full/ngeo756.html .
Given that the causes are far more complex than productivity, pointing to productivity as a central way to decrease expansion seems insufficient.
Thanks for the references and for the touch of understatement. The notion that increased yield will decrease expansion is just plain silly. I have been studying farmers for >30 years and I have yet to meet a farmer who will plant less because the crop has a high yield. The idea that the market mechanisms will discourage planting (“We have all the food we need! Prices dropping! Stop planting and let some trees grow!”) is almost charming in its naivete. The history of industrial agriculture is a history of finding ways to get economic (or political) gain from surpluses. Midwestern corn is giving the highest yields in history, but the govn is spending $100b to promote sales of biofuel made from it.
Indeed. It doesn’t stop it from being a shockingly seductive approach among ecologists… Several attempts have tried to lend much further complexity to the “debate”, but stuff like this continues to be unironically published by (otherwise?) very good scientists: http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12280/abstract ; http://www.sciencedirect.com/science/article/pii/S0960982215009318 ; http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12527/abstract?userIsAuthenticated=false&deniedAccessCustomisedMessage= . I somewhat cynically suspect that its perfection as an academic object (can combine optimization theories and field research; can argue that it is highly applied even if it is of limited utility; difficult enough to generate a very large number of papers and continue exploring indefinitely). Given the endurance and appeal of the idea to both academics and policy-makers, I continue to try to keep my motivated reasoning circuits at bay whenever I see the argument brought up and to analyze it on even terms, despite its disheartening naivete.