Head of scalp has 1 to 1.5 lakhs hair . 100 hair per day are shed normally. So,wearing helmet does not cause hair fall. Air pollution may lead to chemical damage of the hair in the long run. Shampoo twice weekly with a milder shampoo. Condition hair with coconut oil or a hair conditioner twice weekly. Wearing helmet or cap will protect you from pollution and ultra violet light. Please clean the inner side of helmet properly to prevent fungal infection and dandruff.