Pesticides have been a life saver for large scale farmers. They allow farmers to keep weeds away, keep insect pests at bay and increase their crop yield. In fact, large scale farming may well be impossible without the use of pesticides (not that getting rid of large scale farming would be terrible). While pesticides are a savior for farmers, they can have disastrous health consequences on animals and humans. I am sure most of you have at least heard about DDT use in the 1950s which nearly destroyed the population of bald eagles.
Shortly after World War II, a new pesticide, one people had high hopes for, one that was supposed to control pesky mosquitoes and insects, was developed. It was called DDT. Soon enough DDT washed from crops and ended up in rivers, causing levels of DDT to build up in fish. The bald eagles preyed on these fish and became poisoned by DDT, causing the shells of their eggs too become so thin that they broke during incubation. This, along with other factors, caused the population of bald eagles in this country to dwindle down to 487 nesting pairs. Because of this and a book written about the adverse health effects of DDT in humans, the government banned the use of DDT in the 1970s.
There was peace in the land once again. But this was short lived. Soon enough we started using a different class of pesticides called organophosphates. DDT on the other hand was an organochloride pesticide. DDT was dangerous because it built up in our fat cells, was toxic, and stayed in the environment for an extremely long time (at least 10 years). Organophosphates do not build up in our fat cells, we excrete them out usually within a day, and they only stay around in the environment for a few months at most. Sounds like a good deal, eh?
Mechanism of action for pesticides (how they kill living things)
The bottom line is that pesticides are MEANT to kill living things. Nothing shows this better than the story of how a nerve gas was discovered in Germany. In 1936 a German chemist was doing research on insecticides (insecticides are meant to kill insects). During his research he discovered a nerve gas called Tabun. This nerve gas, an organophosphate, works by inhibiting an enzyme in our body, the same way that it works on insects. When this enzyme is inhibited our nervous system cannot work properly. This causes a loss of control over all bodily functions leading to drooling, difficulty breathing, vomiting, blistering of the eyes, and eventually death. If a large amount is inhaled, Tabun can cause death in 10 minutes. This is not a pretty way to go.
The United States Environmental Protection Agency lists organophosphates as very highly acutely toxic to bees, wildlife, and humans. Many people in developing countries intentionally consume pesticides as a form of suicide (mostly Asian countries). People that are exposed to high doses of pesticides but survive suffer from chronic neurological damage and psychiatric disorders. Another interesting and well known fact is that the pesticide neonicotinoid is causing the decline of the bee population worldwide. Italy and France have already banned its use and other governments are currently considering banning it as well.
While the effects of consumption of large levels of pesticides is known, the effects of small amounts consumed every day over the course of one’s lifetime is much less well known. This is the topic I am interested in. Can consumption of small amounts of pesticides from fruits, vegetables, grains and meats eaten almost every day cause us harm?
Pesticide effect on animals
Pesticide use can have severe consequences on other mammals and especially birds. The death of 1200 Canadian geese was attributed to a wheat field in the United States sprayed with a mixture of two different pesticides (1). The United States Environmental Protection Agency has estimated that Carbofuran results in the death of 1-2 million birds a year (1). Carbofurans have one of the highest acute toxicities to humans of any insecticide and a quarter teaspoon (1 mL) can be fatal.If pesticides have this severe an effect on the body of birds, who share a similar nervous and organ system as humans, imagine the long term harm pesticides can have on humans.
Pesticide effect on humans
It has been estimated by one organization that about 3 million people are poisoned and 200,000 people die each year from pesticide use (1). Pesticides are meant to interact with the nervous systems of living things (granted they are insects) so it can be assumed they would also interact negatively with the nervous system of human beings, obviously not enough to kill us immediately but over a long period of time who knows what can happen.
Contaminated food is our major exposure to pesticides, accounting for greater than 90% of our total exposure (2). There are two options for pesticides sprayed on food: they are waterproof or they are not. If they are waterproof that means they will not be washed into the soil when it rains but it also means rinsing fruit under sink water will not remove pesticides. If they are not waterproof that means every time it rains the chemicals get into the soil and it also means that every time it rains farmers must respray the crops- which would get expensive. Based just on this I would expect that pesticides do not wash off easily with water.
