Skeptoid fact check part 1

Brian Dunning’s Skeptoid does an excellent job of debunking pseudoscience, so his podcast on DDT is profoundly disappointing. Dunning claims that DDT use did not have a large impact on bird populations, that elitist environmental groups were killing brown children by blocking DDT use and that DDT is effective even if mosquitoes are resistant. None of these claims are true, as I will detail in this post. But first, why did a sensible fellow like Dunning get it all so badly wrong? Well, his primary source for information about DDT was Steve Milloy‘s One commenter remonstrated:

I trust JunkScience on health and environment like I trust the Discovery Institute on evolutionary biology, or Prison Planet on history.

Dunning responded:

The JunkScience guy has a blatant libertarian agenda. The SourceWatch guy has a blatant anticorporate agenda. Big whoop! They’re both still researchers. I have no problem citing either if they’ve done the research I’m looking for.

If you must insist that this makes everything coming from either guy always right or always wrong, then you should demand to see the voting history of every scientist or researcher in order to determine the quality of their work.

This misses the point. Biased sources aren’t necessarily wrong, but they are unlikely to give you the whole picture and it would be wise to be skeptical about what they say and fact check their claims. This post is the fact check that Dunning failed to do.


Silent Spring’s principal thesis was that DDT harms bird populations through eggshell thinning.

Silent Spring doesn’t say anything at all about eggshell thinning since it wasn’t discovered until after the book was published.

It’s been about five decades since Silent Spring was published, and we’ve learned a lot in those years. One thing we’ve learned is that DDT is only one of many causes of eggshell thinning. Other culprits include lead and mercury toxicity, oil, phosphorus and calcium deficiency, and dehydration. Perhaps most significantly, birds in captivity in order to undergo testing are under stress, and this stress alone is enough to produce eggshell thinning. Although DDT’s mechanism for eggshell thinning is plausible, many studies throughout the 1970’s and 1980’s failed to correlate such thinning with high levels of DDT, even extremely high levels. Other studies have confirmed Rachel Carson’s findings. My own conclusion based on a review is that there probably is a correlation, but it’s not a strong one; and at best it’s only one of many causes. Whether DDT is used or not would probably not have a large impact on bird populations.

This is based on points 39-64 in Milloy’s 100 things you should know about DDT, but Dunning goes beyond Milloy’s claims with the unsupported assertion that the stress of captivity causes thinning. Dunning’s “failed to correlate such thinning with high levels of DDT” corresponds to Milloy’s points 43 and 44. These all cite obscure reports and journals so we can’t check them. Except for this one:

44 Among brown pelican egg shells examined there was no correlation between DDT residue and shell thickness.

[Switzer, B. 1972. Consolidated EPA hearings, Transcript pp. 8212-8336; and Hazeltine, WE. 1972. Why pelican eggshells are thin. Nature 239: 410-412]

Ah, Nature. That we can check. Here’s what Hazeltine’s letter says about that correlation:

“The CFDG data (Table 1) show a nearly perfect correlation of lipid DDE residues to shell thicknesses, and the relationship is positive.”

OK, that’s not exactly what Milloy had, but the point is that the correlation goes the wrong way. Trouble is, Milloy fails to mention that there were four responses to Hazeltine published in Nature. Let me summarize some of the problems with Hazeltine that these letters pointed out. First, Hazeltine’s CFDG data comprised just nine eggs. Those eggs mere a mixture of incubated and non-incubated, and the positive correlation is caused because incubated eggs have thicker shells and higher DDE concentration in the lipid. How? Well, incubation consumes most of the lipid and concentrates DDE in the remaining lipid. And thin eggshells are less likely to survive incubation (that’s the reason why eggshell thinning is a problem in the first place.) If you look at the relationship between whole egg DDE and eggshell thickness there is no statistically significant relationship in Hazeltine’s set of just nine eggs. But other studies with larger samples have found a significant negative relationship between DDE and brown pelican eggshell thickness. Unlike Milloy, Hazeltine cites them in his paper and states:

That DDE is the cause is of thin brown pelican or peregrine eggs is well established in the … scientific literature.”

