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

Paradoxical effects of arsenic in the lungs

High levels (> 100 ug/L) of arsenic are known to cause lung cancer; however, whether low (≤ 10 ug/L) and medium (10 to 100 ug/L) doses of arsenic will cause lung cancer or other lung diseases, and whether arsenic has dose-dependent or threshold effects, remains unknown. Summarizing the results of previous studies, we infer that low- and medium-concentration arsenic cause lung diseases in a dose-dependent manner. Arsenic trioxide (ATO) is recognized as a chemotherapeutic drug for acute promyelocytic leukemia (APL), also having a significant effect on lung cancer. The anti-lung cancer mechanisms of ATO include inhibition of proliferation, promotion of apoptosis, anti-angiogenesis, and inhibition of tumor metastasis. In this review, we summarized the role of arsenic in lung disease from both pathogenic and therapeutic perspectives. Understanding the paradoxical effects of arsenic in the lungs may provide some ideas for further research on the occurrence and treatment of lung diseases.

Geostatistical model of the spatial distribution of arsenic in groundwaters in Gujarat State, India

Geogenic arsenic contamination in groundwaters poses a severe health risk to hundreds of millions of people globally. Notwithstanding the particular risks to exposed populations in the Indian sub-continent, at the time of writing, there was a paucity of geostatistically based models of the spatial distribution of groundwater hazard in India. In this study, we used logistic regression models of secondary groundwater arsenic data with research-informed secondary soil, climate and topographic variables as principal predictors generate hazard and risk maps of groundwater arsenic at a resolution of 1 km across Gujarat State. By combining models based on different arsenic concentrations, we have generated a pseudo-contour map of groundwater arsenic concentrations, which indicates greater arsenic hazard (> 10 μg/L) in the northwest, northeast and south-east parts of Kachchh District as well as northwest and southwest Banas Kantha District. The total number of people living in areas in Gujarat with groundwater arsenic concentration exceeding 10 μg/L is estimated to be around 122,000, of which we estimate approximately 49,000 people consume groundwater exceeding 10 µg/L. Using simple previously published dose-response relationships, this is estimated to have given rise to 700 (prevalence) cases of skin cancer and around 10 cases of premature avoidable mortality/annum from internal (lung, liver, bladder) cancers-that latter value is on the order of just 0.001% of internal cancers in Gujarat, reflecting the relative low groundwater arsenic hazard in Gujarat State.

Advances in the epidemiology of pancreatic cancer: Trends, risk factors, screening, and prognosis

Pancreatic cancer is a malignancy with poor prognosis and high mortality. The recent increase in pancreatic cancer incidence and mortality has resulted in an increased number of studies on its epidemiology. This comprehensive and systematic literature review summarizes the advances in the epidemiology of pancreatic cancer, including its epidemiological trends, risk factors, risk prediction models, screening modalities, and prognosis. The risk factors for pancreatic cancers can be categorized as those related to individual characteristics, lifestyle and environment, and disease status. Several prediction models for pancreatic cancer have been developed in populations with new-onset diabetes or a family history of pancreatic cancer; however, these models require further validation. Despite recent progress in pancreatic cancer screening, the quantity and quality of related studies are also unsatisfactory, especially with respect to the identification of high-risk populations and development of effective screening modality. Apart from the populations with familial genetic risk and those at a high risk of sporadic pancreatic cancer, risk factors such as new-onset diabetes may be a new direction for timely intervention. We hope this work will provide new ideas for further prevention and treatment of pancreatic cancer.

Nutrition, one-carbon metabolism and arsenic methylation

Exposure to arsenic (As) is a major public health concern globally. Inorganic As (InAs) undergoes hepatic methylation to form monomethyl (MMAs)- and dimethyl (DMAs)-arsenical species, facilitating urinary As elimination. MMAsIII is considerably more toxic than either InAsIII or DMAsV, and a higher proportion of MMAs in urine has been associated with risk for a wide range of adverse health outcomes. Efficiency of As methylation differs substantially between species, between individuals, and across populations. One-carbon metabolism (OCM) is a biochemical pathway that provides methyl groups for the methylation of As, and is influenced by folate and other micronutrients, such as vitamin B12, choline, betaine and creatine. A growing body of evidence has demonstrated that OCM-related micronutrients play a critical role in As methylation. This review will summarize observational epidemiological studies, interventions, and relevant experimental evidence examining the role that OCM-related micronutrients have on As methylation, toxicity of As, and risk for associated adverse health-related outcomes. There is fairly robust evidence supporting the impact of folate on As methylation, and some evidence from case-control studies indicating that folate nutritional status influences risk for As-induced skin lesions and bladder cancer. However, the potential for folate to be protective for other As-related health outcomes, and the potential beneficial effects of other OCM-related micronutrients on As methylation and risk for health outcomes are less well studied and warrant additional research.

