Nitrate pollution might not be a familiar term, but it could be affecting your drinking water more than you realize. Nitrates are a naturally occurring form of nitrogen found in soil and water, but human activities, particularly industrial agriculture, have significantly increased nitrate levels in rivers, lakes, and groundwater. This invisible, odorless, and taste-free contaminant poses potential health risks, making it an important issue for communities that rely on these water sources.
Where does nitrate pollution come from?
One of the biggest sources of nitrate pollution is agriculture, particularly from Concentrated Animal Feeding Operations (CAFOs). These large-scale livestock farms produce massive amounts of manure, which can seep into groundwater or run off into nearby rivers and lakes. Other sources of nitrate pollution include:
- Fertilizers – Fertilizers used on crops can leach into groundwater, especially after heavy rains.
- Septic Systems – Poorly maintained septic tanks can release nitrates into the surrounding soil and water.
- Industrial Wastewater – Some industrial processes release nitrogen-based compounds that contribute to pollution.
How does nitrate pollution impact drinking water?
Nitrate pollution was once thought to be a human health risk primarily for “blue-baby syndrome.” High levels of nitrates in drinking water can convert hemoglobin (which carries oxygen) into methemoglobin (which does not carry oxygen), causing the baby’s skin to turn bluish from lack of oxygen.
But recent studies have expanded our understanding of the health risks associated with nitrate-contaminated drinking water, revealing potential links to various cancers. Research indicates that long-term exposure to elevated nitrate levels may increase the risk of thyroid cancer. For example, a study published in Epidemiology found that women who consumed water with average nitrate levels exceeding 5 mg/L for more than five years had a 2.6 times higher risk of developing thyroid cancer – even though these levels are below the federal limit of 10 mg/L.
Further research has suggested associations between high nitrate intake and other cancers. The National Cancer Institute’s Cancer Trends Progress Report notes modest evidence linking higher nitrate consumption to an increased risk of thyroid and ovarian cancers in women. A study in the Environmental Research journal estimated that nitrate pollution in U.S. drinking water could be responsible for over 12,500 cancer cases annually, including colorectal, ovarian, thyroid, kidney, and bladder cancers. 
These findings underscore the need to re-evaluate current nitrate standards in drinking water to better protect public health.
What can be done about this problem?
Preventing nitrate pollution starts with better agricultural practices, improved waste management, stronger water protections, and enacting and enforcing effective environmental laws. Individuals can also take action by testing their well water, supporting policies that reduce agricultural runoff, and supporting legislative efforts aimed at reducing nitrate pollution.
Nitrate pollution may be invisible, but its effects on drinking water are real. Raising awareness is the first step toward cleaner, safer water for everyone.
