The maximum amount of mercury vapour allowed in the work place:
**Core Concept**
The question is testing the knowledge of occupational safety and health guidelines for mercury exposure in the workplace. Mercury vapour is a toxic substance that can cause neurological, renal, and immunological damage. The permissible exposure limit (PEL) is a regulatory limit set by occupational health authorities to protect workers from the adverse effects of hazardous substances.
**Why the Correct Answer is Right**
The correct answer is based on the guidelines set by the Occupational Safety and Health Administration (OSHA) in the United States. The PEL for mercury vapour is 0.05 mg/m³, which is the maximum amount of mercury vapour allowed in the workplace. This limit is based on the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for mercury vapour. Prolonged exposure to mercury vapour above this limit can cause serious health problems, including neurological damage, kidney damage, and respiratory problems.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is below the recommended PEL, and it is not a realistic or practical limit for workplace exposure.
**Option B:** This option is incorrect because it is above the recommended PEL, and it would pose a significant risk to workers' health.
**Option C:** This option is incorrect because it is a different unit of measurement (ppm) and does not match the PEL for mercury vapour.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the PEL for mercury vapour can vary depending on the country and region. Additionally, workers in industries that handle mercury, such as dental offices, laboratories, and manufacturing plants, should be aware of the risks associated with mercury exposure and take necessary precautions to minimize their exposure.
**Correct Answer: 0.05 mg/m³**