SPRING 1999
2305 East 5th Street
Duluth Minnesota 55812-1445

chlorination,
what's all the fuss about?
 
Much has been written and talked about regarding chlorine and its affects on human health. What are the facts? First, let's look at why we use chlorine in our public water supplies. Chlorine is the most common disinfectant used to treat drinking water. The history of drinking water treatment demonstrates the need for disinfection. Great Britain and the United States, in the early 20th century, began disinfecting their drinking water. This resulted in the virtual elimination of waterborne diseases such as cholera, typhoid, dysentery, and hepatitis A, thereby, allowing our human population to expand to the levels seen today.

Water utilities use chlorine for disinfection in a couple of ways. First, it's used to treat the incoming water supply in order to kill all potentially harmful organisms. Second, smaller amounts of chlorine are added to maintain disinfection of the treated water throughout the distribution system. This residual chlorine guards against any recontamination of the water en route to people's homes.

Even though the benefits of chlorine are pronounced, there are potential long-term health implications with its use that are being addressed with increased regulation. The main health issue with chlorine is not the chlorine itself but the by-products that are produced when chlorine and organic matter are brought together. They form compounds called trihalomethanes (THM's) and other disinfection by-products. Repeated exposure to high levels of THMs over a long period of time could increase a person's risk of cancer. Currently, utilities that obtain their water from surface water sources and serve over 10,000 people must test their water for THM's and meet the standard. By the year 2003, all public water supplies that provide disinfection will be required to test their water for THM's and meet the limits set by the Enviromental Protection Agency.

Because organic matter must be present for THM's to form, waters low in organic matter have lower THM levels. Usually ground water has a low organic matter content. Most of the concern about THM formation is with those utilities deriving water from surface water sources. Surface waters more often contain higher levels of organic matter that contribute to THM formation.

Drinking water treatment is a balancing act between protecting public health against microbial disease and the long-term health implications resulting from the use of chlorine. Most water treatment plants are continually trying to upgrade and improve their systems. The ways in which treatment plants are reducing THM formation without compromising public health include using alternative disinfectants, reducing the level of natural organic matter in the water, and adjusting the type and amount of chlorine used.

For more information, contact the Minnesota Department of Health at 651.215.0700, your local water treatment utility, or the University of Minnesota Water Line.

question of the season
 
I have been thinking about clearing most of the natural vegetation in front of my lakeshore cabin for a better view of the lake. Is this good for the lake? Why, or why not?

While creating a better view from your cabin to the lake, the practice of clearing most of the natural vegetation in the area in front of lakeshore cabin is highly discouraged. The area of land close to water bodies is referred to as the riparian zone. An intact natural riparian zone is extremely valuable for a healthy lake environment. The natural vegetation in this area provides an effective filter that absorbs runoff and prevents erosion from human activities. This helps the lake stay clear during the dog days of August. Trees, which fall into the water, provide much needed habitat and structure for fish. Additionally, a natural shoreline offers many species of birds and wildlife a native environment in which they will thrive.

So, what should a person do to minimize their impacts?

We are not proposing that shoreline owners avoid the use of their property, but we are asking individuals to think about the impacts before embarking upon a project in the riparian zone. One way to increase your view of the lake and maintain natural shoreline vegetation is to selectively trim shrubs and branches. For access to the lake, consider constructing a small path or stairway while leaving the majority of your lakeshore in it's native state. For further questions on this topic contact your local county planning office, DNR office, or the University of Minnesota Water Line.