Brian P. Jackson

Rice consumption contributes to arsenic exposure in US women

Emerging data indicate that rice consumption may lead to potentially harmful arsenic exposure. However, few human data are available, and virtually none exist for vulnerable periods such as pregnancy. Here we document a positive association between rice consumption and urinary arsenic excretion, a biomarker of recent arsenic exposure, in 229 pregnant women. At a 6-mo prenatal visit, we collected a urine sample and 3-d dietary record for water, fish/seafood, and rice. We also tested womens home tap water for arsenic, which we combined with tap water consumption to estimate arsenic exposure through water. Women who reported rice intake (n = 73) consumed a median of 28.3 g/d, which is ∼0.5 cup of cooked rice each day. In general linear models adjusted for age and urinary dilution, both rice consumption (g, dry mass/d) and arsenic exposure through water (μg/d) were significantly associated with natural log-transformed total urinary arsenic (, , both P < 0.0001), as well as inorganic arsenic, monomethylarsonic acid, and dimethylarsinic acid (each P < 0.005). Based on total arsenic, consumption of 0.56 cup/d of cooked rice was comparable to drinking 1 L/d of 10 μg As/L water, the current US maximum contaminant limit. US rice consumption varies, averaging ∼0.5 cup/d, with Asian Americans consuming an average of >2 cups/d. Rice arsenic content and speciation also vary, with some strains predominated by dimethylarsinic acid, particularly those grown in the United States. Our findings along with others indicate that rice consumption should be considered when designing arsenic reduction strategies in the United States.

Arsenic, Organic Foods, and Brown Rice Syrup

Background: Rice can be a major source of inorganic arsenic (Asi) for many sub-populations. Rice products are also used as ingredients in prepared foods, some of which may not be obviously rice based. Organic brown rice syrup (OBRS) is used as a sweetener in organic food products as an alternative to high-fructose corn syrup. We hypothesized that OBRS introduces As into these products. Objective: We determined the concentration and speciation of As in commercially available brown rice syrups and in products containing OBRS, including toddler formula, cereal/energy bars, and high-energy foods used by endurance athletes. Methods: We used inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography coupled to ICP-MS to determine total As (Astotal) concentrations and As speciation in products purchased via the Internet or in stores in the Hanover, New Hampshire, area. Discussion: We found that OBRS can contain high concentrations of Asi and dimethyl-arsenate (DMA). An “organic” toddler milk formula containing OBRS as the primary ingredient had Astotal concentrations up to six times the U.S. Environmental Protection Agency safe drinking water limit. Cereal bars and high-energy foods containing OBRS also had higher As concentrations than equivalent products that did not contain OBRS. Asi was the main As species in most food products tested in this study. Conclusions: There are currently no U.S. regulations applicable to As in food, but our findings suggest that the OBRS products we evaluated may introduce significant concentrations of Asi into an individual’s diet. Thus, we conclude that there is an urgent need for regulatory limits on As in food.

Lung Cancer in a U.S. Population with Low to Moderate Arsenic Exposure

Background Little is known about the carcinogenic potential of arsenic in areas with low to moderate concentrations of arsenic (< 100 μg/L) in drinking water. Objectives We examined associations between arsenic and lung cancer. Methods A population-based case–control study of primary incident lung cancer was conducted in 10 counties in two U.S. states, New Hampshire and Vermont. The study included 223 lung cancer cases and 238 controls, each of whom provided toenail clippings for arsenic exposure measurement by inductively coupled–plasma mass spectrometry. We estimated odds ratios (ORs) of the association between arsenic exposure and lung cancer using unconditional logistic regression with adjustment for potential confounders (age, sex, race/ethnicity, smoking pack-years, education, body mass index, fish servings per week, and toenail selenium level). Results Arsenic exposure was associated with small-cell and squamous-cell carcinoma of the lung [OR = 2.75; 95% confidence interval (CI), 1.00–7.57] for toenail arsenic concentration ≥ 0.114 μg/g, versus < 0.05 μg/g. A history of lung disease (bronchitis, chronic obstructive pulmonary disease, or fibrosis) was positively associated with lung cancer (OR = 2.86; 95% CI, 1.39–5.91). We also observed an elevated risk of lung cancer among participants with a history of lung disease and toenail arsenic ≥ 0.05 μg/g (OR = 4.78; 95% CI, 1.87–12.2) than among individuals with low toenail arsenic and no history of lung disease. Conclusion Although this study supports the possibility of an increased risk of specific lung cancer histologic types at lower levels of arsenic exposure, we recommend large-scale population-based studies.

Reproduction, embryonic development, and maternal transfer of contaminants in the amphibian Gastrophryne carolinensis.

