Hi, i'd like to ask that what sorts of harm will happened if potassium permanganate in vegetable wash ?

Depends: None if you wash out the chemical before use. Using potassium permanganate in the wash will not make it safer either. Just wash the vegetables with clean potable water. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.