©2018 Mahoning Valley Water Inc.  Chlorination The Findings      The American Journal of Public Health released an analysis that linked chlorine by- products with bladder and rectal cancer.      The analysis, which was headed by Dr. Robert D. Morris of the Medical College of Wisconsin in Milwaukee, found that 6,500 of the 44,000 rectal cancer cases per year and 4,200 of the 47,000 bladder cancer cases per year are associated with the consumption of chlorinated water.  This statistic is cause for concern since approximately three-fourth's if the United States' drinking water is treated with chlorine for disinfection purposes.      Despite its link to bladder and rectal cancer, however, the experts agree that the findings should not lead to an abandonment of chlorination.  The potential health risks of microbial contamination of drinking water greatly exceed the risks.      Chlorination is commonly used in the United States to disinfect water because of its effectiveness in destroying pathogenic (disease- producing) bacteria and other harmful organisms that may be present in the water. History of  Chlorination      Chlorination was first used in the United States in the early 1900's.  Prior to that time, waterborne diseases such as cholera and typhoid fever were rampant.  Major US cities were suffering 100 or more typhoid deaths a year per 100,000 persons.      During the ten years following the first use of chlorination, thousands of drinking water treatment plants began to use chlorine for disinfection purposes.   The typhoid death rate fell simultaneously.  Consequently, for more than 80 years, chlorination has been the primary means of disinfection for municipal water supplies and has had exceptionally positive results.      Due to improved testing capabilities during the mid-1970's, however, it was detected that trihalomethanes (THM's), including chloroform and many other volatile organic chemicals (VOC's) were present in potable drinking waters.  Since these compounds were usually not present in untreated water before chlorine disinfection, it became clear that THM's were present whenever chlorine was used for disinfection.      THM's are formed when chlorine reacts with naturally-occurring organic matter such as by-products of decayed vegetation.  The US Environmental Protection Agency (USEPA) has classified various THM compounds as either probable or possible human carcinogens and has set a Maximum Contaminant Level (MCL) of 0.10 milligrams per liter for THM's.  In addition, the USEPA has set a Maximum Contaminant Level Goal (MCLG) of zero for THM's.  An MCLG is a non-enforceable but desirable health-related goal established at the level where no adverse effects on the health of persons is anticipated to occur.  An MCL is the enforceable limit set as close to the MCLG as possible, taking into consideration the cost of water treatment by public water systems.      Following the discovery of the by-products produced by chlorination, several studies concerning chlorination were conducted.  However, their results appeared to be inconsistent. Meta-analysis      The findings reported in the American Journal of Public Health are drawn from a combination of 10 of these previous studies (including the National Bladder Cancer Study presented by Dr. Kenneth Cantor, Ph.D.) and uses a statistical method called "meta-analysis".  Meta-analysis pools the results of smaller studies and can produce a unified result from studies that may seem inconsistent when considered individually.  Combining the studies results in larger numbers and provides greater statistical power than the studies would when considered independently.      Morris and his co-authors say that they do not intend to suggest that chlorination should be abandoned.  "Nonetheless," they state, "these findings should provide an impetus to identify, develop, and implement disinfection strategies that are not associated with adverse health effects. Home Water Treatment      Until a new strategy is found, however, there is good news for consumers who may be concerned about chlorine and its by-products in their drinking water.      Treatment technologies that reduce chlorine may be installed in the home after the water has been disinfected at the treatment plant.  Activated carbon or certain specialty media filters will extract chlorine from the water.      Distillation systems that incorporate carbon and reverse osmosis drinking water systems produce high quality water for drinking and cooking purposes.      In addition to reducing the harmful by-products of chlorine, these technologies can also reduce the objectionable chlorine taste and odor that may be present in chlorinated water supplies. MAHONING VALLEY WATER