Hazeltine tried and failed to overturn this. Milloy misrepresented the science by deliberately concealing the existence of the studies that found that there was a correlation between eggshell thinning and DDE.

Now let us examine Dunning’s next paragraph:

But despite the likelihood that it would have some impact, it’s now known that the species Rachel Carson focused on (most notably bald eagles) were already in massive decline from unrelated pressures even before DDT’s introduction. Habitat loss and hunting had been, by far, the greater causes of bald eagle deaths. Hunting had reduced the populations to just a few hundred nesting pairs in the mountains, and lowland eagles were already gone from habitat loss. Rachel Carson did not ignore these issues in her book, but the popular perception that banning DDT was all that was needed to magically restore bald eagle populations was naïve. In the end, it was the Bald Eagle Protection Act and the bird’s 1967 placement on the endangered species list, combined with increased penalties for poaching, that ultimately led to the bald eagle’s successful return to remaining habitats.

One of Dunning’s five references is to a 2007 news story in Science Can the Bald Eagle Still Soar After It Is Delisted?, which states

Just 40 years ago, the bald eagle seemed headed for extinction in the conterminous United States. Nesting females were accidentally crushing their eggs, which were weakened by the ubiquitous insecticide DDT. … Banning DDT has helped the national population of breeding bald eagles to grow.

Looking just in Science there is also a 1994 story:

[Wildlife ecologist Stanley Temple of the University of Wisconsin] says that the return of the eagles and other raptors, including peregrine falcons and and ospreys, “is due almost wholly to the ban on chlorinated hydrocarbon pesticides.” The ban of the number one offender, DDT, took effect in 1972, eliminating a group of pesticides that thinned eggshells, causing the birds’ reproductive rates to plummet.

And a 1982 study:

Reproduction of bald eagles in northwestern Ontario declined from 1.26 young per breeding area in 1966 to a low of 0.46 in 1974 and then increased to 1.12 in 1981. Residues of DDE in addled eggs showed a significant inverse relation, confirming the effects of this toxicant on bald eagle reproduction at the population level and the effectiveness of the ban on DDT. The recovery from DDE contamination in bald eagles appears to be occurring much more rapidly than predicted.

Now it is certainly true that shooting and habitat loss also contributed to the decline of bald eagles as the US FWS states:

By 1963, with only 487 nesting pairs of bald eagles remaining, the species was in danger of extinction. Loss of habitat, shooting, and DDT poisoning contributed to the near demise of our national symbol.

As the dangers of DDT became known, in large part due to the 1962 publication of Rachel Carson’s book Silent Spring, the Environmental Protection Agency took the historic and, at the time, controversial step of banning the use of DDT in the United States. That was in 1972, and it was the first step on the road to recovery for the bald eagle.

But Dunning is wrong to dismiss DDT as a cause — preservation of habitat and bans on hunting and DDT were all necessary to save the bald eagle.

On to Dunning’s next paragraph:

Brown pelicans are another species often cited as having been decimated by DDT use in the United States, along the Gulf coast and in California. Massive declines were indeed correlated with DDT use, but it may have been a coincidence in each case. Along the Gulf coast, hunting by angry fishermen had reduced the pelican population in Texas from 5,000 annual births to just 200 in 1941. The California populations suffered a double whammy in the years following Silent Spring’s publication; first with an oil spill off Santa Barbara in 1969, and then with an outbreak of Newcastle Disease in 1971 that unfortunately required the culling of millions of brown and white pelicans. DDT certainly didn’t help; but it was another case where the bird populations would have dropped sharply whether DDT was in the picture or not.

Compare with Milloy:

96 An epidemic of Newcastle disease resulted in millions of birds put to death to eradicate the disease.

[United Press International. “Newcastle disease epidemic in California (April 1972)] The epidemic among U.S. birds was caused by the migration of sick pelicans along the Mexican coast.

Note that Milloy doesn’t actually say that the birds put to death were pelicans — he just implies that they were and Dunning didn’t stop to think whether it even made sense that an endangered species would have a population in the millions.

