Module 2: Health Impacts of Nitrate and Clinical Considerations

1) An Introduction to the Health Impacts of Nitrate

Nitrate contamination of drinking water is a significant public health concern, particularly in agricultural regions where fertilizers and animal waste can leach into groundwater. High nitrate exposure can reduce the blood's ability to carry oxygen, placing infants, pregnant individuals, and other vulnerable populations at risk for serious health effects, including methemoglobinemia ("blue baby syndrome"). Emerging research also suggests that long-term exposure to nitrate levels below the current federal standard may be associated with increased risks of certain cancers, adverse birth outcomes, and other chronic health conditions. Because many private wells are not routinely monitored, healthcare professionals play an important role in recognizing potential exposure risks, educating patients, and promoting testing and prevention strategies to protect community health.

Watch the following Video Introduction:

2) Specific Health Outcomes Associated with Nitrate Exposure in Drinking Water

Adult Cancer

(Mendy, 2024) - Long-term cancer and overall mortality associated with drinking water nitrate in the United States
(Ward, 2018) - Drinking Water Nitrate and Human Health: An Updated Review
(Essien, 2022)- Drinking-water nitrate and cancer risk: A systematic review and meta-analysis
(Chambers, 2022)
(Picetti et al., 2022) - Nitrate and nitrite contamination in drinking water and cancer risk: A systematic review with meta-analysis
- Note: Found a significant positive association between nitrate exposure and gastric cancer, BUT no clear relationship with colorectoral cancer
(Grout et al., 2023)
(Schullehner, 2018) - Nitrate in drinking water and colorectal cancer risk: A nationwide population-based cohort study
(Ward, 2009) - Too much of a good thing? Nitrate from nitrogen fertilizers and cancer

Pediatric Cancer

(Ward, 2018) - Drinking Water Nitrate and Human Health: An Updated Review
(Outtara, 2022)- Geospatial Distribution of Age‐Adjusted Incidence of the Three Major Types of Pediatric Cancers and Waterborne Agrichemicals in Nebraska
(Taiba 2025) - Exploring the Joint Association Between Agrichemical Mixtures and Pediatric Cancer

Maternal/Fetal (methemoglobinemia)

(Ward, 2018) - Drinking Water Nitrate and Human Health: An Updated Review
(Lin, 2023) - Nitrate contamination in drinking water and adverse reproductive and birth outcomes: a systematic review and meta-analysis
(Stayner, 2022) - Nitrate in drinking water and risk of birth defects: Findings from a cohort study of over one million births in Denmark
(Knobeloch, 2000) - Blue babies and nitrate-contaminated well water
(Sherris, 2021) - Nitrate in Drinking Water during Pregnancy and Spontaneous Preterm Birth: A Retrospective Within-Mother Analysis in California
(Tinney, 2015) - Medical education for obstetricians and gynecologists should incorporate environmental health
(Croen, 2001 - Maternal Exposure to Nitrate from Drinking Water and Diet and Risk for Neural Tube Defects
(Manassaram, 2006) - A Review of Nitrates in Drinking Water: Maternal Exposure and Adverse Reproductive and Developmental Outcomes
(Ebdrup, 2022) - Drinking water nitrate and risk of pregnancy loss: a nationwide cohort study
- Note – No consistent associations were found when investigating the exposure as a categorical variable and null findings were also found in trimester specific analyses. In the spline model using the continuous exposure variable, a modestly increased hazard of pregnancy loss was observed for the first trimester at nitrate exposures between 1 and 10 mg/L, with the highest adjusted hazard ratio at 5 mg/L of nitrate of 1.16 (95% CI: 1.01, 1.34). This trend was attenuated in the higher exposure ranges.
(Royal, 2024) - Nitrate in drinking water and pregnancy outcomes: A narrative review of epidemiological evidence and proposed biological mechanisms

Chronic and acute conditions

(Ward, 2018) - Drinking Water Nitrate and Human Health: An Updated Review
(Fraser, 1981) - Health aspects of nitrate in drinking water