A new study conducted by researchers at the University of Illinois in Chicago and Aarhus University has shown that women whose household drinking water contains high levels of nitrates give birth to infants that weigh, on average, 10 grams less compared to those who do not. The study, recently published in the journal Environmental Health Perspectives, tracked pregnant women living in Denmark.
The researchers found that even low levels of nitrates, approximately half the allowable limit set by the U.S. Environmental Protection Agency (EPA) for drinking water, can cause negative effects on fetal health and growth completion. Vanessa Kaufman, a visiting research specialist at the University of Illinois School of Public Health, stated, "While the effects of high nitrate levels on infant health are known, little research has been done on the impact of low nitrate levels in drinking water on children. This is an important data gap if we want to assess the adequacy and effectiveness of current standards set for nitrate levels in drinking water."
It is noted that drinking water is often contaminated with nitrates when fertilizers leak into drinking water sources. High nitrate levels in tap water can cause methemoglobinemia in infants, a life-threatening condition known as "blue baby syndrome," where the child's skin turns blue due to nitrates preventing red blood cells from carrying oxygen. For this reason, the EPA has set specific standards for nitrate levels in drinking water at 10 parts per million to reduce the risk of infants developing blue baby syndrome.
In the largest study of the relationship between nitrates in drinking water and birth weight, Kaufman and her colleagues reviewed the exposure of mothers to nitrate levels across more than 852,348 live infants in Denmark from 1991 to 2011. They matched residential addresses to nitrate data from a national water quality monitoring database with data obtained from Danish records related to birth weight, length, and head circumference. These records provide an unparalleled resource for epidemiologists, as they are among the most comprehensive and accurate in the world, and rely on national healthcare data, individual demographics, and environmental data spanning decades.
The researchers found that nitrate levels in drinking water consumed by mothers were associated with the weight of infants at birth. Although the weight differences were relatively small, they were significant; children born to mothers whose drinking water contained around half the permissible level of nitrates were, on average, 10 grams lighter than those born to others. Additionally, the researchers noted a decrease in body length alongside increasing concentrations of nitrates in drinking water, while no effect on head circumference was observed. Kaufman remarked, "While the difference in weight and body length may be small, it can have health implications if the child is already underweight for other reasons. Birth weight is an important indicator of health and can have lifelong impacts on health and growth."
