concentrations in three rice syrups (and from two lots of one of the syrups) ranged from 80 to 400 ng/g (). Asi
was 80–90% of Astotal
for two of the three syrups; for the third syrup, only 50% of Astotal
. However, because this syrup was much higher in Astotal
, it also had the highest Asi
concentration of the syrups. All syrups had detectable MMA, ranging from 3 to 4% of Astotal
, but the major organic As species for each syrup was DMA. Our results are similar to those of Signes-Pastor et al. (2009)
who reported dry weight Astotal
concentrations of 80, 100, 120, and 330 ng/g in four rice syrups, with 71% Asi
and 85% extraction efficiency in the highest As syrup. Moreover, given these authors’ estimate of 15% moisture content for the syrups, we estimate that the actual contribution to As concentration in food products that include OBRS as the dried product—such as toddler formulas—would be approximately 1.15 times the concentration listed in .
As concentrations and As speciation for three OBRSs.
We analyzed 17 different formulas. Average Astotal
concentrations in the 15 infant formulas that did not contain OBRS were relatively low, in the range of 2–12 ng/g (Jackson et al. 2012
). Those results were consistent with two other studies of As in infant formula (Ljung et al. 2011
; Vela and Heitkemper 2004
). However, the As concentrations in the two toddler formulas that listed OBRS as the primary ingredient (one dairy-based and one soy-based) were > 20 times the As concentrations in infant formulas that did not contain OBRS (). The proportion of Asi
varied among products and among lots of the soy-based formula, but the concentration of Asi
in the reconstituted formulas with OBRS was either just below (dairy, 8–9 µg/L) or 1.5–2.5 times above (soy) the current U.S. drinking water standard (10 µg/L). In addition, the OBRS formulas contained 19–40 µg/L DMA and trace levels of MMA. Expressed as daily As intake per kilogram of body weight, the exposure of infants and toddlers drinking OBRS-containing milk products is even more apparent (). Using web-based search engines, we found only these two toddler formulas that used OBRS, so the number of infants using this formula is presumably a very low percentage of U.S. formula-fed infants.
Figure 1 Asi and DMA concentrations in milk formulas with and without OBRS. (A) Concentrations of Asi and DMA in prepared formula in reconstituted milk formulas relative to the current WHO and U.S. EPA drinking water standard of 10 µg/L (horizontal line). (more ...)
Infants, in a phase of rapid development, are especially vulnerable to contaminants, and emerging data suggest that As exposure early in life may pose risks not only during childhood but also in adult life (Vahter 2009
). This suggests that we need to pay particular attention to the potential for As exposure during infancy. The standards and guidelines for daily intake of As are currently a matter of debate (Meharg and Raab 2009
; Meharg et al. 2008b
). The WHO established a provisional maximum tolerable daily intake (PMTDI) guideline of 2.1 µg/kg/day in 1983 (Food and Agriculture Organization of the United Nations/WHO 1983). For an infant weighing either 6 or 9 kg, both of the OBRS formulas would be above this value based on Astotal
; for a 6-kg infant, the soy formulas would be above the guideline based only on Asi
. It should be noted that the WHO 1983 PMTDI is based on a safe drinking water limit of 50 µg/L rather than the current limit of 10 µg/L [European Food Safety Authority (EFSA) 2009; Meharg and Raab 2009
]. Currently, only China has a limit for As in food: an Asi
limit of 150 ng/g for rice (Zhu et al. 2008
). Although the OBRS toddler formulas would not exceed this limit on average, Astotal
concentrations of these OBRS formulas are cause for concern.
Cereal and energy bars. OBRS is also a popular sweetener for many cereal/energy bars and high-energy athletic performance products. Our web- and store-based market survey of 100 bars indicated that about 50% contain either OBRS (31%), other rice products (5%), or both (14%). We tested 29 bars and three types (flavors) of an energy product obtained from a local supermarket. The results for the cereal/energy bars are shown in . All of the bars had detectable Astotal with a range of 8–128 ng/g. The 7 bars that did not list any rice product among the top five ingredients were among the 8 lowest As-containing bars we tested. The remaining bars listed at least one of four rice products (OBRS, rice flour, rice grain, and rice flakes) in the first five ingredients and had Astotal concentrations ranging from 23 to 128 ng/g.
As concentrations and speciation in 29 cereal bars, with information about their rice-based ingredients.
We analyzed As speciation in 12 of the rice-containing bars. Of the 12 bars, 11 contained Asi concentrations > 50%, with an average of 70% Asi. All organic As was DMA. The percent recovery (sum of As species as a percentage of Astotal) ranged from 67% to 124%; however, some of this variability is because the bars were not dried before analysis and were analyzed “as is,” with limited homogenization using a ceramic-bladed knife. The amount of Asi ingested when eating one of these bars is a function of the As concentration of the bar and the size (weight) of the bar. The bars we analyzed ranged in weight from 28 to 68 g; at the upper limit of bar weight and Asi content, an individual bar contained up to 4 µg Asi. For example, bar 27 weighed 45 g and contained 101 ng/g Astotal and 79% Asi, equating to an Asi content of 3.6 µg.
Energy shot blocks. We also analyzed As concentration and speciation in three high-energy products for endurance athletes known as “energy shot blocks," each of which contained OBRS. Although an educated consumer might be aware of the potential for rice to contain As (and therefore know that products containing rice ingredients might also contain As), the energy shot blocks are gel-like blocks, so it would not be immediately apparent to the consumer that these too are rice-based products.
The As concentration in one of the energy shot blocks containing OBRS was 84 ± 3 ng/g Astotal (n = 3), which was 100% Asi. The other two energy shot blocks were very similar to one another in Astotal concentrations (171 ± 3.6 ng/g, mean ± SD; n = 6) and speciation (53% Asi). No MMA was detected in the energy shot blocks. All three flavors contained 2.5–2.7 µg Asi per 30-g serving. The manufacturer recommends consuming up to two servings (60 g) per hour during exercise, so an endurance athlete consuming four servings during a 2-hr workout would consume approximately 10 µg Asi per day, equal to the Asi intake resulting from consumption of 1 L of water at the current U.S. EPA and WHO limit of 10 µg/L. Athletes consuming the two flavors containing 171 ng/g Astotal would also consume 2.5 µg DMA per 30-g serving.