Contaminant Levels in Tap Water
Understanding the Levels of Toxins Found in a City Water Report
Apr 5, 2009
A city’s Consumer Confidence Report, sometimes called a Drinking Water Report, shows numbers indicating the levels of contaminants found in the water. These numbers and technical terms can seem daunting at first, but understanding what the units of measurements are and keeping the allowable limits in perspective will help.
How Contaminant Levels Are Measured
The levels of contaminants are detected in different units of measurements.
PicoCuries per liter (pCi/l) is a measurement for radioactive elements such as alpha emitters, radium, and radon. The PicoCuries measure how many radioactive atoms are giving off the radiation.
Grains per gallon (gpg) is a measure of the minerals that make water hard. The higher the number, the harder the water.
pH indicates the alkalinity or acidity of the water. Acceptable drinking water ranges from 6.5 to 8.5, while 7 is completely neutral and considered the most ideal for drinking. A pH of less than 6.5 can leave a bitter aftertaste.
Parts per million, parts per billion, and parts per trillion (ppm, ppb, ppt) indicate one part contaminant per million parts water (or billion or trillion parts of water).
Parts per million, then, is the “big stuff,” parts per billion are smaller, and parts per trillion are the “trace amounts.”
Trace Amounts of Contaminants in Water?
Just because a contaminant is found in smaller, trace amounts does not mean that it is less harmful. It depends on the contaminant. For example, the article "Prozac River" by Paul Rauber reports, “It doesn’t take much estrogen to cause alarming deformities. In the case of fish, abnormalities start appearing at concentrations in the parts-per-trillion range.” (Sierra Magazine, September/October 2007)
Allowable Limits of Contaminants in Perspective
The United States E.P.A. (Environmental Protection Agency) determines allowable limits for contaminants in water. However, these limits can change, as science discovers just what is a safe level of each contaminant to ingest over a period of time.
The allowable limits and the goals are sometimes different. MCL means the Maximum Contaminant Level. This is the highest level allowed of a contaminant based on known health risks. MCLG is Maximum Contaminant Level Goal which is usually the same as the MCL or lower, and is also based on a margin of safety in regards to expected risk to health.
What many call the “acceptable health risk” rule of thumb is exemplified in the hotly debated arsenic ruling in 2001. The E.P.A. web page that details the history of the arsenic rule quotes the E.P.A. Administrator as stating, “the 10 ppb protects public health based on the best available science and ensures that the cost of the standard is achievable." Acceptable health risk, then, is the happy medium between what is safe for most people to drink, and what is economically feasible to clean out of the water by treatment plants.
Health Effects of Contaminants in Water
Scientists and water professionals still admit to inconclusive epidemiology for many contaminants, especially over a period of time. For example, in regards to Pharmaceuticals and Personal Care Products (PPCP's) in drinking water, Burnsville, Minnesota's water report states, “While PPCP’s are found in very low levels in drinking water, there is a concern of possible cumulative effects of long-term exposure. Also, while most PPCP’s are known compounds, they may react in ways that are different from their intended purpose once they are introduced into the environment.” (City of Burnsville Drinking Water Report, 2008)
The health risks of fluoride in drinking water in any amount is also highly controversial and hotly debated. According to the Fluoride Action Network, "an international coalition seeking to broaden public awareness about the toxicity of fluoride compounds and the health impacts of current fluoride exposures," the multiple sources of fluoride exposure are compounding the effects of the harmful levels of fluoride in drinking water.
If the levels of some contaminants pose a health risk, consumers can choose to invest in reverse osmosis water filter systems to reduce or remove them.
When evaluating the Drinking Water Quality Report, remember to keep in mind the levels detected, what the EPA's allowable limits are, and individual health concerns, especially for persons who are immunocompromised.
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