Best way is to switch over to natural, organic food and clean water. It is very difficult, however because it means that you can never eat outside of your own home without getting back into the preservatives.
The owner of my gym is like this most of the time, he buys only organic meats, fruits, vegetables and grains and drinks pure water (that still has minerals in it). I've started doing it a bit myself, but it is hard to find organic stuff in Canada.
If you think about it enough it will stress you out. there are toxins everywhere, especially in the air we breathe and the food we eat everyday.