Introduction
According to Mohamood et al., pesticides are "...toxic chemical substances or biological agents that are intentionally released into the environment" (2016). These toxic chemicals can have a disastrous impact on both human health and environmental health. Pesticide use has been around for hundreds of years and have evolved over time to first be made from natural compounds and now typically made from synthetic compounds. There are six major types of pesticides that are in use, which include:
Organophosphates - Neurotoxins used on pests
Carbamates - Similar to organophosphates, but less toxic
Organochlorine - POPs that have the ability to bioaccumulate in humans and wildlife
Pyrethroid - Synthetic version of pyrethrin from the Chrysanthemum flower which is toxic on the nervous system
Biopesticides - A variety of pesticides/methods that are biologically derived
Herbicides - Pesticides widely used in gardening
(Frumkin et al., 2016; Mahmood et al., 2016)
Environmental Impacts of Pesticides
Loss of biodiversity
Pests may begin to develop genetic resistance to pesticides
Negative consequences on non-target organisms and plant diversity such as the bald eagle
Pesticides that are applied by spraying are more likely to volatilize into the air
Overall air, water, and soil contamination
Bioaccumulation of pesticides in animals leading to negative impacts throughout the food chain
Predatory animals will have the highest amounts of pesticides
(Mahmood et al., 2016)
Human Health Impacts
Infants and children are vulnerable non-target populations
Exposure routes include ingestion, inhalation, and through the skin (dermal)
Primary cause of exposure is due to the ingestion of contaminated food
All routes of exposure have the potential to lead to bioaccumulation of pesticides in fatty tissue in the body
Long-term, chronic exposure to pesticide use includes:
neurological effects such as loss of coordination, memory, and visual ability
damaged immune system and function leading to an increase in allergies and asthma
negative reproductive health impacts such as sterility and stillbirths
overall damage to other organs in the body - lungs, liver, kidneys
(Mahmood et al., 2016)
A Historical Overview of Pesticides
Source Material: (Bertomeu-Sánchez, 2019) unless otherwise listed
Pre-1850
Mineral compounds and extracts of natural products used as pesticides Examples: Tobacco, Chrysanthemum Flower, Derris Root
Start of human concern over pesticide use. Beekeepers concerned with the impact of arsenical pesticides and the harmful effects on bee colonies
1850-1900
1860 - Paris Green is the first large scale insecticide used (Frumkin et al., 2016)
1867 - Paris Green used to control a Colorado Potato Beetle outbreak
New products are starting to be created and introduced - Copper Fungicides, Arsenic Compounds
Continued concern in regards to human health. Toxicologists have developed a way to measure arsenic compounds in corpses to be used as evidence in court. However, we are still not able to full detect chronic, low-dose exposure efficiently.
Photo: https://en.wikipedia.org/wiki/Paris_green
1900 to 1910
New agricultural methods are being developed leading to changes in environmental conditions causing an increase in pests
Monocultures are a method that is discussed throughout
1920s
Aerial spraying is not being used to apply pesticides to large monocultures
Concerns in Britain after scientists detected arsenic in apples from America
Campaign to encourage Britains to eat locally sourced foods
Photo: https://en.wikipedia.org/wiki/Aerial_application
1930s
1938 - Multiple poisoning threats occur from drinks and fruit which leads to the enactment of the Food, Drug, and Cosmetic Act . This act sets limits on the amount of residual pesticide is permitted and safe for food
1940s
Prior to the introduction of new organic pesticides
Insecticides - arsenic group (stomach poisons) and DDT (contact insecticides)
Fungicides - sulphur and copper compounds
Repellents - weed killer and rodent control
Introduction of new organic pesticides
DDT is now more commonly used as a pesticide
Lindane, a hexachlorocyclohexane isomer, is used as a pesticide and against lice
1942-53 - Synthetic pesticides are introduced in Scandinavia and forced to be used by gardeners
End of World War ll
Synthetic pesticides are increasingly used in agriculture
Concerns in Spain over the mass introduction of lead arsenate
Studies began on DDT, which ended up showing evidence of the potential chemical dangers to mammals
Organophosphate chemicals are found to lead to river and soil contamination
Photo: https://oklahomaconservation.org/ddt/
Photo: https://thesocietypages.org/socimages/2011/06/27/ddt-is-good-for-me-e-e/
1950s
Despite studies showing evidence of the consequences of DDT use, global circulation continues. This is due to:
Cold War strategies
Political involvement with the chemical industry
Increase in monoculture farming
Organophosphate chemicals (DDT, etc.) are now showing evidence of the harmful neurological effects on farmworkers and rural communities
1951 - Beginning to see more pesticides labeling and warnings about the harmful effects of exposure
Late 50s - Start of the Green Revolution, the increase in agriculture in developing countries, which prompted the use of chemicals in agriculture
1960s
Soviet Union is transitioning chemical weapon plants into pesticide production plants leading to further contamination.
