The water used to mix baby formula plays the biggest role in whether formula-fed babies are exposed to increased levels of arsenic, according to a new study.
Families that use well water instead of municipal water may need to check it for arsenic levels since well water is not regulated by the U.S. Environmental Protection Agency, the study authors suggested.
The study also found that formula-fed infants took in more and excreted more arsenic than breast-fed babies. However, the amounts detected were low and should not be cause for concern, said study co-author Kathryn Cottingham, a biology professor at Dartmouth College in Hanover, N.H.
"The most significant finding was that exposure to arsenic during early infancy in this U.S. population is quite low, regardless of feeding mode," Cottingham said. "Most of the infants, including the formula-fed infants, in our study were exposed to very low levels of arsenic."
The findings were reported Feb. 23 in the journal Environmental Health Perspectives.
Prior studies have shown that formula powder also contains traces of arsenic, the study authors said. In places where levels of the toxin are high, arsenic exposure has been linked to decreased mental function in children.
The researchers measured arsenic levels in the tap water of 874 New Hampshire families whose drinking water came from private, unregulated wells.
The investigators also tested for arsenic in the breast milk of nine mothers and in the urine of 72 infants at 6 weeks old.
Overall, arsenic levels in the tap water tended to be well below the EPA's recommended upper limit of 10 micrograms per liter (mcg/L), the researchers found. The median amount -- meaning half had less and half had more -- was less than 1 mcg/L.
About 10 percent of the homes' tap water had arsenic levels above the recommended limit, with the highest amount at 189 mcg/L.
"Because our study population uses water from private wells, which are not regulated, families can have high arsenic in their water and not know it," Cottingham said. "Families must arrange for testing of private water sources. State health departments can provide guidance on accredited labs and recommended testing."
The researchers found that the amount of arsenic in the urine of formula-fed infants was approximately 7.5 times higher than what was found in breast-fed infants but was still very low overall, Cottingham said.
The median amounts of arsenic in all the infants' urine was 0.17 mcg/L, with the highest amount at 3 mcg/L, the researchers reported.
"There is certainly no evidence to warrant undue anxiety as a result of these study findings for those exclusively breast-feeding their babies or using public or bottled water to mix formula," said Dr. Kenneth Spaeth, chief of occupational and environmental medicine in the North Shore-LIJ Health System in Great Neck, N.Y.
The amounts in bottled and tap water were similar, the study authors found. Cottingham noted that some bottled water companies will provide data on their websites about possible contaminants in their water.
Based on arsenic amounts in the tap water, the authors estimated that formula-fed infants took in approximately 0.04 micrograms per kilogram per day of arsenic, compared to 0.22 micrograms per kilogram for breast-fed infants.
About 70 percent of the formula-fed infants' arsenic exposure came from the formula powder, the authors estimated, based on prior research. However, when a baby's arsenic exposure was high, that higher amount resulted primarily from high levels in the water, they said.
Some public health experts believe the EPA standard of 10 mcg/L should be lowered, Spaeth said.
New Jersey's maximum is 5 mcg/L, noted Cottingham.
These maximum levels, however, only apply to municipal water or privately owned water companies that have more than 15 service connections and serve at least 25 people, according to the EPA.
The EPA noted that arsenic, which occurs naturally in bedrock, cannot be seen or tasted in water.
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