Owners of a popular brand of water bottles may be exposing themselves to harm, a recently published study said.

Nalgene bottles are made from a polycarbonate known as Lexan, patented by General Electric in 1952. Lexan is promoted as an unbreakable plastic, making Nalgene bottles favorites for outdoor sporting use.

Patricia Hunt, associate professor of genetics at Case Western Reserve University in Cleveland, co-authored a study that tried to connect coming in contact with bisphenol A polycarbonate with having too many chromosomes, which carry genetic material.

In the study, mice who came in contact with the polycarbonate had offspring with birth defects. Having too many chromosomes can cause problems such as miscarriages or birth defects like Down syndrome.

Jenny Bissing, senior in genetics, said she owns several Nalgene bottles and has no plans to stop using them any time soon.

“I wouldn’t stop using [Nalgene bottles] unless I had seen [the danger of Nalgene bottles] published in a reputable journal and other respected people in that community were supportive of the findings,” she said.

Following the publishing of Hunt’s study and subsequent articles by the Sierra Club, Nalgene posted a response on its Web site, www.nalgene-outdoor.com.

The response was critical of the broad implications made by Hunt’s study. Nalgene said Hunt was not looking at long-term effects of exposure to the polycarbonate on the development and reproductive abilities of the mice used in the study and was instead looking at short-term results.

“[W]e feel that the more important issue is that Dr. Hunt’s findings are limited to cellular effects seen in individual mouse eggs and that she has reported no effects from BPA exposure in terms of fertility rates, growth and development, or health of the organism as a whole,” the Web site reads.

The American Plastics Council’s Web site, www.plasticsinfo.org, also faulted Hunt’s study, but based its concerns for human health on the fact the study was done with mice. The council said it repeated Hunt’s study with rats and didn’t get the same results.

Diane Birt, professor and chairwoman of food science and human nutrition, said she uses mice in some of her research because they can be compared to humans in some instances.

“In many cases, the studies with mice have been very good predictors of human reactions. There are very good parallels,” Birt said.

The causes and biology of the reaction must be studied, however, before mice reactions can be said to be the same as human reactions, Birt said.

Hunt’s study was not intended to link bisphenol A polycarbonate and reproductive mutations. She stumbled upon the effects when water bottles being used by mice in another study began leaking the polycarbonate after mistakenly being washed with a harsh detergent, the study said. Hunt noticed a corresponding jump between chromosomal defects and exposure and was able to duplicate the results in separate studies.

Another study, “Bisphenol A Is Released from Used Polycarbonate Animal Cages into Water at Room Temperature,” published in “Environmental Health Perspectives” in July 2003, found bisphenol A polycarbonate can leak from bottles even without being washed by a harsh detergent.

Nalgene’s Web site response said even if the polycarbonate were leaking from its bottles, the amounts were not necessarily enough to cause problems, even if the substance is presumed harmful.

At press time, the Material Safety Data Sheet for bisphenol A polycarbonate, which lists hazardous components and handling issues, had no special health concerns other than its potential to be an inhaled irritant.

“If [a chemical] is causing a disease mechanism in animals, then I recommend avoiding human exposure,” Birt said.