Creative Commons by Flickr user faungg.

ITHACA, N.Y. –– High levels of chlorine dioxide, a chemical disinfectant also used to mitigate taste and odor issues, was found in city water samples taken on Wednesday.

The City of Ithaca released a notice on Monday, Feb. 10 informing residents that Wednesday’s test results showed levels greater than the recommended maximum residual level (MRDL) of 0.80 milligrams per liter (mg/l).

“We do not feel that there is any reason for concern,” the city said in the notice. “Our numbers have been within limits on a regular basis leaving the water plant and into the distribution system. We do not think that has changed. We have had “blips” in analysis before, but re-checks show a lower number. This is normally an analysis issue (i.e., items being used for sampling/analysis not flushed or cleaned well, wrong sample taken, etc.)”

According to the Environmental Protection Agency (EPA), who recommends MRDL guidelines, “some infants and young children who drink water containing chlorine dioxide in excess of the MRDL could experience nervous system effects. Similar effects may occur in fetuses of pregnant women who drink water containing chlorine dioxide in excess of the MRDL. Some people may experience anemia.”

The elevated sample, taken at 4 p.m. on Wednesday, Feb. 5, was 1.58 mg/l. Another two samples taken during that day were less than 0.45 mg/l. In-plant samples taken a day prior on Feb. 4 and the day after on Feb. 6 were less than 0.25 mg/l.

The high reading was not reported by staff and was not caught on daily level log sheets until reviewed on Feb. 7.

As a result, no follow up samples were taken, triggering a city-wide notification.

Charles Baker, chief operator at the water treatment plant said they are taking additional water samples and are testing this week.

Anna Lamb

Anna Lamb is a reporter for the Ithaca Voice. Questions? Story tips? Contact her at