Three recently released research papers that were played up in the national media have provided new insight on disinfection byproducts — and their potentially harmful effects.

The studies, spearheaded by researchers from the Barcelona-based Centre of Research in Environmental Epidemiology (CREAL) and Research Institute Hospital del Mar and the U.S. Environmental Protection Agency, present a comprehensive analysis of disinfection byproducts and provide more findings that correlate certain byproducts of chlorine sanitizers with respiratory problems and bladder cancer, particularly in indoor aquatic environments.

“We examined for the first time in a real-life situation whether some of the chemicals present in pool water could be harmful to our health,” said researcher Manolis Kogevinas, MD, PhD, professor of epidemiology at the Centre for Research in Environmental Epidemiology in Barcelona.

Some of these chemicals have been tested in the lab and with experimental animals and some have been shown to be toxic. However, finding a toxic effect in the lab does not mean necessarily that it is associated with adverse health effects in humans, researchers caution.

The first study included 49 healthy adults; subjects swam for 40 minutes in an indoor chlorinated pool. Both before and afterwards researchers collected blood, urine and exhaled air samples to test for biomarkers linked to cancer. The culprit in the cancer issue is a chemical compound class called trihalomethanes. According to the findings, “after swimming, the total concentration of the four trihalomethanes in exhaled breath was seven times higher than before swimming.”

“What we found is by analyzing blood samples and urine samples, we have an increase in risk markers related to cancer,” Dr. Kogevinas explained in an article published on WebMD.

Above certain exposure levels, THMs have been scientifically shown to lead to cancer in people and animals, said Ed Lightcap, a senior account manager at DuPont Chemical in Wilmington, Del. “In humans, bladder cancer seems to be the most common manifestation,” he noted. Though water-transmitted THMs have been linked to bladder cancer in previous studies, Lightcap added, “typically [it’s discussed] in relation to shower water. Lately, some research has been focusing on pools, too.”

The second study included 48 adult swimmers from the same group. Researchers compared markers of lung injury before and after participants swam for 40 minutes and found an increase in one blood biomarker that could indicate a correlation between asthmatic symptoms and lung damage with inhalation of chloramines in indoor pool environments. But according to the study more research is needed to confirm the results and understand long-term impact. There are also questions over whether results were due to the physical activity itself, rather than exposure to disinfection byproducts.

“Oxidative stress [during exercise] will cause damage to certain lung cells,” said Thomas Lachocki, Ph.D., CEO of the National Swimming Pool Foundation in Colorado Springs, Colo. “But that’s normal, and even positive in many ways. And the body is continually repairing that damage.”

The final study in the trio was an effort to better understand the makeup of DBPs. Using several methods of analysis researchers identified more than 100 DBPs, many containing nitrogen (likely formed from organic matter from humans) and many never before identified DBPs.

All three studies were published online in the journal Environmental Health Perspectives and the findings were picked up by major news organizations, which left some industry professionals displeased with the coverage.

“Some in the media jumped hastily to suggest alternatives to chlorination for disinfecting swimming pools that might impact public health adversely,” said Judith Nordgren, Managing Director of the American Chemistry Council’s Chlorine Chemistry Division. While follow up work is needed, pool operators can minimize any potential risk by optimizing their water quality and minimizing use of chemicals where possible, and educating patrons on healthy swimming behaviors said Dr. Kogevinas and Susan Richardson, Ph.D, a research chemist with the U.S. Environmental Protection Agency who was also a lead researcher on the final study.

Note: Ben Thomas contributed to this report.