Air pollution is a major health concern in many parts of the world. It is especially higher in the winter due to a variety of factors. These include temperature inversions, a decrease in wind speeds, and more burning of fossil fuels. Temperature inversions occur when cold air stays close to the ground and traps pollutants in the air. This can make the air quality worse in urban areas. Wind speeds also decrease in winter, meaning the air is not moved around and pollutants are not dispersed. Lastly, burning fossil fuels releases more pollutants into the air, which is especially problematic in cold weather due to the increase in home heating.