National Drinking Water Clearinghouse
West Virginia University
PO Box 6893
Morgantown, WV

December 2003 is Deadline for Small Systems and DBPs

by Kathy Jesperson
On Tap Editor

“That invisible organisms also thrive and swim around in a watery environment was beyond imagination until a few centuries ago,” said James Olsztynski in “Plagues and Epidemics,” an article from Plumbing and Mechanical Magazine. “And their connection with disease wasn’t established until a scant 100 years ago. People believed divine retribution caused plagues and epidemics—or else bad air, or the conjunction of the planets and stars, or any, or all of these things.”

People still had to learn about microbial organisms. And they still needed to learn about disinfection. That didn’t happen until the mid 1800s, according to the Chlorine Chemistry Council. It was 1846 when employees of the Vienna General Hospital in Austria first recognized chlorine’s potential as a disinfectant. Workers started using chlorine in the hospital’s maternity ward to prevent “child bed fever,” an infectious affliction. It worked.

Within a few years, researchers deduced that chlorine might work to disinfect drinking water supplies and, thereby, might alleviate many diseases. In 1905, London scientists added chlorine to the city’s water supply and ended a raging typhoid epidemic. In the U.S., the Jersey City Water Works had chlorinated its Boonton Reservoir water supply, and by 1908, large-scale disinfection was launched.

With few exceptions, and with historical evidence to back it, disinfection of drinking water supplies did more to advance public health than practically any other modern discovery. But like all silver clouds, disinfection has a dark lining. Despite their ability to inactivate pathogens, some disinfectants can form disinfection byproducts (DBPs) that may be harmful to human health.

Disinfectants React with Organic Matter

DBPs can form when disinfectants react with bromide or natural organic matter, such as decaying vegetation that may be present in source water. Different disinfectants produce different types or amounts of DBPs. They are suspected carcinogens and possible endocrine disruptors.

The DBPs that researchers have identified in drinking water include trihalomethanes, haloacetic acids, bromate, and chlorite.

Trihalomethanes (THM) are a group of four chemicals that form, along with other disinfection byproducts, when chlorine or other disinfectants used to control microbial contaminants react with naturally occurring organic and inorganic matter in water.

The trihalomethanes are chloroform, bromodichloromethane, dibromo-chloromethane, and bromoform. EPA will regulate total trihalo-methanes (TTHM) at a maximum allowable annual average level of 80 parts per billion. This standard replaces the current standard of a maximum allowable annual average level of 100 parts per billion (ppb) for large surface water public water systems.

Haloacetic acids (HAA5) are a group of chemicals that can form along with other disinfection byproducts when water systems use chlorine or other disinfectants to control microbial contaminants in drinking water. The regulated haloacetic acids, known as HAA5, are: monochloroacetic acid, dichloro-acetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid. EPA will regulate HAA5 at 60 ppb annually. During ozone disinfection, bromate forms when ozone reacts with naturally occurring bromide in source water. EPA will regulate bromate at annual average of 10 ppb in drinking water.

Chlorite forms when water systems use chlorine dioxide to disinfect water. EPA will regulate chlorite at a monthly average level of one part per million. The U.S. Environmental Protection Agency (EPA) began regulating DBPs in 1974, shortly after discovering DBPs existed. Over more recent years, EPA has found that disinfectants other than chlorine, including ozone, can cause DBPs.

To evaluate the potential health effects of DBPs, EPA looked at a number of studies. In the past few years, researchers have conducted studies—known as toxicological studies—that measure how exposure to high doses of DBPs effect health. Scientists typically use laboratory rodents in this kind of research.

Animals Develop Cancer
In several of these studies, the research animals developed cancer. In addition, some of them developed reproductive and developmental disorders. This type of research has never been conducted on humans, causing many in the drinking water industry to question how the results could be translated into a drinking water regulation.

EPA researchers decided to take a look at some epidemiological studies. These kinds of studies measure the factors that influence disease in human populations. A number of these studies revealed a relationship between exposure to chlorinated surface water and cancer. However, some of the studies only showed a slight increase in cancer risk, while others showed no relationship at all.

EPA stated that while it cannot conclude that there is a causal link between chlorinated surface water and cancer, the studies suggest an association. The agency believes that there is enough information to support concern about a potential hazard and to warrant regulatory action. Based on the available data, EPA published its Stage 1 Disinfectants/ Disinfection Byproducts Rule. The standard will become effective in December 2003 for small surface water and all groundwater systems.

For more information, visit EPA’s Web site at

Baker, M.N. 1981. The Quest for Pure Water. Volume I. AWWA: Denver.

Chlorine Chemistry Council (CCC). 1996. Chlorine and Drinking Water: Here’s to Your Health. CCC: Arlington, Virginia.

Edstrom Industries, Inc. 1998. Drinking Water Chlorination. Edstrom Industries, Inc.: Waterford, WI.

U.S. Environmental Protection Agency. 1991. Manual of Small Public Water Supply Systems. Office of Water. Washington, DC.

Ibid. 2002. “Disinfection Byproduct Health Effects.” Information Collection Rule.

Ibid. 2001. Stage 1 Disinfectants and Disinfection Byproducts Rule. EPA 816-F01-014.