--- Michael Harney <[EMAIL PROTECTED]> wrote: <snipped most>
> Regarding DDT: Banning DDT was not a mistake, as a > matter of fact, Mr. > Crichton's** insistance that it was a mistake, and > that DDT is safe, are mistakes on his part...
> ...so an internet search of articles with many > sources cited will have to do for now: > http://www.seaweb.org/background/cetaceans.html > http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v375/n6532/abs/375581a0.html > http://www.nature.com/nsu/010719/010719-3.html
Here is the International Programme on Chemical Safety (IPCS) site on DDT: (it is a joint venture of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization) http://www.inchem.org/documents/ehc/ehc/ehc83.htm#SectionNumber:1.8 "The physicochemical properties of DDT and its metabolites enable these compounds to be taken up readily by organisms. High lipid solubility and low water solubility lead to the retention of DDT and its stable metabolites in fatty tissue. The rates of accumulation into organisms vary with the species, with the duration and concentration of exposure, and with environmental conditions. The high retention of DDT metabolites means that toxic effects can occur in organisms remote in time and geographical area from the point of exposure.
"These compounds are resistant to breakdown and are readily adsorbed to sediments and soils that can act both as sinks and as long-term sources of exposure (e.g., for soil organisms).
"Organisms can accumulate these chemicals from the surrounding medium and from food. In aquatic organisms, uptake from the water is generally more important, whereas, in terrestrial fauna, food provides the major source.
"In general, organisms at higher trophic levels tend to contain more DDT-type compounds than those at lower trophic levels. [Raptors are particularly susceptible to DDT's thinning of their eggshells, while ducks and chickens are not. This is detailed in the article.]
"Such compounds can be transported around the world in the bodies of migrant animals and in ocean and air currents...."
This is a very detailed article with summaries of many studies on microbes, fish, amphibians, and birds - also affected were bats.
Our national bird, the bald eagle, was threatened with extinction in the lower 48 states by hunting, habitat destruction, and poisoning: "The greatest threat to the bald eagle's existence arose from the widespread use of DDT and other pesticides after World War II." (Lead poisoning from hunters birdshot was also a significant problem; its use was phased out by 1991.)
http://www.usflag.org/bald.eagle.html "...With these and other recovery methods, as well as habitat improvement and the banning of DDT, the bald eagle has made a remarkable comeback. From fewer than 450 nesting pairs in the early 1960s, there are now more than 4,000 adult bald eagles nesting pairs and an unknown number of young and subadults in the conterminous United States. This represents a substantial breeding population..."
There are groups who deny the toxicity of DDT; here is one site: http://dwb.unl.edu/Teacher/NSF/C06/C06Links/www.altgreen.com.au/Chemicals/ddt.html
But women exposed prenatally to higher levels of DDT have decreased probability of pregnancy: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12842376&dopt=Abstract "The decreased fecundability associated with prenatal p,p'-DDT remains unexplained." [OTOH, DDE exposure seemed to increase pregnancy rates -- these chemicals do have estrogenic +/or antiestrogenic activity; there is speculation that some herbicides, also found to have hormonal activity, may contribute to development of breast cancer.]
In trout, DDT and its relatives/metabolites also have both estrogenic and anti- activity: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12167306&dopt=Abstract
And DDT is merely one of the chemical soup contaminants found in the now-endangered Stellar sea lion: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12826388&dopt=Abstract "..SSL tissues show accumulation of butyltins, mercury, PCBs, DDTs, chlordanes and hexachlorobenzene. SSL habitats and prey are contaminated with additional chemicals including mirex, endrin, dieldrin, hexachlorocyclohexanes, tetrachlorodibenzo-p-dioxin (TCDD) and related compounds, cadmium and lead. In addition, many SSL haulouts and rookeries are located near other hazards including radioactivity, solvents, ordnance and chemical weapon dumps..."
Shrimp larvae exposed to DDT have DNA damage: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12568452&dopt=Abstract
>In vitro< DDT exposure damages or induces apoptosis (cell death) in neural clone cells: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12523960&dopt=Abstract
Yes, it would indeed be nice if someone could find an alternative which was nearly (90%+?) as effective as DDT at killing the insects which spread disease to humans while being much safer (<10% as toxic?) as DDT, and also be cheap enough that the people living in some of the areas where diseases like malaria and yellow fever are endemic can afford it.
FWIW, is it possible that much of the problem with chemicals such as DDT getting into the system where it is not wanted and causes problems is due to overuse, on the principle "if a little is good, a lot is better"?
-- Ronn! :)
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