Now look at what the USDA says

For example, parrots from South America are believed to have caused an outbreak of exotic Newcastle disease (END) in southern California in the early 1970s. Eradicating that disease outbreak cost $56 million over a 3-year period. During that outbreak, more than 12 million birds were destroyed, the vast majority of which were commercial poultry.


In 1992, 26,000 turkeys in North Dakota were destroyed after APHIS diagnosed virulent Newcastle disease in the flock. Cormorants were the suspected source. Hundreds had died from the disease at a lake near where the turkeys were being reared on range. Seal confirmed this suspicion when he compared the genomes of turkey and cormorant isolates.

The episode was part of the United States’ first known Newcastle-related die-off of free-ranging wild birds.

So the number of pelicans dead as a result of the 1971 outbreak of Newcastle Disease was not “millions” as Dunning claimed, but zero.

As for the Dunning’s claim that the pelicans’ troubles were coincidental, this interview Professor Daniel W. Anderson of the University of California at Davis, summarizes the evidence:

DA: Dr. Ray is a little slippery when she says there is no supportive evidence of population declines and that bird populations actually increased. There are many cases, but let me mention one that I personally worked on. She does not mention one of the best case histories in North America of DDE-induced population effect which involves the decline and resurgence of the California brown pelican.

ER: California brown pelican populations were hurt by DDT?

DA: By DDE. But in this case, they were adversely affected not by DDT used as a spray but as DDT and metabolites were put into the sewage system in Los Angeles. It entered the Southern California Bight in large quantities. [A bight is a curve in the coast that forms a bay and also often entrains an oceanographic gyre. ed.] Some people in Professor Risebrough’s group looked at the sediments in Southern California and saw where DDT and its metabolites first appeared.

ER: When did DDE start showing up in the sediments?

DA: About the 1950s. It was like a detective case and when the source was discovered, input stopped pretty quickly.

ER: What was the source?

DA: The major source was found to be a manufacturing plant in Torrance.

ER: When did they make the changeover to landfill disposal?

DA: It started in about 1970. And within a year the DDE residues began a long decline in the pelicans and other wildlife of the bight and the pelicans (and other species too) started to show signs of recovery.

ER: Was there experimental work with the pelicans that showed eggshell thinning after exposure to DDE?

DA: No experimental work like controlled feeding experiments was done in brown pelicans because that species was on the endangered species list. But there was a positive relationship between the amount of DDE residue female pelicans had in their bodies at the time they were laying eggs and the amount of eggshell thinning. Similar relationships have been shown over and over again, all over the world, for many bird species and by many, many investigators.

For more details and references to scientific papers on brown pelicans
see the US FWS’s California Brown Pelican Recovery Plan.

As Daniel Anderson notes in the interview above, there were no
controlled feeding experiments on brown pelicans so you could, I
suppose, argue that the correlation between thin eggshells and DDE,
and the collapse and recovery of pelican breeding associated with the
increase and decrease in DDT use was all a big coincidence. But a
1975 paper by Jeffrey Lincer
would seem to rule that out.

Here’s Figure 3 from Lincer’s paper. The x’s show that in controlled experiments the more DDE fed to kestrels the thinner the eggshells. And it shows that the same relationship occurred in wild kestrels, so it is not true that dosages used in the experiments were unrealistic.


For more on DDT and eggshell thinning see this WHO report written by expert toxicologists.

This post is more than long enough already and we are only half way through the Skeptoid podcast, so the rest of the fact check will be in another post. Part 2 will fact check what Dunning says about DDT and malaria.


  1. #1 Anonymous
    November 25, 2010

    [You know who I feel sorry for in all of this? Absolutely no one. I can’t imagine who it is I’m supposed to feel sorry for.](

  2. #2 Bob Calder
    November 26, 2010

    A person searching for accurate information can’t ignore attribution. If a source has poisoned the well as Milloy has, over and over again, you simply can’t be bothered to re-validate the truth of everything that comes out of his mouth on a daily basis. It’s a waste of time. It’s a better tactic to do more searching and widen your good sources, dropping less qualified sources as you go. Big research fail Brian.

