A five-year study of men aged 40 and above in Shanghai, China, has found that those who drank water from a heavily polluted downstream section of the Huangpu River were approximately 2.8 times more likely to develop esophageal cancer than men whose water came from the unpolluted upstream stretches of the same river. This wide disparity in cancer rates among men age 40 and above did not disappear even after the researchers controlled for other possible cancer- causing factors such as age, disease history, occupational history, lifestyle factors, dietary habits, education, water chlorination, and urban location. The authors cautioned, however, that since the study was conducted on just 71 patients and 1,122 controls, their results may not represent the risk to all 12 million people living in Shanghai. The study was published in the August 25, 1999, issue of the American Journal of Epidemiology.
The study's author, Xuguang Tao, MD, PhD, research associate, Epidemiology, Johns Hopkins School of Public Health, noted that the downstream section of the Huangpu contained high levels of mutagens -- chemicals that when ingested cause alterations in DNA structure that can result in faulty cell function and sometimes in cancer -- and had also been implicated in doubling the risk of stomach and liver cancers in men. Shanghai stopped using this section of the river as a source of drinking water in 1987.
Mutagenic substances are not always dumped into a water supply but can also be produced whenever organic material is acted upon by chlorine. The study's results suggested that adding chlorine to the Huangpu, a river containing high levels of natural organic matter, may actually have increased the men's risk of cancer.
Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham @ 410-955-6878 or paffairs@jhsph.edu.