Arsenic exposure and cancer mortality in a US-based prospective cohort: the strong heart study

BACKGROUND

Inorganic arsenic, a carcinogen at high exposure levels, is a major global health problem. Prospective studies on carcinogenic effects at low-moderate arsenic levels are lacking.

METHODS

We evaluated the association between baseline arsenic exposure and cancer mortality in 3,932 American Indians, 45 to 74 years of age, from Arizona, Oklahoma, and North/South Dakota who participated in the Strong Heart Study from 1989 to 1991 and were followed through 2008. We estimated inorganic arsenic exposure as the sum of inorganic and methylated species in urine. Cancer deaths (386 overall, 78 lung, 34 liver, 18 prostate, 26 kidney, 24 esophagus/stomach, 25 pancreas, 32 colon/rectal, 26 breast, and 40 lymphatic/hematopoietic) were assessed by mortality surveillance reviews. We hypothesized an association with lung, liver, prostate, and kidney cancers.

RESULTS

Median (interquartile range) urine concentration for inorganic plus methylated arsenic species was 9.7 (5.8-15.6) μg/g creatinine. The adjusted HRs [95% confidence interval (CI)] comparing the 80th versus 20th percentiles of arsenic were 1.14 (0.92-1.41) for overall cancer, 1.56 (1.02-2.39) for lung cancer, 1.34 (0.66, 2.72) for liver cancer, 3.30 (1.28-8.48) for prostate cancer, and 0.44 (0.14, 1.14) for kidney cancer. The corresponding hazard ratios were 2.46 (1.09-5.58) for pancreatic cancer, and 0.46 (0.22-0.96) for lymphatic and hematopoietic cancers. Arsenic was not associated with cancers of the esophagus and stomach, colon and rectum, and breast.

CONCLUSIONS

Low to moderate exposure to inorganic arsenic was prospectively associated with increased mortality for cancers of the lung, prostate, and pancreas.

IMPACT

These findings support the role of low-moderate arsenic exposure in development of lung, prostate, and pancreas cancer and can inform arsenic risk assessment.

Cadmium exposure and incident peripheral arterial disease

BACKGROUND

Cadmium has been associated with peripheral arterial disease (PAD) in cross-sectional studies, but prospective evidence is lacking. Our goal was to evaluate the association of urine cadmium concentrations with incident PAD in a large population-based cohort.

METHODS AND RESULTS

A prospective cohort study was performed with 2864 adult American Indians 45 to 74 years of age from Arizona, Oklahoma, and North and South Dakota who participated in the Strong Heart Study from 1989 to 1991 and were followed through 2 follow-up examination visits in 1993 to 1995 and 1997 to 1999. Participants were free of PAD, defined as an ankle brachial index <0.9 or >1.4 at baseline, and had complete baseline information on urine cadmium, potential confounders, and ankle brachial index determinations in the follow-up examinations. Urine cadmium was measured using inductively coupled plasma mass spectrometry and corrected for urinary dilution by normalization to urine creatinine. Multivariable-adjusted hazard ratios were computed using Cox-proportional hazards models for interval-censored data. A total of 470 cases of incident PAD, defined as an ankle brachial index <0.9 or >1.4, were identified. After adjustment for cardiovascular disease risk factors including smoking status and pack-years, the hazard ratio comparing the 80th to the 20th percentile of urine cadmium concentrations was 1.41 (1.05-1.81). The hazard ratio comparing the highest to the lowest tertile was 1.96 (1.32-2.81). The association persisted after excluding participants with ankle brachial index >1.4 only as well as in subgroups defined by sex and smoking status.

CONCLUSIONS

Urine cadmium, a biomarker of long-term cadmium exposure, was independently associated with incident PAD, providing further support for cadmium as a cardiovascular disease risk factor.

