DDT - dangerous to birds? dangerous to humans?

I’m starting this thread in response to a comment in this thread in GQ.

The two questions I’m interested in addressing are:
How good is the evidence for DDT (and its breakdown products, DDD and DDE) as a threat to bird populations?
How toxic is DDT? Or “toxic,” if you prefer. :wink:

According to this article in Wikipedia, it has a demonstrated effect on bird’s egg shells (they grow thinner).

I recall reading in a book on embryonic development (a layman’s explanation: Having Faith) that no one is all that sure exactly what DDT does to humans, since we don’t have any control group–no one is DDT-free, so a proper comparison is impossible. But they think it can affect intelligence and contribute to pre-term labor. It’s also passed through breastmilk, and a first child will recieve the largest dose.

DDT takes about 50 years to break down, so it can easily pass through three generations (for example, my mother was exposed to DDT in youth, she nursed me at 25, I nursed my daughters at 27 and 29, voila–my kids have ingested some of their grandmother’s dosage of DDT).

To birds, humans, or malaria-carrying mosquitoes?

The Junk Science site disputes the claim that it is dangerous to birds - including the claim about eggshell thinging.

I’m not familiar enough with JunkScience.com to know if it is considered reputable. Can any doper chime in on that regard?

A quick glance seems to make them kind of Science debaters with an agenda.

Their agenda seems to be, mostly, against the Greenhouse Effect, with a side order of DDT-advocation. They also seem to publish mostly for FoxNews.com (I’m currently reading this article).


I remember writing a paper on DDT and raptors when I was in college. Long time ago. Seeing as how DDT breaks down into components, like DDE, that are PBT (persistent, bioaccumulative, and toxic), it would naturally affect birds of prey who are at the top of the food chain. DDE almost wiped out the Peregrine Falcon. It thinned the eggshells so badly that offspring could not survive. In fact, some times no shell would be produced at all.

There haven’t been any scientific studies that showed a definite link between shell thickness and DDT concentration, nor has there been any study that has shown a mechanism for shell thinning. Note that one thing that HAS been shown to cause eggshell thinnning is heavy metal poisoning. Birds are particularly susceptible to lead poisoning due to hunting shot.

Obviously, it’s difficult to provide proof of the non-existence of scientific evidence, but note that the wikipedia article linked above only talks about 2 early studies. Those studies suffer from correlation/causation issues, and the key study dealing with quail was flawed in that when the researcher corrected for a low-calcium diet, his results vanished. There has been some research claiming that raptors are more susceptible, but still no clear links that it causes a population downturn.
The most significant study shows that DDE can possibly thin shells. (The peregrine raptor study by lincer, which showed a bit of thinning (max of 20% at very high daily dose diets) but was not conclusive, and is often confused with wildlife population studies – the two are unrelated), DDE is a breakdown component of DDT, but it’s unclear how much DDE is related in organisms to DDT. Further, DDT tends to break down to DDD instead of DDE in anaerobic circumstances as you would find inside an organism (as opposed to on soil).

Furthermore, the quantities used at the height of the DDT era were enormous. Quantities used today for mosquito and small scale insect control would be far less concentrated, and the bioaccumulativeness of DDT is not incredibly high, it does get metabolized out fairly quickly. Claims of getting Grandma’s DDT are mostly hype. IIRC the accumulation from a generation of raptors to offspring was somewhere along the lines of 2-5% (grain of salt, but it’s fairly low). DDT also has a max of about 15 years half life. Lastly, eggshell thickness studies all indicate an inverse relationship between DDE and shell thickness. However, in the wild, eggshells have not thickened up very much, and DDE levels in wildlife have dropped signifcantly.

As far as toxicity, DDT is very safe. Human and animal toxicity studies suffer from the same problem as shell thinning – no one has found any really significant evidence (as in statistically significant) that DDT is harmful. The big claim nowadays is that DDT has some similarity to estrogen and can interfere with an organism’s endocrinological balance. Again, there hasn’t been significant evidence, but there have been a lot of calls for more research. In the 60’s and 70’s, however, there were high-dose and mega-dose primate and other animal trials which didn’t show significant effects.

One thing that is pretty certain is that DDT is less toxic than any of the other pesticides used for mosquito control and often those used on crops.

