<prompt> Permissible level of fluoride in drinking water as per WHO is:0.5 mglitre1.0 mglitre1.5 mglitre2.5 mglitre  <response>: As per WHO, permissible limit of fluoride in drinking water is 1.5 mg litre. As per Bureau of Indian Standards BIS, it is 1 mg litre. Dental fluorosis has been repoed with exposure to levels 1.5 mg litre. Skeletal fluorosis has been repoed on exposure between 3 to 6 mg litre. Ref: Park, 21st Edition, Page 668 