Differential methylation of the arsenic (III) methyltransferase promoter according to arsenic exposure

Inorganic arsenic is methylated in the body by arsenic (III) methyltransferase (AS3MT). Arsenic methylation is thought to play a role in arsenic-related epigenetic phenomena, including aberrant DNA and histone methylation. However, it is unclear whether the promoter of the AS3MT gene, which codes for AS3MT, is differentially methylated as a function of arsenic exposure. In this study, we evaluated AS3MT promoter methylation according to exposure, assessed by urinary arsenic excretion in a stratified random sample of 48 participants from the Strong Heart Study who had urine arsenic measured at baseline and DNA available from 1989 to 1991 and 1998-1999. For this study, all data are from the 1989-1991 visit. We measured AS3MT promoter methylation at its 48 CpG loci by bisulphite sequencing. We compared mean  % methylation at each CpG locus by arsenic exposure group using linear regression adjusted for study centre, age and sex. A hypomethylated region in the AS3MT promoter was associated with higher arsenic exposure. In vitro, arsenic induced AS3MT promoter hypomethylation, and it increased AS3MT expression in human peripheral blood mononuclear cells. These findings may suggest that arsenic exposure influences the epigenetic regulation of a major arsenic metabolism gene.

SLCO1B1 variants and urine arsenic metabolites in the Strong Heart Family Study

Arsenic species patterns in urine are associated with risk for cancer and cardiovascular diseases. The organic anion transporter coded by the gene SLCO1B1 may transport arsenic species, but its association with arsenic metabolites in human urine has not yet been studied. The objective of this study is to evaluate associations of urine arsenic metabolites with variants in the candidate gene SLCO1B1 in adults from the Strong Heart Family Study. We estimated associations between % arsenic species biomarker traits and 5 single-nucleotide polymorphisms (SNPs) in the SLCO1B1 gene in 157 participants, assuming additive genetics. Linear regression models for each SNP accounted for kinships and were adjusted for sex, body mass index, and study center. The minor allele of rs1564370 was associated with lower %MMA (p = .0003) and higher %DMA (p = .0002), accounting for 8% of the variance for %MMA and 9% for %DMA. The rs1564370 minor allele homozygote frequency was 17% and the heterozygote frequency was 43%. The minor allele of rs2291075 was associated with lower %MMA (p = .0006) and higher %DMA (p = .0014), accounting for 7% of the variance for %MMA and 5% for %DMA. The frequency of rs2291075 minor allele homozygotes was 1% and of heterozygotes was 15%. Common variants in SLCO1B1 were associated with differences in arsenic metabolites in a preliminary candidate gene study. Replication of this finding in other populations and analyses with respect to disease outcomes are needed to determine whether this novel candidate gene is important for arsenic-associated disease risks.

In vitro intestinal bioavailability of arsenosugar metabolites and presystemic metabolism of thio-dimethylarsinic acid in Caco-2 cells

Whereas inorganic arsenic is classified as a human carcinogen, risks to human health related to the presence of arsenosugars in marine food are still unclear. Since studies indicate that human inorganic arsenic metabolites contribute to inorganic arsenic induced carcinogenicity, a risk assessment for arsenosugars should also include a toxicological characterization of their respective metabolites. Here we assessed intestinal bioavailability of the human arsenosugar metabolites oxo-DMAA(V), thio-DMAA(V), oxo-DMAE(V), thio-DMAE(V) and thio-DMA(V) in relation to arsenite in the Caco-2 intestinal barrier model. Whereas arsenite and thio-DMA(V) caused barrier disruption at concentrations ≥10 μM, all other metabolites did not cause a barrier leakage, even when applied at 50 times higher concentrations than arsenite and thio-DMA(V). The transfer studies point to a strong intestinal bioavailability of thio-DMA(V) and thio-DMAE(V), whereas oxo-DMAA(V), thio-DMAA(V) and oxo-DMAE(V) passed the in vitro intestinal barrier only to a very small extent. Detailed influx and efflux studies indicate that arsenite and thio-DMA(V) cross the intestinal barrier most likely by passive diffusion (paracellular) and facilitated (transcellular) transport. LC-ICP-QMS based arsenic speciation studies during the transfer experiments demonstrate transfer of thio-DMA(V) itself across the intestinal barrier and suggest metabolism of thio-DMA(V) using the in vitro intestinal barrier model to its oxygen-analogue DMA(V). In the case of arsenite no metabolism was observed. In summary the two arsenosugar metabolites thio-DMA(V) and thio-DMAE(V) showed intestinal bioavailability similar to that of arsenite, and about 10-fold higher than that reported for arsenosugars (Leffers et al., Mol. Nutr. Food Res., 2013, DOI: 10.1002/mnfr.201200821) in the same in vitro model. Thus, a presystemic metabolism of arsenosugars might strongly impact arsenic intestinal bioavailability after arsenosugar intake and should therefore be considered when assessing the risks to human health related to the consumption of arsenosugar-containing food.

