The Environmental Protection Agency?s mandate to reduce the amount of chemicals used to sanitize public water, including pools, may be the cause behind a recent increase in a rare eye infection among contact lens users, especially swimmers.

At least 40 cases of acanthamoeba keratitis were reported between June 1, 2003, and Nov. 30, 2005, in the Greater Chicago area, according to a study at the University of Illinois at Chicago?s Department of Ophthalmology and Visual Sciences. In the past, only two or three cases occurred each year.

In 1998, the EPA passed a rule lowering the amount of hazardous chemical byproducts produced when organic matter reacts with water disinfectants. Chicago, where the study originated, was expected to become completely compliant by January 2004.

As a result, researchers theorized, the lowered amount of disinfectants allowed more acanthamoebas to survive, entering the pool and becoming trapped behind swimmers? contact lenses.

?Clinicians need to be aware that if our hypothesis is correct and the Chicago outbreak is related to recent changes in U.S. EPA regulations, the potential exists for a similar dramatic increase in AK cases nationally,? wrote the authors of the study.

AK is a severe and painful eye infection of the cornea caused by the amoeba Acanthamoeba. It can cause scarring and even blindness. The disease requires intensive therapy and often a surgical transplant of the cornea. According to the study, 85 percent of cases occur in contact wearers, and those with poor lens hygiene or who swim with contacts increase their risks.