    Dunning evidently missed the workshop at the last San Francisco AAAS meeting entitled “Manufacturing Scientific Ignorance” wherein the presenters totally pwnd Milloy using the continuity of addresses, business licenses, and phone numbers to prove the transition from Tobacco Institute funded shill to Exxon funded anti-science climate denial. You simply can’t take the word of a guy that is disclosed on the Exxon annual report as a paid contractor for anything.

    Indeed, the statements that brought me to watching climate FUD were found when I was reading State of Fear and noticed inaccuracies in statistics of malaria deaths I knew to be misleading. When I read the passage, I searched to the quote and found Milloy and his simmering pot of hate. This was Christmas of 2004. Chrichton had adopted Milloy’s horrid attitude of brushing all environmentalists with the same brush, essentially making them into modern terrorists. Thereafter I noticed that Milloy was a public climate science hater and began to get involved. Thank you Michael Chrichton (RIP) for being a great writer and a total sucker for tall tales! Thank you Mike Milloy for being a blithering idiot and liar! It’s been fun, but it’s time to put a lid on it. The only way you can believe Milloy is if you have a huge chip on your shoulder about the UN.

  3. #3 WScott
    November 26, 2010

    Money is pouring in to military budgets, yet the success of the wars has shown little, if any, improvement.

    Uh, yeah, maybe because our underlying strategy is flawed? Which is exactly what I’m arguing with education – you’re proving my point.

    How much money PER CAPITA is going in to the school system compared to the average wealth? It’s going down.

    A fair point (if true – source?), tho I’m not sure why per capita spending is the best measure here. We’re spending less per capita on food – does that mean we’re eating less?

    There are more shinies to spend money on (computers for every child).

    Perhaps, but again there doesn’t seem to be a correlation between how many shinies a school has and how well its student perform.

    Now, to show how much difference funding makes, look at the government run schools in districts that have high average earnings and compare to that of low income areas.

    You just can’t let go of that straw man, can you? As I said before, I wasn’t talking about funding at the level of individual schools. My point, which you have yet to address, is that there is no correlation between how much a country spends on education and how well its students perform. The same lack-of-correlation holds true between states. It seems to hold true at the city level as well, although the data there seems less clear. (Or at least, I haven’t seen it.)

    Look at the better funding of schools in France and you see better levels of education.

    Try looking at more than 2 data points. There are plenty of countries who spend far less than we do for better results. And others who spend more for worse results. Money is not a cure-all.

    Same government control. Same government.

    Within the same school system, yeah. It seems like you’re saying “All other things being equal, more money is better.” To which I can only reply 1) sure, and 2) duh. What I’m saying is that there are overall systemic problems in our education system in this country, and until we address them, throwing more money at it is unlikely to have significant impacts.

    But libertarians don’t want to pay for other people’s education.

    Aaaand the parade of straw men continues. I’m not a libertarian, as should’ve been clear from my previous comments. But even if I was, you’re just using political ad hominems as a substitute for actually looking at the data. Hey, isn’t that what we’re all complaining that Dunning did?

    (Sorry to continue the thread-jack, everyone.)

  4. #4 Brandon
    November 27, 2010

    While I do agree with the overall view that some of Brian’s research in this case has proven faulty, it is interesting that his conclusion, which you think would be equally contentious to self declared true skeptics, isn’t being discussed.

    “DDT does have its place, and its current usage is probably not too far off of what it should be.”

    I still agree with that part completely. What is interesting is that every time anyone says something that others in the skeptical community disagree with, their political leanings, real or imagined, are trotted out. I’ve never got the feel the Brian Dunning is a libertarian outright. In discussing some criticisms of his organic food podcast(s) he, rightly in my view, points out that libertarians logically wouldn’t oppose organic agriculture. It’s what the market is demanding after all. So why do people trot out his organic criticisms as evidence of his ‘obvious libertarianism’?

    Most of the people who I’ve spoken too who started dismissing others out of hand, no matter who, do so because of some ideological opposition rather than a proven history of falsehoods. It’s telling that every time I’ve asked someone what the real support for say, organic food is, as opposed to Brian’s ‘straw man’ supports, they answer with the exact same supports Brian addressed.

