Which of the following is a factor contributing to extrinsic aging?

Extrinsic aging refers to the aging process that results from external factors rather than the body's internal biological clock. All the options listed—pollution, sun exposure, and smoking—are well-documented contributors to extrinsic aging.

Pollution can lead to the formation of free radicals and oxidative stress, which negatively affect skin health. Pollutants can damage the skin barrier, increase inflammation, and contribute to the appearance of fine lines and wrinkles.

Sun exposure is a significant factor in extrinsic aging, primarily due to ultraviolet (UV) radiation. UV rays can cause photoaging, characterized by skin roughness, discoloration, loss of elasticity, and the formation of age spots and wrinkles. Protecting the skin from sun exposure is essential for maintaining its youthful appearance.

Smoking accelerates the aging process by reducing blood flow to the skin, leading to a decrease in oxygen and vital nutrients. The harmful toxins found in cigarettes can also damage collagen and elastin, which are crucial for skin's strength and elasticity. Smokers often develop premature wrinkles, particularly around the mouth and eyes.

Given that all these factors contribute to extrinsic aging, the correct answer encompasses the full range of these external influences on the aging process.