Exposure to a common agricultural contaminant in drinking water, even in small doses, may be linked to increased risks of preterm birth, a new study has found.
The pollutant, called nitrate, is also associated with low birth weight in infants whose mothers consumed affected water during pregnancy, according to the study, published on Wednesday in PLOS Water.
While nitrate is a naturally occurring compound that is necessary to plants and animals for survival, its widespread use in inorganic fertilizers has increased the compound’s presence in the environment.
When excess nitrate is consumed by humans, usually via drinking water contaminated by agricultural runoff, the chemical can interfere with the blood’s ability to carry oxygen, the study explained.
“There is no safe level of prenatal nitrate exposure,” author Jason Semprini, an assistant professor in public health economics at Des Moines University, said in a statement.
While the Environmental Protection Agency (EPA) set a maximum threshold for the compound’s presence in drinking water in 1992, there has been no official recognition of adverse birth outcomes as an associated outcome.
As such, Semprini set out to evaluate possible risks — evaluating 357,741 birth records from Iowa from 1970 to 1988. Linking each birth to county-level nitrate measurements taken within 30 days of conception, he observed that concentrations rose about 8 percent per year.
After controlling for seasonal variables and other factors, Semprini found that early prenatal exposure above 0.1 milligrams per liter — just 1 percent of the current EPA limit — was linked to a rise in preterm birth incidence.
Meanwhile, early prenatal exposure to nitrate at levels greater than 5 milligrams per liter — half of the EPA limit — was associated with an increased likelihood of low birthweight, according to the study.
The research identified no additional risk on birth outcomes at elevated nitrate levels: those greater than the federal regulatory bar.
Although Semprini acknowledged that the scope of the study was limited, due to its focus on one state, he said that more recent data from other states and sources could help bolster the strength of the connection.
Going forward, he expressed hopes that the research could help inform the reevaluation of current federal standards, which remain unchanged since 1992 — despite a surge in nitrate levels in groundwater nationwide.
The current threshold, Semprini continued, could be “insufficient for protecting the in-utero transmission of water-based nitrate during the first trimester of pregnancy.”
While cities nationwide have implemented pilot programs to reduce nitrate contamination in water, such solutions can be expensive and would benefit from “rigorous cost-benefit analyses” that offer quantifiable support for these initiatives, according to the study.
Estimating that the impact from prenatal exposure to nitrate is equivalent to about 15 percent of the harm caused by cigarettes, he pointed out that these pollutants do not receive 15 percent of the attention granted to smoking.
“Ignoring the potential harm from lower levels of prenatal nitrate exposure, the current regulatory standards are not adequately protecting America’s mothers or children,” Semprini added.