In vitro toxicological characterization of two arsenosugars and their metabolites

SCOPE

In their recently published Scientific Opinion on Arsenic in Food, the European Food Safety Authority concluded that a risk assessment for arsenosugars is currently not possible, largely because of the lack of relevant toxicological data. To address this issue, we carried out a toxicological in vitro characterization of two arsenosugars and six arsenosugar metabolites.

METHODS AND RESULTS

The highly pure synthesized arsenosugars, DMA(V) -sugar-glycerol and DMA(V) -sugar-sulfate, investigated in this study, as well as four metabolites, oxo-dimethylarsenoacetic acid (oxo-DMAA(V) ), oxo-dimethylarsenoethanol (oxo-DMAE(V) ), thio-DMAA(V) and thio-DMAE(V) , exerted neither cytotoxicity nor genotoxicity up to 500 μM exposure in cultured human bladder cells. However, two arsenosugar metabolites, namely dimethyl-arsinic acid (DMA(V) ) and thio-dimethylarsinic acid (thio-DMA(V) ), were toxic to the cells; thio-DMA(V) was even slightly more cytotoxic than arsenite. Additionally, intestinal bioavailability of the arsenosugars was assessed applying the Caco-2 intestinal barrier model. The observed low, but significant transfer rates of the arsenosugars across the barrier model provide further evidence that arsenosugars are intestinally bioavailable.

CONCLUSION

In a cellular system that metabolizes arsenosugars, cellular toxicity likely arises. Thus, in strong contrast to arsenobetaine, arsenosugars cannot be categorized as nontoxic for humans and a risk to human health cannot be excluded.

Roxarsone, inorganic arsenic, and other arsenic species in chicken: a U.S.-based market basket sample

BACKGROUND

Inorganic arsenic (iAs) causes cancer and possibly other adverse health outcomes. Arsenic-based drugs are permitted in poultry production; however, the contribution of chicken consumption to iAs intake is unknown.

OBJECTIVES

We sought to characterize the arsenic species profile in chicken meat and estimate bladder and lung cancer risk associated with consuming chicken produced with arsenic-based drugs.

METHODS

Conventional, antibiotic-free, and organic chicken samples were collected from grocery stores in 10 U.S. metropolitan areas from December 2010 through June 2011. We tested 116 raw and 142 cooked chicken samples for total arsenic, and we determined arsenic species in 65 raw and 78 cooked samples that contained total arsenic at ≥ 10 µg/kg dry weight.

RESULTS

The geometric mean (GM) of total arsenic in cooked chicken meat samples was 3.0 µg/kg (95% CI: 2.5, 3.6). Among the 78 cooked samples that were speciated, iAs concentrations were higher in conventional samples (GM = 1.8 µg/kg; 95% CI: 1.4, 2.3) than in antibiotic-free (GM = 0.7 µg/kg; 95% CI: 0.5, 1.0) or organic (GM = 0.6 µg/kg; 95% CI: 0.5, 0.8) samples. Roxarsone was detected in 20 of 40 conventional samples, 1 of 13 antibiotic-free samples, and none of the 25 organic samples. iAs concentrations in roxarsone-positive samples (GM = 2.3 µg/kg; 95% CI: 1.7, 3.1) were significantly higher than those in roxarsone-negative samples (GM = 0.8 µg/kg; 95% CI: 0.7, 1.0). Cooking increased iAs and decreased roxarsone concentrations. We estimated that consumers of conventional chicken would ingest an additional 0.11 µg/day iAs (in an 82-g serving) compared with consumers of organic chicken. Assuming lifetime exposure and a proposed cancer slope factor of 25.7 per milligram per kilogram of body weight per day, this increase in arsenic exposure could result in 3.7 additional lifetime bladder and lung cancer cases per 100,000 exposed persons.

