We require air to survive, but a lot of human activity has contributed to air pollution. This can be indoors air pollution and outdoor air pollution – these usually come from slightly different sources.
Air pollution can be natural – from volcano eruptions, dust storms, pollen and wildfires. It can also be anthropogenic (made by humans) – this includes pollution from vehicles, power generation, chemical use in manufacturing and certain services, and other sources.
Outdoor air pollutants include exhaust from automobiles, heat and power generation, emissions from manufacturing plants, and so on. Read about major pollutants here – https://www.who.int/airpollution/ambient/pollutants/en/. Be sure to click through all of the pollutant types on the bottom of the page.
These pollutants have a harmful effect on human health, including lung health, headaches, cardiovascular disease, and even outcomes of pregnancy. Read more here https://www.niehs.nih.gov/health/topics/agents/air-pollution/index.cfm.
You can check the air quality index here https://airnow.gov/ and be aware that heat makes poor air quality effects worse. If you have asthma or other lung problems or if you like to exercise outdoors, check the air quality index, especially on very hot days.
