Exposure to Arsenic in Breastfed and Formula-Fed Infants
Exposure to Arsenic in Breastfed and Formula-Fed Infants
Background Previous studies indicate that concentrations of arsenic in breast milk are relatively low even in areas with high drinking-water arsenic. However, it is uncertain whether breastfeeding leads to reduced infant exposure to arsenic in regions with lower arsenic concentrations.
Objective We estimated the relative contributions of breast milk and formula to arsenic exposure during early infancy in a U.S. population.
Methods We measured arsenic in home tap water (n = 874), urine from 6-week-old infants (n = 72), and breast milk from mothers (n = 9) enrolled in the New Hampshire Birth Cohort Study (NHBCS) using inductively coupled plasma mass spectrometry. Using data from a 3-day food diary, we compared urinary arsenic across infant feeding types and developed predictive exposure models to estimate daily arsenic intake from breast milk and formula.
Results Urinary arsenic concentrations were generally low (median, 0.17 μg/L; maximum, 2.9 μg/L) but 7.5 times higher for infants fed exclusively with formula than for infants fed exclusively with breast milk (β = 2.02; 95% CI: 1.21, 2.83; p < 0.0001, adjusted for specific gravity). Similarly, the median estimated daily arsenic intake by NHBCS infants was 5.5 times higher for formula-fed infants (0.22 μg/kg/day) than for breastfed infants (0.04 μg/kg/day). Given median arsenic concentrations measured in NHBCS tap water and previously published for formula powder, formula powder was estimated to account for ~ 70% of median exposure among formula-fed NHBCS infants.
Conclusions Our findings suggest that breastfed infants have lower arsenic exposure than formula-fed infants, and that both formula powder and drinking water can be sources of exposure for U.S. infants.
Arsenic occurs naturally in bedrock and is a common global contaminant of well water (Meharg 2005). It is a known human carcinogen associated with skin, lung, bladder, kidney, and liver cancer and can also affect neurological, respiratory, cardiovascular, immunological, and endocrine systems [International Agency for Research on Cancer 2004; National Research Council (NRC) 1999, 2014; Naujokas et al. 2013; Tseng 2009]. The U.S. Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) of 10 μg/L for public drinking water (U.S. EPA 2001). Private well water, however, is not subject to regulation and is the primary water source in many rural parts of the United States. In New Hampshire, these wells serve approximately 40% of the population, with approximately 10% of wells containing arsenic concentrations exceeding the MCL (Nuckols et al. 2011; Peters et al. 2006).
Early life is a period of heightened vulnerability to arsenic exposure (Farzan et al. 2013a; Tseng 2009; Vahter 2008). In populations where drinking-water arsenic concentrations are high, early-life exposure has been associated with increased fetal mortality, decreased birth weight, and diminished cognitive function (NRC 2014). Children in these highly exposed populations have different arsenic excretion rates and metabolic profiles than adults, suggesting that children may be more sensitive to arsenic toxicity (Concha et al. 1998; Fängström et al. 2009). Moreover, effects of chronic early-life exposure can continue into adulthood, as suggested by increased occurrences and/or severity of lung disease, cardiovascular disease, and cancer later in life (Naujokas et al. 2013; Smith et al. 2006). Much less is known about the consequences of low-level exposure, particularly in early life. However, in utero exposure to low levels of arsenic has been associated with increased infant infections and the severity of infections in U.S. infants (Farzan et al. 2013b) and childhood exposure with decreased IQ (Wasserman et al. 2014).
Infants and children often experience higher total contaminant exposures than adults because their intakes adjusted for body mass are relatively high (Tsuji et al. 2007) and dietary diversity is low [European Food Safety Authority (EFSA) 2009]. Newborn infants have a limited diet, ingesting breast milk or formula almost exclusively for the first 4–6 months of life. Recent studies suggest that formula powder can contain low concentrations of arsenic (Food and Drug Administration 2013; Jackson et al. 2012; Ljung et al. 2011; Sorbo et al. 2014). This suggests that both components of reconstituted formula—the powder and the water with which it is mixed—can be sources of arsenic exposure for formula-fed infants. Conversely, breast milk has been found to have relatively low concentrations of arsenic (Björklund et al. 2012), even in women with high exposure via their drinking water (e.g., Concha et al. 1998; Fängström et al. 2008; Samanta et al. 2007).
We therefore hypothesized that breastfed infants in New Hampshire have lower exposure to arsenic compared with formula-fed infants. We tested this hypothesis by measuring urinary arsenic concentrations in a subset of infants enrolled in the New Hampshire Birth Cohort Study (NHBCS). In addition, we used a modeling approach to estimate daily intake of arsenic from breast milk and formula for the larger cohort of NHBCS infants, as well as infants consuming formula made with tap water containing arsenic concentrations of potential toxicological and regulatory interest: 1 μg/L, a level considered to be relatively low (NRC 2014); 5 μg/L, the MCL in New Jersey (New Jersey Administrative Code 7:10 2011); and 10 μg/L, the current U.S. EPA MCL (U.S. EPA 2001).
