There are several tricks to getting or making clean food. The first and most obvious is to grow it yourself. Unfortunately gardening is time-consuming, and you can't get tomatoes in winter. Some folks can't or won't grow food. Grow what you can when you can, and forgive yourself when you can't. Home-grown tomatoes are one of the great pleasures in life.
If you're not going to grow it yourself, perhaps you have a job that will allow you to buy clean organic produce. There's more of it available all the time. If you have a local source of produce that isn't organic certified but is still cleaner than grocery store produce, use that. Farmer's markets are nice because you can talk to the farmer about what they use to manage pests and weeds.
The plant foods that you should try to buy clean are listed by the environmental working group every year as the "dirty dozen". The 2017 list (below) includes many of our favorite fruits and veggies.
Some contaminants are easier to remove than others. Strawberries are covered in little pores and it is impossible to get the pesticides off (out) of them, so it is important to buy those organic or choose another fruit. Apples are also hard to clean because they can have a coat of parrafin (to make them shiny) that seals in the pesticides. Potatoes may be less important to buy organic if you peel off a good layer and boil them too. Boiling has been shown to remove or destroy some of the contaminants.
A review of the literature reveals that washing your veggies in tap water for 30 seconds actually removes most of the pesticides and fungicides. Unfortunately there are some that water does not remove, including chlorpyrifos (a nerve-gas pesticide) and vinclozolin (a fungicide). Thankfully these are removed by soaking in an acid solution, acetic acid being the most effective. Acetic acid is vinegar. The longer you soak your veggies the more of the chlorpyrifos is removed. My rule is to soak my cherries in a 5% vinegar solution for at least an hour.
Why do we care about chlorpyrifos? You may have heard about it in the news. It was originally developed as a nerve gas by the Nazis. Now it is used as a pesticide because it paralyzes insects. No surprise that it also wreaks havoc on the human nervous system. It was slated to be banned until Trump got elected. It's already banned for indoor use. Dow chemical (the maker of chlorpyrifos) donated a million bucks to Trump's inauguration fund to make sure that their profitable poison would remain legal. The EPA reversed course and this toxin will be sprayed on veggies and golf courses, in spite of the fact that it shrinks and deforms children's brains, lowers their IQs, and is linked to lung cancer and Parkinsons. Chlorpyrifos sticks to fruit even when it's rinsed in tap water.
For the foreseeable future we will need to work to avoid this toxin as best we can. This means seeking clean sources for our produce (gardens, farmer's markets, buying organic), washing it, peeling and boiling what can be peeled and boiled, and soaking plants that we eat with the skin on in a vinegar solution for at least an hour.
If you need a little good news to help wash off the sad feeling about all this poison, below are the kinds of food least likely to be contaminated. =-] Eat more of them.