CONCLUSIONS

Conventional chicken meat had higher iAs concentrations than did conventional antibiotic-free and organic chicken meat samples. Cessation of arsenical drug use could reduce exposure and the burden of arsenic-related disease in chicken consumers.

Cadmium exposure and incident cardiovascular disease

BACKGROUND

Cadmium is a widespread toxic metal with potential cardiovascular effects, but no studies have evaluated cadmium and incident cardiovascular disease. We evaluated the association of urine cadmium concentration with cardiovascular disease incidence and mortality in a large population-based cohort.

METHODS

We conducted a prospective cohort study of 3348 American Indian adults 45-74 years of age from Arizona, Oklahoma, and North and South Dakota, who participated in the Strong Heart Study in 1989-1991. Urine cadmium was measured using inductively coupled plasma mass spectrometry. Follow-up extended through 31 December 2008.

RESULTS

The geometric mean cadmium level in the study population was 0.94 μg/g (95% confidence interval [CI] = 0.92-0.96). We identified 1084 cardiovascular events, including 400 deaths. After adjustment for sociodemographic and cardiovascular risk factors, the hazard ratios (HRs) (comparing the 80th to the 20th percentile of urine cadmium concentrations) was 1.43 for cardiovascular mortality (95% CI = 1.21-1.70) and 1.34 for coronary heart disease mortality (1.10-1.63). The corresponding HRs for incident cardiovascular disease, coronary heart disease, stroke, and heart failure were 1.24 (1.11-1.38), 1.22 (1.08-1.38), 1.75 (1.17-2.59), and 1.39 (1.01-1.94), respectively. The associations were similar in most study subgroups, including never-smokers.

CONCLUSIONS

Urine cadmium, a biomarker of long-term exposure, was associated with increased cardiovascular mortality and increased incidence of cardiovascular disease. These findings support that cadmium exposure is a cardiovascular risk factor.

Heritability and preliminary genome-wide linkage analysis of arsenic metabolites in urine

BACKGROUND

Arsenic (III) methyltransferase (AS3MT) has been related to urine arsenic metabolites in association studies. Other genes might also play roles in arsenic metabolism and excretion.

OBJECTIVE

We evaluated genetic determinants of urine arsenic metabolites in American Indian adults from the Strong Heart Study (SHS).

METHODS

We evaluated heritability of urine arsenic metabolites [percent inorganic arsenic (%iAs), percent monomethylarsonate (%MMA), and percent dimethylarsinate (%DMA)] in 2,907 SHS participants with urine arsenic measurements and at least one relative within the cohort. We conducted a preliminary linkage analysis in a subset of 487 participants with available genotypes on approximately 400 short tandem repeat markers using a general pedigree variance component approach for localizing quantitative trait loci (QTL).

RESULTS

The medians (interquartile ranges) for %iAs, %MMA, and %DMA were 7.7% (5.4-10.7%), 13.6% (10.5-17.1%), and 78.4% (72.5-83.1%), respectively. The estimated heritability was 53% for %iAs, 50% for %MMA, and 59% for %DMA. After adjustment for sex, age, smoking, body mass index, alcohol consumption, region, and total urine arsenic concentrations, LOD [logarithm (to the base of 10) of the odds] scores indicated suggestive evidence for genetic linkage with QTLs influencing urine arsenic metabolites on chromosomes 5 (LOD = 2.03 for %iAs), 9 (LOD = 2.05 for %iAs and 2.10 for %MMA), and 11 (LOD = 1.94 for %iAs). A peak for %DMA on chromosome 10 within 2 Mb of AS3MT had an LOD of 1.80.

CONCLUSIONS

This population-based family study in American Indian communities supports a genetic contribution to variation in the distribution of arsenic metabolites in urine and, potentially, the involvement of genes other than AS3MT.

