The study also found that both formula powder and drinking water can contribute to an infant’s exposure to arsenic, but that the powder seems to be the more significant source.
Arsenic exposure, even at low levels, is a health concern, particularly when it occurs early in life. Studies have suggested that babies who are exposed to chronic, low levels of arsenic in utero or during early childhood are at greater risk of developing severe infections and a lower IQ. Early-life exposure to arsenic has also been associated with an increased risk of lung disease, heart disease and cancer later in life.
Arsenic occurs naturally in bedrock and is therefore a common contaminant of well water. The Environmental Protection Agency has set a maximum arsenic contamination level for public drinking water systems, but that level is sometimes exceeded. In addition, private well water, the main source of drinking water in many parts of the United States, is not required to meet the EPA’s standard.
There are no federal limits for arsenic levels in most foods, and arsenic from natural sources has been found in powdered baby formula, particularly those powders made with brown rice syrup. As background information in this study points out, previous research has found that breast milk itself tends to contain very low levels of arsenic, even when mothers have been exposed to high levels of the chemical.
For this study, a team of researchers led by Kathryn Cottingham of Dartmouth College, recruited New Hampshire pregnant women, aged 18 to 45, who were receiving prenatal care at a Dartmouth-affiliated health clinic. Water samples were taken from the women’s home kitchen taps and analyzed for arsenic levels. When their babies were six weeks old, the women were asked to fill out a detailed three-day diary about what they were feeding their infant and to provide a urine sample (a soaked diaper) from their baby. Seventy-two of the samples had sufficient urine to be analyzed for arsenic. Nine mothers were also asked to provide a breast milk sample for analysis.
At the time the food diary and urinary samples were collected, 70 percent of the babies in the study had received only breast milk, 13 percent had received only formula and 17 percent had received a combination of the two. The urinary analysis revealed that arsenic levels were 7.5 times higher for babies fed only formula than for babies who were exclusively breastfed.
The study also found that formula powder accounted for about 70 percent of the arsenic exposure. This is a particular concern, say the study’s authors, because the arsenic found in formula powder tends to be a more toxic form than that found in drinking water.
Limitations and implications
Like all studies, this one had several limitations. Most notably, it included only a small sample of women and babies, particularly babies who were being fed formula, so its findings should be interpreted with caution.
Furthermore, the study’s findings do not necessarily mean that the higher arsenic observed in the formula-fed babies pose a direct health risk to those children.
Still, the finding that arsenic levels are low in breast milk supports previous studies that have also found lower arsenic levels in breast milk than in drinking water.
“Together, these studies suggest that breastfeeding is likely to result in lower infant exposures to arsenic regardless of arsenic concentrations in drinking water,” Cottingham and her colleagues write. “This finding is consistent with studies of other metals such as lead and demonstrates an important public health benefit of breastfeeding.”
Yet, as Cottingham told Reuters reporter Andrew Seaman, mothers should not feel badly if they must give their babies formula. They should, however, pay attention to the water they are using to make the formula, she said. And if they are using water from private wells, they should have it tested for arsenic.
You can read the study in full at the Environmental Health Perspectives website.