My daughter asked me to help her research DDT tonight

for a homework assignment in persuasion - she's taking a "pro-DDT" position. Apparently she was working exclusively off the information from one website. I'm pretty pro-DDT myself, but I gave her a bit of a lecture about trusting the information from one guy. (Though he sounds pretty reasonable - the couple sources I checked check out, but he makes some claims I couldn't verify - one is that bird eggshell thinning and other problems are caused by PCBs, not DDT.)

I showed her what the WHO has to say. I had to download two PDFs for that...small ones ("WHO Position on DDT" and "Frequently asked questions on DDT use for disease vector control." Then we checked out Dean Esmay's discussion.

And NPR.

I've mentioned that the whole "there are two sides to every story" storyline that most news outlets bugs me. I found it a bit annoying that NPR thought it appropriate to oppose the head of the WHO's antimalaria campaign with a guy who'd say,

"This is a chemical that has been studied and evaluated...and over the years has been found to cause cancer, endocrine disruption, adversely affect the immune system and is very problematic from the standpoint that it is persistent." DDT collects "in fatty tissue and in the environment," he adds, and can also be passed on in breast milk.

Such does not appear to be the case. It does build up in fatty tissue and is indeed passed on in breast milk, but whether or not it's a cancer risk to humans is still in question (read that third link - they were "anti" and they came up with nothing, to my mind).

After how many decades of study? [Update: Here's one answer to that question.]

It's a non-issue. The only real issue left is the environmental impact, and I need to dig deeper to see about that. I'm not going to take just anybody's word on it. I have to say, though, that after all this study, that Esmay's and his guest's defense of Rachel Carson (for some reason, I'm not able... Wait, here it... no... Yes! Vic Stein is the guest's name!) at least goes along with what looks to be the "scientific consensus" on DDT. That is that agricultural [or willy-nilly] applications are not the proper use of it.

We've had Silent Spring in the house. I'll see if I can verify that that's what Carson was saying.

I don't want to come off as a Moderate.

[Update(s): From Wikipedia:

Many critics repeatedly asserted that she was calling for the elimination of all pesticides despite the fact that Carson had made it clear she was not advocating the banning or complete withdrawal of helpful pesticides, but was instead encouraging responsible and carefully managed use with an awareness of the chemicals' impact on the entire ecosystem.[50] In fact, she concludes her section on DDT in Silent Spring not by urging a total ban, but with advice for spraying as little as possible to limit the development of resistance.[51]

Conclusion of Reason article:

Meanwhile, Carson's disciples have managed to persuade many poor countries to stop using DDT against mosquitoes. The result has been an enormous increase in the number of people dying of malaria each year. Today malaria infects between 300 million and 500 million people annually, killing as many 2.7 million of them. Anti-DDT activists who tried to have the new U.N. treaty on persistent organic pollutants totally ban DDT have stepped back recently from their ideological campaign, conceding that poor countries should be able to use DDT to control malaria-carrying mosquitoes.

So 40 years after the publication of Silent Spring, the legacy of Rachel Carson is more troubling than her admirers will acknowledge. The book did point to problems that had not been adequately addressed, such as the effects of DDT on some wildlife. And given the state of the science at the time she wrote, one might even make the case that Carson's concerns about the effects of synthetic chemicals on human health were not completely unwarranted. Along with other researchers, she was simply ignorant of the facts. But after four decades in which tens of billions of dollars have been wasted chasing imaginary risks without measurably improving American health, her intellectual descendants don't have the same excuse.

Reason cites this study as proving that natural chemicals are more of a danger than DDT and even PCBs:

Several broad perspectives emerged from the committee's deliberations. First, the committee concluded that based upon existing exposure data, the great majority of individual naturally occurring and synthetic chemicals in the diet appears to be present at levels below which any significant adverse biologic effect is likely, and so low that they are unlikely to pose an appreciable cancer risk.

Much human experience suggests that the potential effects of dietary carcinogens are more likely to be realized when the specific foods in which they occur form too large a part of the diet. The varied and balanced diet needed for good nutrition also provides significant protection from natural toxicants. Increasing dietary fruit and vegetable intake may actually protect against cancer. The NRC report Diet and Health concluded that macronutrients and excess calories are likely the greatest contributors to dietary cancer risk in the United States.

Second, the committee concluded that natural components of the diet may prove to be of greater concern than synthetic components with respect to cancer risk, although additional evidence is required before definitive conclusions can be drawn. Existing concentration and exposure data and current cancer risk assessment methods are insufficient to definitively address the aggregate roles of naturally occurring and/or synthetic dietary chemicals in human cancer causation and prevention. Much of the information on the carcinogenic potential of these substances derives from animal bioassays conducted at high doses (up to the maximum tolerated dose, or MTD), which is difficult to translate directly to humans because these tests do not mimic human exposure conditions, i.e., we are exposed to an enormous complex of chemicals, many at exceedingly low quantities, in our diet. Furthermore, the committee concluded upon analyzing existing dietary exposure databases, that exposure data are either inadequate due to analytical or collection deficiencies, or simply nonexistent. In addition, through regulation, synthetic chemicals identified as carcinogens have largely been removed from or prevented from entering the human diet.

Third, the committee concluded that it is difficult to assess human cancer risk from individual natural or synthetic compounds in our diet because the diet is a complex mixture, and interactions between the components are largely unknown.

The committee's major conclusions are presented in detail below. They address the complexity and variability of the human diet, cancer risk from the diet, mechanisms and properties of synthetic vs. naturally occurring carcinogens, the role of anticarcinogens, and models for identifying dietary carcinogens and anticarcinogens.

In the diet, anyway.

Silent Spring Study Guide.