MTBE (methyl tert-butyl ether) is a chemical compound that has been used as a gasoline additive to increase the oxygen content and reduce air pollution, known as a type of a volatile organic compound (VOCs) that can contaminate water sources through spills and leaks from underground storage tanks or pipelines. MTBE is known to be toxic to humans at high levels of exposure and is classified as a possible human carcinogen by the International Agency of Research of Cancer (IARC). It can also cause taste and odour problems in drinking water even at low levels, leading to MTBE as a gasoline additive being phased out in many countries due to concerns about its potential health and environmental effects, especially in water sources.