DDT was rightly banned for sound scientific reasons. Nobody would have been able to prevent and enforce the ban on a multi-million dollar product and potential litigation without it. To say it was banned without cause is just so much hot air, and should be filed in the bin where it belongs. If people have failed to find a feasible alternative for killing mosquitoes, that has nothing to do with DDT one way or another. It will never be reinstated for large-scale use again, so the question is redundant anyway. In some of the worst insect infested habitats it is still used as far as I'm aware.
By the early 70s, when Bald Eagle populations had doubled from their low point, DDT was already on a serious decline in use in the US (it peaked in 1959 at 80 million pounds) and was almost exclusively used in its later years on Cotton in the US (~80% of use) so when you consider how big the US is and how little was used outside the South (~2.5 Million pounds), it's impact on Bald Eagles would have been at best minor since nearly sterile Cotton fields in the South would not be considered a main hunting ground for this predator. Indeed we have annual bird counts courtesy of the Audubon Society which clearly show that the increasing use of DDT was never correlated to the numbers of Bald Eagles. http://birds.audubon.org/historical-results Table is: Year Birds Counted, Birds per person counting (For elusive birds like Bald Eagles this last number helps to get a better idea of density of birds, so looking at the chart you can see that in 1970 they counted over 10 times as many birds, but only twice as many per person, the real census then likely likes between those two numbers, i.e., in 1945 there were certainly more than 132 Eagles, they just weren’t seen because the number of counters was low, of course in 1970 there weren’t likely to be 10 times as many Eagles either, just fewer were not seen, a more reasonable interpretation is the population was probably three times as large in 1970 as it was in 1945) 1945 132 0.07 <== DDT starts being used 1950 393 0.11 1955 424 0.06 1960 609 0.08 1965 759 0.07 1970 1648 0.13 <== peak sightings per person, nearly twice as many as in 1945 So over the timeframe DDT was used in the US, the density of sightings went up quite a bit and the number of actual birds was maybe two to three times what it was when DDT was first used In contrast, it’s affect on Brown Pelicans is even less likely as the Brown Pelican only lives next to salt water and only feeds on fish living in the ocean, so the amount of DDT that they would consume from eating fish living in the Gulf waters and along the Eastern Seaboard would not be likely be that much. And of course plenty of Brown Pelicans also lived where DDT was not used at all, so it alone would never have caused their extinction, (Teddy Roosevelt created the first Federal Bird Sanctuary, Pelican Island, in Florida in 1903 (now called the Merritt Island National Wildlife Refuge]) the reason is they were being extensively hunted for their feathers and later by fisherman. Indeed the hunting of birds in the US at this time was so extensive that Congress passed the Migratory Bird Treaty Act of 1918, which included protection for the Brown Pelican. The fact is Brown Pelican numbers began to decline sharply in the 1920’s and 1930’s, when adult birds were killed and nesting colonies destroyed by fishermen, in the mistaken belief that pelicans competed with man for food. It is estimated that pelican numbers declined by more than 80% in just 16 years, between 1918 and 1934. This was decades before the use of DDT. From the Audubon Bird Count database we can see that the number of Brown Pelicans also increased significantly and were at much higher counts in 1972 than they were in 1945. 1945 2689 1950 3898 1955 4674 1960 4898 1965 14912 1970 11591 1972 16683 <== year of ban 1975 14019 1980 15296 I know nearly everything one reads blames DDT for the decline of these birds, but the facts really support the conclusion that well before DDT was used men deliberately killed these animals to near extinction; That laws passed before DDT was used were starting to work, such that over the timeframe that DDT was used both of these bird species actually increased in numbers and density. Now I am NOT saying that DDT had no impact on the birds. You can’t make that conclusion from just these numbers. But what you can conclude is that in both cases these two bird populations increased while the amount of DDT was going up and the logical explanation is that while there are certainly biological reasons why DDT might have had a negative impact on some populations of these birds, DDT wasn’t sprayed evenly throughout the country, so clearly there would be places where the impact would be high and others where it would be low. A more plausible explanation then is that during this period we did a much better job of stopping the hunting and destruction of their nesting sites and providing sanctuaries for the birds which allowed them to slowly recover. For some populations, stopping the use of DDT may have also helped. As to Malaria, a ban on its use doesn't matter if no one makes it or is willing to supply it to the poorer countries that needed it, and so if you look at it's use in the world against Malaria it was indeed effectively banned. Please Register or Log in to view the hidden image! http://www.21stcenturysciencetech.com/articles/summ02/DDT.html Last post on this matter. Arthur
