**Core Concept**
Prolonged exposure to certain chemicals, such as those found in textile dyes, can lead to occupational hazards, including the risk of bladder cancer. Workers in the textile industry are at an increased risk of developing bladder cancer due to their prolonged exposure to aromatic amines, a class of chemicals used in textile dye manufacturing.

**Why the Correct Answer is Right**
The patient's prolonged exposure to textile dyes, particularly aromatic amines, increases his risk of developing bladder cancer. A urine examination would be an appropriate screening tool for detecting bladder cancer in this patient. This is because the urine can be tested for the presence of hematuria (blood in the urine) and other abnormalities, which can be indicative of bladder cancer. The examination can also detect the presence of p-terophenol, a metabolite of aromatic amines.

**Why Each Wrong Option is Incorrect**
**Option A:** Pulmonary function tests are not directly related to the risk of bladder cancer associated with textile dye exposure.
**Option B:** Liver function tests are not the primary investigation for detecting bladder cancer or its associated risks.
**Option D:** Complete blood count is not specific for detecting bladder cancer and is more commonly used to evaluate for infections, anemia, or other conditions.

**Clinical Pearl / High-Yield Fact**
Workers in the textile industry, particularly those exposed to aromatic amines, are at an increased risk of developing bladder cancer. A urine examination is a simple and effective screening tool for detecting bladder cancer in these high-risk individuals.

**Correct Answer:**
✓ Correct Answer: C. Urine examination