Ed Darrell writes in yet again, which I think might have earned him the dubious distinction of being my most regular correspondent. Maybe I should buy a carbon offset offset in his name as a prize.
At any rate, Here’s my last response to him, just for a refresher, since it has been a couple weeks since I’ve picked up and run with this discussion.
Toxicity, of course, is not the issue with birds. The question is what does DDT or DDE do to reproduction.
The chemicals are endocrine disruptors. They act as estrogen and other endocrine hormones in the wild.
By focusing on the toxicity studies, you do the same thing Milloy does dishonestly (though I’m giving you the benefit of the doubt — you probably haven’t figured this out). Toxicity is not the problem. Unless the chemicals are toxic, and they aren’t to larger animals simply because size makes the difference, they accumulate in fat tissues. This accumulation lets the chemicals operate in the animal for the rest of its life.
It won’t kill the bird, but it will kill the chick in the bird’s egg. It will thin the shell of the egg, too, so that should the chick manage not to die from estrogen poisoning, the egg will crack prematurely, and the chick will die from prematurity.
DDT’s dangers are not toxicity to larger animals. The dangers are reproductive interruptions and cancer. And while DDT is not a “proven” carcinogen for humans, it is listed as a suspected human carcinogen by every cancer fighting agency on Earth. We know it causes cancer in other mammals, and frankly, there are no known mammal carcinogens that shouldn’t be suspected of causing cancer in humans.
But it’s not humans or the environment that DDT advocates care about — it’s making half-witty remarks against Rachel Carson, scientists, and environmentalists. Who cares how many kids are killed because of misuse of DDT, if we can score points on a blog?
Ed is, of course, bending the truth again, as is befitting a biased activist. But because I’m in a very good, and somewhat charitable, mood, I’ll entertain him for a while.
Let me re-state something I wrote previously:
First, in an analysis of DDT and its derivatives, the International Programme on Chemical Safety found that “DDT and its derivatives DDE and TDE have moderate to low toxicity to birds when given as an acute oral dose or in the diet.” Moreover, it was found that there “is no obvious pattern of relative toxicity between the three compounds. In some species it is DDT that is the most toxic, while in other species it is TDE.” (and remember: what toxicity exists is rated as “moderate to low”) The study does not specifically address eagles, however, noting that in the wild, “the most severely affected species of birds are raptors at the top of food chains. There is little direct laboratory data on toxicity to these birds.”
That should begin to paint us an interesting picture, O Reader, one which I will come back to later. There is “little laboratory data” on the toxicity of DDT and its byproducts to high-level predatory birds like eagles. And yet some people assert with terrifying certainty (when is science ever certain?) that DDT is the causitive factor in the bald eagle’s near brush with extinction.
The study goes on to note that whether or not DDT exposure affected hatchability of eggs (particularly due to eggshell thinning) varied greatly between bird species — some were succeptible to it, some were not. Care must be taken in looking at the results, however, because some of the test birds were also fed a low-calcium diet, which would also negatively impact eggshell thickness. This was specifically being tested for, as earlier studies (most notably by Joel Bitman of the United States Department of Agriculture, in 1969) had exposed the test birds not only to DDT or one of its derivatives, but had also fed them a low-calcium diet.
The reduction of calcium in the diet of test birds was found to be a significant factor in the outcome of the studies (which shouldn’t come as a surprise): “In contrast to the earlier studies, there was no effect of either DDT or DDE on shell thickness or egg weight when dietary calcium was higher. There was an increased incidence of egg breakage in birds fed DDT and DDE, but this was less pronounced than with the low calcium diets.”
Moreover, “Robson et al. (1976) studied the effects of DDE and DDT fed to Japanese quail in two different diets containing adequate or low calcium. DDT was fed at 100 mg/kg diet, whereas DDE was given at 0, 199, or 300 mg/kg diet, and the two calcium levels were 0.5% and 3%.
DDE at 300 mg/kg was detrimental to adult body weight, fertility, and survivability. There was no effect of either DDT or of DDE at up to 100 mg/kg diet on adult body weight, food consumption, egg production, egg weight, fertility, hatchability, cracking of eggs, or eggshell thickness. Low dietary calcium had the effect of reducing the thickness of eggshells, increasing the incidence of cracked shells and decreasing egg production and hatchability.” In other words, DDT and its derivatives (DDE is the most common — it is formed when DDT sheds a hydrogen cholride molecule) did not have at all the same effect on eggshell thickness in test birds as it was found to have in previous studies, because those studies had also involved feeding the birds a calcim-deficient diet, something they probably wouldn’t have been exposed to as frequently in the wild.
It’s not just the Bitman study that is thrown into doubt, either — researchers from the University of Alberta, writing to Nature Magazine, also question the findings of Wiemeyer and Porter’s work with American kestrels, pointing out that in the Wiemeyeer/Porter study, it was the control group of birds who had the thinnest eggshells. This was written in response to an article in Nature Magazine by Blus, Gish, Belisle and Prouty in 1972. The U of A researchers, in their letter, note that to “support their conclusions, the authors [Blus, Gish, Belisle and Prouty] state that concentrations of residues in the female determine shell thickness, a claim which is unreferenced, largely hypothetical, and without consideration of contradictory experimental evidence.”
