Issue Date: June 11, 2007
EPA Limits Implicated In Eye Infections
A study to be released this week in the American Journal of Ophthalmology links an EPA restriction of drinking water disinfectants and disinfection by-products to a recent rash of microorganism infections in contact lens wearers (DOI: 10.1016/j.ajo.2007.05.029). Untreated, the infections can cause blindness.
A nationwide increase in acanthamoeba keratitis—corneal infections by the protozoan Acanthamoeba—has led to a recall of Advanced Medical Optics' Complete MoisturePlus contact lens solution. At the same time, the Centers for Disease Control & Prevention (CDC) connected less than 50% of investigated cases to the solution. A team led by Charlotte Joslin, a professor of ophthalmology at the University of Illinois, Chicago, believes the real source of infection lies elsewhere: in drinking water regulations enacted in 1998 and implemented in 2002–04.
The EPA Stage 1 Disinfectants/Disinfection By-products Rule requires water treatment systems to reduce posttreatment (residual) amounts of the disinfectants chlorine, chloramines, and chlorine dioxide, as well as the disinfection by-products chlorite, bromate, chloroacetic and bromoacetic acids, and the trihalomethanes chloroform, bromoform, bromodichloromethane, and dibromochloromethane. EPA took action after studies linked the chemicals to reproductive and developmental problems, as well as several forms of cancer. In 1998, EPA said the rule would reduce exposure to these chemicals for at least 140 million people. A total of 138 cases of acanthamoeba keratitis were reported to CDC between January 2005 and May 2007.
The problem, Joslin says, is that changes in water disinfection may have led to greater numbers of microorganisms in water, making it more likely for contact lens wearers to get infected when they wear lenses in the shower or pool. She and coworkers hypothesize that the lower residual levels of disinfectants may allow buildup of bacteria- and algae-containing biofilms as water flows farther from the point of disinfection. Such biofilms would provide food for Acanthamoeba. Geographical distribution of acanthamoeba keratitis cases referred to the University of Illinois ophthalmology department shows proportionately more cases arising farther from water treatment plants.
"Of course EPA is concerned about something relating drinking water to adverse health effects," says Eric Burneson of EPA's Office of Ground Water & Drinking Water. However, "my understanding is that CDC has not seen an association between the incidence of keratitis and the disinfection practices of the public water systems" that serve infected patients. He notes that although the Stage 1 rule set maximum disinfectant residual concentrations, there are still minimum concentrations and other ways for water systems to control biofilms in distribution systems. EPA neither regulates nor monitors Acanthamoeba concentrations.
Separately, eye doctors have also seen an increase in corneal infections by Fusarium fungi. Of the cases investigated by CDC, nearly all were connected to Bausch & Lomb's ReNu with MoistureLoc contact lens solution, which was recalled in April 2006. To reduce all kinds of eye infections, CDC recommends that contact lens users follow manufacturers' directions for cleaning, use fresh cleaning solutions, and remove lenses before showering or swimming.
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