We do not need to depend on such naive reasoning - what an underinformed imagination considers to be "likely" - the effect of the actual levels of DDT accumulation on the actual nesting success of eagles and pelicans in the real world has been directly measured, and found to be significant. The serious bad effect of overhunting on large birds in the US is well known. The failure of the populations to recover after the cessation of overkill, and their further decline instead, was a reproductive failure, and DDT is one of the major established causes. But it makes a very big difference in one's justification for removing the curbs on DDT, if they rest on its usefulness against malaria outbreaks. By all means restore the use of DDT as local and targeted application against malaria outbreaks, a goal which would not require a single change in law or treaty - but that is not the goal, is it. The people who want to remove the curbs on DDT have no real interest in malaria fighting, and would be happy to destroy its usefulness in that regard (and many other regards) by industrial scale broadcast agribusiness application once again (a disaster they were well on the way to creating in the years before the curbs). To the extent that DDT is still useful against malaria - a very valuable property of the compound - we can thank the environmentalists who fought to curb its misuse. (btw: to compare with the stats on DDT manufacture (only indirectly correlated with environmental effects, which are often products of accumulation and migration over many years), compare malaria mortality with DDT manufacture in countries such as the US, Soviet Union, etc. You'll find the reduction of malaria mortality only weakly linked with DDT use in most places - malaria, like bald eagles, was not originally killed off by DDT.)
On DDT and malaria http://75453320.nhd.weebly.com/health.html I quote : "Starting in 1945, DDT was used in an attempt to rid America of malaria, with the three main methods being by foot, by car, and by plane. The attempt was a huge success, and malaria was virtually eradicated from the contiguous United States. In 1950, the WHO realized just how effective DDT was at fighting malaria in America, and attempted to eradicate malaria from the entire world. At first, their program appeared to be working; but when DDT's environmental devastation came to light, its use was curtailed, and malaria made a comeback in developing countries."
http://scienceblogs.com/deltoid/2005/02/malaria.php This is consistent with the Wikipedia page on DDT. Widespread agricultural use selects for resistant insect populations. Mean old evolution at work again. Also see DDT ban myth bingo.
There is no denying that mosquitoes can get resistant to DDT, and malathion, and pyrethroids ..... However, if there is no good reason not to use a good tool, you do not ban it, unless you have extremely strong evidence of major harm.
In 1945 malaria had already declined to low levels in the US, and been confined to the southern part of the country, from eradication campaigns in the 1920s on top of a century's decline from other factors. DDT played no role. http://www.princeton.edu/rpds/papers/pdfs/bleakley_malaria_princeton_april2006.pdf DDT did not kill malaria in the US, just as it did not initially kill all the eagles. It came along later. After its US ban, there was no malaria resurgence in the US. DDT has never been banned for anti-malaria use. It's ban for agricultural use was based on extremely strong evidence of major harm, in such use.
iceaura The whole point of this thread is that there was no strong evidence of major harm. If you have such evidence, then post it.
The creation of resistance, the elimination of predators and other natural curbs on pests, the inundation of the landscape with an indiscriminate killer of insect life that bioaccumulates in vertebrate body fat and acts as an estrogen mimic, make the presumption of major harms from industrial agribusiness usage the default position. Meanwhile, people who think DDT played a major role in the suppression of malaria in the US, or that the overhunting population decline of bald eagles means their recovery has nothing to do with banning DDT, or that the millions of people who have died of malaria since DDT use was drastically curtailed would have been saved by DDT's continuing effectiveness in such inundative use, haven't made a "point" of any kind.
icaeaura If you want to claim major harm, you need to post evidence. So far we have seen none. I read a report of DDT treatment of WWII returning veterans. Apparently about half were deloused wth DDT powder. Many years later, researchers decided to see if DDT was carcinogenic by comparing cancer rates between those inundated with DDT powder to delouse them, and those who received no DDT. No difference in cancer rates was seen. I have no doubt that DDT has its downside. After all, what has not? However, if you want to make it into some kind of bogeyman, you must provide evidence.
