Drinking-Water Metals (BIS) — What is the maximum desirable limit for lead (Pb) in potable water as per typical BIS specifications?

Introduction:
Lead is a toxic heavy metal with serious health impacts. Drinking-water standards set stringent limits to protect public health. This question asks for the maximum desirable limit commonly cited in legacy BIS-aligned exam material, recognizing that jurisdictions periodically update values based on risk assessments.

Given Data / Assumptions:

• We refer to widely used values historically taught in many Indian water-quality courses.
• Units are mg/L (milligrams per liter).
• “Maximum desirable limit” denotes the target value for treated water.

Concept / Approach:

Legacy BIS references frequently cite 0.05 mg/L as the limit for lead in potable water in exam contexts. Many modern guidelines (for example, WHO) have moved toward tighter limits; however, within the scope of this question bank and options provided, 0.05 mg/L is the recognized answer. Always consult the latest standard for design and compliance, as regulatory values may change with new evidence.

Step-by-Step Solution:

Verification / Alternative check:

Past syllabi and solved papers often use 0.05 mg/L; engineering design should verify current BIS/IS 10500 editions for the most up-to-date requirement.

Why Other Options Are Wrong:

B–D are higher than typical health-protective limits. E is also too high and not aligned with potable standards.

Common Pitfalls:

Memorizing a single number without checking the latest code revision. Standards evolve; designers must confirm current values before specification.

Final Answer:

0.05 mg/L