|This latte should not be so happy. It's full of toxins. (Source)|
Out of the 120 items tested, only one even reached 1% of the FDA's imposed limit, and it was only at 2%. Only seven (5.8%) exceeded 0.1% of the limit. Literally, 94% of the "dirty dozen" was below 1/1000th of the FDA limit. Over 75% of the samples contained less than 0.01%, which corresponds to 1,000,000 times below the chronic No Observable Adverse Effect Levels from animal toxicology studies), and 40.8% had exposure estimates below 0.001% of the FDA limit. If you're concerned that perhaps the FDA limits are arbitrary or too conservative, please understand that every pesticide, by regulation under FIFRA, requires extensive acute and chronic toxicity testing, and the residue limit is set at least 100 times less than the established "no effect" level. The EPA periodically reviews new evidence to see if their toxicity classification is still justified, and can pull a pesticide off the market if there's quality experimental evidence that supports making that decision. So yeah, although we discover new things all the time about how chemicals interact with our bodies, when exposures are so negligible, it's sort of a parallel issue. It's just not worth worrying about.
|Pesticide residues found on the 2011 "most dirty" produce: celery. Reference dose is the FDA limit. Notice how exceedingly small the exposure is. We're talking nanograms per kilogram of your body weight. (Source: UC Davis study)|
On its face, it seems logical that mere presence could matter. After all, these chemicals are designed to kill things. However, as with pretty much everything in life, the reality is a tad bit more complex. Regular table salt kills slugs, but we know that up to a point it enhances flavor without additional health risk. Drinking too much water can friggin kill people. It takes 10 times less copper sulfate, a chemical sometimes used as pest control in organic farming to kill 50% of a test population in rats than the synthetic pesticide glyphosate, so it's possible that using the Dirty Dozen list to buy organic actually points you in the wrong direction from a health perspective. This measurement is called to the LD50, the standard of acute toxicity. If you want to understand risk better, take a look at the table of various chemicals from the LD50 link above, which includes natural and synthetic ones, to get a sense of how we determine how toxic something is. Read about the limitations of the test and make your own informed decision. Using the "appeal to nature" line of reasoning, in which synthetic is inherently bad at any level, is sort of the mirror image of climate skeptics scoffing at the risk of increased carbon dioxide in the atmosphere by proclaiming it "plant food". Context is everything. If you're interested in convincing fence-sitters about the dangers of applying pesticides, preying on chemophobia has the opposite effect you're looking for. If you're really interested in improving the food system or making a positive impact on public health, it's of vital importance to stick to evidence and be up-front about what we do and don't know. People don't respond to alarm very well even when the science totally justifies it, so it stands to reason that people won't respond to alarm when science doesn't really justify it.
There are, of course, a wide variety of pesticides on the market. Some are used because they're specifically good at killing insects, some because they kill weeds, and some are used to prevent fungal infections. Furthermore, each type of pesticide has several distinct classes within them. For instance, within insecticides, there are organochlorides, organophosphates, and neonicotinoids, which all have different biochemical mechanisms for their lethal effects on their targets. So in order to be heed my advice on being up-front about the uncertainties that do exist, I should acknowledge that while the FDA sets limits for individual pesticide residues, it doesn't limit how many pesticides may be used. Often, farmers will apply more than one pesticide on their fields, and we really don't know so much whether small exposures of each simultaneously combines to create more of a health issue than each one individually. Here's a study that suggests an antagonistic effect between DDT and dieldrin, greater than what would have been predicted by just adding the two individually. Both chemicals have been banned in most developed countries for decades, so I'm wondering about how rigorous this study really is by claiming it as part of the French diet less than 10 years ago, but the implication that individually assessing exposures might be insufficient to accurately determine actual health risks in real world exposures is worth noting. This doesn't mean that .0000843 micrograms/kilogram of imidacloprid and 0.000809 of malathion would necessarily combine to create a health hazard, but scientists have not historically looked much into testing it. Prior plausibility would suggest that it's exceedingly unlikely, but it's a legitimate uncertainty.
On the other hand, glyphosate is the most widely used herbicide in the US, and is considered by the EPA to be a toxicity class III pesticide, "slightly toxic" on a scale where class IV is the least harmful. It's only really harmful if you drink a large amount of it. It doesn't bioaccumulate, and it is not harmful to birds, amphibians, and fish in comparison with older pesticides, particularly if it's a formulation without a surfactant called POEA. It kills a wide variety of plants by disrupting a protein synthesis pathway that is specific to plants, and thus does not exist in mammals. Chronic effects have not been observed in animal studies at levels nearly 300 times the FDA limit. Animal studies thus far suggest that it's not carcinogenic, and the EPA considers it to be as such. It is absorbed poorly through the skin, and roughly 30-36% absorbed through ingestion. Two people poisoned by glyphosate (presumably from attempting suicide) had undetectable levels in their bodies after 12 hours. Small exposures do not add up, and large exposures literally go away in a relatively short time frame. If you're familiar with toxicology and/or science-minded, here's everything you'd ever want to know about it, produced by the National Pesticide Information Center at Oregon State University. The FDA doesn't even monitor glyphosate residue on produce because its level of toxicity doesn't warrant it, but if a test were to show my apple has 0.01% of the FDA level of glyphosate on it, I'm confident that it's going to be just fine. I'd rather we have a food system where we don't use it at all, but there's plenty of more pressing health risks that we ignore than those presented by glyphosate.
Pesticides are an artifact of a larger, unsustainable system, in which a combination of better crop management and alternative pest control methods could and hopefully will help reduce our reliance on them for the environment's sake, as well as the health of farmers, their workers, and their neighbors. Some accumulate in the environment and can cause genuine ecological harm. In large concentrations at high doses, some are very toxic, and can cause some permanent conditions in farm workers who mix and apply them. If you're an expecting mother or have an infant, I think it's perfectly reasonable for physicians to recommend avoiding conventional produce as much as possible just to be safe. Infants don't have fully developed systems for detoxifying compounds like adults do, and it's sound advice to be more aware of pesticide residues.
I'm convinced that people respect and respond to intellectual honesty more than they do fear, because fear so often comes from a not-so-rational place with crucial pieces of the puzzle missing. This opens itself up to an avalanche of conflicting information, which just confuses people and drives them to dig in to their preferred version of reality. People aren't robots, but the tools to avoid all of this are out there. It'd be totally boss if more people were aware of them, and we could confront misconceptions that arise because of how poorly we educate people in chemistry. Now, if we could just do something about all that 2-Oxo-L-threo-hexano-1,4-lactone-2,3-enediol in citrus fruits.
UPDATE 4/26/13: So, this thing is going around a lot lately. It's a paper that claims glyphosate might be behind a whole host of common diseases like inflammatory bowel disease, obesity, depression, ADHD, autism, Alzheimer's disease, Parkinson's disease, ALS, MS, cancer, etc., I guess because it's a "textbook example of exogenous semiotic entropy" (WTF?!). This should raise red flags anyway, but you should really download it just for fun to see if you can make any sense of it. I guarantee you, it won't come easy. It's possibly the most bizarre academic paper I've ever read. Unfortunately, Reuters uncritically covered it, and even called it a "study", which it most definitely is not. It's a review full of pseudoscientific assertions, and although the authors say they did a "systematic review", they clearly don't quite grasp what that means. Which, I suppose, is probably why a paper involving issues of toxicology and biochemistry ends up in a fairly obscure physics and information science journal.
In a word, "no". Just "no".