NOTE FROM JEFF: This excellent article is from a small publication sent to us by the Fish and Wildlife Service in the USA which was created in honour of Rachel Carson, who used to work for them. Pimentel is a major and impartial global authority on pesticides and their affects on life and the biosphere.
“The major problem with the recommended use of pesticides is that so little actually reaches the target pests. The estimate is that less than 0.01% of the pesticides that are applied reaches the target pests…This, of course, means that 99.9% of the pesticide that is applied pollutes the environment… In the United States, as mentioned, more than 1 billion pounds of pesticides are applied and worldwide about 5 billion pounds are applied each year… Worldwide… 26 million people [are] poisoned and about 220,000 die each year…In addition, pesticides cause cancer and the estimate is that there are more than 10,000 cases of cancer that are the result of pesticide exposure…Pesticides also disrupt the endocrine, immune, and neurological responses in humans and other animals… Most pesticides applied to crops eventually end up in ground and/or surface water.”
“Environmental Effects of Pesticides On Public Health, Birds, and Other Organisms”
David Pimentel
Professor, College of Agriculture and Life Sciences, Cornell University
This is a tribute to Rachel Carson and her book, Silent Spring (1962). She had the foresight and knowledge to warn us against the ecological hazards of pesticides to public health and other organisms. Carson’s book was also instrumental in giving recognition to the growing field of science of ecology. For all of Carson’s many contributions, all of us are indebted.
From the time that the United States started using synthetic pesticides in 1945 to the time that Carson’s book was published, pesticide use increased about six fold (Pimentel, 1975). It took 10 years from the time that her book was published before DDT was banned in 1972. By the time that DDT was banned, pesticide use has increased ten-fold to about one billion pounds. The total quantity of pesticide in terms of pounds has not increased, however, the actual toxicity of pesticides has increased 10 to 20 times (Pimentel et al., 1993). The prime benefit with the new highly toxic pesticides that replaced DDT and similar chemicals is that the new toxicants to not persist for long periods of time in the environment. DDT persists in the soil for 30 to 50 years, whereas the newer insecticides persist only up to 3 months.
The major problem with the recommended use of pesticides is that so little actually reaches the target pests. The estimate is that less than 0.01% of the pesticides that are applied reaches the target pests (Pimentel and Levitan, 1986). This, of course, means that 99.9% of the pesticide that is applied pollutes the environment. The result is numerous birds, fish, and other species are killed or affected by the applied pesticides.
In this article, I will briefly review the environmental impacts of pesticides on public health, birds, and other organisms.
Human Pesticide Poisonings
In the United States, as mentioned, more than 1 billion pounds of pesticides are applied and worldwide about 5 billion pounds are applied each year (Pimentel and Hart, 2000). Some humans are directly exposed to the pesticide sprays, especially those people who apply pesticides. In addition, pesticides contaminate human food and water resources. For example, about 35% of the food that isi purchased has measurable amounts of pesticide residues, with 1% to 3% having residues that are above accepted tolerance level.
In the U.S., about 110,000 humans are poisoned with pesticides, with about 25 accidental deaths each year ( Benbrook, et al., 1996). Worldwide, the situation is far more serious with 26 million people poisoned and about 220,000 deaths each year (WHO, 1992). In addition, pesticides cause cancer and the estimate is that there are more than 10,000 cases of cancer that are the result of pesticide exposure (Pimentel & Hart, 2001). Pesticides also disrupt the endocrine, immune, and neurological responses in humans and other animals (Colborn et al., 1996). It is interesting that these disruptors tend to make male animals become female in structure. In addition, the production of sperm is greatly reduced or is zero.
Bird Poisonings
Like humans, birds are also poisoned by pesticides. Birds, like the canary in the coal mine, make excellent “indicator species.” In fact, the suggestion in the title of Rachel Carson’s book was that if we continued to apply DDT and other pesticides we would have a Silent Spring – without birds singing. Birds are poisoned by the direct exposure to pesticides, poisoned by feeding on contaminated prey, and have reduced growth and reproduction because of the exposure to sub-lethal doses of pesticides. In the U.S., approximately 3 pounds of pesticide are applied per acre per year on about 400 million acres (Pimental et al., 1993). Incidentally, home-owners apply about 8 pounds per acre per year, or nearly 3 times the pesticide damage that farmers apply per acre. The full extent of bird kills by pesticides is difficult to determine, because birds are secretive, camouflaged, highly mobile, and live in dense grass, shrubs, and trees.
