Experts warn Des Moines' water nitrate standards may not be enough
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Central Iowa Water Works (CIWW) runs one of the world's largest public nitrate filtration systems, but research increasingly suggests that levels well below the current federal standards it follows may be unhealthy.
Why it matters: The metro's tap water has frequently exceeded 5 mg/L of nitrates for decades — only half the federal limit that the metro is already struggling to stay under.
Driving the news: A scientific report commissioned and released by Polk County recommends that the metro's drinking water utilities adopt more stringent standards, specifically noting the 5 mg/L threshold.
- The report was released less than a month after the metro's first lawn-watering ban started when utilities couldn't keep up with nitrate removal to meet demand.
- Many of the scientists behind the project will participate in their first public forum about the report on Monday.
State of play: From 2006 to 2023, nitrate levels in the metro's drinking water were at or above 5mg/L about 40% of the time.
- It reached 8mg/L on roughly 9% of days, per Polk County's report.
Zoom in: Des Moines University professor Jason Semprini says the EPA's 10 mg/L standard, which was set in 1992, focuses on blue baby syndrome, but it doesn't address other prenatal concerns.
- Semprini, who specializes in cancer research, studied 360,000 Iowa birth records from 1970 to 1988. He found that exposure to nitrate levels at even 5 mg/L was associated with low birth weights and preterm births.
Iowa State researcher Lu Liu expressed similar concerns to Axios. Several studies show concentrations as low as 3 mg/L can hurt more vulnerable populations and contribute to adverse births, colorectal and bladder cancers and thyroid dysfunction.
Between the lines: Iowa has the second-highest rate of new cancer diagnoses in the U.S. and is one of only two states with rising cancer rates (second to Connecticut), which has prompted concerns that the rise is linked to farming.
- While cancer is difficult to trace to one cause due to complex factors like smoking, genetics, rising HPV and diet, Semprini says agricultural exposure, including nitrates, is likely contributing to some portion of the state's elevated cancer rates and compounds with other environmental risks.
Friction point: If the threshold were cut in half, there would be times when meeting a 5mg/L standard would be difficult, Tami Madsen, executive director of CIWW, tells Axios.
- "In order to do that, we would have to implement a significant investment in infrastructure that may not even be possible," Madsen said.
Yes, but: The members of CIWW — a regional water production authority created last year that includes DSM Water Works — remain open to conversation about the threshold, Madsen said.
The bottom line: Water utilities should prepare for the possibility of lower nitrate standards in the future, but ultimately, people should be looking at the root cause and work to reduce that, Semprini says.