Many fruits and vegetables are covered in wax which protects the pesticides and makes them harder to remove (3). This property actual makes it safer to eat fruits where you peel the whole skin off, such as an orange, but is a disadvantage on green leafy vegetables which you can only wash. Pesticides are also capable of dissolving into the plant, making it impossible to remove by washing it (3).
Removal of pesticides depends not only on the type of fruit and vegetable but also on the type of pesticide used. Sometimes the pesticide is held loosely on the surface, as in the case of DDT, and can be effectively washed away by only using water (home washing removed 78% of DDT from tomatoes) (3). Washing green beans did not remove any DDT as it was deep inside the green bean and not on the surface (3).
How long do pesticides stay in the body?
How long pesticides remain in our body is largely determined by the class of pesticide. Some types of pesticides are almost completely excreted from our body in 24 hours. Most pesticides are excreted in our urine rather quickly (within a few days) and LIKELY do not build up in our body. Older organochloride pesticides like DDT are stored in our fat cells and can remain in our body for a very long time.
How effective washing is at removing pesticides
Washing obviously works best with pesticides that are held loosely on the vegetable or fruit. Since everyone likes charts I put a chart together summing up the results of various studies using water to remove pesticides. PPM is parts per million and PPB is parts per billion (a measure of pesticide residue in a given quantity of solution). They are extremely small numbers. Overall, about 40% of the pesticides were removed from all of the following plants. This leaves a significant amount of pesticide residue on the plant.
|Food||Original pesticide concentration||Percent reduced||Final concentration|
|Bitter gourds||18.97 ppm & 26.01 ppm||59% & 43%||7.78 ppm & 14.93 ppm|
|Rice grains||456 ppb & 3.4 ppb||60%||182.4 ppb & 1.36 ppb|
|Eggplant||167 ppm & 179 ppm||80%||33.4 ppm & 35.8 ppm|
|Mango||Unknown||31% & 73%||Unknown|
|Peaches||1.23 ppm||49%||0.61 ppm|
|Chickpea grains||.051 ppm||16%||0.042 ppm|
|Potatoes||3.8 ppm||40%||2.28 ppm|
|Cucumber||.822 ppm||22.30%||0.633 ppm|
|Grapes||.49-1.84 ppm||75%||.122-.46 ppm|
|Tomatoes||.886 ppm||68%||.284 ppm|
|Green beans||1.49 ppm||45%||.82 ppm|
Pesticides in children and switching to organic food
A 2005 study measured the urine levels of pesticides of 23 elementary school children while on their normal diet and then for 5 days on a diet which substituted most of the children’s conventional (non organic) food items for organic food items (5). Although the metabolites (broken down products) of many pesticides were found in the urine of the children while on their normal conventional diet, the period of organic food substitution resulted in these pesticide metabolite residues reaching non-detectable levels (5). The pesticides that were reduced were organophosphorus pesticides, metabolites of chlorpyrifos and malathion. This shows that these pesticides are not stored in our body and that switching to organic food can significantly reduce our pesticide intake.
For me, the most important finding from this study was that it showed that food is the major contributor to our exposure to organophosphorus pesticides. This is an important finding as these pesticides are also used in a variety of household products and building materials. According to the United States Environmental Protection Agency, chlorpyrifos are “one of the most widely used organophosphate insecticides” in agriculture. It is considered mildly toxic to humans (well if it is only mild I feel much better) and exposure to it has been linked to neurological effects, autoimmune disorders, and persistent developmental disorders. Scary to think that this pesticide was so common in the urine of children.
How common are pesticides in fruit?
