Re: Is DDT "nasty stuff"?

[Bernard L Cohen <blc+@pitt.edu>]

	I believe the statements about "suspected carcinogen" are a 
hold-over from the 1960s and early 1970s. At the time DDT was banned in 
about 1972, there were very extensive hearings and all the evidence was 
carefully investigated. It was concluded that there is no evidence for 
carcinogenicity. It is true that it concentrates in human fat and is lost 
only slowly, but there is no evidence that this has been harmful to 
health. DDT has caused problems in a few species of birds due to shell thinning
but I said "harm to human health". 
	There are lots of things that would cause trouble if 20 grams 
were ingested. I believe that much copper would be fatal. Is copper "nasty 
stuff"? The fact that organisms sometimes mutate to become resistant is 
true of almost anything. For example, does that make penicillin "nasty 
stuff"? If you do enough studies, you will probably find problems with 
any substance, and there is probably nothing that has been studied as 
thoroughly as DDT--- surely not the insecticides that have replaced it. DDT 
has been sprayed at regular intervals in the homes of hundreds of 
millions of people for many years, without evidence for harm to them. It 
was sprayed on millions of people (e.g. war refugees for de-lousing) without 
evidence of harm.    
	DDT was over-used by farmers, but no obvious harm was done. Ruckels-
house banned DDT as a political move to win support for EPA from 
environmental groups at a critical time, and he later admitted as much. 
The ban was against the recommendations of his advisory committee that 
had held the extensive hearings. 
	DDT has saved many millions of lives, relieved hundreds of 
millions from the scourge of malaria, and harmed no human. Do you know 
anything else that has been as valuable? That's why I object to it being 
singled out as a prime example of "nasty stuff".

Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu


On Mon, 29 Apr 1996 js_dukelow@ccmail.pnl.gov wrote:

> On  Mon, 29 Apr 1996 09:24:25 -0400 (EDT) 
> Bernard L Cohen <blc+@pitt.edu> wrote
> 
> > I object to characterizing DDT as "nasty stuff". There is no evidence 
> > that DDT has harmed the health of any human, and it has saved millions 
> > of lives. 
> > 
> > Bernard L. Cohen
> > Physics Dept.
> > University of Pittsburgh
> > Pittsburgh, PA 15260
> > Tel: (412)624-9245
> > Fax: (412)624-9163
> > e-mail: blc+@pitt.edu
> 
> Dr. Cohen and I are both out of our areas of expertise here, but I have 
> the advantage of having recently researched the toxicity of DDT, in 
> order to respond to an accusation made on the RISKANAL risk analysis 
> mailing list that Rachel Carson was responsible for the deaths of 
> millions of people because her book _Silent Spring_ led to the banning 
> of DDT.
> 
> DDT and its metabolites are not highly toxic, but that isn't the same as 
> being non-toxic or as there being "no evidence that DDT has harmed the 
> health of any human," as Cohen would have it.
> 
> The following information on the toxicity of DDT is available from the 
> WWW page of the National Toxiclolgy Program of the National Institutes 
> of Health and the National Cancer Institute. 
> 
>    Human poison by ingestion and possibly other routes.  Experimental 
>    poison by ingestion, skin contact, subcutaneous, intravenous and 
>    intraperitoneal routes.  A suspected human carcinogen.  An 
>    experimental carcinogen, neoplastigen, tumorigen and teratogen.  
>    Experimental reproductive effects.  Human systemic effects by 
>    ingestion.  ...  Human mutagenic data.  A dose of 20 grams has 
>    proved highly dangerous though not fatal to man.  This dose was 
>    taken by 5 persons who vomited an unknown portion of the material 
>    and, even so, recovered only incompletely after 5 weeks.  Smaller 
>    doses produced less important symptoms with relatively rapid 
>    recovery.  Experimental ingestion of 1.5 g resulted in great 
>    discomfort and moderate neurological changes.  Recovery was complete 
>    on the following day.  The fatal dose for humans is not known.  
>    Judging from the literature, no one has ever been killed in the 
>    absence of other insecticides and/or a variety of toxic solvents.  
>    However, these common solvent formulations are highly fatal when 
>    taken in small doses, partly because of the toxicity of the solvent, 
>    and perhaps because of the increased absorbability of the compound; 
>    several fatal cases in humans have been reported.  
> 
>    Little is known of the hazard of chronic poisoning.  Human 
>    volunteers have ingested up to 35 mg/day for 21 months with no ill 
>    effects. This compound and some of its degradation products, 
>    particularly DDE, are stored in fat.  This storage effect leads to 
>    a concentration of this compound at higher levels of the food 
>    chain.  DDT stored in the fat is at least largely inactive since a 
>    greater total dose may be stored in an experimental animal than is 
>    sufficient as a lethal dose for that same animal if given at one 
>    time.  A study based on 75 human cases reported an average of 5.3 
>    ppm of DDT stored in the fat.  A higher content of DDT and its 
>    derivatives (up to 434 ppm of DDE and 648 ppm of DDT) was found in 
>    workers who had very extensive exposure.  Without exception, the 
>    samples were taken from persons who were either asymptomatic or 
>    suffering from some disease completely unrelated to DDT.  Careful 
>    hospital examination of workers, who had been very extensively 
>    exposed and who had volunteered for examination revealed no 
>    abnormality which could be attributed to DDT. Much higher levels 
>    have been found in humans than have been observed in the fat of 
>    experimental animals which were apparently asymptomatic.  DDT 
>    stored in the fat is eliminated only very gradually when further 
>    dosage is discontinued.  However, weight loss can speed the 
>    release of this stored DDT (and DDE) into the blood.  After a 
>    single dose, the secretion of DDT in the milk and its excretion in 
>    the urine reach their height with in a day or two and continue at 
>    a lower level thereafter. 
> 
> Dr. George Waldbott, in _Health Effects of Environmental Pollutants_, 
> Mosby, 1973, and Carson, in _Silent Spring_, 1962, report several 
> incidents of DDT poisoning.  These resulted from consumer misuse of 
> household bug sprays or agricultural worker exposures.  DDT causes 
> liver cancers in mice and is considered a "probable human carcinogen" by 
> the EPA.
> 
> Cohen's other assertion about "millions of lives being saved" may be 
> true, but needs to be carefully qualified.  DDT was very effective at 
> controlling the insect vectors of several important human diseases, for 
> a short period of time -- typically, a few years -- until the insects in 
> question developed resistant strains.  Even before DDT was "banned" in 
> the U.S. in 1972, its "victory" over malaria in several countries in the 
> tropics had been reversed by resistant strains of mosquitos.  DDT's 
> short-lived victories came at a high price:  it disperses widely in the 
> environment; it is highly persistent in the environment and in humans 
> and animals; and it tends to bioconcentrate, both in individual 
> organisms (where it concentrates in fatty tissue) and in the food chain 
> (where it concentrates in the predators at the top of the food chain, 
> such as raptors, and humans, for that matter).  Several avian raptor 
> populations approached extinction, at least partly because of egg shell 
> thinning caused by DDT.  DDT's "banning" was only partial; it is still 
> being manufactured and used in a number of countries around the world. 
> 
> Best regards.
> 
> Jim Dukelow
> Pacific Northwest National Laboratory 
> Richland, WA
> 
> js_dukelow@pnl.gov
> 
> These thoughts are mine and have not been reviewed and/or approved by my 
> management or by the U.S. Department of Energy.
>