The EWG (Environmental Working Group, based in USA) researched the amount of pesticides found in some of the most common foods, and found certain foods have a higher amount of pesticides in them.
The Clean Fifteen is a list of foods that have the lowest trace pesticides found in them. These foods are safe to eat, even if they are non-organic. The only thing to be worried about here is the corn, and if you eat corn, try to buy organic non-GMO corn. It is safe to buy corn grown in Saudi Arabia because Saudi Arabia has banned any growth of GMOs. (GMOs destroy ecosystems, the environment and also the farmer. Studies have shown there is a relation between GMO and cancer too. Source )
The Dirty Dozen is a list of foods that have high amounts of trace pesticides. Where possible, you should buy these organically.
A suggestion to reduce some of the pesticides in these vegetables is to soak these in vinegar and peel them before you eat them. Place the vegetables in a bowl and then cover with the vinegar and water solution. The suggestion is one cup of vinegar to five liters of water.
To see the full list of 48 fruits and vegetables ranked from highest to lowest in pesticides, click here.
For more information on The Environmental Working Group, please visit their website.