DDT - dangerous to birds? dangerous to humans?

[Haunted]

The EPA’s motives on the DDT ban were also questinable, since the scientific panel recommended against a ban, and was overidden by the politically appointed head of the EPA.

I think the problem is that you don’t understand how decisions are made at EPA. It’s called “Risk Management.” Check it out. The job is determining, with a reasonable certainty, whether a given pesticide will or will not harm a person’s health. I think you’re confusing very high safety standards with a disregard for statistical significance.

The EPA’s motives on the DDT ban were also questinable

Well, as you yourself pointed out:

casting doubt on motives is easy to do, but doesn’t prove much.

And, do you really believe that this decision has never been revisited?

In 1972, EPA issued a cancellation order for DDT based on adverse environmental effects of its use, such as those to wildlife, as well as DDT’s potential human health risks. Since then, studies have continued, and a causal relationship between DDT exposure and reproductive effects is suspected. Today, DDT is classified as a probable human carcinogen by U.S. and international authorities. This classification is based on animal studies in which some animals developed liver tumors.

I’ll be glad to discuss scientific findings and policies, but there’s no point in rugurgitating wikipedia and google searches. Let me leave you with this: What WOULD convince you that DDT is safe? If you can’t think of anything, it might be time to re-examine your rationality on the issue.

Maybe you’re the one who should re-examine your rationality on the issue. Maybe you’re too focused on the statistical tree to see the real world forest.

[GIGObuster]

And, like if gaining resistance and causing other bugs to be resistant is not a problem, (as the evidence showed, it was one reason why DDT was discontinued rather than just the say so of environmentalists) I do take into consideration the evidence to say that cancer is not much of an issue, but it is a lie to say that there is no science for finding DDT is harmful to the environment, as much as you dismiss Wikipedia and Reason Magazine they do not pull what they say out of thin air.

DDT, Eggshells, and Me

It’s not DDT per se that is thought to do the damage to eggshells, but a DDT metabolite known as DDE. Thus the most persuasive feeding study refers to it: “DDE-induced Eggshell Thinning in the American kestrel: A Comparison of the Field Situation and Laboratory Results.” This groundbreaking study was published in the Journal of Applied Ecology by Jeffrey Lincer in 1975.

Kestrels, commonly called sparrow hawks, are small falcons. Lincer noted that the “inverse correlation between DDE in North American raptor eggs and eggshell thickness is clear but does not prove a causal relationship since other chemicals or factors could be involved.” So to find out what effect DDE might have, Lincer fed captive kestrels a DDE-laced diet and then compared their eggs with those taken from the nests of wild kestrels. Lincer found that dietary levels of three, six, and 10 parts per million (ppm) of DDE resulted in eggshells that were 14 percent, 17.4 percent, and 21.7 percent thinner respectively. “Despite the recent controversy, there can be little doubt now as to the causal relationship between the global contaminant DDE and the observed eggshell thinning and the consequent population declines in several birds of prey,” concluded Lincer. As best as I can tell, he’s right.

BTW that was posted before and you did claim to read the article, are we to assume that you are lying when you are saying “I still have yet to see any scientific evidence”?

Rachel Carson's birthday bashing

What her critics seem unwilling to admit is that Carson was just one person, and DDT is just one tool. DDT plays a part in the fight against malaria, but it’s one drop in a very big puddle.

[Haunted]

I’ve been reading your articles again, Mosk. Interesting. Especially this:

As we shall see, the 95 percent confidence interval (CI) corresponds to a p-value of 0.05, but low p-values, even as low as p=0.006 or p=0.009, do not establish causation; they only denote strong statistical associations not due to chance. Statistics are not science and cannot prove cause and effect relationships. For an amusing yet informative review of this subject for the busy clinician, neurosurgeon and neuroscientist, I strongly recommend Steven J. Milloy’s book, Junk Science Judo, published by the Cato Institute in 2001.

Statistics are not science. Statistics cannot prove cause and effect relationships. Excellent points. Maybe you should keep them in mind.

I wonder if LS Milloy even grasps that his “work” can be applied to both sides of the argument. I imagine that, if he figures it out, he will be sending a bill to EPA.

[jshore]

@MoskTheDissenter

So in summary:

1. DDT doesn’t have significant health risks, especially compared to other approved pesticides like Pyrethrins, Pyrethroids, PBO, and others (Some of which are acutely toxic as well).

Well, I would state it as that there have not been shown to be significant health risks to the use of DDT, at least at the levels used for indoor spraying. And, I would add that because of its persistance in the environment, we have to be particularly careful.

2. There is no evidence for environmental effects at the low levels that would occur in IRT mosquito control. (And not a lot of evidence even at higher levels)

I agree, more or less, with your first statement. Your last parenthetical phrase is not true. In fact, even Malaria Foundation International admitted that DDT was harmful to wildlife when used at the levels used for agriculture. (They have re-organized their website and I can’t find the page where they said this.)

3. Even if it were unbanned tomorrow, no one is likely to spray it in the massive quantities used historically – we don’t spray that way with any chemicals today, because it is inefficient and has PR risks.

Why do we need to unban DDT tomorrow in the U.S. or other Western countries? What do we need to use it for? As for a ban in other countries where malaria is prevalent, since such a ban does not exist (nor does any international ban exist), this can’t be what you are talking about.

4. Resistance is not an issue with IRT spraying. DDT acts as a repellant as well as an insecticide and IRT spraying does not put enough pressure on the mosquito population to build species-wide resistance.

