Customers in six Middlesex County towns have been warned about the presence of toxic and potentially harmful chemicals found in their drinking water. Middlesex Water Company announced Monday that the level of Perfluorooctanoic Acid (PFOA) in the water of all its customers in South Plainfield, Clark, Edison, Metuchen, Woodbridge and Carteret had exceeded acceptable state-mandated standards. PFOA are part of polyfluoroalkyl and perfluoroalkyl substances (PFAS), a family of thousands of chemicals found in a range of products from nonstick cookware to firefighting foam. PFAS have been linked to ca…