(CNN)– A new report warns millions of Americans may be drinking contaminated tap water. According to a study released Thursday, April 24, by the Environmental Working Group about 1 in 5 people could be exposed to potentially harmful levels of nitrates. Nitrates are naturally occurring compounds , but they can become dangerous when fertilizer runoff contaminates water supplies. The report links even low levels to serious health concerns including certain cancers, thyroid disease, and birth complications. Click here for more news from ABC Columbia. Categories: News ...read more read less