42 U.S.C. § 300j–17

In addition to the substances referred to in section 346a(p)(3)(B) of title 21 the Administrator may provide for testing under the screening program authorized by section 346a(p) of title 21 , in accordance with the provisions of section 346a(p) of title 21 , of any other substance that may be found in sources of drinking water if the Administrator determines that a substantial population may be exposed to such substance.