An alarming new report from the Centers for Disease Control and Prevention finds that an astonishing 80 percent of public swimming pools and hot tubs in five U.S. states in 2013 had health or safety violations.

The CDC looked at Arizona, California, Florida, New York and Texas for the study due to the fact that they have the most public swimming pools. They found that one out of every eight swimming pools had violations so serious that they were shut down immediately, as well as one out of five children’s wading pools, according to the report.

Michael Beach, CDC’s associate director for healthy water, called the revelations “troubling,” according to news reports. Children are more likely to swallow water and thus are at greater risk of contracting an illness from a contaminated pool.

A total of nearly 350 disease outbreaks began in swimming pools between 2003 and 2012, the CDC said.

The typical violations included not using enough disinfectant like chlorine, or inadequate safety equipment in the event of a drowning. A total of 4,000 people drown in U.S. pools each year.

“No one should get sick or hurt when visiting a public pool, hot tub, or water playground,” said Beth Bell, M.D., M.P.H., director of CDC’s National Center for Emerging and Zoonotic Infectious Diseases. “That’s why public health and aquatics professionals work together to improve the operation and maintenance of these public places so people will be healthy and safe when they swim.”