It is assumed that the pesticides inflicted on birds occur on the 400 million acres of cropland that receives most of the pesticide, and the bird population is estimated to be 1.8 birds per acre of cropland (Boutin et al., 1999), then about 720 million birds are directly exposed to pesticides. If it is conservatively estimated that only 10% of the bird population is killed, then the total number of birds killed is approximately 72 million.
Therefore the conservative estimate is that about 72 million birds are killed each year because of direct exposure to pesticides. This 72 million birds does not include the nestlings lost because one or more parents is killed and/or that pesticide-contaminated insects and earthworms are brought to the nest and fed to the nestlings. The actual number of birds killed might be twice the 72 million figure.
The American bald eagle and other predatory birds suffered high mortalities because of DDT and other chlorinated insecticides. The bald eagle population declined primarily because of pesticides and was placed on the Federal endangered species list. After DDT and the other chlorinated insecticides were banned in 1972, it took nearly 30 years for the bird populations to recover. The American bald eagle was recently removed from the endangered species list (Millar, 1995).
Beneficial Natural Enemies
In both natural and agricultural eco-systems, a large number of species of predators and parasites control and limit the feeding pressure of plant-feeding arthropod populations (Pimentel, 1988). The biological control organisms help the eco-system remain “green” with foliage on trees, shrubs, and other plants. The beneficial parasites and predators help control pest arthropods in agricultural crops (Pimental et al., 1993).
In the U.S., I estimate that while pesticides provide approximately 10% of pest control, natural control provides about twice this amount of control (Pimentel & Hart, 2001). Many cultural controls such as crop rotation, soil and water management, fertilizer management, planting time, crop-plant density, trap crops, mechanical cultivation, and poly-culture provide additional benefits for pest control. Together, these non-chemical controls could be used effectively to reduce U.S. pesticide use by more than 50% without any reduction in crop yields and/or cosmetic standards (Pimentel et al, 1993). Confirmation that pesticide use in the U.S. could be reduced by 50% comes from the fact that Sweden reduced pesticide use by 50% from 1992 to 1997 and is now on a program to reduce pesticide use another 50% (Pimentel, 1997). In Indonesia, most of the pesticide was applied to rice. Dr. I.N. Oka was able to reduce pesticide use by 65% and increase rice yields by 12%. This illustrates what can be done, if pesticides are used judiciously.
Pesticides frequently have adverse impacts on beneficial natural enemies. For example, the following pests have reached outbreak levels following the destruction of natural enemies by pesticides: bollworm, tobacco budworm, cotton aphid, spider mites, and cotton loopers (Pimentel et al., 1993). Significant pest outbreaks also have occurred in other crops.
When outbreaks of pests occur because their natural enemies have been destroyed by pesticides, additional and usually more expensive and toxic pesticide treatments are required to sustain crop yields. It is estimated that the destruction of natural enemies by pesticides, the subsequent crop losses, and additional pesticide application cost the U.S. more than $500 million per year (Pimentel et al., 1993).
Pesticide Resistance
The widespread use of pesticides has resulted in the development of pesticide resistance in insect pests, plant pathogens, and weeds. The estimate is that more than 1,000 species of pests are now resistant to pesticides. As pesticide use increases, the number of pesticide-resistant pests explodes.
Increased pesticide resistance in pest populations frequently requires several additional applications of pesticides. The additional pesticide applications tend to compound the problem by increasing selection in the target pests. Despite numerous attempts to deal with this problem, pesticide resistance continues to develop at a rapid rate (Pimentel et al., 1993). Assuming a 10% loss in major crops that also receive heavy pesticide treatments in the U.S. because of resistance, total losses due to pesticide resistance are estimated to be about $1.4 billion per year (Pimentel et al., 1993).