1962 - Rachel Carson's Silent Spring began alarming the population about the consequences of spraying DDT and the impact on non-target organisms
Ultimately lead to the banning of DDT by the EPA (see below)
During this time, many opponents of Carson are blaming her for the consequences of banning DDT, increased famine and vector-borne diseases in third world countries.
1963 - WHO and Food and Agriculture Organization (FAO) create international standards of acceptable amounts of chemical residues on food
Late 1960s - Introduction of Integrated Pest Management (IPM)
1970s
1972 - DDT is officially banned and restrictions are placed on the use of Endosulfan, Dieldrin, and Lindane
Mid 1970s - China begins to pioneer the use of various IPM strategies
1976 - Italy has a chemical plant that released a toxic cloud of dioxin which impacted thousands in the area
Lead to increased safety regulation
1976 - Switzerland farmer adviser research groups begin creating crop protection strategies that have presently developed into IPM strategies (Barzman et al., 2015)
Late 1970s - Pesticide companies begin moving production and use to countries with less stringent regulations
1979 - The Federal Integrated Pest Management Coordinating Committee is first established by President Carter (USDA, n.d.)
1980s
1984 - Bhopal, India pesticide plant has a methyl isocyanate gas leak
1986 - Sandoz, Switzerland agrochemical warehouse has a chemical spill resulting in large quantities of air pollution, soil contamination, and organophosphate insecticide and fungicides released in and around the Rhine
Sandoz Warehouse Fire
The agrochemical warehouse fire that lead to the Sandoz chemical spill in Switzerland.
Burned Pesticide Barrels
Following the Sandoz agrochemical warehouse fire, a number of pesticide barrels and their contents were discovered to have been burned.
Washed Up Eels
Shortly after the fire and burning of pesticides, eels began washing up on the shore of the Rhine.
1990s
1991 - Córdoba, Mexico has a chemical spill where pesticides are released into the air, soil, and water
Results emerge from the Soviet Union transition (see 1960s) that during that time a significant amount of pesticides were used leading to "...one out of every ten people...seriously ill" (2019)
2000s
2000 - Salamanca, Mexico a similar incident occurs as the 1991 Córdoba, Mexico incident
2001 - Stockholm Convention
Global treaty reposted that a majority of harmful POPs identified were associated with pesticide use.
Treaties goal was to stop production, trade, and use of these POPs
Lindane as a pesticide is banned in many countries due to long-term environmental effects
2010s to Present
2010 - Izúcar de Matamoros, Mexico a similar incident occurs as the 1991 and 2000 incidents
2014 - EU member states are required to develop a National Action Plan to ensure the eight IPM principals are implemented among large scale pesticide users (Barzman et al., 2015)
Integrated Pest Management
Photo: www.stocksnap.io
Integrated Pest Management (IPM) is defined as:
"A comprehensive approach to pest control that uses a combined means to reduce the status of pests to tolerable levels while maintaining a quality environment"
(Frumkin et al., 2016)
There are several key aspects of IPM that will be discussed, but a key factor is to ensure that combination of IPM strategies are used (Stenberg, 2017; Barzman et al., 2015). Overall, the goals of IPM are long-term sustainability as a pest control method and a decreased negative impact of pesticides on human and environmental health (Barzman et al., 2015).
Long-term sustainability is achieved if IPM is implemented on a continuum. On this continuum, an agricultural company may gradually transition from no IPM use to high IPM use. Additionally, this allows the company to asses whether there are changes among pest populations, threats, or policies.
