I’ve seen a few claims on web pages like ‘Bad Science’ in regards to the safety of DDT.
Supposedly, all the science done 30 years ago was done wrong, and the science done nowadays seems to indicate that DDT has no harmful effects on birds.
I emailed Cecil about this, maybe a year ago, and he didn’t ever tackle this question.
What’s the straight dope on DDT?
-Kelly
I found the URL I had previously read on the ‘debunking’ of the dangers of DDT:
http://www.junkscience.com/ddtfaq.htm
Hard to judge which is correct.
Two things come into play when dealing with pesticides: Toxicity and hazard.
Toxicity is what it is. It can’t be changed. It’s like the calories in food. A pesticide has a certain level of toxicity, period.
Hazard is entirely in the hands of the applicator. Reckless application of even a low-toxicity pesticide can have horrible results. Safe application of a high-toxicity pesticide can solve a certain pest problem and not disrupt the surrounding environment/ecosystem.
To illustrate, let’s take it out of the realm of toxic chemicals and controlled substances.
Take gasoline. Any adult can get some. And it’s useful, even necessary in some cases. And if you store and use it properly, you won’t really be creating a hazard. But if you store it in an open coffee can next to your furnace, you’re an idiot.
It may be the case with DDT that hazardous applications made by untrained laypeople caused problems that led to a knee-jerk reaction, result-oriented testing, and the subsequent banning of the substance from US markets.
Understand I say this without cites, without formal research, with nothing, in fact, besides my own experience and training in the pesticide field. I have heard it said, though, (again, no cites) that nearly all the illnesses, injuries, and deaths occurring from pesticide poisoning are the result of improper application by homeowners, not pest control professionals.
And finally, most people don’t realize it, but the vast majority of pesticides in use by both professionals and in over-the-counter formulations have no higher a level of toxicity than household cleansers. In other words, ounce for ounce, Mr. Clean will kill you just as efficiently as Raid.
OK, I was far from clear.
The issue that I’m really curious about is the effect of DDT on bird’s eggs. Supposedly 30 years ago, it was banned because eagles and condors and other large birds of prey were dying off. The DDT supposedly was concentrated in fish, and the bird’s ate the fish.
This supposedly led to the birds laying eggs that were too fragile. The shells broke from being sat on by the nesting females.
There was a thread a while back (maybe six months or so?) about this very thing. I can’t remember if it was in GD or GQ, and the search engine won’t let me search on a term as short as “DDT”. IIRC, the consensus from knowledgeable people here was that DDT was harmful, but no one was quite sure how harmful, and where it had been applied in the past was one of the major reasons it was bad.
I know, not very helpful. Hopefully someone will come through with a link to that old thread.
Any pesticide can have adverse affects on non-target organisms. Many of the products in use for residential pest control even now are extremely toxic to fish. Just a little bit contaminating an aquarium or pond could kill every fish in it.
It’s not outside the realm of possibility that DDT was applied either incorrectly too near streams and ponds, or the danger was not realized right away, and there was a build-up of the chemical in the fish. Subsequently, when ingested by the birds, it resulted in non-viable eggs or softer shelled eggs.
There is more sensitivity to the environmental impact of chemicals today than there was thirty or forty years ago.
Also, I was under the impression that DDT did not break down over time, and so dangerous build-ups of DDT were easily possible. Most products now are designed to break down over time.
Wasn’t DDT applied in massive quantities, that was simply overkill and harming the ecosystem? I remember seeing a video where they sprayed kids at a picnic table eating hot dogs at the local pool with DDT.
I am biologist with a lot of experience in the environmental toxicology field. You won’t find anyone in the field that doesn’t work for chemical manufacturer that will say that DDT doesn’t harm birds. That may be a little self-serving among this population, because no one gets grants for studying the effects of non-hazardous pollutants. Some people have thrown some stones at the rigor and quality of the science that directly linked DDT to bird shell thickness. Maybe they have a point. But several things is sure without a doubt: DDT is very persistent in the environment and migrates through the foodchain, concentrating in top predators, especially fish eaters, including people. Fish pick it up from diet and from the water (see web page at SPMD Basics. I’m the author of that.) Eagles and other large birds like pelicans have recovered tremendously since DDT was banned. This is at least partly due to better egg shell thickness and better hatching rate (sorry that I don’t have time to track down a cite on that, but I did see a seminar once describing that research.) The Texas coast was down to one breeding pair of brown pelicans after the end of DDT usage in this country. Eagles were so rare that to see one in most of the lower 48 was cause for awe. Now both of those species are fully recovered except certain subpopulations and subspecies of eagles. I work on the lower Missouri River now, and I see an eagle about every other time that I go out. That would have been unheard of thirty years ago. Something happened to save those birds and I think Rachel Carson got it right.
As far as fish are concerned, DDT, like most insecticides, is very toxic to fish. Fish kills, though, were usually the result of poor application practices, rather than excessive toxicity or bioaccumulation from low environmental concentrations.
It’s true that DDT in concentrations that were found in the environmental probably doesn’t hurt people very much, or mammals very much, in terms of direct toxicity, but it has been linked to cancer.
DDT was so widely used, and so persistent, that it was building up in people everywhere. The ubiquity of the chemical was phenominal. DDT concentrates in lipids, and thus DDT is passed on to babies quite well through breast milk. I’m glad that DDT was mostly removed from the US environment before my wife was old enough to pick up a lot of it and pass it to our kids.
Fishhead
Uh - I want to clarify something - that web site I posted in the last post. I wrote most of it, but our stupid PR person “improved it” with the first and last paragraphs. There is another paragraph in the middle that one of our chemists added with info on an exposure chamber, with my blessing. I’m going to try to get the first and last paragraphs taken off or changed. Makes me sound rabid. and sensationalist, which I am not.