木鱼桥

DDT and Silent Spring

这是下面的书中DDT一栏的全文(包括reference)。当然,这本书内还有其他很多地方也提到了DDT以及silent spring,但比较分散,而且输入也比较困难。若有兴趣的可以去找这本书看原文。若有什么输入错误的地方,请指正。

这段文字现在还只有英语,没有中文翻译。小白和我比较忙,这些天应该没有时间翻译,大家将就着先看。

Book Name: Standard handbook of Environmental Science, Health, and Technology

Editor: Jay H. Lehr & Janet K. Lehr

Location: (p21.63-21.66)

21.3.11 DDT

“The greatest killer in Africa is not AIDS or sleeping sickness, but malaria which kills an estimated 2 million children each year” (1)

Did you know?

DDT has saved more lives in the past 50 years than have antibiotics as a group. The banning of DDT is probably the largest act of genocide in human history. The Nationals Academy of Sciences estimated that DDT saved 500 million lives before it was banned (2).

Since DDT was banned, the incidence of malaria has increased enormously worldwide and the disease has again become a leading cause of death. Every 12 seconds, a child dies of malaria (3).

There is evidence suggesting that DDT is an anticarcinogen (4).

DDT’s “cousin” DDD is an anticancer drug used against inoperable adrenal-gland cancer (4, 5).

My guess is that most of you hadn’t heard the above facts. Rather, what you’ve heard, or read, is that DDT is toxic, has caused eggshell thinning in birds, accumulates in fat tissues in our bodies, and is still found in the environment. The facts are that DDT was given a bad rap in 1972 when it was banned from usage, and over 25 years later many people are still unaware of the truth.

Let’s look at some of the facts. Early in this century, the only effective way to control malaria was to eliminate stagnant water, such as swamps and landfills, where Anopheles mosquitoes bred. Then beginning in 1943, the organochlorine pesticide DDT became available and this proved to be a godsend in the Third World, curtailing the disease dramatically. In India, by the early 1960s, the annual incidence of malaria had declined from one million to 100,000 (6) and in Sri Lanka, the number of cases dropped from over two million to 17 (7). In 1942 DDT was shown to kill body lice without adverse effect on humans, and it was used by all Allied troops during World War II. Thanks to DDT, a 1944 typhus epidemic in Naples was halted. No Allied soldier was stricken with typhus fever (carried by lice) for the first time in the history of warfare. In World War I, by contrast three million people died of typhus in Russia and Eastern Europe, and more soldiers died from typhus than from gunfire.

In 1962, Rachel Carson’s best seller, Silent Spring, Indicated DDT as a killer of birds, fish, and wildlife (9). This eventually led to a long (seven-month) federal hearing in 1972 on the risk and benefits of the material. The DDT hearings were ordered by then EPA administrator William Ruckelshaus, who appointed Judge Edmund Sweeney as the hearing examiner. Scientists were not the only ones to give exonerating testimony that DDT used properly presented little harm to humans, beast, or birds. The World Health Organization also pleaded at the EPA hearing that DDT was very beneficial in fighting malaria in many parts of the world and should not be banned (10). After 125 witnesses and 9362 pages of testimony, Judge Sweeney’s final conclusions were that:

DDT is not a carcinogenic hazard to humans
DDT is not a mutagenic or teratogenic hazard to humans
The use of DDT under the registrations involved does not have a deleterious effect on fish, estuarine organisms, wild birds, or other wildlife (7, 10).

In a better world this would have been good news. It was met instead with journalistic and environmental hysteria across the nation. Less than two months after the hearing, the EPA administrator Ruckelshaus single-handedly banned almost all DDT (8, 10). This ban on DDT was considered the first major victory for the environmentalist movement in the United States (11). It Gave credibility to pseudoscience, and created an atmosphere in which scientific evidence can be pushed aside by emotion, hysteria, and political pressure. This technique of making unsubstantiated charges, endlessly repeated, has since been used successfully against asbestos, PCBs, dioxin, and Alar to mention a few (7).

DDT was soon replaced by less persistent organophoshates, such as parathion and malathion. These chemicals belong to the same chemical family as nerve gas and are far more dangerous than chlorinated hydrocarbons such as DDT. They have caused serious poisoning, often fatal, among unsuspecting farm workers who had been accustomed to handling the relatively nontoxic DDT (6).

