he states that “While DDT is highly toxic to insects and fish and can poison other animals in large enough doses, in moderate amounts it’s not especially harmful to birds and mammals, including humans.”
The problem is that birds and mammals don’t get a small dose of DDT. My biology textbook claims that DDT is a main source of the decline in Bald Eagles in the USA. In a study, it was shown that the eagles had been eating contaminated fish, and due to biomagnification (toxins accumulate in animals which are higher on the food chain) the level of DDT in the eagles was ONE MILLION TIMES the level in the water.
Fine, “moderate” amounts might not hurt us, but as high as we are on food chain, wouldn’t we get a nice dose?
It probably varies by individual. Some of us eat lots of fish, and others are vegetarians, after all. However, I suspect Cecil would agree with your general point that concentration of fat-soluble toxins as we go up the food chain is an important factor.
Cecil’s article states that “(t)he cause of eggshell thinning is … poorly understood” OK, but it seems to be accepted among biologists that organochlorines are bad for bald eagles. See, for example, http://www.pwrc.usgs.gov/bioeco/baldeagl.htm for the statement “Levels of DDE in eggs before and after the DDT ban were significantly different and were correlated with reproductive productivity.” (This is but one of many similar reports.) Bald eagles are particularly susceptible to the bad effects of DDT because of their diet and biology, and they are the DDT ban’s poster creatures for obvious reasons. But a prudent person would not assume that it’s just bald eagles who suffer, and the rest of us can relax. Some restriction on DDT use made sense in 1972 and still does today.
On the whole, Cecil is to be commended not just for a lucid and well-researched answer (we expected that), but for not dismissing the question in the first place. When we go to www.21stcenturysciencetech.com, after all, we find articles on cold fusion, Lyndon LaRouche on SDI, etc. Not to put too fine a point on it, they’re a bunch of loonies. Where a lesser man might have dumped this one in the circular file, Cecil saw an opportunity to shed light on a serious scientific question. Well done.
Since 1972, when DDT was banned, several chlorinated solvents have been deemed dangerous to humans. DDT ends in “trichloroethane,” and it may well have been thrown in the same trash can; however, since the ban all research on DDT stopped.
I agree that Cecil gave a very researched and enlightening answer, I just thought he should have been more clear on the dangers of DDT. I’m sure, however, there are many things more harmful that didn’t get nearly as much press. In my opinion, the exaggeration of Rachel Carson surely shouldn’t denounce the harms of DDT. That was the point of my post.
This report just blows me away. The bald eagle comback is huge around here, and largely accredited to the banning of DDT. I wished Cecil had expanded on the eggshell aspect.
I seem to remember reading something written by the son of the man who invented DDT, and how he had “proved” it was harmless by ingesting gobs of it over the years.
I, for one, have fond memories of DDT. As a young child and Navy brat, I lived in the Philippines for two years (1958-60, Subic Bay). We lived in Naval housing (West Kalyaan) a few miles from the base.
Each evening, around dusk, a pickup truck would drive slowly up and down all the streets, towing a trailer that would spew a dense fog of DDT. We used to play a running hide-and-seek/tag game in it (yes, it was that dense), and it smelled wonderful. It also wiped out large numbers of the mosquitoes that would have otherwise given many of us (natives and Yanks alike) malaria.
Of course, it did nothing for the cobras and bamboo vipers… …bruce…
I think Cecil’s take is basically correct, but he just had to sum it up with grandiosity at the end.
“In a time of rising global pestilence…” :rolleyes:
This is the sort of empty, vague, alarmist pronouncement I would expect from a ditzy local news anchor. Clearly not the insightful and incisive verbiage I’ve come to expect from the Master.
I for one am glad DDT is banned. If the use was continued many/most/all nasty creepy crawlies would become immune to it. While, as stated above about biomagnification, most if not all raptors would have become extinct. When I was a kid bald eagles only existed in Alaska and some parts of Canada. Now I hear they are strong in Louisiana. Perigrin falcons were extict in the wild. Now they are back in force. I say shred the formula and forget it.
I am an environmental toxicologist. Raptors are not the only birds that have recovered hugely since the banning of DDT. There are lots of good examples, but the best one is the brown pelican. Texas was down to one breeding pair, and the species is fully recovered now (despite still having tremendous body burdens of PCBs in some cases). Most people think that the eggshell thickness thing is most important in large birds, because the big birds are more likely to break their eggs while incubating them (or perhaps because large birds have large eggs, that may be more susceptible to breakage). I’d agree that the eggshell thickness thing is poorly understood, but the circumstantial evidence is pretty strong. Cecil has a point, though, that sometimes you have to make a societal value judgement - what is more important, mass human mortalities due to malaria infections or the loss of fish-eating predators? Sometimes I think that humans are too damn abundant anyway, so screw them. But if my kids were threatened, I think I’d break out the “Drop Dead Twice” insecticide. Humans are pretty damn resistant to that sort of thing, remarkably so, in fact. We’re a pretty tough species, chemically.
Fishhead covers this pretty well. DDT isn’t particularly dangerous to humans. But we ban it out of a sense of environmental responsibility–which in this case means not wanting to see every avian species on Earth go extinct. Get the facts.
foolsguinea, you are exaggerating and need to get the facts yourself. Fishhead said it more accurately:
Loss of large fish-eating predators, although certainly not “good”, is not even close to the same thing as "every avian species on Earth go[ing] extinct.
