1. Apples: They're currently the top offender on the non-profit Environmental Working Group's "Dirty Dozen" list of most-polluted produce (celery — see page 2 — and strawberries are the next biggest offenders).
The organization says 98 percent of conventional apples contain pesticide residues. You can buy certified organic instead, but also consider patronizing small producers who follow the same ethos without the cost-boosting paperwork.
Certified organic products are produced without use of most conventional pesticides. Plus, the organic standards prohibit use of irradiation, sewage sludge, synthetic fertilizers and genetically modified materials, while animals must be given no antibiotics or growth hormones.
If farmers market vendors say their food is "spray-free" or "pesticide-free" or "hormone-free," ask what that means. It may tack on an extra 10 to 20 percent to the price, but it may be worth it.
2. Salmon: Farmed Atlantic salmon is a few dollars per pound cheaper than wild-caught Pacific salmon, but it's also been linked to high levels of PCBs and antibiotics overuse. Wild salmon is pricier but cleaner; the canned version is budget-friendly, going for around $3 at Trader Joe's. Frozen salmon is also fine.
3. Milk: If worries about overuse of antibiotics in animals don't make you go organic (organic milk can cost half-again as much as conventional milk), at least look for labels that specify cows have not been treated with rBST. This is a hormone used to increase milk production; it's banned in the European Union and Canada.
The American Cancer Society says it's "not clear" whether milk produced using the hormone adds to the risk of cancer, taking no stand on its use, but notes that it does cause health problems for cows. Milk from smaller farms, which might pasteurize at lower temperatures or use grass-fed cows, can also taste far less bland than big brands.
4. Ground beef: By some counts, up to 70 percent of ground beef in the nation contains the filler dubbed "pink slime"-fatty scraps that have been heated and centrifuged to separate out lean bits of meat and treated with ammonium hydroxide.
The USDA says this is safe to eat, and companies aren't required to list it as an ingredient. But the ick factor is still causing an uproar. To avoid it, go for certified organic beef, or meat from local producers who don't use national processing plants. Another option is to ask your local market to grind your beef from whole cuts, which also helps you avoid other health worries.