Photo: Cheatgrass, southwest Montana. © 2020 Delena Norris-Tull
The Impacts of Pesticides on the Environment and Human Health
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020, updated 2024.
In this section, I relied primarily on recent research reports (2000-2010), and I focused on reports that included an extensive review of existing research in each area. These sections refer to both herbicides and other pesticides.
In The Eco Principle: Ecology and Economics in Symbiosis, Dahl (1996, p. 36-37) points out that, “One of the consequences of both the growing human population and the rising resource consumption of the rich has been increasing pressure on renewable resources. The original natural endowment of the planet included vast forests that generated rich and productive soils in many temperate lands. These have become the major agricultural areas of the world, and some of them have been cultivated for centuries. However, the drive for ever-higher productivity and profit in agriculture has brought increasing chemical fertilizer and pesticide use, large-scale mechanization and soil clearing with its risk of erosion, reduced fallow or other soil regeneration techniques, the spread of irrigation with its potential for salt accumulation or waterlogging, and other changes that are collectively threatening long-term agricultural productivity.”
Dahl (1996, p. 32) states, “Since the richest one-fifth of the population today uses about four-fifths of the world’s resources, the existing world population cannot be brought up to, say, European living standards using present technologies and consumption levels.”
Dahl (1996, p. 21) points out that by not taking a systems approach to ecology and economy, we are ignoring the long-term costs of environmental pollutants. “(M)any developed countries are discovering thousands of old industrial sites contaminated with hazardous materials since the beginning of the industrial revolution, and now requiring expensive clean-up.” Damages to the ozone layer and the global climate are additional examples of unaccounted for costs that future generations will have to bear. Resource managers are not adequately taking into account the likely future damages and expenses of dealing with the aftermath of decades of widespread use of chemicals in agriculture and in industry, and the now widespread use of chemicals in managing invasive plant species.
In analyzing both ecological and economic systems, it is crucial to examine both extent of growth and change, as well as rates of growth. The current economic system is poorly designed to deal with rates of growth. “Part of the problem is due to the different scales and paces of growth between human activities, which we can control, and the natural world, where rates are beyond our influence and scales can exceed our capacity to respond. The speed with which chemicals move in the environment and are detoxified or recycled by natural processes… cannot necessarily be accelerated” (Dahl, 1996, p. 25).
in a 2013 interview with Becky McMillen, Lars Baker, retired Fremont County, Wyoming, Weed and Pest Supervisor who worked for the County for 38 years, stated: “I have concerns about the lack of research on chemicals. We are not thinking about the non-target impacts of chemicals. Some chemicals, such as Tordon, kill all broadleaf species, including crops and native species. It also kills trees. Chemicals are a temporary treatment. The chemical may do the job for two-three years, but eventually the chemical dissipates in the soil, and the weeds return because we have not changed the environmental conditions that allowed the weeds to grow there in the first place. RoundUp-Ready corn is not going to work for very long.
“Chemicals seem like an easy fix, but the environmental cost is too high. We don’t take into account the indirect costs, the environmental costs of spraying, the environmental cost of tractor tires, diesel fuel, the farmers’ exposure to the sun and to the chemicals. We have to change the environmental conditions to control weeds.
“In the early days, if we wanted to know how a new product worked, we had to do our own local research. We tried it on a plot, and we recorded the results. Harold Alley, at the University of Wyoming, did some of the early research on chemicals. He was one of the first Weed Scientists in the United States. He was followed by many others like Steve Miller and Tom Whitson who worked so hard to improve weed control practice in Wyoming.
“Chemicals do have a role in stopping a small weed population before it becomes an infestation. We can use it effectively for part of our Early Detection and Rapid Response program, to prevent the spread of a weed. The Nature Conservancy did some interesting research on controlling leafy spurge. They found that it is not effective to spray the inside of a patch of weeds, the most heavily infested lands where the most economic loss is. You have to map out the area, to find out where the weeds are, and you have to treat from the outside of a patch, to slow down the spread. You rarely have enough money to pay for enough chemicals to treat the entire patch, but if you treat the edges the first year, the second year you can treat closer to the center. Each year, you treat further toward the center. If you start in the middle and work out, the weeds continue to spread.”
