Metals

http://aviationjustice.org/impact/aviation-and-air-pollution/ http://www.scientificamerican.com/podcast/episode/airplane-pollution-needs-to-descend-13-10-06/ http://news.nationalgeographic.com/news/2010/10/101005-planes-pollution-deaths-science-environment/ http://thinkprogress.org/yglesias/2010/11/22/199156/trains-planes-and-pollution/ https://www.edf.org/media/airplane-pollution-danger-public-health-us-epa-says-initial-finding http://www.ceh.org/avgas/