In drinking water, recommended fluoride level is_____ ppm

Ans. b (0.5-0.8 ppm) (Ref. Park's textbook of PSM - 22nd/511, 582)# The permissible concentration of fluorides in drinking water is0.5 to 0.8 mg/L# Drinking water is known to protect gainst dental caries with Fluoride content at about1 mg/litre# "Mottling of dental enamel" reported at levels above1.5 mg/L intake.# Endemic fluorosis has been observed when the drinking water contain excess fluorine i.e.3-5 mg/L# Skeletal Fluorosis/Genu valgum is observed when the lifetime daily intake of fluorine is of>3.0-6.0 mg/L.ENDEMIC FLUOROSIS# Certain parts e.g., Andhra Pradesh, Punjab, Haryana, Karnataka, Kerala, and TN are known for endemic flurosis.# Dental Fluorosis: Ingested during the years of tooth calcification essentially during the first 7 years of life.# Mottling is best seen on the incisors of the upper jaw.# Prevention: Changing the water source.# Nalgonda technique for defluoridation of water.The presence of following chemicals in excess of prescribed limits may constitute ground for rejection of the water as a source of public water supply:A. Inorganic constituents:# Arsenic: recommended maximum limit of concentration is 0.01 mg/L.# Cadmium 0.003 mg/L maximum limit.# Chromium# Cyanide: maximum limit 0.07 mg/L.# Fluoride Should not be more than 1.5 mg/L# Lead# Mercury: 0.001 mg/L minimum upper limit. Bacterial plate count on yeast extract agar after incubation at 22degC for 7 days might serve as the best general-purpose indicator of microbiological quality.# Selenium# Nitrite and Nitrate: When nitrate level in drinking water exceeds 50 mg/L, methemoglobinemia may occur; most susceptible are bottle-fed infants of less than 3 months. Nitrate is good indicator for past contamination.B. Organic constituents# Polynuclear aromatic hydrocarbons and Pesticides