Although many amphibian populations around the world are declining at alarming rates, the cause of most declines remains unknown. Environmental contamination is one of several factors implicated in declines and may have particularly important effects on sensitive developmental stages. Despite the severe effects of maternal transfer of contaminants on early development in other vertebrate lineages, no studies have examined the effects of maternal transfer of contaminants on reproduction or development in amphibians. We examined maternal transfer of contaminants in eastern narrow-mouth toads (Gastrophryne carolinensis) collected from a reference site and near a coal-burning power plant. Adult toads inhabiting the industrial area transferred significant quantities of selenium and strontium to their eggs, but Se concentrations were most notable (up to 100 μg/g dry mass). Compared with the reference site, hatching success was reduced by 11% in clutches from the contaminated site. In surviving larvae, the frequency of developmental abnormalities and abnormal swimming was 55–58% higher in the contaminated site relative to the reference site. Craniofacial abnormalities were nearly an order of magnitude more prevalent in hatchlings from the contaminated site. When all developmental criteria were considered collectively, offspring from the contaminated site experienced 19% lower viability. Although there was no statistical relationship between the concentration of Se or Sr transferred to eggs and any measure of offspring viability, our study demonstrates that maternal transfer may be an important route of contaminant exposure in amphibians that has been overlooked.

Nondestructive indices of trace element exposure in squamate reptiles

Compared with birds, mammals, fish, and even amphibians, very little is known about the effects of contaminants on reptiles. Recent evidence that many reptile populations may be declining has stimulated demand for toxicological studies of reptiles as well as development of nondestructive sampling techniques useful for assessing and monitoring contaminant exposure. The current study experimentally evaluated the utility of shed skins, tail clips, and blood samples as nondestructive indices of trace element exposure in banded water snakes, Nerodia fasciata. For 13.5 months, snakes were either fed fish from a coal ash-contaminated site or uncontaminated food from a reference site. Snakes fed contaminated prey accumulated As, Cd, Se, Sr, and V in various organs (i.e. liver, kidney, and/or gonads). Moreover, non-parametric discriminant function analysis revealed that snakes could be placed in two groups that reliably reflected their experimental diet based upon Se, Sr, and As concentrations in tail clips, blood, and/or shed skins. We suggest that nondestructive sampling techniques, particularly analyses of blood and tail clips, may be easily applied in evaluations of contaminant exposure in the field and laboratory and may prevent excessive destructive sampling of potentially threatened reptile species.

Arsenic and selenium speciation in coal fly ash extracts by ion chromatography-inductively coupled plasma mass spectrometry

Ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) affords a sensitive technique to quantify inorganic As and Se species at trace levels; however, few studies have used the multi-element capabilities of ICP-MS as a detector for chromatographic applications. Here, IC coupled with ICP-MS was used to determine As(iii), As(v), Se(iv), and Se(vi) in aqueous extracts of coal fly ash. All four species were resolved, with retention times of 1.1, 2.9, 4.8, and 6.3 min for As(iii), Se(iv), Se(vi), and As(v), respectively. Because all species were fully resolved, the resulting chromatograms were obtained by summing signal intensities form/z 75+m/z82. Absolute detection limits of 7.2, 87, 117, and 28 pg for As(iii), Se(iv), Se(vi), and As(v), respectively, were obtained, corresponding to 0.072, 0.868, 1.174, and 0.284 µg l–1 for a 100 µl injection volume. The technique was used to determine the speciation of As and Se in aqueous extracts of 24 coal fly ash samples including NIST SRM 1633b. The predominant species were As(v) and Se(iv), with As(iii) detected in two low pH fly ashes. Extraction of fly ashes at pH 5 altered the concentrations of total soluble As and Se but did not affect the predominant As and Se speciation.

Bioavailability, toxicity, and bioaccumulation of quantum dot nanoparticles to the amphipod Leptocheirus plumulosus

Understanding the relative toxicities of different modes of nanoparticle exposure as compared with their dissolved metal ions are emerging areas in ecotoxicology. Here, we report on bioavailability, toxicity, and bioaccumulation of carboxyl-functionalized CdSe/ZnS quantum dots (QDs) to the amphipod Leptocheirus plumulosus exposed to equivalent Cd concentrations via dissolved Cd, QDs in water, or QDs in algal food. Both modes of QD exposure were accumulated to greater extent than dissolved Cd. Exposure to QDs via algae resulted in high amphipod mortality. Cadmium and Se in amphipods exposed to QDs in water were highly correlated and spatially localized within the amphipod. In contrast, when exposed to QDs via algae the metals were more disperse and not highly correlated suggesting QD dissolution and resultant metal ion toxicity. This study suggests QDs are accumulated to a greater extent than the dissolved ion and could lead to trophic transfer. QDs ingested with algae are bioavailable and result in toxicity, which is not observed in the absence of algae.

Laboratory diet profoundly alters gene expression and confounds genomic analysis in mouse liver and lung.