DDT is remarkably benign for humans, in general (it should not be ingested by women who will nurse children in the reasonably near future) - a major virtue, and one of the best reasons for protecting its effectiveness against insect pests. But if all I want to do is point out that it should not be broadcast over the landscape wholesale for the short term profit of agribusiness concerns, the claims no one here has disputed (the eggshells thinning, the resistance developing, the wide variety of insects affected, the risks of estrogen mimicry and accumulation in fat, etc) are easily sufficient.
Broadcast spraying of strong pesticides is probably not a good idea in general. However, is there anything about DDT specifically which sets it apart, or is it just another pesticide?
It is durable in the environment and bioaccumulates - concentrates up the food chain in fat deposits - where it mimics estrogen. That makes it an almost uniquely cumulative danger, as insect poisons go. It doesn't immediately poison people, or cause them immediate distress, in ordinary exposures. That makes it a uniquely tempting danger. It's cheap. Those, especially the second and third, make it uniquely valuable undamaged - its effectiveness should be protected. There aren't many good replacements.
DDT in fat deposits is actually reasonably benign. In that fatty tissue it remains inactive. it is only when released into more metabolically active tissue that it becomes toxic. I read of one man, a crop sprayer, who had been badly exposed to DDT over many years, who showed absolutely no harm from DDT. However, he was obese, and when he came down with a fever, he lost a lot of weight in a hurry, and died of DDT poisoning. Such cases, though, are very rare, making DDT a lot less toxic than many other poisons, due to its inactivation in fatty tissues.
You're just now discovering this? It never was bad, damn. It does kill cats though, but not everyone likes cats, so here u go.
Fat is metabolically active - fat people get diabetes for a reason - but the issue is the accumulation: DDT accumulates up the food chain, building up in the fat stores of each successive level. While doing this, it can travel as far and as widely as the fat stores travel - DDT broadcast in Malawi will end up in both arctics and on the other side of the planet. In animals that gain and lose weight regularly, especially those that employ fat stores for reproduction, an accumulation of an estrogen mimic in body fat is a hazardous situation. And of course some animals are just straight out poisoned by the stuff. These vulnerabilities can exist with only distant and indirect connections to the ostensible targets of the employment. It's durable, cheap, kills far from target, and bioaccumulates. That's one issue. Another one is that kills all kinds of arthropods - good and bad, necessary and pest. Used indiscriminately long term, accumulating in the environment, it thereby usually gives advantage to pest species and degrades the local environment. That's another issue.
I would like to address the benefits of DDT to third world nations- particularly African nations. It kills off the mosquitoes which carry malaria and it's other side effects are mitigatable if used properly. In the larger context I find it surprising that the US would outlaw ANY chemical, as we have over 100,000 chemical compounds in use here and abroad.
Iceaura The animal that accumulated more DDT than any other turns out to be the polar bear. They had, at one stage, substantial DDT in their fat deposits. There is no evidence it did them any harm whatever. When the ban on shooting polar bears was implemented, they had lots of DDT accumulation going on, and their population grew quite rapidly from 5,000 to 22,000, during a period of DDT take up. I do not advocate widespread spraying of DDT or any other product. Spot spraying is better, and any spraying needs to be carefully managed. DDT is now in use in South Africa for malaria control. Their method is to spray the interior of people's homes, and leave a thin film of DDT. Any invading mosquito will alight on an interior surface before seeking out its human target. Landing on a film of DDT turns out to be a fatal experience. This spraying needs to be done only once a year, and costs next to nothing.
DDT works effectively as a repellant for mosquitos. Used in this way it has virtually no negative side effects. http://www.nypost.com/p/news/international/porno_sama_had_big_jihad_on_QSLrV2tQkxSRIROmP81naP Arthur