In 2017, I interviewed George Beck, retired Weed Scientist at Colorado State University, who has worked with perennial noxious weed issues in rangeland and pastures since 1985. He told me, “We have the least amount of data on how herbicides remaining in the soil impact the growth of native plants.”
In 2018, I interviewed Jim Pike, District Conservationist for the NRCS Laramie County Field Office, now retired. He commented that he served in the Vietnam War, and thought nothing at the time about being drenched in Agent Orange. That early experience with the country’s lack of concern with the potential toxicity of chemicals causes him to be much more aware of the possibility that we are poisoning our environment and ourselves even more, in the current use of herbicides and pesticides to manage weeds and pests.
The USGS, through its National Water Quality Program, conducts surveys to evaluate the prevalence of herbicides and pesticides in our waterways. In the USGS water quality report for 2013-2017, Covert, et al., 2020, found that, “In the study of 72 rivers and streams across the contiguous U.S., five or more pesticides were detected in 88% of the more than 5,000 samples collected during 2013–17… The potential for toxicity of the pesticide mixtures to fish was low, but about 12% of samples were predicted to have potential acute (rapid) or chronic (longer-term) toxicity to aquatic invertebrates.” Of the 221 chemicals detected, 17 (13 insecticides, 2 herbicides, 1 fungicide, and 1 synergist) were evaluated to be the primary drivers of toxicity.
“In a given sample, a single pesticide compound generally was responsible for most of the potential toxicity of the pesticide mixture… in [samples] with…potential chronic toxicity to fish, the greatest contributor to that toxicity was likely to be the herbicide acetochlor, the fungicide degradate carbendazim, or the synergist piperonylbutoxide” (Covert, et al., 2020).
For aquatic invertebrates, insecticides were the most toxic. “For cladocerans [microcrustaceans], the pesticide compounds driving the [toxicity] scores were bifenthrin, carbaryl, chlorpyrifos, diazinon, dichlorvos, dicrotophos, diflubenzuron, flubendiamide, and tebupirimfos. For benthic invertebrates, atrazine (an herbicide)” (Covert, et al., 2020).
Sheley, et al., 2011, also cite research that suggests that atrazine has played a role in “global declines in amphibian populations.” They also found that “chemicals that target dicots can decrease plant community diversity, thereby reducing the food available for some wildlife species… For example, 2,4-D applied to western Colorado rangeland to favor grasses over forbs and shrubs reduced densities of northern pocket gophers… and least chipmunks…, while increasing densities of montane voles.”
Sheley, et al., 2011, found that “the impact of… herbicides on [soil, water, and air] resources is dependent on type of herbicide used, application rate, and soil characteristics, among other factors…. Glyphosate tightly adheres to soil,” thus reducing the risk of the chemical leaching into groundwater or affecting soil biota. But “dicamba and picloram are highly mobile in the soil… High application rates, high rainfall following application, or direct application… to water bodies can pose a significant threat to water resources.” But little research has been conducted on the impacts of herbicides on water and soil resources and wildlife. And few studies have compared impacts of herbicides on native versus invasive plant species. “Herbicides such as 2,4-D, clopyralid, or picloram…[used to control broadleaf weeds] can greatly decrease native forb density and cover… There is evidence suggesting that herbicide effects on native forbs are long-lasting and can drive a local decline in species richness… Desirable rangeland grasses have shown varying degrees of susceptibility to imazapic, a herbicide used to control invasive annual grasses, with evidence suggesting grasses within the Hordeae tribe may be more tolerant to imazapic than other grass species.” They concluded that, “The effect of herbicide on desirable vegetation remains difficult to predict.”
Insecticides and Human Health
Chlorpyrifos, an organophosphate, has been in use as a pesticide since 1965. As an insecticide, it is used to kill various insects and worms on various crops (corn, soybeans, fruit and nut trees, Brussels sprouts, etc.). It is also used on turf, on golf course greens, and in greenhouses. Approximately 10 million pounds are applied in U.S. agricultural fields each year. It is also used to kill mosquitos, roaches, and ants.