    Dismissing everything Brian has to say because you disagreed with something he said that you’re an ‘expert’ on, and even most of those haven’t been real disagreements as much as objections over simplifications, is poor form.

    These sort of ‘not a true skeptic’ lectures come off as hissy fits. Oh, not the article at the top of course, but much of the feedback.

  5. #5 Pinko Punko
    November 28, 2010

    Brandon, a libertarian skeptic could both note something that the market desires but is also somehow BS, like snake oil or homeopathy. There is no inherent conflict. The “corporatist” libertarian might have a view towards promoting big business in the face of either a presumed liberal sawhorse or a presumed grass roots movement. The purported contradiction you note about organic food doesn’t indicate anything about Dunning’s putative libertarianism, though based on this one article, he’s got zero credibility. Making such pronouncements so late in the game regarding the now very stale and very canned DDT arguments suggests something extremely faulty about his method.

  6. #6 Brandon
    November 28, 2010

    “The purported contradiction you note about organic food doesn’t indicate anything about Dunning’s putative libertarianism, though based on this one article, he’s got zero credibility.”

    Perhaps you’d rather base your opinion of his credibility, and his ‘corporatist libertarianism’ on more than just this one article. I’ve heard lots of criticisms of various Skeptoid pod casts, and this is the first time I’ve found a major flaw in research that hasn’t yet been correct in one of his ‘Things I’m wrong about’ articles.

    I seriously doubt he is a ‘corporatist libertarian,’ if that means what I think it means, based on many things, but mostly how he’s spoken in favor of several types of government regulation and even used the usefulness of government regulation as the crux of several arguments.

    Besides that, even if he was a libertarian, that in and of itself says nothing about his arguments. Dismissing him as a shill for big this or that is basically the same thing.

    Again it’s worth noting that I’m not accusing Mr. Lambert of this, but pointing out that ‘trend’ in the feedback here. Skeptoid is ‘a critical examination of pop phenomena’. It isn’t a scientific research paper. By necessity it has to discuss ‘both sides’. A lot of pop ‘information’ does sound a lot like a straw man to many learned people because it’s so stupid and lots of people do really support things like Whole Foods and organic agriculture for the reasons Mr Dunning addresses.

  7. #7 Pinko Punko
    November 28, 2010


    I just want to point out that my comment did not relate to many of the dismissals of Dunning based on perceived politics. I would dismiss him out of hand because his research here was so shoddy that for me to listen to him and believe him on any topic, I would have to double check anything he would say. This makes him valueless as a digest of possible facts on any topic. This does not mean I can’t listen to the cases he states, it means I have to give them zero weight based on my perception of his methods.

  8. #8 Brandon
    November 28, 2010

    Isn’t double checking one of the keys to general skepticism? That’s why citing of sources is critical. I’ve used the references and further reading section of many Skeptoid articles to get more in depth research, and to find out the claims being made.

    But giving him zero weight? A wise man (I know using that term is a fallacy) once said, “Brian Dunning’s Skeptoid does an excellent job of debunking pseudoscience,” so don’t dismiss that man’s research methods so easily. Lots of very smart well meaning people are very wrong, profoundly wrong, from time to time.

  9. #9 Pinko Punko
    November 28, 2010

    B- I’m not naive, I’m actually a practicing scientist, and at this late date, anyone who cites a Milloy-related site, gets zero weight. The history of misinformation and corporate messaging from Milloy is both well known and extensive. Certainly there may be things that are actually correct amongst those sites, but I will go elsewhere.

    Dunning may very well have done admirably in the past, but the DDT episode signals to me that I do not have time or effort to expend on determining whether he’s putting me on.

  10. #10 Wow
    November 29, 2010

    > Uh, yeah, maybe because our underlying strategy is flawed?

    Just like, uh, the spending of education money is flawed, therefore it’s not that education is funded adequately, it’s that it’s funded inadequately.

    > A fair point (if true – source?), tho I’m not sure why per capita spending is the best measure here.

    Because you have to teach more children, each of which has a head.