Honey Bee and Wild Bee Poisonings
Honey bees and wild bees are vital to the pollination of about one-third of the crops in the U.S., especially fruits and vegetables. The benefits of bees for pollination are estimated to be about $40 billion per year if forages and pastures are included in the assessment (Pimentel et al., 1997). Because most insecticides and some fungicides and herbicides are toxic to bees, these pesticides have a major impact on both honey bee and wild bee populations (MacKenzie & Winston, 1989; Pimental et al., 1993).
For most agricultural crops, both yield and quality are enhanced by effective pollination. For example, adequate pollination of fruits and vegetables provide major benefits. With effective pollination, melon yields were increased 10% and quality was raised 25%, as measured by the dollar value of the crops (Pimentel et al., 1993).
Approximately 20% of all honey bee colonies are adversely affected by insecticides, and the yearly estimated loss from partial bee kills, reduced honey production, and the cost of moving colonies total about $25 million per year. Also, as a result of heavy pesticide use on certain crops, bee-keepers are excluded from 10 to 15 million acres of otherwise suitable apiary locations, and the yearly loss in potential honey production in these regions is about $27 million each year (Pimentel et al., 1993).
Based on the analysis of honey bee and pollination losses caused by insecticides, pollination losses attributed to pesticides are about 10% of the pollinated crops, at a yearly cost of about $200 million per year. The combined annual costs of reduced pollination and direct loss of honey bees due to insecticides can be estimated to be at about $320 million each year (Pimentel et al., 1993).
Ground and Surface Water Contamination
Most pesticides applied to crops eventually end up in ground and/or surface water. Aircraft application of pesticides is the most effective means of contaminating the environment. For instance, under ideal weather conditions only 50% of the spray from an aircraft or helicopter reaches the target acre, the remaining 50% drifts off to contaminate the environment. The current growing technology is the use of ULV (ultra low volume) spray technology. Because concentrated pesticide spray is applied, little or no water is added to the spray. Of course, this means breaking the pesticide spray into very small particles to obtain good coverage of the crop plants. The very small and lightweight droplets are more prone to drift. Thus, under ideal weather conditions, only 25% of the pesticide lands in the target areas and 75% drifts off into the environment (Pimentel et al., 1993).
Pesticide contamination of ground and surface waters is a serious concern in the U.S. One study showed that pesticide residues were found in 92% of Midwestern reservoirs (Solomon et al., 1996). Also in the Midwest, in Iowa herbicide residues were found in 75% of the wells sampled (Koplin, et al., 1998a). Also in the Midwest, 54% of the shallow ground water sites were found to be contaminated with pesticides (Koplin, et al., 1998b). In the Northeast, in the Hudson River Basin of New York State, pesticides were found in 69% of the well networks (Phillips, et al., 2000).
Approximately 60% of all drinking water comes from groundwater. Detectable levels of pesticides are found in about 15% of U.S. wells. If an adequate job were done in monitoring pesticide levels in groundwater, the cost would be about $1.3 billion per year (Nielson & Lee, 1987). Remember this is only monitoring but does nothing to correct the water contamination problem.
Conclusion
We currently spend about $8 billion each year in the recommended use of pesticides and this use of pesticides returns about $32 billion each year. However, these benefits do not include the environmental and public health costs of using pesticides. These costs are estimated to total about $9 billion per year.
If as has been done in Sweden and several other countries, including Norway, Denmark, Netherlands and Indonesia, and in the province of Ontario, pesticide use in the U.S. could be reduced by more than 50% without any reduction in crop yields or cosmetic standards. Reducing the recommended use of pesticides would significantly reduce the environmental and public health impacts of pesticides. It is long overdue that we reduce the use of pesticides and use them in a judicious manner that will benefit farmers, the environment, and the public.
References
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Boutin, C., Freemark, K.E., & Kirdk, D.E. (1999). “Spatial and temporal patterns of bird use of farmland in southern Ontario”, Canadian Field Naturalist. 113 (3). 430-460.
Carson, R. (1962). Silent Spring. Boston: Houghton-Mifflin Co.
Colborn, T., Dumanoski, D., & Myers, J.P. (1996). Our Stolen Future: Are WE Threatening Our Fertility, Intelligence and Survival? New York: Dutton
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Koplin, D.W., Barbash, J.E. & Gilliom, R.J. (1998b). Environmental Science & Technology. 32(5) March 1, 1998, 558-566.
MacKenzie, K.E. & Winston, M.L. (1989). “Effects of sub-lethal exposure to diazinon on longevity and temporal division of labor in the honey bee (Hymenoptera: Apidae). Journal of Economic Entomology. 82(1), 75-82
Millar, J.G. (1995) “Fish and Wildlife Service’s proposal to reclassify the bald eagle in most of the lower 48 states.” Journal of Raptor Research. 29(1): 71
Nielson, E.G. & Lee, L.K. (1987). The Magnitude and Costs of Groundwater Contamination from Agricultural Chemicals: A National Perspective, U.S. Dept. of Agriculture, Economic Research Service, National Resources Economics Division, Washington, D.C. ERS Staff Report, AGES870318
Phillips, P.J., Wall, G.R., & Ryan, C.M. (2000) “Pesticides in wells in agricultural and urban areas iin the Hudson River Basin” Northeastern Geology and Environmental Sciences 22(1), 1-9
Pimentel, D. (1975) Insects, Science and Society. New York: Academic Press
Pimentel, D. (1988) “Herbivore population feeding pressure on plant host: feedback evolution and host conservation”, Oikos, 53, 289-302
Pimentel, D., McLaughlin, L., Zepp, A., Lakitan, B., Kraus, T., Kleinman, P., Vancini, F., Roach, W.J., Graap, E., Keeton, W.S., & Selig, G. (1991) Environmental and Economic Impacts of Reducing U.S. Agricultural Pesticide Use. Boca Raton, FL: CRC Press
Pimentel, D., Acquay, H., Biltonen, M., Rice, P., Silva, M., Nelson, J., Lipner, V., Giordano, S., Horowitz, A. & D’Amore, M. (1993) “Assessment of environmental and economic costs of pesticide use” in The Pesticide Question: Environment, Economics and Ethics (D. Pimentel & H. Lehman, eds)(pp. 47-88) New York: Chapman and Hall
Pimentel, D. & Hart, K. (2001) “Pesticide use: ethical, environmental, and public health implications” in New Dimensions in Bioethics: Science, Ethics and the Formulation of Public Policy (W. Galston & E. Shurr, eds)(pp. 79-108) Boston: Kluwer Academic Publishers
Pimentel, D. & Levitan, L. (1986) “Pesticides: Amounts Applied and Amounts Reaching Pests” Bioscience, 36, 86-91
Solomon, K.R., Baker, D.B., Richards, R.P., Dixon, K.R., Klain, S.J., La Point, T.W., Kendall, R.J., Weisskopf, C.P., Giddings, J.M., Giesy, J.F., Hall, L.W., & Williams, W.M. (1996) “Ecological risk assessment of atrazine in North American surface waters”, Environmental Toxicology and Chemistry. 15(1), 31-76.
WHO. (1992) Our Planet, Our Health: Report of the WHO Commission on Health and Environment. Geneva: World Health Organization
"Mankind has gone very far into an artificial world of his own creation. He has sought to insulate himself, in his cities of steel and concrete, from the realities of earth and water and the growing seed. Intoxicated with a sense of his own power, he seems to be going farther and farther into more experiments for the destruction of himself and his world… We have looked first at man with his vanities and greed and his problems of a day or a year; and then only, and from this biased point of view, we have looked outward at the earth he has inhabited so briefly and at the universe in which our earth is so minute a part. Yet these are the great realities, and against them we see our human problems in a different perspective…Here and there awareness is growing that man, far from being the overlord of all creation, is himself part of nature, subject to the same cosmic forces that control all other life. Man's future welfare and probably even his survival depend upon his learning to live in harmony, rather than in combat, with these forces….the more clearly we can focus our attention on the wonders and realities of the universe about us the less taste we shall have for the destruction of our race.” Rachel Carson