High doses are highly toxic to humans and can cause respiratory paralysis and death. In a 2000 EPA decision, its use in homes was greatly reduced, to require the use of child-resistant packaging for ant and roach baits, to avoid accidental poisoning of children. Its use in treating wood for construction, to kill termites, was ordered to cease by 2005. And additional restrictions were added, to better protect agricultural workers.
In addition, in 2000, reductions in its use were mandated to protect wildlife. It was determined that, “a single application of chlorpyrifos poses risk to small mammals, birds, fish and aquatic invertebrate species.”
In 2012, the EPA ordered a reduction in the aerial application rates, to create “no-spray” buffer zones, to reduce the amount of spray drift that was occurring, to better protect public spaces. In 2014, with additional review of the research, the EPA placed additional restrictions on its use in sprays. As additional concerns arose relating to possible toxicity that could cause developmental delays in infants, the EPA stated that “epidemiologic and biomonitoring studies, indicate that chlorpyrifos likely played a role in the neurodevelopmental outcomes reported by the epidemiologic study…investigators. However, uncertainties such as the lack of an established MOA/AOP for neurodevelopmental effects and the potential exposure to multiple AChE-inhibiting pesticides preclude definitive causal inference. However, there is sufficient uncertainty in the human dose-response relationship for neurodevelopmental effects to prevent the Agency from reducing or removing the statutory 10X FQPA Safety Factor. The FQPA 10X Safety Factor will be retained for infants, children, youths, and women of childbearing age for all exposure scenarios” (US EPA Chlorpyrifos Human Health Risk Assessment).
As of 2020, the safety of chlorpyrifos, particularly in regards to infant development, remains controversial. The EPA maintains that the standards they have set for its use are adequate. On August 9, 2018, the U.S. Ninth Circuit Court of Appeals ordered the EPA to ban chlorpyrifos within 60 days. The following month, the US Department of Justice asked the Ninth Circuit to reconsider its opinion. Several States have moved to ban its use.
Herbicide suspensions
In October 2024, based on the review of studies on potential thyroid toxicity in human fetuses, the EPA announced the cancellation of all products containing Dacthal.
As of November 2024, there were over 5800 active lawsuits pending in the Paraquat Multidistrict Litigation. The affected individuals claim that Paraquat has caused or significantly contributed to the development of Parkinson's Disease in agricultural workers. Ten bellweather cases are moving towards trial. Over 6000 cases are being addressed in the Southern District of Illinois.
Pesticide use in Potato Crops
Americans have become averse to blemishes on their foods. McDonald’s is one of many fast food chains that relies on unblemished foods. The Russet Burbank potatoes the chain uses for their French fries are prone to have a defect called net necrosis, little brown lines or spots caused by aphids and fungus. The company has come to demand that their potatoes be free of this blemish. Blanching helps eliminate the blemishes. But pesticides are also used.
McDonald’s now likes to claim that the farmers they work with do not use the toxic insecticide, Monitor, on their potatoes. What they neglect to mention is that Monitor was in widespread use on potatoes from 1972 until 2009.
An insecticide previously used on potatoes, cotton, and tomatoes, Monitor, methamidophos, was so toxic that the U.S. voluntarily suspended its use in 2009. It is banned in several countries, but is still widely used on rice in China. It is toxic not only for humans and other mammals, but also highly toxic for birds, fish, aquatic invertebrates, and bees.
In northern Minnesota, concerns about pesticide drift, the distance a chemical can blow in the breeze, caused the leadership of the White Earth Nation to join with other concerned citizens, including the Pesticide Action Network, to form the Toxic Taters Coalition. This group is trying to educate the public about the use of pesticides in the potato industry, and trying to influence companies like McDonald’s to stop the use of pesticides.
While many companies have been averse to changing to more sustainable agricultural practices, other companies, like the sports clothing company Patagonia, have been so effective in supporting organic farming, that many farmers now grow organic cotton.
References:
Links to other Impacts of Pesticides:
The Impacts of Pesticides on the Environment and Human Health
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020, updated 2024.
In this section, I relied primarily on recent research reports (2000-2010), and I focused on reports that included an extensive review of existing research in each area. These sections refer to both herbicides and other pesticides.
