**Core Concept**
Mercury poisoning is a well-documented occupational hazard, particularly in dentists who use amalgam fillings. **Mercury exposure** can lead to a range of systemic and neurological symptoms due to its toxic effects on various organs and tissues.

**Why the Correct Answer is Right**
The patient's elevated urine mercury level indicates mercury exposure, which can cause tremors, a classic symptom of **mercurialism**. Mercury poisoning affects the nervous system, leading to tremors, muscle weakness, and coordination problems. The patient's prolonged exposure to mercury as a dentist has likely contributed to his symptoms. Mercury also affects the kidneys, leading to elevated urine levels.

**Why Each Wrong Option is Incorrect**
* **Option A:** Kidney failure would be a more severe consequence of mercury poisoning, not a specific symptom.
* **Option B:** While memory loss can be associated with neurological disorders, it is not a direct consequence of mercury poisoning.
* **Option D:** Seizures are not a typical symptom of mercury poisoning; tremors and muscle weakness are more characteristic.

**Clinical Pearl / High-Yield Fact**
Mercury poisoning is a preventable occupational hazard in dentists. **Proper ventilation** and **personal protective equipment** can significantly reduce the risk of mercury exposure.

**Correct Answer:** C.