Welcome to the study of environmental science. One of the most critical topics in this field is the quality of the air we breathe. Air pollution is officially defined as “the presence in the atmosphere of any substance (or combination of substances) that is detrimental to human health and welfare; offensive or objectionable to man, either externally or internally; or which by its presence will directly or indirectly adversely affect the welfare of man.” These harmful substances are known as air pollutants.

While a significant amount of air pollution occurs from natural events like volcanic eruptions and soil erosion, the pollutants that pose the greatest threat to our health and cause the most damage to property are primarily the result of human activities. These activities include the burning of fuel for heat and power, the processing of materials to create food and goods, and the disposal of waste.

To make sense of the many different pollutants in our atmosphere, scientists group them into categories. This guide will help you understand the fundamental types of air pollutants by exploring how scientists classify them.