The United States Environmental Protection Agency (EPA) maintains and approves test methods, which are approved procedures for measuring the presence and concentration of physical, chemical and biological contaminants; evaluating properties, such as toxic properties, of chemical substances; or measuring the effects of substances under various conditions.
[1][2] There are other types of methods such as the ASTM and United States Pharmacopeia, but the EPA Methods are developed through a regulatory process involving public notice, comment and revision and are legally binding whereas ASTM methods are developed through a consensus process and compliance is voluntary.
[3][4][5][6] The mission of EPA is to protect human health and the environment.
EPA works to ensure that: The method numbers generally range from 1 to 9000 and may have modification letters appended to the end, signifying a newer version of the method has been released.
Some ranges of numbers appear to be organized with intention, for example methods 1-99 being air methods or the 7000s being for hazardous waste.