Now, I’m not sure exactly how Ed jumped from reading the above, which I have excerpted directly from the article linked in the opening paragraph, to concluding that I chose only to focus on the toxicity of DDT and its derivatives whilst demonstrating utter neglect of the issue of the effect of those chemicals on avian reproduction. As the Reader can plainly see, the issue of egg cracking is directly discussed, and the studies I link to suggest that eggshell thickness varies not only in relation to DDT/DDE concentration, but to bird species as well — some birds seem succeptible, others do not. And indeed, the validity of the initial studies of eggshell thickness relative to DDT/DDE concentration are called into doubt because of the fact that the test birds were fed a low-calcium diet, which had a very obvious detrimental effect on eggshell thickness wholly apart from any DDT/DDE exposure.
(Tangentially, I wonder if Ed is as concerned about the estrogen imbalances and the effect they have on reproduction and offspring viability in human women, specifically in regard to birth control?)
Ed remarks that “while DDT is not a “proven” carcinogen for humans, it is listed as a suspected human carcinogen by every cancer fighting agency on Earth. We know it causes cancer in other mammals, and frankly, there are no known mammal carcinogens that shouldn’t be suspected of causing cancer in humans.” I admire his youthful idealism, of course, but he seems unable to accept the fact that cancer-fighting agencies could succumb to political pressures, or could act — on occasion — out of political, and then less than noble, motives. Yes, DDT is listed as a possible carcinogen in humans, and yet repeated studies have demonstrated no tangible connection between the development rates of various cancers and DDT/DDE exposure in humans. One would think that in the thirty or so years that we’ve been researching this matter, some kind of connection might have been demonstrated or observed…and yet, time and again, this is shown not to be the case.
Documented cases of people dying from DDT exposure are not exactly common either (in fact, they are rare); documented cases of people dying from malaria spread by resurgent mosquito populations as a result of the DDT ban are, unfortunately, very common, to the tune of (well) over a million per year.
Ed and I are both trying to framework our arguments, in part, around the issue of death tolls inflicted on real human beings. But whereas Ed is more repulsed by the fact that a chemical agent might cause cancer (although more and more studies seem to be showing no tangible link between DDT, or any of its derivatives, and cancer rates) in a few human beings, and in so doing kill them, I choose to be more repulsed by the fact that discontinuing the use of DDT was directly responsible for the re-increase in rates of malaria infections in many countries around the world, causing millions of deaths. Ed is chasing phantoms and decrying shadows; I prefer to deal with somewhat harsher and more concrete realities.
What’s really unfortunate, though, is that this whole discussion emerged out of nothing more than a throwaway comment I made in an article that was primarily focused on how the production of biofuel — another obsession of environmentalists — was forcing the prices of food staples, grains especially, to skyrocket world-wide.
A significant contributor to the problem - one estimate puts it at 30 per cent of the problem - is the growing reliance on biofuels, such as ethanol and biodiesel. Last year, 20 per cent of the U.S. corn crop was used to produce ethanol; this year, it is expected to reach as high as one-third.
Biofuels have been pursued as a way to cut greenhouse gas emissions while enabling the world to maintain its reliance on the internal combustion engine. In theory, they are carbon neutral because the carbon they produce when burned is offset by the amount they absorb while growing. But because of the carbon produced when they are harvested, refined and transported, the picture is not so rosy.
Further, ethanol is seen as desirable because it can locate fuel production in the Western world, rather than in countries seen as politically less reliable.
The result of this shift to biofuels can be catastrophic. In Mexico, for example, the shift in the use of maize to ethanol has been a major cause of the astronomical increase in the cost of a staple food.
That the world would sacrifice land needed for food production to produce more fuel for private transportation shows how crazy our addiction to fossil fuels has become. We would place the lives and well being of hundreds of millions of people in jeopardy in order to maintain our way of life.
If the price of bread triples in Canada, most of us will still be able to get by. Six dollars might seem a lot to pay for bread, admittedly, but most Canadians (not all, though) can still survive such an increase. Poor people in Canada, and the majority of the people living in poor and developing nations, however, cannot weather such steep food price increases. And out of a selfish desire to live the most “carbon neutral” lifestyle possible, the rich liberals of the West think nothing of how their thirst for biofuel forces starvation upon many in the third world.
Funnily, Ed didn’t seem to have any comment on that larger issue, preferring instead to sidetrack the discussion into a topic of a battle his side has already won, more or less — DDT. I wonder what Ed thinks about biofuels? He seems so passionate about protecting the environment, and at least feigns passion (he might be sincere, but of this I am less certain) where preventing the deaths of human beings is concerned. I honestly wonder if he advocates for the increased use of biofuels, even though such an increase would condemn many people world-wide to deeper poverty and/or starvation? After all, when the issue becomes — very directly — a tradeoff between comparatively minor environmental harm and a massive human death toll, Ed comes down in favour of a massive human death toll where DDT usage is concerned. Biofuel is another issue in which a very minor (if at all existant) environmental impact conflicts directly with the well-being and survivability of what could be millions of human beings. Why did Ed choose to sidetrack the discussion in the first place, and what is his stance on biofuel?
One is not inclined to be all that hopeful in one’s assumptions in this regard.
