Latest from the Environmental Working group on which produce is worst and best to buy "conventional". Organic is always best but sometimes people can't find it, what to do? Try to stay away from the dirty dozen if possible, but personally I'd still eat dirty produce over McDonald's, etc. And if you have to get it, wash it really well! Subsequent washings/rinsings with a complete drain-off in between has been shown to be more effective than a single long wash/rinse.
Here is an article on washing produce:
Also, I would tend to soak, dump, rinse, drain fully, and repeat 3 times to get the maximum removal of whatever. Subsequent rinses have been shown to be more effective in removing contamination. I cannot find an article for this at the moment, but remember it from when I worked in chemistry.