Pesticides, by definition, kill pests. But they are also harmful to humans and other non-target animals. One of their most damaging effects is inducing oxidative stress.
Oxidative stress is an imbalance of free radicals and antioxidants. Too many free radicals without enough antioxidants eventually causes cell death.
Our built-in antioxidant system, including substances like glutathione, is the first line of defense against free radicals. If the oxidative stress exceeds what this system can handle, antioxidant vitamins like C, E, and A (which we must consume from food and supplements) scavenge free radicals.
While numerous studies correlate pesticide exposure with oxidative stress, it’s important to remember these studies are performed on workers exposed to these chemicals via inhalation, not ingestion via food consumption.
Oxidative stress alters antioxidant levels. Depleted levels of your body’s innate antioxidants — including superoxide dismutase, glutathione peroxidase, catalase, and thiroedoxin reductase — indicate oxidative stress. In a study, hospitalized human victims of pesticide poisoning had a significant decrease in plasma antioxidant capacity.
The fatty acids in the cell membranes are vulnerable to free radical attacks, causing damage to the barrier that holds and protects cell contents. Called lipid peroxidation, this indication of cellular damage is common in studies of humans exposed to pesticides.
Ultimately, oxidative stress kills cells. Several researchers have studied the effect of oxidative stress on brain cells that release the neurotransmitter dopamine. This chemical messenger is critical to our ability to think, plan, move, and respond with emotions. The pesticide parquat, in particular, has been associated with the oxidative stress-induced loss of dopamine-releasing neurons.
In other studies, primarily on rats, researchers have related pesticide exposure to changes to glucose metabolism. They believe free radical production is involved. The researchers observed glutathione depletion in the pancreas, the organ that bears much of the responsibility for managing blood glucose.
A common source of pesticide-induced oxidative stress is the inhibition of the nervous system enzyme acetylcholinesterase. The depleted acetylcholinesterase coupled with increased antioxidant activity due to oxidative stress showed DNA damage in workers chronically exposed to pesticides.
Pesticides come in several different chemical compositions, each damaging the body in different ways.
Bipyridyl herbicides + oxidative stress
Paraquat and diquat. They poison invasive plants. Paraquat is absorbed through skin, ingestion, and inhalation while the less toxic diquat is absorbed through ingestion. Both cause oxidative stress, primarily in the lungs where it ultimately results in healthy cells being replaced by fibrous tissue.
Pyrethins + OXIDATIVE STRESS
These are natural insecticides derived from plants with their first known use dating back to the 1800s. Their synthetic derivatives, pyrethroids, are more stable. Because they have high toxicity to insects and low toxicity to mammals, both the natural and synthetic variations of these insecticides are often sprayed in public areas. Several studies show that the synthetic pyrethroids induce oxidative stress in the liver, brain, kidney, and some red blood cells.
Organophosphates + OXIDATIVE STRESS
As these insecticides are also used as chemical warfare agents, it should be no surprise they are the most toxic of all pesticides to humans. Several studies report evidence of oxidative stress in human red blood cells.
Organochlorines + OXIDATIVE STRESS
These fat-soluble insecticides are among the most controversial, including the banned DDT. As they can store in fatty tissue, repeated small exposures can accumulate and cause oxidative stress in various organs of test rats.
Resources:
Abdollahi, Mohammad. “Pesticides and oxidative stress: a review.” Med Sci Monit, 2004; 10(6): RA141-147.
Cortes-Iza, Sandra Catalina. “Oxidative stress and pesticide disease: a challenge for toxicology.” Rev. Fac. Med. 2018 Vol. 66 No. 2: 261-7.
Ledda, Caterina et. al. “Oxidative stress and DNA damage in agricultural workers after exposure to pesticides.” Journal of Occupational Medicine and Toxicology (2021) 16:1.