The Pesticide Data Program, a program started by the United States Department of Agriculture, is the largest tester of pesticide residues on food sold in the United States. It began in 1991, and has since tested over 60 different types of food for over 400 different types of pesticides – with samples collected close to the point of consumption. Their most recent summary results are from the year 2005:
|Fresh Fruit and
Possible long term effects of pesticide use
A UK study compared retired police workers to current and past sheep farmers who were/are exposed to consistent but low levels of organophosphate pesticides to see if there were neuropsychological and psychiatric differences between the groups (6). The study found that farm workers, retired and current, performed significantly worse on measures of memory, response speed, fine motor control, mental flexibility, and strategy making compared to the retired police workers (6). When comparing depression and anxiety a higher proportion of farm workers scored in the clinical range for anxiety and depression (46.9% of farmers vs 6.5% of police for depression and 41.5% of farmers vs 22.1% of police for anxiety) (6).
When asked to report their history of exposure to organophosphates during “sheep dipping” (literally dipping sheep in a bath of pesticides to protect them from parasites), 33.8% of the current farm workers and 50.9% of the retired farm workers reported that throughout their working career they had multiple episodes of flu like symptoms including fatigue, headache, muscle pain, and general malaise, following their exposure to organophosphates, all symptoms seen in cases of mild exposure to organophosphates (6).
After analysis, the researchers found that duration of exposure to organophosphates was linked to lower scores on auditory memory, visual memory, verbal ability and strategy making (6). A majority of the farmers also reported feelings of fatigue, memory problems, joint pain, sleep disturbance, irritability, and feeling mentally slowed down (6).
Pesticides and Gulf War Syndrome
Gulf War Syndrome is a chronic multi symptom disorder affecting returning military veterans and civilian workers of the Gulf War. The syndrome itself consists of multiple illnesses such as: fatigue, headache, memory problems, neurological problems, and terminal tumors just to name a few. Because there are such varied symptoms it is hard to pin point an exact illness but some suggestions are chronic inflammation, exposure to nerve gas, exposure to organophosphate pesticides (used to keep pest borne illnesses low) and a nerve gas antidote. The symptoms of this illness mirror symptoms seen in populations of people that have had low level pesticide exposure. Studies have also found that greater pesticide exposure was linked to more illness among soldiers. A 465 page report compiled by the Research Advisory Committee on Gulf War Veterans’ Illness concluded “Taken together, all available sources of evidence combine to support a consistent and compelling case that pesticide use during the Gulf War is causally associated with Gulf War illness (8).”
Tolerance levels for pesticides and how they are determined
This was taken from the Environmental Protection Agency (EPA) website:
“EPA has developed a table of human health benchmarks for approximately 350 pesticides that are currently registered to be used on food crops. These human health benchmarks for pesticides are levels of certain pesticides in water at or below which adverse health effects are not anticipated from one-day or lifetime exposures.”
So the EPA sets levels allowed which no adverse health effects are anticipated. How are these tolerance limits set? If you are imaging studies performed by government agencies you are wrong. Why trust the government when we can just have the companies test the safety of their own pesticides? Also taken from the EPA website: “Pesticide companies, or registrants, must submit a wide variety of scientific studies for review before EPA will set a tolerance.”
All of the testing is performed on animals, likely mice. Obviously testing pesticide exposure on humans would be unethical but I am not convinced that testing pesticides in mice and extrapolating this data for safe or “tolerable” levels for humans is accurate. While generally similar, mice have much shorter life spans than humans and different types of enzymes than humans. I am not trying to downplay the importance of animal research I am just pointing out that the processes in a mouse do not always mirror the processes in humans as shown through countless drugs which worked wonders in animals but proved to be ineffective in human clinical trials (7). This is a complex topic and I will discuss it more in a later blog.
The point I am getting at is I do not trust using animals to determine tolerable limits for pesticides in our food. One of the largest differences between humans and mice is our life span and this is also of critical importance as we want to know the effects of small pesticide ingestion over our life span, effects which may never appear in the short life span of a mouse. As in the blog about toxins in water (LINK) I do not agree with tolerable limits of chemicals which are meant to affect the nervous system of living things.
