PHMDC Header

DRINKING WATER: Common Water Quality Concerns


Radium is a naturally occurring radioactive element commonly found in drinking water supplies that has been associated with an increased risk of bone cancer development when consumed in elevated levels over prolonged periods of time. Dane County municipal wells are routinely sampled to monitor water quality and to ensure compliance with regulatory standards including those for radioactive components. The MCL for radium of 5 picoCuries per liter (pCi/L); in most communities the concentration of radium ranges from 0 to 5 pCi/L. Recent testing in the City of Madison have indicated that one municipal well had a reported radium level of 5.8 pCi/L; a level slightly above the MCL but not a level that would significantly alter the risk of bone cancer development. Additional samples will be collected to confirm these results.

For further information about Radium:


The trace amounts (0 to 2 µg/L) of hexavalent chromium (Cr VI) found in Madison drinking water is much lower than the current US EPA water quality standard (100 µg/L for "total chromium") and thousands of times lower than levels suggested increasing human disease risk. As a result, the risk of human illness, specifically stomach cancer, from the consumption of Madison drinking water is negligible. In fact, rates of stomach cancer in our area are low compared with state and national averages and appear to be declining. PHMDC will continue to monitor this issue and any potential developments or improved guidance released from the US EPA.

For further information about chromium:


Exposure to lead harms the development of infants and young children (under 5 years of age). Important issues regarding lead in water are:

  • Old Pipes: Homes built before 1930 may have lead pipes, service lines and solder. Lead in pipes and solder were banned in 1986. But brass fixtures and galvanized pipe may still release lead into drinking water.
  • Hot water: It is important when making infant formula never to use hot water straight from tap or to boil water for too long a time (more than 1 minute) because small amounts of lead or other minerals can become more concentrated in the water.
  • Flush the lead: In homes with lead plumbing, it is always safest to run the drinking water tap for a few minutes each morning to flush out any possible lead sediment.
  • Ongoing challenge of lead: Recent changes to water quality laws by the EPA have required many water utilities to take action. However, even with more strict standards, problems may occur such as the time when a local office building was found to have consistently high lead levels (100 ppb).

1, 4-dioxane

1, 4-dioxane is a chemical contaminant that has been found in some City of Madison municipal drinking water wells during a preliminary screening conducted by the City of Madison Water Utility. Although the chemical is considered by the US EPA as "likely to be carcinogenic to humans" additional research is necessary to determine the relative risk of low level exposure in drinking water. The levels reported in this subset of the most susceptible municipal wells are very low and pose a negligible individual risk to human health. Further sampling is planned to evaluate the levels of 1, 4-dioxane in each of the municipal drinking water wells to further investigate if additional wells are impacted.


Long-term consumption of drinking water with high levels of manganese may cause neurological problems. Concerns about manganese in Madison’s drinking water were addressed in 2006 and 2007. The solution involved shutting down two wells, the installation of a costly filter system and the implementation of a stronger citywide flushing program.


A small amount of fluoride is essential to healthy teeth, but too much can be harmful. Many public water utilities in Dane County add fluoride to drinking water to levels of approximately 1ppm, which is within the range recommended by the Center for Disease Control and Prevention (CDC). See PHMDC policy statement on Fluoridation of Public Drinking Water (PDF).

For additional information on water fluoridation, see the following resources:


Drinking water can be contaminated with nitrates from fertilizers, manure and septic systems. High nitrate levels are dangerous to pregnant or breast feeding mothers and infants by decreasing the capacity of blood to carry oxygen, which can cause “blue baby syndrome.” All new wells and any well that supplies water to women and children should be tested for nitrates annually. Levels of nitrate between 2 and 10ppm suggest the need for more frequent, seasonal testing.


Pesticides can be released in to drinking water from agricultural and residential applications of these chemicals. Exposure may increase your risk for chronic illness.


Drinking water contaminated by bacteria, viruses and protozoa can cause sudden or ongoing intestinal illness. Although all public water utilities in Dane County, except for the Town of Dane, chlorinate drinking water to kill microbes, occasional problems can occur. One potential problem area is that private well water is not chlorinated at all.

Examples of serious problems are:
  • In 1993 in Milwaukee, 400,000 people became ill when a water purification plant failure allowed the protozoa Cryptosporidium, to enter the system.
  • In urban Dane County, in 2006, the newly installed drinking water system of a new office building was heavily contaminated with bacteria because the system was not sufficiently protected and disinfected during construction.


Copper is commonly used in plumbing components, including piping and in brass fixtures. Copper may dissolve in water and has been known to cause health problems at relatively low concentrations. In 1993, illnesses related to copper leaching from copper pipes were reported in the City of Monona. Investigation revealed that a treatment chemical that was added to one of the municipal wells to reduce iron content had the side effect of leaching copper into the water. This high copper concentration was not detected during routine water utility testing.


Sodium (Na) is an essential element required for normal body function including nerve impulse transmission, fluid regulation, and muscle contraction and relaxation. Sodium is found in the drinking water of all Dane County communities; including the City of Madison. Public Health Madison & Dane County occasionally receive questions from individuals expressing concern about the safety of consuming drinking water containing sodium for individuals subject to salt restrictive diets. For further information, see Sodium in Drinking Water (pdf).