The Environmental Protection Agency (EPA) is a government agency that works to protect human health and the environment. One of their main concerns is toxins, which are substances that can cause harm to humans and other living things. Emissions from factories and vehicles are another EPA concern, as they can lead to air pollution such as SMOG. SEWAGE is also an EPA concern, as it can contaminate water sources and lead to health risks. The Air Quality Index (AQI) is used to measure air quality, and the EPA is concerned with keeping this number low. The EPA also regulates fuel efficiency standards, measured in miles per gallon (MPG), and works to reduce the presence of pollutants such as polychlorinated biphenyls (PCBs). The EPA also works to promote ecologically sustainable practices, such as the Clean Air Act, and to reduce secondhand smoke.