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In Midwest farm states, nitrate pollution of tap water is more likely in lower-income communities

  • In Midwest farm states, nitrate pollution of tap water is more likely in lower-income communities

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In three leading Midwestern agricultural states, communities whose drinking water is contaminated with nitrate are more likely to be lower income.

A new Environmental Working Group analysis of state test data found that in Iowa, Minnesota and Wisconsin, communities with elevated nitrate in drinking water were more likely to have median household incomes lower than the state median.

Treating drinking water to remove nitrate is very expensive. Smaller communities have the highest costs per person, because costs are shared by fewer residents. Small, lower-income communities are likely to struggle the most to afford nitrate treatment.

Nitrate is a primary chemical component of fertilizer and manure that can run off farm fields and get into drinking water supplies. Although nitrate pollution can also come from wastewater treatment plants and septic systems, fertilizer and manure are the main culprits.

Nitrate levels in drinking water at or above the federal legal limit of 10 milligrams per liter, or mg/L, can cause blue baby syndrome, a potentially fatal condition that starves infants of oxygen if they ingest too much nitrate. But recent studies have shown strong evidence of an increased risk of colorectal cancer, thyroid disease and neural tube birth defects at levels of 5 mg/L or even lower.

For EWG’s analysis, communities with “elevated nitrate” had at least one test at or above 3 mg/L – the level federal and state regulators consider contamination that is both human-caused and likely to get worse. Across all three states, there were 654 community water systems serving 2.95 million people that had elevated nitrate.

In each state, communities with higher levels of nitrate were more likely to have median incomes below the state’s median income:

  • In Iowa, 68 percent of communities with elevated nitrate had incomes below the state’s median. But that jumped to 85 percent for communities with levels at or above the federal Safe Drinking Water Act’s legal limit of 10 mg/L.
  • In Minnesota, 73 percent of communities with elevated nitrate had incomes below the state’s median, rising to 75 percent for communities at or above the legal limit.
  • In Wisconsin, 66 percent of communities with elevated nitrate had incomes below the state’s median, and 71 percent of communities with levels at or above 10 mg/L were below the state’s median. 

Case studies

The majority of communities with elevated nitrate in these three states were lower income. But 227 elevated nitrate communities were actually “low income,” meaning they had median household incomes that were at or below 80 percent of the state’s income.

The case studies below are snapshots of a community in each state that was low income and also had nitrate tests at or above the legal limit of 10 mg/L.

Waterloo, Iowa

The community water system in Waterloo serves 70,070 people in northeastern Iowa. In 2018, the median household income of the city was $46,297, or 79 percent of the state’s median income of $58,580.

Between 2003 and 2017, two tests in Waterloo found nitrate at or above 10 mg/L. In 2015, the nitrate levels in one of Waterloo’s wells were so high that the city had to stop using it altogether. The city is now looking into nitrate removal water treatment processes to see whether the well can safely be brought back online.

Adrian, Minnesota

Adrian is a small town in the heavily agricultural, rural area of southwest Minnesota. The community water system serves 1,211 people. In 2018, Adrian’s median income was $53,000, or 77 percent of Minnesota’s median income of $68,411.

Adrian has had a long history of nitrate contamination of drinking water. Between 1995 and 2018, the city had an astonishing 31 nitrate tests at or above 10 mg/L. The city installed a nitrate removal drinking water treatment system in 1998, but nitrate levels are so high that the system sometimes fails to lower nitrate to a safe level. When the system is working properly, residents must pay $44 a year for it.  

Last year Adrian received a state grant of more than $400,000 to buy farmland surrounding its wells. The city hopes that when nitrate-limiting conservation practices are applied to the land, or the land is no longer farmed, less nitrate from the fields will get into the drinking water supply.

Beloit, Wisconsin

Beloit is a city on the southern border of Wisconsin, where the community water system serves a population of 37,110. The city is also surrounded by farmland. Beloit had a 2018 median income of $42,169, or 71 percent of the state’s median income of $59,209.

Between 2003 and 2017, eight tests in the city found nitrate at or above 10 mg/L. The city is in Rock County, which also has a long history of high and increasing nitrate levels in private wells. County health officials maintain that 30 percent of private well tests in Rock County show nitrate levels at or above 10 mg/L.

Fixing the problem

Nitrate contamination of drinking water due to agricultural pollution is an incredibly expensive problem for water utilities to fix. It is potentially much cheaper and more effective to prevent nitrate from getting into drinking water in the first place. Instead of lower-income communities being forced to pay for nitrate treatment, farmers should be required to implement conservation practices to reduce the amount of nitrate running off farm fields and getting into surface water or seeping into groundwater.

Methodology 

To conduct this analysis, EWG looked at drinking water nitrate tests of community water systems in Iowa, Minnesota and Wisconsin provided through public records requests.

Our definition of communities with elevated nitrate levels includes any community water system that tested at or above 3 mg/L at least once. For Iowa and Wisconsin, we have included all water systems that tested at or above 3 mg/L between 2003 and 2017. Since we had more data for Minnesota, we included all systems that tested at or above 3 mg/L between 1995 and 2018.

Although 10 mg/L is the legal limit that water systems must meet, we chose 3 mg/L because the Minnesota Department of Health says this level indicates human-caused contamination that is likely to increase over time. The Environmental Protection Agency says that levels at or above 3 mg/L “generally indicate contamination.”

We then crossed the systems that had elevated nitrate with city-level census data from the 2018 American Community Survey, which provides averages for demographic characteristics, drawing on information from 2014 to 2018. Each water system was assigned the median household income from the census data for the city it serves – for example, Des Moines Water Works serves the city of Des Moines, so the system was assigned the median household income for the city of Des Moines.

We also found the three states’ median household incomes through the 2018 American Community Survey. “Lower income” communities were those with median household incomes below the state’s median household income, and “low income” communities were those with median household incomes less than or equal to 80 percent of the state’s median household income.

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