If you went to a beach where one in 28 swimmers later experienced diarrhea, stomachache or nausea, would you jump right in?

The U.S. Environmental Protection Agency is proposing new water quality standards that would allow just such a beach to remain open, according to the National Resources Defense Council.

"EPA has a duty to protect the public from all of these illnesses, but EPA seems to refuse to acknowledge this duty," says Steve Fleischli, a senior attorney in the water program at NRDC who has written about the proposed criteria.

The proposed EPA criteria for coastal and Great Lakes beaches aren't more lax than the current ones. They're the same standards EPA first established back in 1986. What's changed is the definition of illnesses from contaminated water. As evidence, NRDC points to the EPA's own draft for Recreational Water Quality Criteria.

The original standards measured symptoms including vomiting, diarrhea with fever or stomachache with fever in 8 to 10 days after a trip to the beach. But the latest understanding of waterborne illness doesn't require fever and includes gastrointestinal illnesses in the 10 to 12 days after a trip to the beach.

Based on EPA's research, the same contaminated water once thought to sicken 8 out of 1,000 swimmers is now seen as sickening 36 out of 1,000 swimmers.

"Therefore, at the same level of water quality, more ... illnesses will be observed," EPA says in the draft.

Asked about this, EPA gave CNN a statement saying, "It is a useful, but uncertain estimation."

Exceeding the EPA threshold prompts state or local governments to issue a beach advisory warning the public of unsafe water conditions.

EPA defended the proposed standards:

"EPA's draft national Recreational Water Quality Criteria would protect more than 99 percent of swimmers from gastrointestinal illnesses with fever due to exposure to pathogens in the water over a swimming season [and] has largely prevented disease outbreaks related to water recreation activities in lakes, rivers, streams and at beaches since the mid-1980s."

The statement added: "EPA considered the latest science and the best available scientific methods when developing the draft criteria recommendations."

Fleischli disagrees.

"It's more disappointing than discouraging," Fleischli says. "We have time, hopefully, to educate EPA on the flaws in their approach."

The Beaches Environmental Assessment and Coastal Health Act of 2000 gave EPA five years to issue recreational beach criteria to protect swimmers' health at coastal and Great Lakes beaches. When the agency missed its deadline, the NRDC sued. A court ordered the EPA to finalize the criteria by October 15.