Winter smog is a complex mixture of various pollutants that can have adverse effects on air quality and human health. Smoke rises from a brick kiln during a smoggy morning in Kathmandu, Nepal. It includes particulate matter, Nitrogen Oxide, Sulfur Dioxide, Volatile Organic Compounds (VOCs), Ground-Level Ozone (O3), Carbon Monoxide (CO), Heavy Metals and Ammonia (NH3).