Abstract and Introduction
Abstract
Background Previous studies indicate that concentrations of arsenic in breast milk are relatively low even in areas with high drinking-water arsenic. However, it is uncertain whether breastfeeding leads to reduced infant exposure to arsenic in regions with lower arsenic concentrations.
Objective We estimated the relative contributions of breast milk and formula to arsenic exposure during early infancy in a U.S. population.
Methods We measured arsenic in home tap water (n = 874), urine from 6-week-old infants (n = 72), and breast milk from mothers (n = 9) enrolled in the New Hampshire Birth Cohort Study (NHBCS) using inductively coupled plasma mass spectrometry. Using data from a 3-day food diary, we compared urinary arsenic across infant feeding types and developed predictive exposure models to estimate daily arsenic intake from breast milk and formula.
Results Urinary arsenic concentrations were generally low (median, 0.17 μg/L; maximum, 2.9 μg/L) but 7.5 times higher for infants fed exclusively with formula than for infants fed exclusively with breast milk (β = 2.02; 95% CI: 1.21, 2.83; p < 0.0001, adjusted for specific gravity). Similarly, the median estimated daily arsenic intake by NHBCS infants was 5.5 times higher for formula-fed infants (0.22 μg/kg/day) than for breastfed infants (0.04 μg/kg/day). Given median arsenic concentrations measured in NHBCS tap water and previously published for formula powder, formula powder was estimated to account for ~ 70% of median exposure among formula-fed NHBCS infants.
Conclusions Our findings suggest that breastfed infants have lower arsenic exposure than formula-fed infants, and that both formula powder and drinking water can be sources of exposure for U.S. infants.
Introduction
Arsenic occurs naturally in bedrock and is a common global contaminant of well water (Meharg 2005). It is a known human carcinogen associated with skin, lung, bladder, kidney, and liver cancer and can also affect neurological, respiratory, cardiovascular, immunological, and endocrine systems [International Agency for Research on Cancer 2004; National Research Council (NRC) 1999, 2014; Naujokas et al. 2013; Tseng 2009]. The U.S. Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) of 10 μg/L for public drinking water (U.S. EPA 2001). Private well water, however, is not subject to regulation and is the primary water source in many rural parts of the United States. In New Hampshire, these wells serve approximately 40% of the population, with approximately 10% of wells containing arsenic concentrations exceeding the MCL (Nuckols et al. 2011; Peters et al. 2006).
Early life is a period of heightened vulnerability to arsenic exposure (Farzan et al. 2013a; Tseng 2009; Vahter 2008). In populations where drinking-water arsenic concentrations are high, early-life exposure has been associated with increased fetal mortality, decreased birth weight, and diminished cognitive function (NRC 2014). Children in these highly exposed populations have different arsenic excretion rates and metabolic profiles than adults, suggesting that children may be more sensitive to arsenic toxicity (Concha et al. 1998; Fängström et al. 2009). Moreover, effects of chronic early-life exposure can continue into adulthood, as suggested by increased occurrences and/or severity of lung disease, cardiovascular disease, and cancer later in life (Naujokas et al. 2013; Smith et al. 2006). Much less is known about the consequences of low-level exposure, particularly in early life. However, in utero exposure to low levels of arsenic has been associated with increased infant infections and the severity of infections in U.S. infants (Farzan et al. 2013b) and childhood exposure with decreased IQ (Wasserman et al. 2014).
Infants and children often experience higher total contaminant exposures than adults because their intakes adjusted for body mass are relatively high (Tsuji et al. 2007) and dietary diversity is low [European Food Safety Authority (EFSA) 2009]. Newborn infants have a limited diet, ingesting breast milk or formula almost exclusively for the first 4–6 months of life. Recent studies suggest that formula powder can contain low concentrations of arsenic (Food and Drug Administration 2013; Jackson et al. 2012; Ljung et al. 2011; Sorbo et al. 2014). This suggests that both components of reconstituted formula—the powder and the water with which it is mixed—can be sources of arsenic exposure for formula-fed infants. Conversely, breast milk has been found to have relatively low concentrations of arsenic (Björklund et al. 2012), even in women with high exposure via their drinking water (e.g., Concha et al. 1998; Fängström et al. 2008; Samanta et al. 2007).
We therefore hypothesized that breastfed infants in New Hampshire have lower exposure to arsenic compared with formula-fed infants. We tested this hypothesis by measuring urinary arsenic concentrations in a subset of infants enrolled in the New Hampshire Birth Cohort Study (NHBCS). In addition, we used a modeling approach to estimate daily intake of arsenic from breast milk and formula for the larger cohort of NHBCS infants, as well as infants consuming formula made with tap water containing arsenic concentrations of potential toxicological and regulatory interest: 1 μg/L, a level considered to be relatively low (NRC 2014); 5 μg/L, the MCL in New Jersey (New Jersey Administrative Code 7:10 2011); and 10 μg/L, the current U.S. EPA MCL (U.S. EPA 2001).
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