Researchers are looking for 3,000 more volunteers -- on top of the 7,000 they've already recruited -- to expand a study of the health effects of activities such as boating, canoeing, kayaking and fishing on Chicago's waterways.

The University of Illinois at Chicago School of Public Health launched the study with $3.75-million in funding in 2007, and researchers recently got another $4.3-million to expand the scope of their work.

They hope their study will be completed by the end of the year. 

The study is funded by the Metropolitan Water Reclamation District of Greater Chicago. It is linked to the district's effort to avoid disinfecting treated sewage before it is discharged into the Chicago River system.

The Illinois Environmental Protection Agency recommended disinfection after conducting a five-year study to review existing and potential uses of the river.  The study found more people than ever are using the river for recreation.

District officials say installing and operating disinfection equipment would cost nearly $1 billion over 20 years. Further, they say, there’s no proof disinfection will cut illnesses among people exposed to river water.

 “We don’t know if people are getting sick by coming in contact with this water, or how they’re getting sick,” Superintendent Richard Lanyon said in an interview last year. “If you don’t know, how can you say that spending a lot of money to provide bacterial treatment is going to provide a benefit? “

Dr. Samuel Dorevitch, the study’s top investigator, says his team is looking to see if people using the city’s waterways are getting gastrointestinal or skin infections, and eye, ear or respiratory conditions.

Participants will be studied before and after they use the waterways. In a new part of the study, Dorevitch will measure the amount of water that some participants swallow or inhale, as well as how much water gets splashed on them.

Researchers will study water samples to identify pathogens that cause disease. Other studies have only looked at indicators of pollution, Dorevitch says.

“It’s not usually E. coli that makes people sick,” he says. “But the presence of E. coli in the water indicates that there may be sewage contamination.”

Dorevitch and his team will begin recruiting additional participants at various events starting in April. For more information, including how to participate, visit the study’s Web site, www.cheerschicago.org.