Well, one problem is that because of widespread use in the past (e.g., in agriculture), some mosquito populations have built up resistance. However, your statement is again a bit too strong as even Malaria Foundation International uses a softer statement, i.e.,

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.

(bolding added)

@MoskTheDissenter

5. Mosquito control works best with multiple approaces. Nets help, but are expensive (two dollars is expensive in the extreme poverty of tropical africa). Nets also can be damaged, and if there is a risk of DDT resistance, there is a risk of malathion resistance. IRT spraying helps, but doesn’t lower populations. Habitat reduction helps, but doesn’t protect people from bites.

Agreed.

None of these statements are particularly controversial; the more expensive pesticides we’re using today are not more ecologically friendly or non-toxic. All that’s left is knee-jerk reaction, misconceptions about the science, and lack of understanding of the impact of malaria on poverty-stricken tropical areas.

Agreed. However, while there has been some “knee-jerking” on the environmental side, most of the knee-jerking has been on the other side. I.e., even the main environmental organization taking up this issue (World Wildlife Fund) when the treaty on persistent organic pollutants was negotiated was originally only asking for a phase-out in DDT use because they felt the pressure of such a phase-out was needed to push for the development of alternatives. And, they eventually changed their stance and decided not to push for a phase-out at all but only to be sure that DDT can only be used for disease control and not for agricultural uses.

By contrast, among the anti-environmental backlash movement, there are those who basically present DDT as a miracle cure and completely distort the history to make it sound as if the reason malaria is still prevalent today is because environmentalists blocked its use. This is just malicious and false.

[jshore]

@jshore

Your last parenthetical phrase is not true. In fact, even Malaria Foundation International admitted that DDT was harmful to wildlife when used at the levels used for agriculture. (They have re-organized their website and I can’t find the page where they said this.)

A little more searching led me to the statement that I was looking for:

DDT is hazardous to certain wildlife species and should not be used outdoors or in natural areas.

Note that that page also talks some about the issue of resistance (presumably due mainly to past widespread spraying for agricultural purposes):

Are There Regions Where DDT No Longer Works? Anopheles mosquitoes are physiologically resistant to DDT in some regions, and thus DDT is not effective in these areas. Currrent insecticide resistance test data should be used when planning malaria control efforts. Much resistance test data is 15-30 years old, and current resistance test data should be gatbered.

Are There Regions where DDT is Still Effective? In some regions. the vectors of malaria are still susceptible to DDT, and the compound remains effective in blocking malaria transmission. An example is control of Anopheles funestus in South Africa.

[wevets]

I’ve been remiss in not attending my own thread - real life has intruded on my spare time - so I’m going to have to do some reading to catch up with you all. I am encouraged to see the debate, though.

[jshore]

By the way, although I tend to side with those who say that indoor spraying with DDT should be used in some cases as part of a strategy for malarial control since this seems to be the point of view of most of the people in the field as near as I can ascertain, it is worth noting that this is not an open-and-shut case. For example, here is what looks to be a reasonable research paper on the CDC website that argues that the negative effects of DDT could be of the same order as the positive effects (in terms of prevented malaria deaths):

Although dichlorodiphenyl trichloroethane (DDT) is being banned worldwide, countries in sub-Saharan Africa have sought exemptions for malaria control. Few studies show illness in children from the use of DDT, and the possibility of risks to them from DDT use has been minimized. However, plausible if inconclusive studies associate DDT with more preterm births and shorter duration of lactation, which raise the possibility that DDT does indeed have such toxicity. Assuming that these associations are causal, we estimated the increase in infant deaths that might result from DDT spraying. The estimated increases are of the same order of magnitude as the decreases from effective malaria control. Unintended consequences of DDT use need to be part of the discussion of modern vector control policy.

I don’t think this one paper alone argues against the use of indoor spraying with DDT where public health advocates think it would be useful but it does make it clear that, even when only the issue of human health is considered, there is still some uncertainty in regards to whether benefits do outweigh the risks.

[intention]

jshore, I must commend you for a clear, nuanced, and sophisticated view of the scientific debate on the indoor spraying of DDT. In these times of hype, extremisms, and rigid positions, it is indeed a pleasure to see the acknowledgment of uncertainty in a discussion of such a potentially polarizing subject.

I have had malaria four times, my wife twice, and my daughter once. I have a friend who died of malaria, I have friends who had a child die of malaria, and I’ve had the inside of my house sprayed with DDT. I’m about to move back to a malarious country for the next two years.

As a result, I have strong views on the subject, views which have recently been tempered and refined by your excellent posts.

Thank you for your contributions,

w.

[jshore]

Thanks, intention. It is very interesting to hear the point-of-view of someone such as yourself who has actually experienced malaria firsthand.

[scotandrsn]

@wevets

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.

In 1975, at the request of the House Appropriations Committee, the EPA undertook a review of the science and economy of the 1972 DDT ban. The report can be found here: http://www.epa.gov/history/topics/ddt/DDT.pdf
Use Acrobat to go to page 67 out of 312 and read up on the effect on birds, with references to the literature of the time.

According to the Duke University Chemistry Department :

So exactly how much DDT can my body tolerate before I should really start worrying? That depends on how much you weigh. At concentration above 236 mg DDT per kg of body weight, you’ll die. Concentration of 6-10 mg/kg leads to such symptons as headache, nausea, vomiting, confusion, and tremors.

That page also has information on effects on birds.

[Haunted]

For fun, try and calculate how much DDT would be lethal for you.

:dubious:

(That’s from the second link. Thanks, scotandrsn.)