The key aspects of IPM include pest control (mechanical, physical, biological, selective pesticide use), structural maintenance, monitoring, control measures, and consumer education (Frumkin et al., 2016; Barzman et al., 2015).
Ultimately, IPM is working to reduce the impact of particular pest rather than total eradication. Many countries have already begun working towards the eight key IPM principles (Barzman et al., 2015):
Prevention and Suppression
Monitoring
Decision Based on Monitoring and Threshold
Non-Chemical Methods
Pesticide Selection
Reduced Pesticide Use
Anti-Resistance Strategies
Evaluation
IPM in Action
Microbial Pesticides and Plant Incorporated Protectants (PIPs)
Microorganisms are used as an active agent. They are genetically added to the plant and when a pest eats the plant it is then toxic to them (Frumkin et al., 2016). Example: Bacillus thuringiensis - See video below
Biochemical Pesticides
Biochemical pesticides are nontoxic methods for controlling pests. While there are many types, a prime example of this type of pesticide is insect sex pheromones.
Pheromones are used to disrupt matting patterns for insects through two different methods.
Method 1: An excessive amount of sex pheromone is released into the environment which causes males to be unable to locate females. Because they are unable to locate females, reproduction does not occur.
Method 2: Use of pheromone traps to trap a large number of genetically male/female insects. This would mean that they are unable to reproduce at previous levels because there is less of one sex.
(Stenbern, 2017; Frumkin et al., 2016)
Botanical Pesticides
Botanical pesticides are pesticides that are derived from plants and typically display low mammalian toxicity. Because they are naturally derived, these forms of pesticides degrade more quickly and release less toxins as they decompose meaning they will have less of an impact on the environment (Landscape IPM). Commonly used botanical pesticides and the sources they are derived from include:
Pyrethrins - derived from pyrethrum flower dust (chrysanthemum)
Rotenone - derived from legumes and cube root to form a dust
Sabadilla - derived from the seeds on a tropical lily plant
Ryania - derived from a shrub commonly found in South America
Nicotine - derived from the tobacco plant
d-Limonene and Linalool - derived from citrus oils
Neem - derived from the Neem tree in which an oil is created that is applied to plants to suffocate insects
(Frumkin et al., 2016; Landscape IPM)
Intrinsic Heritable Plant Resistance
Plants develop traits that create direct or indirect defenses against pests and pathogens (Stenbern, 2017):
Direct Defense
"...directly defy attackers, making the plant less detectable, attractive, edible, or susceptible to infection"
In this example, the plant has developed a powdery mildew as a method of making the plant less attractive to pests. In most cases, direct defense is not actually harmful to the plant, but does offer protection to the plant or crop. Direct defenses can occur naturally, but are often breed out within the agricultural industry because it may interfere with crop taste and texture.
Indirect Defense
"...attract and reward the natural enemies of pests, thereby engaging them as ‘bodyguards’"
In this example, the plant has developed traits that accumulates herbivorous aphids. The ants are then attracted to the aphids for consumption. This could be both beneficial or harmful to the plant where either the ants remove the aphids saving the plant or removing the aphids harms the plant causing it to die. Indirect defenses also occur naturally, but are not purposefully breed out, primarily due to lack of awareness of its existence.
Unfortunately, as crops continue to become more domesticated, we are seeing a decrease in the differences in defense traits. Initially this was due to the increase in chemical pesticide use meaning resistant traits were not longer required to allow crops to flourish (Stenbern, 2017).
Plant Vaccination
Plants are primed with direct and indirect defenses to protect themselves. The more they are attacked by a pest, the more they are primed. Because of this method of priming, there is a reduction in metabolic cost.
As an example by Sternbern (2017):
"...tomato plants grown from jasm-onate and b-aminobutyric acid-treated seeds reportedly have stronger induced defenses than controls against both arthropod pests and pathogenic fungi."
Crop Diversity and Rotation
Crop Diversity - We need a variety of the same species if a monoculture is being used. If there are multiple different varieties of the same plant, the pest is less likely to be able to destroy the plant in the event there is an outbreak.
Crop Rotation - avoiding use of the same crop multiple cultivation cycles in a row. A clear example is in Europe with the Western Corn Rootworm. This pests life cycle lasts through two cultivation cycles. If we were to rotate to an entirely different crop after one cultivaiton cycle this would break the cycle in development of the Rootworm and decrease the overall population.
