Question

The maximum permissible concentration of fluoride in drinking water is

• A. \(0.5\ \mathrm{mg/L}\)
• B. \(1.0\ \mathrm{mg/L}\)
• C. \(1.5\ \mathrm{mg/L}\)
• D. \(2.5\ \mathrm{mg/L}\)

Hint:

BIS drinking water standards: \[ \boxed{ \begin{aligned} \text{Acceptable limit} &= 1.0\ \mathrm{mg/L}\\ \text{Permissible limit} &= 1.5\ \mathrm{mg/L} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Know the two limits BIS sets for fluoride.
Under IS 10500, the desirable or acceptable level of fluoride in drinking water is $1.0\ \mathrm{mg/L}$.
Step 2: Identify the permissible limit.
When no alternate water source is available, the standard allows the concentration to go up to a maximum permissible limit before the water is rejected.
Step 3: Match this to the options.
$0.5$ and $1.0\ \mathrm{mg/L}$ are too low for the permissible cutoff, and $2.5\ \mathrm{mg/L}$ is beyond what BIS allows even in the absence of an alternate source.
\[ \boxed{1.5\ \mathrm{mg/L}} \]