The Environmental Watch Group (EWG ) singles out produce with the highest pesticide loads for its Dirty Dozen™ list every year. Each of these foods tested positive for a number of different pesticide residues and showed higher concentrations of pesticides than other produce. These produce should be bought organic if possible.
For 2017, the list includes:
Sweet bell peppers
The Dirty Dozen Plus: The Plus category highlights types of food that contain trace levels of highly hazardous pesticides. Leafy greens like kale and collard greens and hot peppers etc do not meet traditional Dirty Dozen™ ranking criteria but were frequently found to be contaminated with toxic pesticides. EWG recommends that people who eat a lot of these foods buy organic instead. The entire list of fruits and vegetables with pesticide residue can be found here: https://www.ewg.org/foodnews/list.php