A new study led by researcher in the United States (U.S), has found that even low levels of nitrate—a common agricultural runoff and drinking water contaminant—are associated with increased risks of preterm birth and low birthweight babies.

Results of the study are published in ‘PLOS Water’ by Jason Semprini of Des Moines University College of Health Sciences in the U.S. Nitrate is a naturally occurring compound increasingly found in inorganic fertilisers and, through runoff, in groundwater.

When consumed by humans, nitrates can interfere with the blood’s capacity to carry oxygen. Since 1992, the U.S. Environmental Protection Agency (EPA) has a maximum contaminant level for water-based nitrate at 10mg/L.

To evaluate possible reproductive risks, Semprini analysed 357,741 birth records from Iowa spanning 1970 to 1988, linking each birth to county-level nitrate measurements taken within 30 days of conception.

During the study period, nitrate levels rose an average of eight per cent per year, with a mean exposure of 4.2 mg/L.