Bronze sculptures in museum collections are vulnerable to various forms of deterioration due to their material composition and environmental exposure. The most common causes include:

1. Corrosion: Bronze, an alloy of copper and tin, reacts with moisture, oxygen, and pollutants, leading to surface corrosion like verdigris (green patina) or more damaging chloride-induced "bronze disease."

2. Relative Humidity Fluctuations: High humidity accelerates corrosion, while low humidity can cause cracking in patinas. Stable humidity levels (40-60%) are critical for preservation.

3. Airborne Pollutants: Sulfur dioxide, nitrogen oxides, and particulate matter from urban environments can tarnish and corrode bronze surfaces over time.

4. Improper Handling: Physical contact with bare hands transfers oils and salts, accelerating corrosion. Improper cleaning or restoration techniques can also cause irreversible damage.

5. Light Exposure: Prolonged exposure to UV light can degrade organic components in patinas or wax coatings, leading to discoloration.

6. Microbial Growth: In humid conditions, microorganisms can colonize bronze surfaces, contributing to localized corrosion.

To mitigate these risks, museums employ controlled environments, regular inspections, and professional conservation practices to ensure the longevity of bronze artifacts.