Arsenic exposure, diabetes prevalence, and diabetes control in the Strong Heart Study

This study evaluated the association of arsenic exposure, as measured in urine, with diabetes prevalence, glycated hemoglobin, and insulin resistance in American Indian adults from Arizona, Oklahoma, and North and South Dakota (1989-1991). We studied 3,925 men and women 45-74 years of age with available urine arsenic measures. Diabetes was defined as a fasting glucose level of 126 mg/dL or higher, a 2-hour glucose level of 200 mg/dL or higher, a hemoglobin A1c (HbA1c) of 6.5% or higher, or diabetes treatment. Median urine arsenic concentration was 14.1 µg/L (interquartile range, 7.9-24.2). Diabetes prevalence was 49.4%. After adjustment for sociodemographic factors, diabetes risk factors, and urine creatinine, the prevalence ratio of diabetes comparing the 75th versus 25th percentiles of total arsenic concentrations was 1.14 (95% confidence interval: 1.08, 1.21). The association between arsenic and diabetes was restricted to participants with poor diabetes control (HbA1c ≥8%). Arsenic was positively associated with HbA1c levels in participants with diabetes. Arsenic was not associated with HbA1c or with insulin resistance (assessed by homeostatic model assessment to quantify insulin resistance) in participants without diabetes. Urine arsenic was associated with diabetes control in a population from rural communities in the United States with a high burden of diabetes. Prospective studies that evaluate the direction of the relation between poor diabetes control and arsenic exposure are needed.

Urine arsenic and prevalent albuminuria: evidence from a population-based study

BACKGROUND

Long-term arsenic exposure is a major global health problem. However, few epidemiologic studies have evaluated the association of arsenic with kidney measures. Our objective was to evaluate the cross-sectional association between inorganic arsenic exposure and albuminuria in American Indian adults from rural areas of Arizona, Oklahoma, and North and South Dakota.

STUDY DESIGN

Cross-sectional. SETTING & PARTIPANTS: Strong Heart Study locations in Arizona, Oklahoma, and North and South Dakota. 3,821 American Indian men and women aged 45-74 years with urine arsenic and albumin measurements.

PREDICTOR

Urine arsenic.

OUTCOMES

Urine albumin-creatinine ratio and albuminuria status.

MEASUREMENTS

Arsenic exposure was estimated by measuring total urine arsenic and urine arsenic species using inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography-ICPMS, respectively. Urine albumin was measured by automated nephelometric immunochemistry.

RESULTS

The prevalence of albuminuria (albumin-creatinine ratio ≥30 mg/g) was 30%. Median value for the sum of inorganic and methylated arsenic species was 9.7 (IQR, 5.8-15.6) μg per gram of creatinine. Multivariable-adjusted prevalence ratios of albuminuria (albumin-creatinine ratio ≥30 mg/g) comparing the 3 highest to lowest quartiles of the sum of inorganic and methylated arsenic species were 1.16 (95% CI, 1.00-1.34), 1.24 (95% CI, 1.07-1.43), and 1.55 (95% CI, 1.35-1.78), respectively (P for trend <0.001). The association between urine arsenic and albuminuria was observed across all participant subgroups evaluated and was evident for both micro- and macroalbuminuria.

LIMITATIONS

The cross-sectional design cannot rule out reverse causation.

CONCLUSIONS

Increasing urine arsenic concentrations were cross-sectionally associated with increased albuminuria in a rural US population with a high burden of diabetes and obesity. Prospective epidemiologic and mechanistic evidence is needed to understand the role of arsenic as a kidney disease risk factor.

Arsenic speciation in food chains from mid-Atlantic hydrothermal vents

Arsenic concentration and speciation were determined in benthic fauna collected from the Mid-Atlantic Ridge hydrothermal vents. The shrimp species, Rimicaris exoculata, the vent chimney-dwelling mussel, Bathymodiolus azoricus, Branchipolynoe seepensis, a commensal worm of B. azoricus, and the gastropod Peltospira smaragdina showed variations in As concentration and in stable isotope (δ¹³C and δ¹⁵N) signature between species, suggesting different sources of As uptake. Arsenic speciation showed arsenobetaine to be the dominant species in R. exoculata, whereas in B. azoricus and B. seepensis arsenosugars were most abundant, although arsenobetaine, dimethylarsinate, and inorganic arsenic were also observed, along with several unidentified species. Scrape samples from outside the vent chimneys, covered with microbial mat, which is a presumed food source for many vent organisms, contained high levels of total As, but organic species were not detectable. The formation of arsenosugars in pelagic environments is typically attributed to marine algae, and the pathway to arsenobetaine is still unknown. The occurrence of arsenosugars and arsenobetaine in these deep sea organisms, where primary production is chemolithoautotrophic and stable isotope analyses indicate food sources are of vent origin, suggests that organic arsenicals can occur in a food web without algae or other photosynthetic life.

