“Air.” Pollution Causes, Facts, and Solutions to Pollution. N.p., n.d. Web. 20 May 2015.
“Air Pollutants.” EPA. Environmental Protection Agency, n.d. Web. 20 May 2015. <http://www.epa.gov/air/airpollutants.html>
“Air Pollution: MedlinePlus.” U.S National Library of Medicine. U.S. National Library of Medicine, n.d. Web. 20 May 2015. <http://www.nlm.nih.gov/medlineplus/airpollution.html>
“Air Pollution.” - National Geographic Education. N.p., n.d. Web. 20 May 2015. <http://education.nationalgeographic.com/education/encyclopedia/air-pollution/?ar_a=1>
“Going Out On A Limb With A Tree-Person Ratio.” NPR. NPR, n.d. Web. 20 May 2015. <http://www.npr.org/templates/story/story.php?storyid=96758439>
“Water Quality Facts.” — Catawba Riverkeeper Foundation. N.p., n.d. Web. 20 May 2015. <http://www.catawbariverkeeper.org/news/waterqualityfacts>