In chronic arsenic poisoning, the MOST diagnostically significant change observed on a transverse section of the hair shaft using neutron activation analysis is:
- A Alternating bands of high and low arsenic concentrations (Mees bands) ✓
- B Uniform high arsenic throughout the full length of the hair
- C Arsenic concentrated exclusively at the hair bulb
- D No arsenic; arsenic does not bind to keratin
Correct answer: A. Alternating bands of high and low arsenic concentrations (Mees bands)
Explanation
Arsenic binds avidly to keratin via sulfhydryl groups; in cases of repeated intermittent dosing, alternating bands of high arsenic (during toxic exposure) and low arsenic (during recovery) are incorporated into hair as it grows (~1 cm/month). These transverse alternating bands seen by neutron activation analysis can be used to reconstruct the time-course of poisoning, analogous to the Mees lines on fingernails. Continuous chronic exposure would produce uniformly elevated levels, not alternating bands.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.