1. World Health Organization2019 https://www.who.int/airpollution/ambient/health-impacts/en.
2. United States Environmental Protection Agency2019 https://www.epa.gov/criteria-air-pollutants.
3. United States Environmental Protection Agency EPA2014 https://blog.epa.gov/2014/03/03/cleaner-cars-cleaner-fuels-and-a-cleaner-bill-of-health/#more-26565.
4. United States Environmental Protection Agency EPA2019 https://www.epa.gov/clean-air-act-overview.
5. Air Resources Board California2019 https://ww2.arb.ca.gov/our-work/programs/low-emission-vehicle-program.