Nutritional studies in laboratory animals have long shown that various dietary components can contribute to altered gene expression and metabolism, but diet alone has not been considered in whole animal genomic studies. In this study, global gene expression changes in mice fed either a non-purified chow or a purified diet were investigated and background metal levels in the two diets were measured by ICP-MS. C57BL/6J mice were raised for 5 weeks on either the cereal-based, non-purified LRD-5001 diet or the purified, casein-based AIN-76A diet, as part of a larger study examining the effects of low dose arsenic (As) in the diet or drinking water. Affymetrix Mouse Whole Genome 430 2.0 microarrays were used to assess gene expression changes in the liver and lung. Microarray analysis revealed that animals fed the LRD-5001 diet displayed a significantly higher hepatic expression of Phase I and II metabolism genes as well as other metabolic genes. The LRD-5001 diet masked the As-induced gene expression changes that were clearly seen in the animals fed the AIN-76A diet when each dietary group was exposed to 100 ppb As in drinking water. Trace metal analysis revealed that the LRD-5001 diet contained a mixture of inorganic and organic As at a total concentration of 390 ppb, while the AIN-76A diet contained approximately 20 ppb. These findings indicate that the use of non-purified diets may profoundly alter observable patterns of change induced by arsenic and, likely, by other experimental treatments, particularly, altering gene and protein expression.

Genetic and Non-genetic Predictors of LINE-1 Methylation in Leukocyte DNA

Background: Altered DNA methylation has been associated with various diseases. Objective: We evaluated the association between levels of methylation in leukocyte DNA at long interspersed nuclear element 1 (LINE-1) and genetic and non-genetic characteristics of 892 control participants from the Spanish Bladder Cancer/EPICURO study. Methods: We determined LINE-1 methylation levels by pyrosequencing. Individual data included demographics, smoking status, nutrient intake, toenail concentrations of 12 trace elements, xenobiotic metabolism gene variants, and 515 polymorphisms among 24 genes in the one-carbon metabolism pathway. To assess the association between LINE-1 methylation levels (percentage of methylated cytosines) and potential determinants, we estimated beta coefficients (βs) by robust linear regression. Results: Women had lower levels of LINE-1 methylation than men (β = –0.7, p = 0.02). Persons who smoked blond tobacco showed lower methylation than nonsmokers (β = –0.7, p = 0.03). Arsenic toenail concentration was inversely associated with LINE-1 methylation (β = –3.6, p = 0.003). By contrast, iron (β = 0.002, p = 0.009) and nickel (β = 0.02, p = 0.004) were positively associated with LINE-1 methylation. Single nucleotide polymorphisms (SNPs) in DNMT3A (rs7581217-per allele, β = 0.3, p = 0.002), TCN2 (rs9606756-GG, β = 1.9, p = 0.008; rs4820887-AA, β = 4.0, p = 4.8 × 10–7; rs9621049-TT, β = 4.2, p = 4.7 × 10–9), AS3MT (rs7085104-GG, β = 0.7, p = 0.001), SLC19A1 (rs914238, TC vs. TT: β = 0.5 and CC vs. TT: β = –0.3, global p = 0.0007) and MTHFS (rs1380642, CT vs. CC: β = 0.3 and TT vs. CC; β = –0.8, global p = 0.05) were associated with LINE-1 methylation. Conclusions: We identified several characteristics, environmental factors, and common genetic variants that predicted DNA methylation among study participants.

Trophic and maternal transfer of selenium in brown house snakes (Lamprophis fuliginosus)

Excessive concentrations of dietary Se are toxic to oviparous vertebrates (i.e., fish and birds) but little is known about its accumulation and effects in reptiles. We exposed female brown house snakes, Lamprophis fuliginosus, to 10 and 20 microg/g Se by injecting seleno-D,L-methionine into their prey items and compared the snakes to individuals receiving background levels of approximately 1 microg/g dietary Se. Snakes were fed meals equaling 25% of their body mass 2-3 times a month for 10 months. Snakes exposed to excessive Se accumulated significant concentrations of Se in kidney, liver, and ovarian tissue, but accumulation had no effect on female survival, food consumption, growth, or body condition. Fewer females exposed to excessive Se reproduced than females exposed to 1 microg/g Se (67% vs. 91%, respectively), but the reduction in reproductive activity was not statistically significant. Total reproductive output of females did not differ among the three dietary treatments. However, snakes exposed to 10 and 20 microg/g Se transferred significant concentrations of Se to their eggs. In the 20 microg/g treatment, maternal transfer resulted in Se concentrations in eggs that surpassed all suggested reproductive toxicity thresholds for birds and fish. Further studies are needed to more rigorously determine whether maternal transfer of Se in this snake species affects the viability of developing embryos or the health of offspring.