Prenatal Exposure to Compliant Nitrate in Iowa Public Drinking Water (1983-1988)
- 1Des Moines University
Abstract
Essential for nutrient growth, due to intensive farming practices nitrate has become a common water contaminant in agricultural states. US nitrate regulations are designed to protect the health of newborns and infants, but have never been revised to consider potential harms of prenatal exposure. Recent evidence, however, suggests that exposure below the 10 mg/L regulatory limit may be associated with adverse birth outcomes. This current study examines whether first-trimester exposure below the regulatory limit is associated with adverse birth outcomes in Iowa (an intensive agricultural state). Finished drinking-water nitrate measurements from Iowa public water systems were linked to birth records. Nitrate measures were aggregated to a balanced county-quarter panel (1983 to 1988). Each pregnancy was assigned an average nitrate exposure over a 98-day first-trimester window. All births with a first trimester county-quarter nitrate measure >= 10 mg/L were excluded. Linear probability models with county-by-year and year-by-conception-quarter fixed effects, with standard errors clustered by county, estimated both uncorrected and Sidak corrected inference. The final analytic sample included 113,328 singleton births. Relative to lowest exposure category (0.1 mg/L or below), exposure to 5 mg/L or more nitrate was associated with a 1.04 percentage-point increase in the probability of preterm birth (CI = 0.24 to 1.83), a 13.5% relative increase, and associated with a 0.53 percentage-point increase in very preterm birth (CI = 0.08 to 0.97), a 46.2% relative increase. The statistical significance of both estimates persisted after correction for multiple tests. Exposure to > 0.1 mg/L and < 5 mg/L was not associated with any outcome. These preterm and very preterm birth associations were consistent across several sensitivity checks. Because nitrate concentrations between 5 to <10 mg/L comply with current rules, these findings warrant reassessing approaches to protect the health of pregnant women and their children.
Related
- Maternal exposure to nitrate in drinking water and risk of cyanotic congenital heart defects
- Associations between Prenatal Exposure to Perchlorate, Thiocyanate, and Nitrate and Child Neurodevelopment in the MARBLES Study.
- Prenatal extreme heat exposure and neonatal mortality in Bangladesh, 2015 to 2025: a national birth-history study
- Cord blood metabolic network profiles link prenatal rare earth element exposure to neurodevelopmental delay in 2-year-old children
- Prenatal exposure to acrylamide and neuropsychiatric disorders: a biomarker-based birth cohort study with 34 years of follow-up
BibTeX
@misc{semprini2026prenatal,
title = {{Prenatal Exposure to Compliant Nitrate in Iowa Public Drinking Water (1983-1988)}},
author = {J. Semprini},
howpublished = {medRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.14.26363048},
url = {https://www.medrxiv.org/content/10.64898/2026.09.14.26363048v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Prenatal Exposure to Compliant Nitrate in Iowa Public Drinking Water (1983-1988)
AU - J. Semprini
PY - 2026
DA - 2026/09/14
PB - medRxiv
DO - 10.64898/2026.09.14.26363048
UR - https://www.medrxiv.org/content/10.64898/2026.09.14.26363048v1
AB - Essential for nutrient growth, due to intensive farming practices nitrate has become a common water contaminant in agricultural states. US nitrate regulations are designed to protect the health of newborns and infants, but have never been revised to consider potential harms of prenatal exposure. Recent evidence, however, suggests that exposure below the 10 mg/L regulatory limit may be associated with adverse birth outcomes. This current study examines whether first-trimester exposure below the regulatory limit is associated with adverse birth outcomes in Iowa (an intensive agricultural state). Finished drinking-water nitrate measurements from Iowa public water systems were linked to birth records. Nitrate measures were aggregated to a balanced county-quarter panel (1983 to 1988). Each pregnancy was assigned an average nitrate exposure over a 98-day first-trimester window. All births with a first trimester county-quarter nitrate measure >= 10 mg/L were excluded. Linear probability models with county-by-year and year-by-conception-quarter fixed effects, with standard errors clustered by county, estimated both uncorrected and Sidak corrected inference. The final analytic sample included 113,328 singleton births. Relative to lowest exposure category (0.1 mg/L or below), exposure to 5 mg/L or more nitrate was associated with a 1.04 percentage-point increase in the probability of preterm birth (CI = 0.24 to 1.83), a 13.5% relative increase, and associated with a 0.53 percentage-point increase in very preterm birth (CI = 0.08 to 0.97), a 46.2% relative increase. The statistical significance of both estimates persisted after correction for multiple tests. Exposure to > 0.1 mg/L and < 5 mg/L was not associated with any outcome. These preterm and very preterm birth associations were consistent across several sensitivity checks. Because nitrate concentrations between 5 to <10 mg/L comply with current rules, these findings warrant reassessing approaches to protect the health of pregnant women and their children.
ER -