This ban didn’t help third world people. National Institutes of Health malaria expert Robert Gwadz says, “The legacy of Rachel Carson was not altogether positive. The incidence of malaria in India is now back up to more than a million and more than 500,000 in Sri Lanka” (6). In South America where DDT spraying has been continued until more recent times, data from 1993 to 1995 showed that countries that recently discontinued their spray programs are reporting large increases in malaria incidence. The only country in South America reporting a large reduction in malaria rates (61 percent), is Ecuador, which has increased use of DDT since 1993 (12, 13). The allegations against DDT have been repeated so often and stated with such passion that over 25 years later that the public remains convinced of their validity (14).

 

Toxicity of DDT

DDT is known to be safe to humans. It has never caused death, even in persons attempting suicide (15). Farm workers were sometimes poisoned by organophosphate insecticides, such as the parathions, which are hundreds of times more toxic to man than DDT and which were touted as superior substitutes to DDT (15). It is known from controlled studies in human volunteers that experimental ingestion of 35 mg DDT per kg of body weight per day, for a period of two years, produced no adverse effects, acute or chronic, in any of the subjects (5, 7). Doses of five grams of DDT (and even more) have been administered to human beings in the successful treatment of barbiturate poisoning, according to Walter Ebeling of UCLA. Professor Ebeling notes also that five grams of DDT are roughly four times as much as the average American will assimilate in a 70-year lifetime (16). A study of workers at the Montrose Chemical Company, who accumulated 38 to 647 ppm of DDT residues in their fatty tissues, revealed no cases of cancer in 1300 person-years of exposure – a statistically improbable event (17).

One of the more interesting examples verifying the nontoxicity to humans is the experience of J.G. Edwards, Professor of Biology at San Jose State University. Says Edwards, “After remembering my own days of dusting hundreds of civilians during the war in Europe with 10 percent DDT to kill lice and help prevent millions of cases of deadly typhus, I thought I should try to convince people that the environmental extremists were wrong. Thereafter, at the beginning of each DDT speech I made I would publicly eat a tablespoon of DDT powder. I believe it was a successful effort. It resulted in a full page photograph of me doing that in Esquire magazine (September 1971). The caption stated that I was eating 200 times the normal intake of DDT to show it’s not as bad as people think” (18). Today, as Edwards approaches his 80th birthday, he is still as adamantly opposed to the anti-DDT propaganda as he was 26 years ago. Edwards, an avid climber, continues to conquer peaks than 10,000 ft. DDT exposure surely hasn’t hurt him.

In 1969, rodent studies suggested DDT was a carcinogen. However, there results were refuted by a 1978 National Cancer Institute report that concluded, after two years, of testing on several different strains of cancer prone mice and rats, that DDT was not carcinogenic (11). In a 1994 study in the journal of the National Cancer Institute, researchers concluded that their data did not support an association between DDT and breast cancer (19). Very recently, Robert Golden, a Ph.D. toxicologist in Potomac, Maryland, stated, “The one endocrine modulator environmentalists love to hate, the pesticide DDT, would cause no endocrine effect in a fetus exposed to more than a pound of DDT over a course of a pregnancy” (20).

Bruce Ames and his colleagues at the University of California, Berkeley, have developed a method of ranking possible carcinogenic hazards (21).  They call this a HERP Index (Human exposure over rat potency). A value of 100 on this scale means that people are getting the same dose in mg/kg that caused cancer in half the tested rats. DDT has three major breakdown products: DDA, DDE, and DDD (18). Table 21.3.11 shows that the average U.S. daily intake of DDE from DDT (HERP = 0.0003 percent) is less than the HERP from chloroform in a glass of tap water and thus appears to be insignificant compared to the background of natural carcinogens in our diet. Even daily consumption of 100 times the average intake of DDE/DDT would produce a possible hazard that is small compared to other common exposures such as mushrooms, coffee, beer, and wine shown in Table 21.3.11.

Table 21.3.11 Ranking Possible Carcinogenic Hazards*

Possible hazard#

 

Human dose of rodent

HERP %

Daily human exposure

carcinogen

0.0003

DDE/DDT, daily dietary intake

DDE, 2.2 ug

0.001

Tap Water, 1L

Chloroform, 83 ug

0.1

Mushroom, one raw

Hydrazine mixtures

0.005

Coffee, 1 cup

Furfural

2.8

Beer, 354 ml

Ethyl alcohol, 18 ml

4.7

Wine, 250 ml

Ethyl alcohol, 30 ml

  • *From Ames and Gold (21).
  • # U.S. EPA’s one-in-a-million hypothetical risk is 0.000015 on the HERP scale, or about 400,000 times below the level that would give cancer to a rat.

 

Further support is provided by Stephen Safe, a toxicologist at Texas A&M, who tested the effects of organochlorine compounds in the average human diet. He concluded that the total estrogenic activity of these compounds is 40-million-fold lower than that from the natural components of vegetables and other foods consumed daily such as soybeans, barley, cabbage, and corn (20, 22).

