Environmental Protection Agency audits show that many states are failing to accurately note health violations such as elevated levels of arsenic and chlorine in drinking water, ­according to a new report .

The U.S. Government Accountability Office reviewed EPA audits of 43 states, including Virginia and Maryland, conducted between 2007 and 2009. In 2009, 84 percent of monitoring violations noted by states were not reported to the EPA. That same year, 26 percent of health violations were not reported or were inaccurately reported, undermining the reliability of data collected by the EPA under the Safe Drinking Water Act as well as its ability to conduct oversight, according to the GAO.

The GAO did not break down the findings by state. It emphasized that drinking water in the United States is among the world’s safest, but “waterborne-disease outbreaks caused by ­microorganisms do still occur.”

Chlorine and other disinfectants placed in water to reduce microorganisms can cause anemia, as well as eye and nose irritation, the report said. Long-term ingestion of water with those substances can increase the risk of cancer and might attack the nervous system and kidneys, it added.

The report noted that arsenic that occurs naturally and in industrial waste can cause skin damage, circulatory system problems and increase cancer risks. Nitrate in fertilizer runoff, septic tanks and natural erosion can harm infants, cause shortness of breath and contribute to so-called blue baby syndrome.

In a letter to Rep. Henry A. Waxman (D-Calif.) and two of his colleagues, the GAO assessed the problem and its threat. Americans rely on 51,000 community water systems to provide drinking water. Though the water is mostly safe, “11 states had 20 outbreaks of illness associated with drinking water in 2005 and 2006 that resulted in 612 illnesses and four deaths,” the agency said.

“They say that if it ain’t broke, don’t fix it — but when it comes to drinking water, it turns out that all too often, EPA has no idea whether it’s broke,” said Rep. ­Edward J. Markey (D-Mass.), a member of the Natural Resources Committee.

Markey assailed a proposal put forth by House Republicans to cut $134 million dollars from the EPA-managed Drinking Water State Revolving Fund program, saying it would compound the problem highlighted by the report.

States, territories such as Puerto Rico and tribal agencies are authorized by the EPA to monitor water under the Safe Drinking Water Act. To do that, they review data from community drinking water systems to determine whether they are in compliance. The jurisdictions are responsible for deciding if violations have occurred and taking action.

The report concluded that the EPA “needs complete and accurate data” to determine the level of contaminants in drinking water and protect public health. The GAO recommended that the EPA resume data collection, discontinued in 2009, that reveals whether health violations are accurately reported by states. The agency should also seek to determine whether states followed up with enforcement action.

The GAO also recommended that the EPA collect more data on the numerous monitoring violations that often allow health violations to occur. Congressional budget cuts have led the EPA to give lower priority to certain ­aspects of data collection under the Safe Drinking Water Act.

The EPA agreed to resume collecting data that accurately reflects health violations by states, but it did not commit to any data collection beyond this, as the GAO strongly suggested.