These days, it’s pretty easy to look around on the Internet and find lists of the best and worst fruits and vegetables ranked by the level of pesticide contamination. Look, we have one, too.

And they’re pretty much all based on the same study from the United States Department of Agriculture (USDA). But, have you ever wondered which pesticides are the worst? That’s what we’re here to find out.

Unsurprisingly, that information can also be found in the same study, the Pesticide Data Program. Roughly every year, the USDA tests a mix of domestic and imported food products for their pesticide levels, including fresh, canned, and frozen produce, meat and poultry, grains, water, and oddly, catfish. Samples are collected from states around the country, representing a majority of the population, and the results are then weighed against the Environmental Protection Agency’s (EPA) established thresholds for pesticide residues.

The one bit of good news is that, at least for 2010, which is the latest year examined, the results were within acceptable standards on the whole. Although, whether you feel like the EPA’s standards are safe enough for you is a personal (and perhaps, even political) decision.

But because the food you find at the supermarket comes increasingly from other countries (the Congressional Research Service estimates imports of fruits and vegetables alone have risen roughly 6 percent each year since 1990, with more than half the imports coming from Mexico, Canada, and Chile), we supplemented the government’s list with some information relevant on a more international scale.

The Stockholm Convention on Persistent Organic Pollutants (organic, here, is not used in the "good" sense), a treaty aimed at reducing the worldwide use of certain persistent and pervasive toxic chemicals, has been ratified by 177 countries and went into effect May 17, 2004, drafted and adopted with the support of the United Nations Environment Program. Notably, the United States is not a party to the convention. However, the reduction in the use of such chemicals by other countries who are party to the treaty still has a significant impact on Americans.

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Not only do these pesticides make their way into our imported food, but some of them also travel readily and easily through the atmosphere. Many of these pesticides are a great cause of concern for several other reasons — they accumulate in increasing concentrations as they move up the food chain, attaching themselves to the fatty tissues of people, livestock, and other animals; they also tend to persist in the environment for a very long time and often contaminate sources of fresh water; and they are associated with a host of health issues, including disruption of mental and physical development, cancer, and weakening of immune systems.

And Americans clearly care: In the wake of the economic downturn, sales of organic food have continued to climb. According to the latest report from the Organic Trade Association, sales of organic food (domestic and imported) totaled $31.5 billion in 2011, up 9.5 percent from the prior year. It looks like there are plenty of Americans who, amid growing concerns about the impact of pesticides and conventional farming practices on their health and on the environment, have made eating greener and healthier a priority.

To borrow an oft-used cliché (only because it fits), that’s certainly food for thought.

Diphenylamine (DPA), a fungicide, was found in 82.7 percent of the apples sampled by the USDA in the latest iteration of their Pesticide Data Program report. Apples are notorious for their pesticide content; the same analysis found more than 40 pesticides remaining on a typical apple after 10 seconds of washing. DPA can accumulate in the kidneys, liver, and bladder and cause damage in the long-term.

This pesticide works against pests like termites, grasshoppers, rootworm (which affects corn), but it is also toxic to birds, fish, and people (5 grams is all that is needed to kill an adult male). Aldrin finds its way into meat and dairy products.

Not to incite paranoia, but it’s in the air and it’s everywhere. (The Mayans are coming for us anyway.) This chemical is used to deal with termite problems and is used on a wide variety of crops. It persists in the environment for a long time; its half-life (the time it takes for a substance to decay to half its original mass) is one year. It impacts the immune system and is a potential carcinogen. Chlordane is primarily airborne, however, and studies have found chlordane in homes in the United States and Japan.

Although the use of this chemical has been banned in the United States, it is still widely used as a treatment against mosquitoes carrying malaria in various countries. And just because it isn’t sprayed on crops in this country anymore doesn’t mean that we aren’t still impacted by it. The patina of DDT residue has been found in areas as far-reaching as the Arctic, and the Stockholm Convention maintains that DDT "has been detected in food from all over the world."

Endrin is used on grain crops to help eliminate rodents. It does break down in the body, meaning it doesn't bind to fatty tissues like many of these other pesticides. However, it remains in the environment for a very long time; its half-life is 12 years. And it is lethal to fish.

Added to the list of Persistent Organic Pollutants when the Stockholm Convention reconvened in 2009, endosulfan is a pesticide used to eliminate tsetse flies, parasites, and other pests from a variety of crops, most notably coffee, rice, sorghum, and soy. It has been in use since the 1950s. Argentina, Australia, Brazil, China, India, Mexico, Pakistan, and the United States are the top users of endosulfan and utilize approximately 15,000 tons of this chemical each year. Endosulfan is associated with birth defects, impaired mental function, and even death in farmers and villagers in close proximity who have been exposed in high concentrations.

See the slideshow of all 12 hidden poisons here

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