Arsenic species in poultry feather meal

Organoarsenical drugs are widely used in the production of broiler chickens in the United States. Feathers from these chickens are processed into a meal product that is used as an animal feed additive and as an organic fertilizer. Research conducted to date suggests that arsenical drugs, specifically roxarsone, used in poultry production result in the accumulation of arsenic in the keratinous material of poultry feathers. The use of feather meal product in the human food system and in other settings may result in human exposures to arsenic. Consequently, the presence and nature of arsenic in twelve samples of feather meal product from six US states and China were examined. Since arsenic toxicity is highly species-dependent, speciation analysis using HPLC/ICPMS was performed to determine the biological relevance of detected arsenic. Arsenic was detected in all samples (44-4100 μg kg(-1)) and speciation analyses revealed that inorganic forms of arsenic dominated, representing 37 - 83% of total arsenic. Roxarsone was not detected in the samples (<20 μg As kg(-1)). Feather meal products represent a previously unrecognized source of arsenic in the food system, and may pose additional risks to humans as a result of its use as an organic fertilizer and when animal waste is managed.

Arsenic species and selected metals in human urine: validation of HPLC/ICPMS and ICPMS procedures for a long-term population-based epidemiological study

Exposure to high inorganic arsenic concentrations in drinking water has been related to detrimental health effects, including cancers and possibly cardiovascular disease, in many epidemiological studies. Recent studies suggest that arsenic might elicit some of its toxic effects also at lower concentrations. The Strong Heart Study, a large epidemiological study of cardiovascular disease in American Indian communities, collected urine samples and performed medical examinations on 4,549 participants over a 10-year period beginning in 1989. We used anion-exchange HPLC/ICPMS to determine concentrations of arsenic species (methylarsonate, dimethylarsinate and arsenate) in 5,095 urine samples from the Strong Heart Study. We repeated the chromatography on a portion of the urine sample that had been oxidised, by addition of H(2)O(2), to provide additional information on the presence of As(III) species and thio-arsenicals, and by difference, of arsenobetaine and other non-retained cations. Total concentrations for As, Cd, Mo, Pb, Sb, Se, U, W, and Zn were also determined in the urine samples by ICPMS. The dataset will be used to evaluate the relationships between the concentrations of urinary arsenic species and selected metals with various cardiometabolic health endpoints. We present and discuss the analytical protocol put in place to produce this large and valuable dataset.

Quantitative determination of small selenium species in human serum by HPLC/ICPMS following a protein-removal, pre-concentration procedure

Protein precipitation was incorporated into a sample preparation method for the quantitative determination of small "non-protein" selenium species in human serum by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC/ICPMS). The advantages of cleaner matrix and concomitant concentration of the small compounds result in quantification limits in the native serum at the sub-micrograms Se per litre level. Spiking experiments with methyl 2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 1), trimethylselenonium ion, selenomethionine, methylselenocysteine (MeSeCys) and selenate yielded recoveries from 73% to 103%. Selenite had a low recovery (44%), possibly owing to protein binding. The validated method was applied to serum samples from two volunteers before and after ingestion of a selenium food supplement. HPLC/ICPMS analysis showed, besides ingested selenate, the presence of selenosugar 1 and trace amounts of MeSeCys and methyl 2-amino-2-deoxy-1-seleno-β-D-galactopyranoside, which have not been reported in human serum before.

