June 25, 2025

expert reaction to observational study linking nitrate in drinking water to pre-term birth rates

A observational study published in PLOS Water looks at the link between nitrate in drinking water and premature births.

Prof Oliver Jones, Professor of Chemistry, RMIT University, said:

“The headline on this research may sound scary; however, to my mind, there are several issues with this paper. 

“Firstly, the data are from 1970-1988 and so are not current. Secondly, the author did not perform any measurements themselves but instead used public health data and water quality data. The water quality data was self-reported and so may not be accurate, and it only comes from one place in the USA, so it does not reflect conditions elsewhere. 

“This data was used to show a very weak possible association between estimated early prenatal nitrate exposure and birth outcomes. An association between two factors does not mean one causes the other. The apparent relationship can be due to a range of different factors that have nothing to do with the two variables being considered. I am inclined to think that this is the case here because there is a large overlap in the data and because the effect disappears above 10 mg/L, which does not make sense from a toxicological point of view. Other factors that may affect health, such as the mother’s health or diet, were not available, so could not be taken into account. This is quite important in this case since at concentrations of less than 10 mg/L, the main source of nitrate is actually food, not water. It is thus possible that the results reflect diet, not nitrate.

“Arguing that a policy change is needed on a very well-studied compound based on a single paper that at best only found a weak statistical association from 40-year old data from one part of the USA and which shows no increased risk at the higher exposure concentrations, is, in my view, possibly a little overzealous.” 

‘Early prenatal nitrate exposure and birth outcomes: A study of Iowa’s public drinking water (1970-1988) by Semprini was published in PLOS Water at 19:00 UK time on Wednesday 25^th June. 

DOI: 10.1371/journal.pwat.0000329

Declared Interests

Prof Oliver Jones “I am a Professor of Chemistry at RMIT University in Melbourne, Australia. I have no direct conflicts of interest to declare; however, I have received research funding from the Water Industry and EPA Victoria for research on environmental pollution in the past.”