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CORVALLIS, Ore. – According to a new study, bathers suffer from millions of severe illnesses each year due to coastal water contamination in Southern California.

The study, to be published in the fall issue of the Archives of Environmental & Occupational Health, is the most comprehensive of its kind. The researchers, which include lead author and Oregon State University Master of Public Health graduate Dr. Mitchell Brinks, looked at data collected from the entire coastline of Southern California over a five-year period starting in 2000. The researchers used simulation modeling to estimate illness rates using the scientific relationships that serve as the basis for U.S. Environmental Protection Agency and World Health Organization water quality standards.

Brinks, currently a medical doctor in Oregon, said the EPA and WHO relationships estimate that between 689,000 to 4 million severe gastrointestinal illnesses and nearly 700,000 severe respiratory illnesses occurred each year along this coastline. These large estimates, and even the more conservative estimate from the EPA scientific relationship, reveal that fecal contamination leads to many more illnesses than are likely to be acceptable to the public or to health agencies in the area.

“Ours is the first study that looks at every beach in Southern California over such a long period of time,” Brinks said. “These findings are a public health concern because they suggest that these beaches are a large source of illness from contaminated water exposure.”

The study investigated the potential for only relatively severe illnesses that are characterized by symptoms such as vomiting and disabling diarrhea, as well as respiratory illness accompanied by fever, among others. These illnesses can occur from exposure to recreational waters contaminated with fecal matter, with human fecal matter being the most infectious.

The study also identifies beaches that were major sources of illnesses. Surprisingly, although many infamously polluted beaches were more risky to swim at, popular beaches with lower pollution levels were the source of most of the illnesses. The large number of visitors to these beaches, especially during the warm summer months, was the strongest influence on the health consequences of water pollution.

Brinks said, “The study findings have implications for other coastal areas where people are engaged in recreation and raise concerns about EPA water quality standards. Our study estimated that 71 percent of illnesses occurred in water considered acceptable by current EPA standards.”

This might not be that surprising, given that about one out of every 50 bathers would get a severe stomach illness at a contamination level equal to the current water quality standard.

Strengthening water quality standards won’t be enough, Brinks said. “Adjustments to the standards will not stop illnesses. Reducing pollution inputs into recreational waters is the only way to reliably reduce these health risks.”

Brinks worked on the study along with Ryan Dwight; Nathaniel Osgood of the University of Saskatchewan; Gajapathi Sharavanakumar, Jan Semenza, Mahmoud El-Gohary and Josh Caplan of Portland State University; and David Turbow of Touro University International.