In The Eco Principle: Ecology and Economics in Symbiosis, Dahl (1996, p. 36-37) points out that, “One of the consequences of both the growing human population and the rising resource consumption of the rich has been increasing pressure on renewable resources. The original natural endowment of the planet included vast forests that generated rich and productive soils in many temperate lands. These have become the major agricultural areas of the world, and some of them have been cultivated for centuries. However, the drive for ever-higher productivity and profit in agriculture has brought increasing chemical fertilizer and pesticide use, large-scale mechanization and soil clearing with its risk of erosion, reduced fallow or other soil regeneration techniques, the spread of irrigation with its potential for salt accumulation or waterlogging, and other changes that are collectively threatening long-term agricultural productivity.”
Dahl (1996, p. 32) states, “Since the richest one-fifth of the population today uses about four-fifths of the world’s resources, the existing world population cannot be brought up to, say, European living standards using present technologies and consumption levels.”
Dahl (1996, p. 21) points out that by not taking a systems approach to ecology and economy, we are ignoring the long-term costs of environmental pollutants. “(M)any developed countries are discovering thousands of old industrial sites contaminated with hazardous materials since the beginning of the industrial revolution, and now requiring expensive clean-up.” Damages to the ozone layer and the global climate are additional examples of unaccounted for costs that future generations will have to bear. Resource managers are not adequately taking into account the likely future damages and expenses of dealing with the aftermath of decades of widespread use of chemicals in agriculture and in industry, and the now widespread use of chemicals in managing invasive plant species.
In analyzing both ecological and economic systems, it is crucial to examine both extent of growth and change, as well as rates of growth. The current economic system is poorly designed to deal with rates of growth. “Part of the problem is due to the different scales and paces of growth between human activities, which we can control, and the natural world, where rates are beyond our influence and scales can exceed our capacity to respond. The speed with which chemicals move in the environment and are detoxified or recycled by natural processes… cannot necessarily be accelerated” (Dahl, 1996, p. 25).
in a 2013 interview with Becky McMillen, Lars Baker, retired Fremont County, Wyoming, Weed and Pest Supervisor who worked for the County for 38 years, stated: “I have concerns about the lack of research on chemicals. We are not thinking about the non-target impacts of chemicals. Some chemicals, such as Tordon, kill all broadleaf species, including crops and native species. It also kills trees. Chemicals are a temporary treatment. The chemical may do the job for two-three years, but eventually the chemical dissipates in the soil, and the weeds return because we have not changed the environmental conditions that allowed the weeds to grow there in the first place. RoundUp-Ready corn is not going to work for very long.
“Chemicals seem like an easy fix, but the environmental cost is too high. We don’t take into account the indirect costs, the environmental costs of spraying, the environmental cost of tractor tires, diesel fuel, the farmers’ exposure to the sun and to the chemicals. We have to change the environmental conditions to control weeds.
“In the early days, if we wanted to know how a new product worked, we had to do our own local research. We tried it on a plot, and we recorded the results. Harold Alley, at the University of Wyoming, did some of the early research on chemicals. He was one of the first Weed Scientists in the United States. He was followed by many others like Steve Miller and Tom Whitson who worked so hard to improve weed control practice in Wyoming.
“Chemicals do have a role in stopping a small weed population before it becomes an infestation. We can use it effectively for part of our Early Detection and Rapid Response program, to prevent the spread of a weed. The Nature Conservancy did some interesting research on controlling leafy spurge. They found that it is not effective to spray the inside of a patch of weeds, the most heavily infested lands where the most economic loss is. You have to map out the area, to find out where the weeds are, and you have to treat from the outside of a patch, to slow down the spread. You rarely have enough money to pay for enough chemicals to treat the entire patch, but if you treat the edges the first year, the second year you can treat closer to the center. Each year, you treat further toward the center. If you start in the middle and work out, the weeds continue to spread.”
In 2017, I interviewed George Beck, retired Weed Scientist at Colorado State University, who has worked with perennial noxious weed issues in rangeland and pastures since 1985. He told me, “We have the least amount of data on how herbicides remaining in the soil impact the growth of native plants.”