 

Persistence in the Environment

One often heard claim is that DDT cannot be broken down in the environment. Actually, DDT is broken down rather rapidly by heat, cold, moisture, sunlight, alkalinity, salinity, soil micro-organisms, hepatic enzymes of birds and mammals, and a great many other environmental factors (18). Only in unusual circumstances where soil is dark, dry, and devoid of microorganisms will DDT persist. Under normal environmental conditions, DDT loses its toxicity to insects in a few days (7). If it didn’t break down, it would have been unnecessary to apply it again in order to control pests. Edwards provides a list of more than 140 articles documenting the breakdown of DDT in the environment (18).

A key reason that traces of DDT are sometimes still found in environmental samples is that we can now detect extremely minute amounts of anything. In the span of about two decades, detection limits have been reduced by about six orders of magnitude (23). Some analysts have even reported DDT in samples collected before DDT existed. For example, University of Wisconsin chemists were given 34 soil samples to analyze. They reported that 32 of 34 samples contained DDT. What the chemists didn’t know was that the soil samples had been hermetically sealed in 1911, and no DDT existed in the United States until 1940 (24, 25). The author wrote later: “The apparent insecticides were actually misidentifications caused by the presence of co-extracted indigenous soil components.” Still later it was found that red algae also produces halogen compounds that are misidentified as DDT by gas chromatography. Also, halogen compounds containing bromine or iodine, rather than chlorine, may falsely register as DDT on the gas chromatograph (26). Various PCBs were commonly misidentified are chlorinated hydrocarbon insecticides during the 1959s and 1960s, and were routinely reported as “DDT residues.”

 

Claims About Bird Declines

In Silent Spring, published on 1962, Rachel Carson stated that the American robin was on the verge of extinction (9). That same year, Roger Tory Peterson, America’s leading ornithologist, wrote that the robin was most likely the most numerous North American bird (18, 27). Carson’s notion that the most prolific bird was about to fall extinct was one of the most eye-catching assertions in Silent Spring and brought the book considerable publicity.

Peregrine falcons and eagles were also high on Carson’s list. In reporting on declines in population of these species she tended to heap the entire blame on pesticides and ignored all data that would refute her theory (16). Peregrine falcons were extremely rare in eastern United States long before there was any DDT present. By the time DDT was introduced there were literally no peregrine populations in eastern United States, but the anti-pesticide extremists later placed the blame on DDT anyway (18). Bald eagles in the lower 48 states were on the verge of extinction in the 1920s and 1930s, long before DDT was discovered. They were shot on sight for fun, bounty, or feathers, trapped accidentally, killed by impact with buildings and towers, or electrocuted by power lines. There is still high mortality because of the physical hazards, but much less to shooting and trapping (because if caught engaging in either activity you may now face a prison term). The most surprising thing is that the environmental industry and the news media continue to attribute the increase to just one thing – the 1972 ban on DDT (18). Continuing the saga of showing that DDT was not bad on eagles, a recent study at the University of Wisconsin at Madison Reported that lack of a suitable food supply in Lake Superior and, not DDT, was responsible for reproductive problems in eagles (28).

There was no mention at all in Silent Spring of the increases of birds observed by naturalists, including those participating in the Audubon Christmas Bird Counts. Naturalists counting hawks migrating over Hawk Mountain, PA, also reported great increases in the number of raptors, following the widespread use of DDT. Dr. J. Gordon Edwards, of San Jose State University, has documented those bird increases and also cited numerous feeding experiments that revealed DDT in normal bird diets did not cause the deaths of any birds (18, 26). Dr. William Hazeltine, another concerned California scientist, regarded pesticides as one of the least important causes of avian dislocations. The chief culprits, he said, were hunters, trappers, falconers, campers, and general encroachment of humans into nesting and feeding areas (16).

 

Bird Egg Shell Thinning

On close inspection even the oft-repeated eggshell thinning threat to bird life holds little validity. DDT opponents alleged then and now that DDT caused eggshells to be thinned/softened for certain types of birds, causing failure to hatch and populations to decline. Thin egg shells are a phenomenon that predates use of DDT. It’s been known for decades and there are many causes: diets low in calcium or vitamin D, fright, high or low daily temperatures, various toxic substances, and bird diseases such as Newcastle disease (7). It has been demonstrated repeatedly in caged experiments that DDT and its breakdown products do not cause significant shell thinning, even at levels many hundreds of times greater than wild birds would ever accumulate (26). The most notorious cause of thin eggshells is the deficiency of calcium in the diet. Some early researchers deliberately fed their birds only calcium deficient food (0.5 percent rather than the necessary 2.5 percent calcium) and then attributed all shell problems to the DDT and DDE they had added to that calcium deficient diet. Edwards reported that after much criticism about the use of calcium deficient diets that were known to give the false impression regarding DDT shell thinning, the tests with DDT and DDE were repeated, but with adequate calcium in the birds’ diet. The results proved that with sufficient calcium in their food the quail produced eggs without thinned shells (26).

Another method to obtain data is to measure the thickness of eggshells in museum collections. Measurements of the shells of hundreds of museum eggs have revealed that red-tailed hawk eggs produced just before DDT was used had much thinner shells than did eggs produced 10 years earlier. Then, during the years of heavy DDT usage, those hawks produced shells that were 6 percent thicker. Golden eagle eggshells during the DDT years were 5 percent thicker than those produces before DDT was present in the environment (26). More recently, R.E Green found that thrush eggshells in Great Britain were thinning by the turn of the century, 47 years before DDT hit the market. He speculated that the thinning may have been an early consequence of industrialization and that acids formed when pollutants belched out of coal furnaces and smokestacks may have changed soil and water chemistry enough to reduce the availability of calcium, which is critical in the diet of birds that are producing eggshells (29).

PCBs were later shown to cause dramatic thinning of eggshells, as well as other adverse effects on birds, yet environmentalists continued to place the blame on DDT despite the fact that feeding birds high levels of that pesticide did not cause them to produce thin eggshells. There are many environmental contaminants that do cause shell thinning. Oil, lead, mercury, cadmium, lithium, manganese, selenium and sulfur compounds have been shown to have adverse effects upon birds, including severe shell thinning (26).

 

Bioaccumulation and Biomagnification

“Bioaccumulation” refers to an increase in the concentration of a chemical in the environment (e.g., in water, sediment, soil.) “Biomagnification,” on other hand, refers to increses of chemicals as they are passed up food chains. As Ottoboni (5) points out, “The quantity of chemical that can be stored in any body can never exceed that which would be in equilibrium with the exposure. The chemical cannot remain in the storage depot without being replenished continually from the outside. Thus, the popular notion that foreign chemicals stored in a depot become immobilized and permanently fixed in the body, with additional exposure increasing the quantity stored ad infinitum, has no basis in fact. The claim that our bodies can become ‘walking time bombs’ is nonsense.” She sums it up best by pointing out that bioaccumulation in not inherently good or bad, but in the public mind it is considered, almost universally, to be the latter.

Biomagnificatiion proponents claim that pesticide levels are “magnified” at each step of food chain, for example, from algae to planktonic crustaceans to small fish to large fish to predatory birds or mammals. The consumption of low levels of pesticides within each prey animal is presumed responsible for increased amounts in higher predators (8). DDT is constantly broken down and excreted by the animals at each step of the food chain. If tiny crustaceans are analyzed, wet-weight, but the fish that ate them are analyzed dry-weight, the difference in the amounts of dilution by water creates an impression that the dry sample contains a greater amount of pollutants than the wet sample. DDT is attracted to fat tissues more than to muscle tissues, so comparisons between samples of these two types will indicate “magnification” into the fatty tissues, even if they are samples from the same animal. Likewise, brain tissues attract more DDT than fatty tissues. Anti-DDT activists were careful to measure crustaceans, wet-weight, and compare them with levels in dry-weight muscle samples in fish, dry-weight fatty tissue in ducks that ate the fish, and dry-weight fatty tissue in ducks that ate the fist, and dry-weight brain tissue in the hawks that ate the fish. If they measure ALL sample wet-weight, there is not “biomagnification.” (18, 26, 30).

 

Summary

There days a lot of effort is spent reminding people, particularly the younger folks, about the Holocaust and World War II because it’s now more than two generations since these occurred and people tend to forget. As Tenner (31) wisely says, “With each generation, part of the collective memory of the last terrible events is lost.” Well, it’s been over one generation since DDT was banned and clearly, most people today only speak ill of DDT. They have to clue about how valuable it was, nor the politics behind its banning. Speaking of holocausts, the banning of DDT was a holocaust. Malaria, which was being controlled by DDT, has proliferated since the abandonment of DDT. As Mooney (32) points out, this was an early example of western priorities being imposed on Third World people who may have made a different trade-off had the choice solely been theirs. Also, from Ottoboni (5), “The thought that substitution of nonresistant pesticides for persistent ones will solve all of the environmental problems attributed to the latter is am example of the myopic thinking that permeates so many decisions relating to environmental protection. People apparently haven’t realized that all nonresistant pesticides merely degrade to other chemicals! The only difference is that most of these new chemicals do not have the same pesticidal action as their parent chemicals.”

