While the potential health risks of pesticides on produce are still being debated, it doesn't hurt to take precautions now to safe-guard your well-being. Recently I read an article listing the worst tainted produce items.
From worst to least (relatively speaking), the most tainted are:
3. Bell Peppers
10. Grapes (imported)
Some precautions you can take:
1) Choose organic produce whenever possible.
2) Wash/scrub/rinse all produce with a vegetable scrubber.
3) Use special produce soap when possible, or rinse the produce off with a mixture
of water and vinegar.
Here's a handy wallet guide you can download or copy to your iPhone to use while shopping.