The two “hottest” contaminants today are fuel additives that have found their way into ground water supplies all across the country - perchlorate and methyl tertiary butyl ether (MTBE). Rocket Science: The most recent chemical on the EPA's radar screen as a possible health risk in drinking water is perchlorate. Most of the perchlorate manufactured in the United States, about 90 percent, is used as the primary ingredient of solid rocket propellant - rocket fuel for military missiles and the NASA space shuttle. The rest is used in fireworks, safety flares, matches and car air bags. Waste from the manufacture and improper disposal of perchlorate-containing chemicals increasingly are being found in soil and ground water. It is very water-soluble and does not biodegrade easily.