**Question:** Which of the following causes malignant mesothelioma?

- A. Asbestos exposure
- B. Silica exposure
- C. Radiation exposure
- D. Human papillomavirus (HPV) infection

**Core Concept:** Malignant mesothelioma is a type of cancer that develops from mesothelial cells, lining various organs like the lungs, heart, and abdomen. This disease is primarily caused by environmental factors.

**Why the Correct Answer is Right:** Asbestos exposure is the primary cause of malignant mesothelioma. Mesothelial cells lining the lungs, heart, and abdomen are highly susceptible to asbestos fibers, which can lead to chronic inflammation, tissue scarring, and eventually malignant cell proliferation.

**Why Each Wrong Option is Incorrect:**

A. Silica exposure: Although silica can also cause lung fibrosis and inflammation, it is not as strongly linked to malignant mesothelioma as asbestos.
B. Radiation exposure: While radiation can cause cancer, its association with malignant mesothelioma is weaker than that of asbestos.
D. Human papillomavirus (HPV) infection: HPV is primarily associated with cervical, anal, and oropharyngeal cancers, not malignant mesothelioma.

**Clinical Pearl:** Malignant mesothelioma is a preventable disease. Asbestos was widely used in construction and manufacturing before its harmful effects became evident. Nowadays, avoiding asbestos exposure is crucial to prevent this disease.

**Correct Answer:** Asbestos exposure (Option A) is the primary cause of malignant mesothelioma. Asbestos fibers are known to cause chronic inflammation, tissue scarring, and eventually malignant cell proliferation in mesothelial cells that line various organs.