    You can work out whether it’s true or not by looking at the purchasing power of the dollar from the 1970s to today. You’ll find it’s a lot less than half, making the “twice as much” spend on education buy less than the money spent in 1970.

    > Perhaps, but again there doesn’t seem to be a correlation between how many shinies a school has and how well its student perform.

    Because that isn’t something I’m saying is the dependent.

    I’m saying that the underfunding of schools is the problem and that one way money is frittered away is spending on shinies rather than spending on teachers.

    > You just can’t let go of that straw man, can you?

    It isn’t a strawman.

    YOUR position is that the funding of schools has gone up but there’s no discernible increase in quality.

    Yet when you take schools from a district that funds it adequately, the school performs better.

    It’s a strawman to call it a strawman. An ad-hominem where the argument is the homin you’re dismissing because you don’t like it and can’t counter.

    > As I said before, I wasn’t talking about funding at the level of individual schools.

    But, as the average wage of the bottom 50% drop, the value spent on schools is less for more children.

    But a drop in pay is not felt in the haves in the upper 50% of the payscale, who all live in the same elite catchment areas.

    Whilst the funding for schools depends on the money in the catchment area, YOU CANNOT ignore the funding on individual schools, because the schools are funded individually, not as a whole.

    You may not like it, but you can’t avoid it by screaming “strawman”.

    > Try looking at more than 2 data points.

    Why don’t you look at more than 1?

    > I’m not a libertarian, as should’ve been clear from my previous comments.

    And your strawmanning continues. Never said you were, but libertarians do not want to pay for others’ education. Since they vote too, their actions impact on non libertarians’ children too.

    (apologies for trying to educate this moron, making the thread continue OT).

  11. #11 Brandon
    November 29, 2010

    Pinko, if you want to dismiss anyone who ever links to Milloy, that’s fine. However, I don’t think you being a ‘practicing scientist’ should hold any weight with anyone. Even if it’s true, after all on the internet no one knows that you’re a dog, it does not really matter.

    Brian isn’t a practicing scientist so maybe he was ignorant of Milloy’s rep. I know I was when I first started reading his junkscience page a few years ago. It’s very well done propaganda for someone without a background in the related fields and it took me almost a month of casual looking to figure out what complete BS it was. Granted, I was in college and barely looking it and not a seasoned internet researcher. (I’m fully expecting some sort of ad-hom from someone out of my comment there.) To find someone being taken by those links, many of which seem valid (although they are not), irredeemable seems very harsh to me, but your mileage may very.

    Also, look elsewhere? Please tell me where you’re looking that doesn’t require time and effort to confirm validity, besides established scientific journals. Of course even those get confirmed with repetition of results, but that’s semantics.

  12. #12 Dale Husband
    November 30, 2010

    To put it simply, anyone who takes claims of Libertarians at face value has no business calling himself a skeptic. Libertarians can be incredibly gullible and full of themselves, just like any political extremist.

    See an example of one Libertarian who made an @$$ of himself. I took him down, HARD!

  13. #13 Pinko Punko
    December 4, 2010

    Brandon, you don’t have to believe I know what I’m talking about, of course my stating anything about myself opens up the internet for “argument from _____” comments, and allows me to counter with “your argument is structurally predictable and trite” and we could go forever.

    It does not make sense that you realize personally that Milloy is not to be trusted and an extreme propagandist, and that it is a well known and publicized fact, and then in the same comment thread argue that the magnitude of this mistake of Dunning’s doesn’t tell us anything about his methods (that he would both use Milloy and then try to defend aspects of it. It seems to, in the internet argument cliché, “speak volumes.” I would argue that you are being inconsistent.

  14. #14 Jon
    February 24, 2012
  15. #15 trav
    February 3, 2013

    I trust JunkScience on health and environment like I trust the Discovery Institute on evolutionary biology, or Prison Planet on history.

    …and I trust you like I trust the recent NatGeo chasing ufos

  16. #16 Douglas Barnes
    Ontario, Canada
    December 15, 2014

    When it comes to DDT disinformation, why does it always comes from libertarians, and how many times must their disinformation be debunked before they stop trying to resurrect it?

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