As far as the junk science guy goes, he is a little, ah, bombastic. But he is not way out on a limb, and there’s not much of his research that is arguable. Most of the counter-DDT claims come from the more radical environmental groups, and most are short on science and long on ad hominem tactics. One of the big problems is that people don’t get the idea of statistically significant, and they don’t bother to look at the data themselves, preferring quick summaries (like this one :P). I think a partiularly telling feature of the debate is that most of the argument against DDT comes from the standpoint of “Well, duh, DDT is all over and we KNOW it kills birds” as opposed to hard scientific data. It makes just as much sense to say things like “Since we made shooting bald eagles illegal, banned lead shot, and prevented the destruction of raptor nests, the population has come back” as it does to claim the DDT ban caused the comeback. There are quite a few people who toss out casual statements that DDT kills birds, etc, but no convicing proof – most of the scientific “proof” given comes from things like the EPA website (all based on the above-mentioned studies) and other sources in a sort of chain of disinformation.

FInally, why should we care? DDT is incredibly cheap and effective. It’s probably the most efficient insecticide ever made. That means we can use less, and poor nations who suffer from malaria epidemics can afford it. Since the ban, most organizations will not give aid if countries will use DDT, so our bans are third world country bans as well. I realize this is one long rant, but it seems awfully suspect to contribute in a large way to the deaths of millions of people without solid scientific evidence to back up our policy.

That is the biggest load of crap I have heard in a long time.
Can you say, “Pro-pesticide lobbyist?”
Which, by the way, is clearly what that website is. It’s basically a “Yay, Pesticides!” website. Gosh, I wonder who funds it?

Anybody who tells you that DDT is not a bad actor is lying. Look it up (on some reputable sites).


Anybody who tells you that DDT did not affect the raptor population is lying. Look it up on some reputable sites.


I’m an apprentice falconer. My sponsors and larger falconry association are part of and largely responsible for the action and captive breeding practices that helped pull the peregrine back from the brink in the US. I have a feeling they’d find the suggestion that DDT had nothing to do with it to be laughable, but I can’t say for certain. I do know that they’ve got several decades worth of experience captive breeding birds that were exposed to DDT in a wild environment and others that were not due to being captive-bred, perhaps the comparison data would be helpful?
If you’d like me to ask them any particular questions I’m happy to.

Ask the Bald Eagles.

DDT hasn’t been banned & is still used for malaria control in some places. However, mosquitos can develop resistence to DDT. Continued widespread use in an agricultural setting definitely contributed to the resistence.

Yes, the owner of this site has opinions. But references are included.

Two NYT articles (may need free registration?): April, 2004 and September, 2006.

I thought I read another piece that was more recent, but that’s what I could locate quickly.

True, DDT bans are really only in Western countries. BUT we and other groups will no allow foreign aid to be spent on DDT spraying, thus our ban is as good as a local ban in poor countries.

There is a little resistance issue with DDT. Most of the studies find that resistance builds up faster with heavy use as in US agriculture. DDT repels insects as well, sp at the usage level for mosquito treatment, resistance shouldn’t be an issue. Still something to watch for, but not a dealbreaker.

This is exactly the kind of peoblem I discussed earlier. There’s no science here other than “look it up on the web”. Obviously anyone who disagrees MUST be biased, stupid, or just plain lying. This is, of course, not a new phoenomenon, ask Galileo and Magellan and Darwin…

But in any case, the link provided above to the PAN database is “reputable”? With two clicks you can get to the org that runs the site: http://www.panna.org/
I don’t think anyone can claim with a straight face that the “Pesticide Action Network” is an unbiased actor here. It’s not as if eco-action groups are rigorously scientific and are above a little scaremongering to raise “awareness” in their chosen cause.

Here’s a quote from another notorious pro-pesticide lobbyist: “How much labor and waste of time these wicked insects do cause us… . . but a ray of hope, in the use of DDT, is now held out to us.” – Albert Schweitzer

From the Eco-Terrorists at USAID.

Back to MoskTheDissenter:

Which studies? Links would be appreciated.

And that was a lovely quotation from Albert Schweitzer. Who died in 1965.

Are you seriously suggesting that a bunch of lying pesticide pushers who are trying to use malaria as a scare tactic to sell DDT are on a par with Galileo, Magellan, and Darwin?

That junkscience website is an insulting joke. Putting a DDT tee shirt on a pic of Rachel Carson? Yeah, that makes the whole thing more credible.

Brilliant. DDT isn’t patented, and it’s very inexpensive. Obviously a goldmine for pesticide pushers (who, coincidentally, provide the far more expensive chemicals used to spray today). Maybe I should make a t-shirt with some dead African kids on it that says “Scare Tactic”.

I’m done responding to you, you’re obviously a zealot who won’t bother to provide any worthwhile info.

on resistance:

Am jr. Tropical med

Jrnl mosquito Control

USAID has never said that they will not provide funding for DDT. They do require that countries look for alternatives, and for a long time deferred to the WHO. The WHO has only recently, with the change in leadership, started promoting DDT use. Worldbank has also changed position recently, allowing others to “take the lead” — they appear to be tired of the policical pressure from both sides and are falling in line behind the WHO.

“USAID has never had a “policy” as such either “for” or “against” DDT for IRS. The real change in the past two years has been a new interest and emphasis on the use of IRS in general” – coinciding with the presidential push and WHO changes.

If you want more info, the two NYT links above will lead you to plenty of places. But it’s beside the point anyway; the science is pretty clear that DDT isn’t a health risk to people or the environment when used for household spraying. Your claim seems to be that we aren’t doing it for some reason, and that reason must be that it doesn’t work or isn’t efficient. It’s starting to turn around, but there is still a lot of disinformation being spread.

P.S. - your earlier link had lots of references, true. unfortunately, all of them supported the opposite side.

Well, Mosk, I guess it’s a good thing I don’t care what you think of me.

I’m sorry you didn’t find any of the info in the many links I provided worthwhile.

You know, this thing that’s been happening is one of the most despicable things I have ever seen. This thing is the trashing of Rachel Carson. Blaming a dead woman (a woman who died of breast cancer in 1964) for hundreds of thousands (or however many the current number is) of deaths is despicable. It’s despicable because in order to do it, you have to twist the facts so much that they scream for mercy. Trying to discredit the environmental movement by pissing on Rachel Carson’s memory is a scumbag move. It also involves a lot of LYING. It makes me sick. Rachel Carson probably did more good for this planet and its inhabitants than we will ever know. I think she’s a hero. Your Steven Milloy? Just check Wiki for the scoop on this… individual.

What’s interesting about all this is that all you have to do to get the truth is visit Wiki. It’s one stop shopping for the truth in this case.

Steven Milloy: http://en.wikipedia.org/wiki/Steven_Milloy
Rachel Carson: http://en.wikipedia.org/wiki/Rachel_carson
DDT: http://en.wikipedia.org/wiki/DDT

Cite? :confused: I know the USA etc would not pay for DDT, but that is not the same* as not allowing other nations to use it. *

Here is the cite from wiki:*Stockholm Convention, ratified in 2001 and effective as of 17 May 2004, outlawed several persistent organic pollutants, and restricted the use of DDT to vector control. The Convention was signed by 98 countries and is endorsed by most environmental groups. Recognizing that a total elimination of DDT use in many malaria-prone countries is currently unfeasible because there are few affordable or effective alternatives for controlling malaria, the public health use of DDT was exempted from the ban until such alternatives are developed. Malaria Foundation International states:

The outcome of the treaty is arguably better than the status quo going into the negotiations over two years ago. For the first time, there is now an insecticide which is restricted to vector control only, meaning that the selection of resistant mosquitoes will be slower than before.[14]

As of 2006, DDT continues to be used in other (primarily tropical) countries where mosquito-borne malaria and typhus are serious health problems. Use of DDT in public health to control mosquitoes is primarily done inside buildings and through inclusion in household products and selective spraying; this greatly reduces environmental damage compared to the earlier widespread use of DDT in agriculture. It also reduces the risk of resistance to DDT.[15] This use only requires a small fraction of that previously used in agriculture; for the whole country of Guyana, covering an area of 215,000 km², the required amount is roughly equal to the amount of DDT that might previously have been used to spray 4 km² of cotton during a single growing season.[16]

In September 2006, the World Health Organization announced that DDT will be used as one of the three main tools against malaria. WHO is hence recommending indoor residual spraying (IRS) in epidemic areas, as well as in places with constant and high malaria transmission.[17] The USAID subsequently announced that it would fund the use of DDT.[18].*

So what Ban are you talking about?
There is no scientific doubt that DDT- used in the HUGE amounts it was used in the 1960’s- was dangerous to the environment. Look at this line from Wiki again: “This use only requires a small fraction of that previously used in agriculture; for the whole country of Guyana, covering an area of 215,000 km², the required amount is roughly equal to the amount of DDT that might previously have been used to spray 4 km² of cotton during a single growing season.” Could we use much smaller and reasonable amounts here in the USA? Well, maybe, but we don’t need to and the risk is too high.

National Geographic just had a fascinating article on Malaria and how the DDT ban probably cost several million lives, mainly children.

It goes on to show how targeted use of DDT can reduce malaria infection and mortality while minimizing the environmental risks.

I’ve seen a few cases of malaria in my career. Nasty, nasty disease! <<shudder>>