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Research has shown it’s the mechanical action of rubbing produce under water that removes residues.

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The Question

Is rinsing fruit and vegetables under water effective at removing pesticides? Should I use a store-bought produce wash instead? Are there some fruits and vegetables that, no matter how I clean them, I should buy organically grown?

The Answer

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There is a growing concern among Canadians about consuming synthetic pesticide residues in food.

According to a 2013 survey commissioned by the Pierre Elliott Trudeau Foundation, half of Canadians believe that food pesticides – along with air pollution and chemical contaminants – pose a major risk to health.

Based on data from the Canadian Council of Food and Nutrition, that's up from 13 per cent who cited pesticide residues as a food safety concern in 2006.

Pesticides are chemicals – synthetic or derived from natural sources – that kill unwanted insects, plants, fungi and other potentially harmful pests. They're used to protect our food supply.

Many scientists and watchdog groups worry that pregnant and breastfeeding women, infants and young children are most vulnerable to the harmful effects of synthetic pesticide residues, especially during critical periods of development.

In 2012, the American Academy of Pediatrics issued a report that cited research linking pesticide residues early in life to attention deficit hyperactivity disorder, cognitive deficits, birth defects and childhood cancers.

It's not surprising, then, that many people try to minimize their intake of pesticide residues on foods, especially women of child-bearing age and parents of young children.

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But it's not necessary to spend money on expensive fruit and vegetable washes to do so. Rinsing vegetables with plain water is just as effective at reducing these contaminants.

Research conducted at the Connecticut Agricultural Experiment Station in 2000, for instance, compared three methods of removing nine different pesticide residues from 196 samples of lettuce, strawberries and tomatoes.

Seven treatments were applied to each sample: four brands of a commercial fruit and vegetable wash, a dilute dish soap (Palmolive) solution and rinsing under tap water for one minute.

Rinsing under tap water worked just as well as fruit and vegetable washes to significantly reduce the residues studied.

And it wasn't because pesticide residues dissolve in water. According to the researchers, it's the mechanical action of rubbing produce under water that removes residues.

Rinsing reduces pesticides on the surface of fruit and vegetables, but it can't remove those that are absorbed by the roots and make their way into the plant's tissue.

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Should you trade in conventional produce for organically grown fruit and vegetables then? Studies do show that people who eat organic produce have lower levels of pesticide metabolites in their urine than people who eat conventionally grown produce.

Organic foods are grown and harvested without the use of synthetic pesticides and fertilizers. If needed, organic farmers used pesticides derived from natural sources. (Organic foods are also produced without growth hormones, antibiotics, genetically modified organisms, irradiation and artificial additives.)

According to the Environmental Working Group (EWG), a non-profit environmental research group based in Washington, there are certain fruits and vegetables that you should consider buying organically grown (if you're willing to spend the extra money).

Each year, the watchdog group ranks pesticide contamination in popular fruits and vegetables to help consumers choose produce with the fewest pesticide residues. The EWG's "Dirty Dozen" list highlights produce available in the United States with the highest number and concentrations of pesticides.

The list is compiled by analyzing data from the U.S Department of Agriculture's annual national pesticide residue monitoring program that tests fruits and vegetables "as eaten." That means produce samples are thoroughly washed and, if applicable, peeled, before testing for pesticides.

The 2015 Dirty Dozen includes apples, peaches, nectarines, strawberries, grapes, celery, spinach, sweet bell peppers, cucumbers, cherry tomatoes, imported snap peas and potatoes. (Unless stated, results are for domestic and imported produce combined.)

Kale, collard greens and fresh hot peppers didn't make it to the Dirty Dozen list but they did end up on the Dirty Dozen Plus list because they contained trace levels of pesticide residues considered highly toxic.

If you eat these foods often, the EWG recommends choosing their organic counterparts, especially kale, collard greens and hot peppers. If you can't find organic – or they're too expensive – eat leafy greens and hot peppers cooked since pesticide levels typically diminish during cooking.

Even if produce is organic it doesn't mean it's free of synthetic pesticide residues. Chemicals sprayed on conventional crops can unintentionally drift onto nearby organic farms and contaminate the soil and water. Still, past studies have found that the quantity and frequency of pesticide residues showing up on organic produce is considerably lower than on non-organic produce.

Earlier this year, Consumer Reports Food Safety and Sustainability Center released similar guidelines to the EWG after analyzing 12 years of USDA pesticide data. Based on the number and concentration of pesticides found, and their toxicity, fruits and vegetables were ranked from very low to very high risk, based on the risk to a three-year-old.

For produce deemed high-risk, Consumer Reports recommended buying organic versions or low-risk conventional versions based on the country where it was grown.

Buying organic foods is a personal choice based on availability, price, taste and personal values.

Keep in mind that the health benefits of eating a diet plentiful in fruits and vegetables outweigh the potential risks of pesticide residues. So don't stop eating produce on the "Dirty Dozen" list.

Whether you eat conventional or organic produce, rinse it with water to remove pesticide residues, dirt and bacteria.

Produce with a tough rind or peel (e.g., carrots, melon, cucumbers, potatoes, squash) should be scrubbed with a clean brush under water. Throw away outer leaves on leafy vegetables such as lettuce, spinach, kale, collards and cabbage.

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.

Dirty dozen (plus)

Produce available in the United States found to contain the highest number and concentrations of pesticides. Unless stated, results are for domestic and imported produce combined.

1. Apples

2. Peaches

3. Nectarines

4. Strawberries

5. Grapes

6. Celery

7. Spinach

8. Sweet bell peppers

9. Cucumbers

10. Cherry tomatoes

11. Snap peas – imported

12. Potatoes

+ Hot peppers

+ Kale/collard greens

The clean fifteen

Produce least likely to hold pesticide residues; few pesticides were detected and in low concentrations.

1. Avocados

2. Sweet corn

3. Pineapples

4. Cabbage

5. Sweet peas, frozen

6. Onions

7. Asparagus

8. Mangoes

9. Papayas

10. Kiwi

11. Eggplant

12. Grapefruit

13. Cantaloupe

14. Cauliflower

15. Sweet potatoes

From the Environmental Working Group's 2015 Shopper's Guide to Pesticides in Produce

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