(Barzman et al., 2015; Stenbern, 2017)
Environmental Justice Perspective
From an environmental justice perspective, transitioning to IPM is not only beneficial to our environment, but also to human health. Agricultural workers, who are regularly exposed to chemical pesticides, are at an increased risk for cancer, Parkinson's disease, Alzheimer's disease, reproductive disorders, and birth defects (Kaur & Kaur, 2018). In the case of pesticide use, humans are considered non-target species after exposure and often times appropriate protective personal equipment such as gloves or respirators are not worn. Overtime, pesticides will bioaccumulate in the body leading to a disruption in a number of body systems including (Kaur & Kaur, 2018):
Nervous System
Reproductive System
Respiratory System
Immune System
Cardiovascular System
While regular exposure to pesticides can be detrimental to the health of agricultural workers, transitioning to IPM focused strategies can resolve many of those issues. With the use of IPM strategies, workers are no longer exposed to the same degree of harmful toxicants.
Regulatory Perspective
Per the USDA, the Office of Pest Management Policy allows for the communication between federal agencies to promote the development of pest management strategies. Under this policy, federal agencies are required to encourage IPM practices through regulation and activities. Chaired by this policy is the National Road Map for Integrated Pest Management. This roadmap plays a key role in providing guidance on effective, economical, and safe IPM strategies. There are three potential approaches that may be used to strength IPM that are discussed within this roadmap (Integrated Pest Management, n.d.):
"Improve economic and social analyses of adopting and implementing IPM practices;
Reduce potential human health and safety risks from pest and related pest management strategies; and
Minimize adverse environmental effects from pests and related management practices."
There is currently a Swiss agricultural policy that was created to subsidize IPM. According to Barzman et al., this policy has lead to 98% of Swiss agriculture contributing to ecological services and 88% of that falls under IPM (2015).
Additionally, as discussed, there are a number of monitoring systems in place throughout Europe.
Our Killer Environment Podcast Episode
References
Barzman, M., Bàrberi, P., Birch, A. N., Boonekamp, P., Dachbrodt-Saaydeh, S., Graf, B., Hommel, B., Jensen, J. E., Kiss, J., Kudsk, P., Lamichhane, J. R., Messéan, A., Moonen, A.-C., Ratnadass, A., Ricci, P., Sarah, J.-L., & Sattin, M. (2015). Eight Principles of Integrated Pest Management. Agronomy for Sustainable Development, 35(4), 1199–1215. https://doi.org/10.1007/s13593-015-0327-9
Bertomeu-Sánchez, J. R. (2019). Introduction. pesticides: Past and present. HoST - Journal of History of Science and Technology, 13(1), 1–27. https://doi.org/10.2478/host-2019-0001
Freeman, B.C. and Beattie, G.A. 2008. An Overview of Plant Defenses against Pathogens and Herbivores. The Plant Health Instructor. DOI: 10.1094/PHI-I-2008-0226-01
Frumkin, H., Mark Robson, Hamilton, G., Siriwong, W., & Maldonado Pérez, H. (2016). Pest Control and Pesticides . In Environmental health: From global to local (3rd Edition, pp. 483–489). essay, Jossey-Bass. A Wiley Brand.
Frumkin, H., Mark Robson, Hamilton, G., Siriwong, W., & Maldonado Pérez, H. (2016). Pest Control and Pesticides . In Environmental health: From global to local (3rd Edition, pp. 490). essay, Jossey-Bass. A Wiley Brand.
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Kaur, K., & Kaur, R. (2018). Occupational Pesticide Exposure, Impaired DNA Repair, and Diseases. Indian journal of occupational and environmental medicine, 22(2), 74–81. https://doi.org/10.4103/ijoem.IJOEM_45_18
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Mahmood, I., Imadi, S. R., Shazadi, K., Gul, A., & Hakeem, K. R. (2016). Effects of pesticides on environment. Plant, Soil and Microbes, 253–269. https://doi.org/10.1007/978-3-319-27455-3_13
NPIC at OSU. (2015, February 16). Bacillus thuringiensis (bt). YouTube. Retrieved November 25, 2021, from https://www.youtube.com/watch?v=3aLj1WmzL98.
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