Iowa County Sanitarians have been testing Iowa wells since July 1 for arsenic under the new Chapter 24 rules in the Iowa Administrative Code (IAC 641.24). The updated code allows Grants-to-Counties funding to be used for arsenic testing in addition to the routine testing of wells for nitrate and total coliforms.

The Grants-to-Counties program provides free water testing to Iowa residents in participating counties whose primary source of drinking water is from private wells. The State Hygienic Laboratory and Iowa Department of Public Health receive funding to support Grants to Counties, which is coordinated by the laboratory.

As part of the survey, the Hygienic Laboratory performed 490 arsenic tests for well water throughout Iowa. From these, 189 tests – 38.6 percent – showed the presence of arsenic at or above the quantitation limit of 1 parts per billion (ppb). The quantitation limit is the lowest amount of analyte, in this case arsenic, that can be measured with precision and accuracy.

Twenty-two tests, or 4.5 percent of the total number of tests performed, measured arsenic levels at or above the maximum contaminant level (MCL) of 10.0 ppb. The range of those results at or above the MCL (n=22) was 10 ppb to 62 ppb.

The Hygienic Laboratory’s six-month survey of testing results will help sanitarians understand the extent of arsenic in wells and what has been observed to date.

Wells that were tested were not chosen in a representative way. A well with a high arsenic level does not necessarily mean that a well down the street or in the same city will also have a high arsenic level. Similarly, wells that have no detectable arsenic do not indicate there is little or no risk in surrounding wells. Each well should be tested for assurance that the water is safe to drink.