Steps to decrease pesticide concentration from foods
Fruit and vegetable wash
Since I showed that washing with water only removes about 40% of the pesticides, what are other ways can you increase pesticide removal? You probably have noticed “Fruit and vegetable wash” in the produce section of your supermarkets. There are various brands but they all claim to reduce the pesticide residue by significantly more than rinsing with water alone. I have been using them off and on for years but never checked the validity of their claim.
A study using Proctor and Gambles “Fit Fruit and vegetable wash” found that this vegetable wash did not remove a much larger percentage of pesticides than water alone. They only measured two pesticides so it is hard to draw conclusions about the dozens of other pesticides used. They used Captan (a fungicide) and Methomyl (insecticide) and found that water alone reduced pesticide levels by 39% compared to 45% by vegetable wash in Study 1, in Study 2 water reduced levels by 81% while the vegetable wash reduced it by 90% and in Study 3 water reduced the levels by 18% while the vegetable wash reduced it by 39% (4).
These numbers do not come close to the claim of “98% more effective at removing pesticides than water,” but at least they remove a slightly higher percentage. These washes are inexpensive so it could not hurt to use them. The more pesticides removed the better off we are; even just a few percent less can add up over time.
Peeling would certainly remove a large percentage of pesticides in foods like potatoes, apples and carrots but in the case of potatoes and apples you would be removing many of the beneficial nutrients found on the skin of these foods.
I just cannot wrap my head around allowing hundreds of essentially nerve gas chemicals to be sprayed on food crops, foods that children and pregnant mothers are eating. It is unfortunate that the agricultural industry is so tied to pesticides and that our government is so tied to the agricultural industry. This is understandable as if we just stopped using pesticides most crops would likely be destroyed by pests and we may end up with a food shortage. What the government can do is promote smaller scale farming and find alternatives to using such dangerous pesticides on the majority of our foods.
Writing this blog really sparked my interest in this topic. I enjoyed writing this blog second only to my blog on fiber. I have about 80 journal articles left to go over until I will feel content in knowing almost everything I need to know about pesticides. I will post blogs here and there sharing any interesting findings. This blog is just a small piece of the whole picture. I hope you enjoyed reading it and that it helped you learn more about pesticides and how to reduce them in your diet!
- Wilson, C., & Tisdell, C. (2001). Why farmers continue to use pesticides despite environmental, health and sustainability costs. Ecological economics, 39(3), 449-462.
- González-Rodríguez, R. M., Rial-Otero, R., Cancho-Grande, B., & Simal-Gándara, J. (2008). Occurrence of fungicide and insecticide residues in trade samples of leafy vegetables. Food Chemistry, 107(3), 1342-1347.
- Street, J. C. (1969). Methods of removal of pesticide residues. Canadian Medical Association Journal, 100(4), 154.
- Krieger, R. I., Brutsche-Keiper, P., Crosby, H. R., & Krieger, A. D. (2003). Reduction of pesticide residues of fruit using water only or plus Fit™ Fruit and Vegetable Wash. Bulletin of environmental contamination and toxicology, 70(2), 0213-0218.
- Lu, C., Toepel, K., Irish, R., Fenske, R. A., Barr, D. B., & Bravo, R. (2006). Organic diets significantly lower children’s dietary exposure to organophosphorus pesticides. Environmental health perspectives, 114(2), 260.
- Mackenzie Ross, S. J., Brewin, C. R., Curran, H. V., Furlong, C. E., Abraham-Smith, K. M., & Harrison, V. (2010). Neuropsychological and psychiatric functioning in sheep farmers exposed to low levels of organophosphate pesticides. Neurotoxicology and teratology, 32(4), 452-459.
- Mestas, J., & Hughes, C. C. (2004). Of mice and not men: differences between mouse and human immunology. The Journal of Immunology, 172(5), 2731-2738.
- . Research Advisory Committee on Gulf War Veterans’ Illnesses (2008-11-01). “Gulf War Illness and the Health of Gulf War Veterans: Scientific Findings and Recommendations” (pdf). U.S. Department of Veterans Affairs. Retrieved 2012-05-09.