Question

Choose the correct statment(s):

• A. The $F^{–}$ ions can make the enamel on teeth harder.
• B. $F^{–}$ ion concentration above 2 ppm causes brown mottling of teeth.
• C. Excess fluoride (over 10 ppm) causes harmful effect to bones and teeth.
• D. Excess of lead concentration (>50 ppb) in drinking water can cause damage to liver , reproductive system

Answer 1

Answer: (A), (B), (C), (D)

Excess of lead concentration (>50 ppb) in drinking water can cause damage to liver , reproductive system

Chemicals in drinking water	Prescribed upper limit	Adverse effects
Lead	50 ppb	can damage kidney,liver, reproductive system
Sulphate	>500 ppm	laxative effect
Nitrate	50 ppm	methemoglobinemia (‘blue baby’ syndrome).

The $F^{–}$ ions make the enamel on teeth much harder by converting
hydroxyapatite, $\left[3\right(C{a}_3(PO4{)}_2.Ca(OH{)}_2]$, the enamel on the surface of the teeth, into much harder fluorapatite $\left[3\right(C{a}_3(PO4{)}_2.Ca{F}_2]$
$F^{-}$ ion concentration above 2 ppm causes brown mottling of teeth.
Excess fluoride (over 10 ppm) causes harmful effect to bones and teeth.