Doesn't buying organic mean that pesticides have not been used on food?
Organic food is produced according to certain production standards. For crops, it means they were grown without the use of conventional pesticides, artificial fertilizers, human waste, or sewage sludge, and that they were processed without ionizing radiation or food additives. For animals, it means they were reared without the routine use of antibiotics and without the use of growth hormones.
Increasingly, organic food production is legally regulated. Currently, the US, the European Union, Japan and many other countries require producers to obtain organic certification in order to market food as organic. [Wikipedia
There are other problems as well as cancer that have been linked to pesticide and fertilizer use: premature births, and there are social justice / fair trade implications. Organic crops have been shown to have higher levels of Vitamin C, magnesium and phosphorus[http://www.bbc.co.uk/food/food_matters/organicfood.shtml],
Check this: http://www.organicconsumers.org/
I used to live in a town where fertilizers and pesticides had leached into the local river and canal, causing duckweed to grow like crazy. The fish started to die, and the ducks were left with nowhere to swim and nothing to eat
the council had to manually dredge the river every summer.