Human biomonitoring for mercury exposure: What is the commonly cited maximum permissible limit of mercury in human blood, expressed in micrograms per 100 c.c. (mL)?

Introduction / Context:
Mercury exposure arises from occupational settings, environmental contamination, and diet (notably methylmercury in fish). Blood mercury concentration is a standard biomonitoring index. Recognising a typical upper permissible limit aids screening and clinical triage.

Given Data / Assumptions:

• Units are micrograms per 100 c.c. (mL), a traditional clinical convention.
• Question targets a widely referenced guideline value rather than a specific jurisdiction’s most recent threshold.

Concept / Approach:
Historical public health references often cite a screening threshold near 7 micrograms per 100 mL for total mercury, above which further evaluation is warranted. While modern guidance may use micrograms per litre and distinguish organic/inorganic species, the offered choices reflect classic textbook values; hence 7 µg/100 mL is the best match.

Step-by-Step Solution:

Verification / Alternative check:
Many screening programs flag results in this vicinity for further assessment of exposure source and neurological symptoms, especially in pregnant individuals due to fetal susceptibility.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing units (µg/L vs µg/100 mL) and speciation (methylmercury vs inorganic) when interpreting laboratory results.

Final Answer:
7