 

References:

  1. Richburg, K. B>, Out of American, BasicBooks, 1997.
  2. Access to Energy, Vol. 24, No. 12 (August 1997).
  3. Wirth, D.F., and Cattani, J., Technology Review, 100: 52, Aug/Sept 1997
  4. Gribble, G. W., “Environmental Issues,” Priorities, 10(2-3): 50, 1998.
  5. Ottoboni, M.A., The Dose Makes the Poison, Second Edition, Van Nostrand Reinhold (1997).
  6. Chase, A.S., Bugs in Environmentalism, S. J. Milloy, www.junkscience.com 1997.
  7. Ray, D. L., and Guzzo, L., Trashing the Planet, HarperPerennial, 1992.
  8. Flynn, L. T., “The Birth of Environmentalism, ” Issueds in the Environment, American Councial on Science and Health, New York, June 1992.
  9. Carson, R., Silent Sprint, Houghton-Mifflin, New York, 1962.
  10. Fox, M.R., “DDT Updated,” S.J. Milloy, www.junkscience.com, Washington D.C., August 28, 1998.
  11. Lieberman, A.J., Fact Versus Fear, American council on Science and Health, New York, Sept 1997.
  12. Roberts, D.R., Laughlin, L.L., Hsheih, P., and Legters, L.J., “DDT Global Strategies and a Malaria Control Crisis in South America,” Natiional Center for infectious Disease (July-Sept 1997).
  13. Roberts, D.R., U.S. Medicine, 34:36, March 1998.
  14. Wildavsky, A., But Is It True?, Harvard University Press, 1995.
  15. Mellanby, K., “With Safeguards, DDT Should Still Be Used,” Wall Street Journal, Sept 12,P. A26, 1989.
  16. Grayson, M.J., and Shepard, T.R. Jr., The Disaster Lobby, Follett Publishing Co., 1973.
  17. DDP newsletter, Vol. XIV, No. 3, May 1997.
  18. Edwards, J.G., Remembering Silent Spring and It’s Consequences, DDP Salt Lake City, Utah (August 3, 1996).
  19. Sturgeon, S.R., et al., “Geographic Variation in Mortality from Breast Cancer among White Women in the United States,” JNCI, 87, 1896, Journal of the National Cancer Institute, Dec 20, 1995.’
  20. Fumento, M., “Truth Disrupters,” Forbes, 162: 146, Nov 16, 1998.
  21. Ames, B.N., Magaw, R., and Gold, L.S., “Ranking Possible Carcinogenic Hazards,” Science, 236: 271, April 17, 1987.
  22. Safe, S.H., “Environmental and Dietary Estrogens and Human Health­­-Is There a Problem?” Environmental Health Perspectives, 103:346, 1995.
  23. Marco, G.J., Hollingworth, R.M., and Durham, W., eds., Silent Spring Revisted, American Chemical Society, Washington, D.C., 1987.
  24. McKetta, J.J., “Don’t Believe Everything You Read,” in Rational Readings on Environmental Concerns, Lehr, J.H., ed., Van Nostrand Reinhold, New York, 1992.
  25. Frazier, B.E., Chesters, G., and Lee, G.B., Pesticides Monitoring Journal, 4(2): 67, 1970.
  26. Edwards, J.G., “DDT Effects on Bird Abundance and Reproduction,” in Rational Readings on Environmental Concerns, Lehr, J.H., ed., Van Nostrand Reinhold, New York, 1992.
  27. Jukes, T.H., “The Tragedy of DDT,” in Rational Readings on Environmental Concerns, Lehr, J.H., ed., Van Nostrand Reinhold, New York, 1992.
  28. Milloy, S., Environment News, Heartland Institute, Chicago, Illinois, 2:9 Oct. 1998.
  29. Milius, S., “Birds’ Eggs Started to Thin Long Before DDT,” Science News, 153:261, April 25, 1998.
  30. Edwards, J.G., “The Myth of Food-Chain Biomagnification,” in Ratiional Readings on Environmental Concerns, Lehr, J.H., ed., Van Nostrand Reinhold, New York, 1992.
  31. Tenner, E., Why Things Bite Back, Alfred A. Knopf, New York, 1996.
  32. Mooney, L., “The WHO’s Misplaced Priorities,” Wall Street Journal Europe, August 25, 1997.
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2007年03月7日 - Posted by | 无法归类

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