Biological Exposure Indices (BEIs) in occupational health differ from Threshold Limit Values (TLVs) in that:
- A TLVs measure the concentration in biological fluids while BEIs measure air concentration
- B BEIs are legally enforceable while TLVs are only advisory
- C BEIs reflect internal dose (biological matrices — blood, urine, exhaled air) integrating all routes of exposure, while TLVs measure only airborne workplace exposure ✓
- D BEIs apply only to carcinogens, TLVs apply to all chemicals
Correct answer: C. BEIs reflect internal dose (biological matrices — blood, urine, exhaled air) integrating all routes of exposure, while TLVs measure only airborne workplace exposure
Explanation
TLVs (Threshold Limit Values, set by ACGIH) are maximum permissible airborne concentrations in the workplace and measure only inhalation exposure. BEIs (Biological Exposure Indices) measure the chemical or its metabolite in biological matrices (urine, blood, exhaled air) and integrate ALL routes of exposure — inhalation, skin absorption, and ingestion. For chemicals with significant dermal absorption (e.g. organophosphates, aromatic amines), BEIs are more reliable indicators of actual internal dose than TLVs alone.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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