It is always encouraged to have a balanced diet with lots of fruits and vegetables as they are rich in vitamins, antioxidants and nutrients.
They seem to be the healthiest option.
However, there is the “Dirty dozen” and “Clean fifteen” lists. Those are the two lists published every year by Environmental Working Group (EWG) which shows the fruits and vegetables which are most contaminated by pesticides (Dirty Dozen) and those which have the lowest traces of pesticides (Clean Fifteen).
It is advised to get to know both lists as they are useful when doing grocery shopping. It is recommended to buy organic (when affordable) those vegetables and fruits which are on the Dirty dozen list and conventional when the fruits and vegetables are on the Clean Fifteen list.
How does the EWG check this? They wash/peel the fruits and vegetables the way customer would, if they were to consume the product and they check the concentration of pesticides.
When EWG refers to Dirty Dozen, they refer to 12 dirtiest crops that farmers use most pesticides on. The list is below.
It is very important because as much fruits and vegetables are great sources of vitamins and minerals there is lots of pesticides being used to grow them. When we are exposed to pesticides in high doses it can lead to various health issues.
In 2013 National Centre of Biotechnology noted “There is a huge body of evidence on the relation between exposure to pesticides and elevated tole of chronic diseases such as different types of cancers, diabetes, neurodegenerative disorders like Parkinson, Alzheimer & amyotrophic lateral sclerosis (ALS), birth defects and reproductive disorder.”
More on EWG website
2. Sweet corn
4. Frozen sweet peas
15. Honeydew melons