What would halache on modern vegetables and fruits which are now sometime sick or covered in pesticides or had been grown with polluted water ?

I had recently warned at a religious shop that the content of fruit and vegetables are kisher but not their exterior- they explained that you have to remove the skin of what they sell ( apples, tomatoes , cucumbers , bananas etc) .

I had not thought about before but now that we have pesticides and growing vegetables and fruits with sewer water it does seem you need more than just to search for insects or to wash them with a brush.