Is it safe to boil your water? And should you?
Des Moines residents have expressed confusion on social media after updated guidelines from Central Iowa Water Works in light of high nitrate levels.
A Thursday, June 27, news release from CIWW informed residents that their tap water remains safe to consume, and they can also use it for things such as cooking, bathing and making coffee and tea.
But the release also noted that you shouldn’t boil water when the nitrate concentration reaches or exceeds 7 mg/L.
A different section of the release informed readers that the concentration of nitrates in the water leaving CIWW’s McMullen Treatment Plant was at 6.43 mg/L and water leaving the Fleur Drive Treatment Plant was at 8.68 mg/L.
On Saturday, those readings were at 6.58 mg/L at the McMullen and 8.39 at Fleur Drive treatment plants.
Both the Raccoon and Des Moines rivers remain above recommended nitrate levels, at 12.25 mg/L and 13.99 mg/L, respectively. Because of those high levels, a watering ban remains in place in the Des Moines area so treatment plants can handle demand.
Why doesn’t boiling your water help with nitrates?
Authorities often issue boil-water advisories in communities with major pipe breaks or a large loss of water pressure, but is to counteract bacterial contamination.
Boiling doesn’t work for high nitrate levels, and in some circumstances, can actually make the problem worse.
Boiling the affected water stresses the bacteria so it is no longer a threat, said David Cwiertny, a professor of environmental engineering and chemistry and director of the Center for Health Effects of Environmental Contamination at the University of Iowa.
Nitrates, however, are a chemical, and they do not dissipate when water is boiled. Instead, as water evaporates, the nitrate concentration actually increases, making the boiled water more dangerous to consume than unboiled water.
“The nitrate is very stable,” Cwiertny said. “It’s also pretty mobile. It stays in the water, so it’ll move with the water, and that’s what poses a challenge.”
There is no reason for Des Moines residents to be boiling their water for safety purposes, said Tami Madsen, the executive director for Central Iowa Water Works.
“If drinking water safety is a concern, boiling the water does not reduce the nitrate level,” Madsen said in an email to the Register. “In fact, excess boiling can make the nitrates more concentrated.”
So, does that mean I shouldn’t boil my water at all?
Madsen, however, said it is safe to boil water to do things such as cooking pasta.
Foods such as pasta do not absorb the nitrates as they boil, said Cwiertny. It would only become hazardous if residents drank the water they had boiled for the pasta, because the nitrate concentration would have been elevated in the process.
“Cooking food in our water is considered in the safe drinking water standard and is an appropriate use of our water,” Madsen said. “We have not exceeded the safe drinking water standard.”
Is the water safe to make tea or coffee?
Making tea or coffee also is safe, Cwiertny said, because the water is not heated to the point where it is evaporating enough to substantially increase the nitrate concentration.
Madsen suggests that if you are making tea, avoid excessively boiling the water.
“There is a difference between bringing water to a boil and excessive or longer periods of boiling, which creates noticeable water loss,’ she says, thus, raising nitrate concentrations.
Why are high nitrate levels dangerous?
In the event that nitrate levels in the water exceed the recommended standard of 10 mg/L, the byproducts produced by your body’s attempt to break down the chemical can interfere with the way oxygen is transported in the blood, Cwiertny said.
Water with high nitrate concentrations is particularly dangerous to infants. It can cause methemoglobinemia, which is commonly referred to as blue baby syndrome. In severe cases, it can be fatal.
“There’s a lot of more recent science that suggests longer-term exposures, what we call chronic risks, can happen with exposure to nitrate below that 10 mg/L limit,” Cwiertny said. “That’s where there’s a lot of science that has talked about things like different forms of cancer that might associate with drinking water nitrate, or thyroid disorders or even birth defects or other adverse birth outcomes.”
These adverse effects are not yet reflected in the EPA’s safe drinking water standard because the agency hasn’t determined whether that science merits adjusting the standard to less than 10 mg/L, according to Cwiertny.
So, is my water safe?
Madsen reiterated that the water remains safe to drink, although watering ban remains in place.
“All water produced by Central Iowa Water Works meets all safe drinking water standards,” she said.
Norah Judson is a reporter for the Register. Reach her at njudson@gannett.com.
This article originally appeared on Des Moines Register: Should I boil my water? What to know about Des Moines’ high nitrate levels
Reporting by Norah Judson, Des Moines Register / Des Moines Register
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