A miniaturized microtiter plate protocol for the determination of in selenized yeast via enzymatic hydrolysis of protein-bound

This paper describes a simple/low volume enzymatic extraction method for selenomethionine (SeMet) determination in selenized yeast samples. In contrast to traditional methods which generally utilize large sample volumes consuming significant amounts of costly enzymes, the modified protocol employs a microtiter plate format allowing a reduction of the required sample volumes to 1 mL per extract. The extraction is performed in a parallel (5 × 4 = 20 position microtiter plate) reaction platform made out of sintered silicon carbide, fitted with standard disposable glass HPLC/GC vials. Due to the high thermal conductivity of silicon carbide, this set-up can be placed on a standard hotplate to accurately maintain the desired extraction conditions (37 °C, 20 h) for all positions of the microtiter plate. Hydrolysis of selenium-enriched yeast with a combination of protease XIV and lipase VII (ratio 2 : 1, w/w) using these low-volume conditions provided identical results to the more traditional high-volume method. The amount of SeMet was determined by HPLC/ICPMS and confirmed a high recovery rate for SeMet (93 ± 2%, n = 3) for the certified reference material SELM-1.

Seafood intake and urine concentrations of total arsenic, dimethylarsinate and arsenobetaine in the US population

BACKGROUND

Seafood is the main source of organic arsenic exposure (arsenobetaine, arsenosugars and arsenolipids) in the population. Arsenosugars and arsenolipids are metabolized to several species including dimethylarsinate (DMA).

OBJECTIVE

Evaluate the association of seafood intake with spot urine arsenic concentrations in the 2003-2006 National Health Nutrition and Examination Survey (NHANES).

METHODS

We studied 4276 participants ≥ 6 years. Total arsenic was measured using inductively coupled plasma dynamic reaction cell mass spectrometry (ICPMS). Urine DMA and arsenobetaine were measured by high-performance liquid chromatography coupled with ICPMS.

RESULTS

Participants reporting seafood in the past 24-h had higher urine concentrations of total arsenic (median 24.5 vs. 7.3 μg/L), DMA (6.0 vs. 3.5 μg/L), arsenobetaine (10.2 vs. 0.9 μg/L) and total arsenic minus arsenobetaine (11.0 vs. 5.5 μg/L). Participants reporting seafood ≥ 2/wk vs. never during the past year had 2.3 (95% confidence interval 1.9, 2.7), 1.4 (1.2, 1.6), 6.0 (4.6, 7.8) and 1.7 (1.4, 2.0) times higher (p-trend <0.001) concentrations of total arsenic, DMA, arsenobetaine and total arsenic minus arsenobetaine, respectively. In participants without detectable arsenobetaine and in analyses adjusted for arsenobetaine, seafood consumption in the past year was not associated with total arsenic or DMA concentrations in urine.

CONCLUSION

Seafood intake was a major determinant of increased urine concentrations of total arsenic, DMA, arsenobetaine and total arsenic minus arsenobetaine in the US population. Epidemiologic studies that use total arsenic, DMA, the sum of inorganic arsenic, methylarsonate and DMA, and total arsenic minus arsenobetaine as markers of inorganic arsenic exposure and/or metabolism need to address seafood intake.

Arsenic species in certified reference material MURST-ISS-A2 (Antarctic krill)

Arsenic compounds were quantified in the certified reference material MURST-ISS-A2 (Antarctic krill) using HPLC/ICPMS. The data should prove useful for assessing the accuracy of arsenic speciation procedures.

Arsenic-containing lipids are natural constituents of sashimi tuna

Arsenic occurs naturally in many types of seafood as water- and fat-soluble organoarsenic compounds. Although water-soluble compounds have been well characterized, the fat-soluble compounds, so-called arsenolipids, have until recently remained unknown. We report that sashimi-grade tuna fish, with a total arsenic content of 5.9 microg of As/g dry mass, contains approximately equal quantities of water- and fat-soluble arsenic. The water-soluble arsenic comprised predominantly arsenobetaine (>95%) with a trace of dimethylarsinate. Two fat-soluble compounds, which together accounted for about 40% of the lipid-arsenic, were isolated and characterized. The first was identified as 1-dimethylarsinoylpentadecane [(CH(3))(2)As(O)(CH(2))(14)CH(3)] by comparison of HPLC/mass spectrometric data and accurate mass data with those of an authenticated synthesized standard. The second arsenolipid was postulated as 1-dimethylarsinoyl all-cis-4,7,10,13,16,19-docosahexane from mass spectrometric data and analogy with non-arsenic-containing lipids found in fish. The remaining fat-soluble arsenic consisted of less polar arsenolipids of currently unknown structure. This is the first identification of arsenolipids in commonly consumed seafood.