Let me ask this, though: why is all the uproar about DDT’s harm to nature concentrated on the birds? There may be an indirect effect on birds, but DDT is an insecticide. It kills mosquitos by the billions. A “silent spring” with no birdsong? What about a “silent summer” with no mosquitoes buzzing?
I’m being (partly) facetious to point out that people very often tend to worry about the extinction of “nice” or “cute” species that are macroscopic, like birds.
It’s not only about “cute” species, but yes, we mainly focus on macroscopic species’. Since mosquitos reproduce so much faster and in such greater numbers than birds such as the bald eagle, they’re in relatively no danger of going extinct (huge number of newborns, and quicker reproduction means quicker evolution). The chemical was banned because it caused (debatable, but I believe it) many species’ to near extinction. These species’ are naturally the ones we’re worried about.
A few years ago I worked for Orkin spraying farms. To get the job that years crop of applicants were sent to a week long school to be trained. One of the things I remember about it(it turned into a weeklong party) was someone asked about DDT and the instructor told us that the ONLY reason we don’t use DDT everyday now is that it works TOO well. That is the current pesticide had to be reapplied every 28 days but DDT lasted far longer. He also said that behind all the environmental groups was chemical company money(at least on this one issue)…so he told us anyway.
BTW those of you who don’t care just as long as DDT is not used…the pesticide I used was an organic pesticide that accumulated in the body and was as deadly to humans as insects.
Plus it could be absorbed through the skin(we had some that adding ONE pint to 500 gallons of water would drop flies right out of the sky). Needless to say getting even a drop of undiluted pesticide on your arm was more than frowned on.
One last thing…when I left that job that incredibly deadly pesticide was barely working anymore…the flies had grown resistant to it. God only knows what they are using now.
Actually, the overall, global pestilence level in the 20th century was far below what it had been for the last couple millenia at least. Think Black Death. Wasn’t it one third of Europeans who died from the plague? Not to mention smallpox, polio, leprosy, etc.
I agree with Fishhead, the environmental toxicologist who posted in this same thread above, saying “Sometimes I think that humans are too damn abundant anyway, so screw them”.
People are breeding like rats. If there’s a recent, slight blip on the global pestilence level, it’s probably because there are now over 6 billion people on this planet that can only sustainably support a couple billion? If we’re all cheek by jowl, we can expect to get sneezed on a lot. What we need now is a good plague. I have a lot more sympathy for the birds and fish than I do for my fellow, warmongering, selfish humans.
No, I’m not exaggerating. If western society had continued to use nice, safe, not-toxic-to-humans DDT & its CHC cousins for, say, 150 years–occasionally increasing the standard amount applied to deal with rising resistance–every bird species on Earth (OK, except maybe hummingbirds & large running birds like ostrich) would be endangered. Why? Because birds (except, say, hummingbirds) are almost universally predators. They eat insects & annelids or they eat fish. (I don’t know what ostrich eat.) Anything in the water supply will eventually get the fish-eaters, anything that gets into the worms & bugs & frogs will get the rest. DDT on the flowers may even get the hummingbirds.
I get so mad, because people who’ve never read Rachel Carson pooh-pooh her, & they don’t even know what she was writing about. This was clearly happening in the 20th century. They don’t want to accept that this is real, this is enormous, and it’s still going on. The chemicals are different, but the agricultural attitudes are still in operation.
and your last post has toned down that claim a bit:
So you agree your original post was an exaggeration. Not every avian species but many, and not extinct but endangered.
By the way, Ostriches are indeed herbivores. There are also very many other herbivorous birds, such as cedar waxwings, Canada geese, pigeons, canaries, goldfinches, grouse…by no means are birds “universally predators”. Certainly herbivory is less common.
My reason for seeming to pick such nits is that, in my opinion, if one tend to overstate one’s claims, one’s claims become less credible. I’ve read Carson’s book, and in my opinion that is what she was doing. Starting with what is a valid scientific observation, and then carrying it way, way, way out beyond where the science will support it.
This isn’t an either/or decision, and Rachel Carson was correct to point out dangers that had been ignored in the largely successful efforts to stymie a major killer.
It is (and was) quite possible to stop malaria in many places using the chemical. It is (and was) dangerous to many animals (including, at the end of the food chain, humans) to use DDT indescriminately.
There was a long article a while ago in the New Yorker, which I don’t have handy, all about the guy who pushed for the widespread use of DDT during and right after WWII. While his insistance on blanketing areas (to get ALL the carrier bugs) worked, it’s still a bit disturbing to realize that this came about not so much because the medical community wanted to deal with malaria, but so that our troops would be safe when stationed overseas.
And Cecil gives short shrift to the right wingers who try to deny the whole thing; they’re the same people who have been denying global warming and who think the country’s problems would have been solved if Strom Thurmond had been elected President in 1948.
I don’t know why it’s disturbing to want to prevent a deadly disease from killing your country’s citizens, wherever they may be located. But that’s beside the point. By far, most DDT has been used in tropical countries, where Americans do not live. It’s hard to make the argument that it was used only for the benefit of Westerners.
Hello, straw man. What do global warming and Strom Thurmond have to do with DDT? Please don’t turn this into a Great Debate about politics.