Is Arsenic "Lactation Intolerant"?
Study Indicates Low Excretion in Breast Milk
Arsenic is known to readily cross the placenta, but few data exist
on postnatal exposure to arsenic in breast milk. Results of a study
conducted in Bangladesh now suggest that infants who are exclusively
breastfed are protected against arsenic, despite high maternal
exposures
[
EHP 116:963–969; Fängström et al.].
Numerous studies have linked arsenic exposure in adults to various
diseases, including cancer, cardiovascular disease, and diabetes
mellitus. Exposure in school-age children has been associated with
neurodevelopmental disorders. During fetal development, the brain is
particularly vulnerable to arsenic exposure, as it readily crosses the
placenta, possibly altering fetal programming and leading to a higher
risk of susceptibility to disease later in life.
The subjects in the current study included 98 mothers and their
3-month-old infants who participated in the Maternal and Infant
Nutrition Interventions of Matlab in Bangladesh, one of the most
severely affected countries in terms of high prevalence of extremely
elevated levels of arsenic in drinking water supplies. The
investigators evaluated nutritional status and arsenic exposure as
reflected by arsenic metabolites in infant urine and maternal blood,
urine, and saliva samples. They also analyzed breast milk samples at 2
months postpartum for arsenic. Questionnaires completed by the mothers
provided data on infant feeding practices.
The median sum of arsenic metabolites in infant urine was 1.2 µg/L,
with significantly lower concentrations in infants who were exclusively
breastfed compared with those who received some solid food. Arsenic
concentrations in breast milk were low (median 1.0 µg/kg) and mostly in
the form of trivalent inorganic arsenic. The researchers observed a
significant association between arsenic in infant urine and breast
milk, but noted that some mothers with low breast milk arsenic had
infants with high urine concentrations, possibly because the infants
had been given water to drink. Median maternal blood and urine
concentrations were high (5.7 and 67 µg/L, respectively), whereas
median maternal saliva concentrations were low (1.3 µg/L). Among
infants who were exclusively breastfed, urine levels did not exceed 19
µg/L inorganic arsenic and its metabolites, whereas infants who
received infant formula prepared with local drinking water in addition
to some breast milk had urine levels up to 1,100 µg/L.
The authors demonstrate for the first time that arsenic in human
breast milk is mostly the inorganic arsenite form. Although there was a
significant relationship between arsenic concentrations in milk and in
maternal blood, arsenic concentrations in breast milk were relatively
low despite the mothers' high exposures. The findings suggest that
breastfeeding exclusively can protect infants from arsenic exposure
during this critical development period, but the authors note that
researchers have yet to determine the extent to which breastfeeding
decreases the health risks associated with prenatal arsenic exposure.
http://www.ehponline.org