In 2018, I interviewed Jim Pike, District Conservationist for the NRCS Laramie County Field Office, now retired. He commented that he served in the Vietnam War, and thought nothing at the time about being drenched in Agent Orange. That early experience with the country’s lack of concern with the potential toxicity of chemicals causes him to be much more aware of the possibility that we are poisoning our environment and ourselves even more, in the current use of herbicides and pesticides to manage weeds and pests.
The USGS, through its National Water Quality Program, conducts surveys to evaluate the prevalence of herbicides and pesticides in our waterways. In the USGS water quality report for 2013-2017, Covert, et al., 2020, found that, “In the study of 72 rivers and streams across the contiguous U.S., five or more pesticides were detected in 88% of the more than 5,000 samples collected during 2013–17… The potential for toxicity of the pesticide mixtures to fish was low, but about 12% of samples were predicted to have potential acute (rapid) or chronic (longer-term) toxicity to aquatic invertebrates.” Of the 221 chemicals detected, 17 (13 insecticides, 2 herbicides, 1 fungicide, and 1 synergist) were evaluated to be the primary drivers of toxicity.
“In a given sample, a single pesticide compound generally was responsible for most of the potential toxicity of the pesticide mixture… in [samples] with…potential chronic toxicity to fish, the greatest contributor to that toxicity was likely to be the herbicide acetochlor, the fungicide degradate carbendazim, or the synergist piperonylbutoxide” (Covert, et al., 2020).
For aquatic invertebrates, insecticides were the most toxic. “For cladocerans [microcrustaceans], the pesticide compounds driving the [toxicity] scores were bifenthrin, carbaryl, chlorpyrifos, diazinon, dichlorvos, dicrotophos, diflubenzuron, flubendiamide, and tebupirimfos. For benthic invertebrates, atrazine (an herbicide)” (Covert, et al., 2020).
Sheley, et al., 2011, also cite research that suggests that atrazine has played a role in “global declines in amphibian populations.” They also found that “chemicals that target dicots can decrease plant community diversity, thereby reducing the food available for some wildlife species… For example, 2,4-D applied to western Colorado rangeland to favor grasses over forbs and shrubs reduced densities of northern pocket gophers… and least chipmunks…, while increasing densities of montane voles.”
Sheley, et al., 2011, found that “the impact of… herbicides on [soil, water, and air] resources is dependent on type of herbicide used, application rate, and soil characteristics, among other factors…. Glyphosate tightly adheres to soil,” thus reducing the risk of the chemical leaching into groundwater or affecting soil biota. But “dicamba and picloram are highly mobile in the soil… High application rates, high rainfall following application, or direct application… to water bodies can pose a significant threat to water resources.” But little research has been conducted on the impacts of herbicides on water and soil resources and wildlife. And few studies have compared impacts of herbicides on native versus invasive plant species. “Herbicides such as 2,4-D, clopyralid, or picloram…[used to control broadleaf weeds] can greatly decrease native forb density and cover… There is evidence suggesting that herbicide effects on native forbs are long-lasting and can drive a local decline in species richness… Desirable rangeland grasses have shown varying degrees of susceptibility to imazapic, a herbicide used to control invasive annual grasses, with evidence suggesting grasses within the Hordeae tribe may be more tolerant to imazapic than other grass species.” They concluded that, “The effect of herbicide on desirable vegetation remains difficult to predict.”
Insecticides and Human Health
Chlorpyrifos, an organophosphate, has been in use as a pesticide since 1965. As an insecticide, it is used to kill various insects and worms on various crops (corn, soybeans, fruit and nut trees, Brussels sprouts, etc.). It is also used on turf, on golf course greens, and in greenhouses. Approximately 10 million pounds are applied in U.S. agricultural fields each year. It is also used to kill mosquitos, roaches, and ants.
High doses are highly toxic to humans and can cause respiratory paralysis and death. In a 2000 EPA decision, its use in homes was greatly reduced, to require the use of child-resistant packaging for ant and roach baits, to avoid accidental poisoning of children. Its use in treating wood for construction, to kill termites, was ordered to cease by 2005. And additional restrictions were added, to better protect agricultural workers.
In addition, in 2000, reductions in its use were mandated to protect wildlife. It was determined that, “a single application of chlorpyrifos poses risk to small mammals, birds, fish and aquatic invertebrate species.”
