Today's question: What information should I look for in the water quality report from my supplier?
"Plain Talk" answer: Most reports contain a table of constituents found in the local drinking water. For each constituent, the table usually shows USEPA's maximum contaminant level (MCL) and the amount found in your drinking water. If the amount in your supply is the same as or less than the MCL, your supply is all right. This will be the case in the majority of the situations.
Note that the amounts of some constituents may be listed as "not detected" (ND) or "below detection limits" (BDL). This is not the same as zero, because a level of zero would mean that not any of that constituent was in the water - not even one molecule. Because testing instruments cannot measure that small an amount, only the smallest amount of material that will cause a reading is known. If no reading is obtained, any trace of that constituent in the sample was too small to register. The instrument operator then reports ND or BDL for that constituent.
If the MCL for some constituents is listed as "treatment technique," instead of a number, the utility is required to install and properly operate water treatment processes that reliably remove certain contaminants that are economically or technologically feasible to measure, including Giardia, Legionella and Cryptosporidium.
For more information on this and many other water-related topics, check out "Plain Talk About Drinking Water" by Dr. James M. Symons.