It is always a challenge to keep pests off crops. However, as pests (both plants and animals… probably bacteria and fungi, too) evolve and become resistant to pesticides, oftentimes more toxic pesticides need to be brought into use.
Unfortunately, many pesticides are toxic chemicals, and can be a problem for natural wildlife surrounding farms as well as the farm workers who are exposed to heavy amounts of pesticides (see PANNA‘s webpage on pesticide drift). Approaches such as such Integrated Pest Management can be utilized in an effort to be control pests in a more environmentally-friendly and less toxic way.
A recent paper was just published looking at organophosphate residue (a type of pesticide) in food. Organophosphates, such as parathion and malathion, have cholinergic effects on the nervous system (they activate the parasympathetic nervous system- the one that is responsible for “resting and digesting”). They act on the enzyme acetylcholinesterase (which breaks down acetylcholine, the neurotransmitter used by the parasympathetic nervous system to send messages), inhibiting its action, so too much acetylcholine accumulates. Organophosphates are thus nerve agents. They are a common cause of poisonings, and the antidote pralidoxime (which regenerates acetylcholinesterase) must be given to prevent paralysis of respiratory muscles, along with atropine (a competitive inhibitor of acetylcholine).
A recent article on this study stated the following:
For the past three decades, overall use of OPs [organophosphates] has declined. But recent U.S. Department of Agriculture (USDA) data shows them to be among the top insecticides used on crops that include apples, peaches, and blueberries. According to the latest data from the U.S. Environmental Protection Agency (EPA), more than 33 million pounds of OPs were used in the U.S. in 2007.
Treated crops include broccoli, cantaloupe, grapes, green beans, lettuce, nectarine, oranges, pears, spinach, strawberries, tomatoes, sweet potatoes, mangoes, and onions. So if you’re eating conventionally grown produce grown in the U.S., it’s more than likely that you’re eating some that was treated with OPs. Washing and/or peeling will remove some residue, but not necessarily all of it.
According to the article, the study showed that:
Curl and colleagues analyzed participants’ urine samples for evidence of OPs, then they compared these results from a subset of 720 people to the USDA’s measurements of pesticide residues on the fruit and vegetables the participants reported eating. They found that people who ate conventionally grown produce had high concentrations of OP metabolites in their urine, while people who reported eating organic produce had significantly lower levels. In fact, those who ate the least organic produce had as much as twice the pesticide levels as those who ate organic the most frequently.
To summarize, many conventionally grown fruits and vegetables contain organophosphate residues. But research is still being conducted on the possible negative effects of consuming produce with organophosphate residue.
Thus, as a consumer, we may wonder about the amount of pesticides in our food, and how to avoid them. Organic farming does not permit the use of synthetic pesticides, though “natural” pesticides can be used. But organic produce can be expensive or difficult to find.
The Environmental Working Group has a “Shopper’s Guide to Pesticides in Produce“. Here, they list the “Dirty Dozen” and the “Clean Fifteen”, which are lists of conventionally grown fruits and vegetables with the highest and lowest levels of pesticide residue, respectively. Apples, strawberries, and grapes are currently at the top of the list as having the most pesticide residue detected, while avocados, sweet corn, and pineapples have the least amount of pesticide residue found. In general, skimming through their lists, it appears that fruits and vegetables with the thinnest, most delicate skins have the most pesticide residue, while those with thicker skins have the least residue.
For a more detailed list of pesticides found on food, one can search the database of “What’s on my food?“.
[Disclosure: I have been paid by PANNA in the past (small sums) for some work I did for another group]