In 2012, the EPA ordered a reduction in the aerial application rates, to create “no-spray” buffer zones, to reduce the amount of spray drift that was occurring, to better protect public spaces. In 2014, with additional review of the research, the EPA placed additional restrictions on its use in sprays. As additional concerns arose relating to possible toxicity that could cause developmental delays in infants, the EPA stated that “epidemiologic and biomonitoring studies, indicate that chlorpyrifos likely played a role in the neurodevelopmental outcomes reported by the epidemiologic study…investigators. However, uncertainties such as the lack of an established MOA/AOP for neurodevelopmental effects and the potential exposure to multiple AChE-inhibiting pesticides preclude definitive causal inference. However, there is sufficient uncertainty in the human dose-response relationship for neurodevelopmental effects to prevent the Agency from reducing or removing the statutory 10X FQPA Safety Factor. The FQPA 10X Safety Factor will be retained for infants, children, youths, and women of childbearing age for all exposure scenarios” (US EPA Chlorpyrifos Human Health Risk Assessment).
As of 2020, the safety of chlorpyrifos, particularly in regards to infant development, remains controversial. The EPA maintains that the standards they have set for its use are adequate. On August 9, 2018, the U.S. Ninth Circuit Court of Appeals ordered the EPA to ban chlorpyrifos within 60 days. The following month, the US Department of Justice asked the Ninth Circuit to reconsider its opinion. Several States have moved to ban its use.
Herbicide suspensions
In October 2024, based on the review of studies on potential thyroid toxicity in human fetuses, the EPA announced the cancellation of all products containing Dacthal.
As of November 2024, there were over 5800 active lawsuits pending in the Paraquat Multidistrict Litigation. The affected individuals claim that Paraquat has caused or significantly contributed to the development of Parkinson's Disease in agricultural workers. Ten bellweather cases are moving towards trial. Over 6000 cases are being addressed in the Southern District of Illinois.
Pesticide use in Potato Crops
Americans have become averse to blemishes on their foods. McDonald’s is one of many fast food chains that relies on unblemished foods. The Russet Burbank potatoes the chain uses for their French fries are prone to have a defect called net necrosis, little brown lines or spots caused by aphids and fungus. The company has come to demand that their potatoes be free of this blemish. Blanching helps eliminate the blemishes. But pesticides are also used.
McDonald’s now likes to claim that the farmers they work with do not use the toxic insecticide, Monitor, on their potatoes. What they neglect to mention is that Monitor was in widespread use on potatoes from 1972 until 2009.
An insecticide previously used on potatoes, cotton, and tomatoes, Monitor, methamidophos, was so toxic that the U.S. voluntarily suspended its use in 2009. It is banned in several countries, but is still widely used on rice in China. It is toxic not only for humans and other mammals, but also highly toxic for birds, fish, aquatic invertebrates, and bees.
In northern Minnesota, concerns about pesticide drift, the distance a chemical can blow in the breeze, caused the leadership of the White Earth Nation to join with other concerned citizens, including the Pesticide Action Network, to form the Toxic Taters Coalition. This group is trying to educate the public about the use of pesticides in the potato industry, and trying to influence companies like McDonald’s to stop the use of pesticides.
While many companies have been averse to changing to more sustainable agricultural practices, other companies, like the sports clothing company Patagonia, have been so effective in supporting organic farming, that many farmers now grow organic cotton.
References:
- Covert, S.A., Shoda, M.E., Stackpoole, S.M., & Stone, W.W. (Nov., 2020). Pesticide mixtures show potential toxicity to aquatic life in U.S. streams, water years 2013–2017. Science of the Total Environment, 745.
- Dahl, A.L. (1996). The Eco Principle: Ecology and Economics in Symbiosis. Oxford: George Ronald Publisher.
- Sheley, R.L., James, J.J., Rinella, M. J., Blumenthal, D., & DiTomaso, J.M. (2011). Invasive plant management on anticipated conservation benefits: A scientific assessment. In D.D. Briske (Ed.) Conservation benefits of rangeland practices: Assessment, recommendation, and knowledge gaps. (pp. 293-336). USDA Natural Resources Conservation Service.
Links to other Impacts of Pesticides: