Which foods should you buy organic?

Many of us are trying to take steps to care for our health, but the price of organic vegetables and fruits can be so high that many people can't afford to go completely organic all the time.

Enter the Environmental Working Group's latest update to the annual Shopper's Guide to Pesticides in Produce. This simple list breaks down the "Dirty Dozen" -- the 12 fruits and vegetables found to contain the most pesticide residue. If you are trying to avoid pesticides, it may be worth it to shell out the extra cash to buy these items organic.

If, on the other hand, a product made the "Clean Fifteen" list, it has been found to contain the least amount of chemical residue, and buying these items organic may not be as critical.

Here are some key findings of the 2015 review (the full list is below):

• Pick organic apples. If there's anything to consistently buy organic, it's apples. Last year, one report showed that 80 percent of apples sold in the United States were contaminated with a chemical called diphenylamine (DPA), and it hasn't changed much since then. DPA is deliberately applied to the fruit to keep the skin looking vibrant and prevent spotting.
• Save your cash on avocados and pineapples. EWG lists avocados as the cleanest: Only 1 percent showed any detectable pesticides. And 89 percent of pineapples had zero residues.
• Spring for organic leafy greens. For the past few years in a row spinach has made the Dirty Dozen list, and it's back on it this year. While kale and collard greens did not meet the criteria, they were added to what EWG calls the "Dirty Dozen Plus" list because they were found to contain trace levels of insecticides that can be toxic to the human nervous system. So, if your diet includes lots of leafy greens, you may want to look for the USDA organic seal.

Consumer demand for organically produced food is increasing dramatically. USDA economists reported that organic produce sales spiked from $5.4 billion in 2005 to an estimated $15 billion last year. Still, EWG found that consumers are often ingesting pesticides with their conventionally-grown produce.

Nearly two-thirds of the 3,015 produce samples tested by the U.S. Department of Agriculture in 2013 contained pesticide residues, the EWG reports.

The Shopper's Guide to Pesticides in Produce ranks pesticide contamination on 48 popular fruits and vegetables based on an analysis of more than 34,000 samples taken by the U.S. Department of Agriculture and the Food and Drug Administration. The produce is washed and peeled to mimic what a consumer would do before it's tested.

Once EWG compiles the data, analysts classify fruits and veggies into two lists that reflect the overall pesticide loads of the most common fruits and vegetables.

Here are the EWG's 2015 "Dirty Dozen" and "Clean Fifteen":