Probiotics: a Promising Generation of Heavy Metal Detoxification

Different environmental toxins especially heavy metals exist in soil, water, and air recording toxic effect on human, animal, and plant. These toxicant elements are widespread in environment causing various disturbances in biological systems. Numerous strategies have been applied recently to alleviate heavy metal contamination; however, most of these strategies were costly and seemed unfriendly to our environment. Probiotics are living cell bacteria with beneficial characteristics for human health. Lactobacillus and Bifidobacterium are the major probiotic groups; however, Pediococcus, Lactococcus, Bacillus, and yeasts are recorded as probiotic. The vital role of the probiotics on maintenance of body health was previously investigated. Probiotics were previously recorded to its powerful capacity to bind numerous targets and eliminate them with feces. These targets may be aluminum, cadmium, lead, or arsenic. The current review discusses the history of probiotics, detoxification role of probiotics caused by heavy metals, and mechanism of their action that modulate different signaling pathway disturbance associated with heavy metal accumulation in biological system.

Association between urinary arsenic, blood cadmium, blood lead, and blood mercury levels and serum prostate-specific antigen in a population-based cohort of men in the United States

Exposures to heavy metals have been linked to prostate cancer risk. The relationship of these exposures with serum prostate-specific antigen (PSA), a marker used for prostate cancer screening, is unknown. We examined whether total urinary arsenic, urinary dimethylarsonic acid, blood cadmium, blood lead, and total blood mercury levels are associated with elevated PSA among presumably healthy U.S. men. Prostate cancer-free men, aged ≥40 years, were identified from the 2003-2010 National Health and Nutrition Examination Survey. Logistic regression analyses with survey sample weights were used to examine the association between heavy metal levels and elevated PSA for the total population and stratified by black and white race, after adjusting for confounders. There were 5,477 men included. Approximately 7% had elevated PSA. Men with an elevated PSA had statistically significantly higher levels of blood cadmium and blood lead compared to men with a normal PSA (p-values ≤ 0.02), with black men having higher levels. After adjusting for age, race/ethnicity, body mass index, smoking, and education, there was no association found between any of the heavy metal levels and elevated PSA for the total population. In addition, there was no association found when stratified by black and white race. Further investigation is warranted in a larger cohort of men who persistently are exposed to these heavy metals.

Arsenic, blood pressure, and hypertension in the Strong Heart Family Study

BACKGROUND

Arsenic has been associated with hypertension, though it is unclear whether associations persist at the exposure concentrations (e.g. <100 μg/L) in drinking water occurring in parts of the Western United States.

METHODS

We assessed associations between arsenic biomarkers and systolic blood pressure (SBP), diastolic blood pressure (DBP), and hypertension in the Strong Heart Family Study, a family-based cohort of American Indians from the Northern plains, Southern plains, and Southwest. We included 1910 participants from three study centers with complete baseline visit data (2001-2003) in the cross-sectional analysis of all three outcomes, and 1453 participants in the prospective analysis of incident hypertension (follow-up 2006-2009). We used generalized estimating equations with exchangeable correlation structure conditional on family membership to estimate the association of arsenic exposure biomarker levels with SBP or DBP (linear regressions) or hypertension prevalence and incidence (Poisson regressions), adjusting for urine creatinine, urine arsenobetaine, and measured confounders.

RESULTS

We observed cross-sectional associations for a two-fold increase in inorganic and methylated urine arsenic species of 0.64 (95% CI: 0.07, 1.35) mm Hg for SBP, 0.49 (95% CI: 0.03, 1.02) mm Hg for DBP, and a prevalence ratio of 1.10 (95% CI: 1.01, 1.21) for hypertension in fully adjusted models. During follow-up, 14% of subjects developed hypertension. We observed non-monotonic relationships between quartiles of arsenic and incident hypertension. Effect estimates were null for incident hypertension with continuous exposure metrics. Stratification by study site revealed elevated associations in Arizona, the site with the highest arsenic levels, while results for Oklahoma and North and South Dakota were largely null. Blood pressure changes with increasing arsenic concentrations were larger for those with diabetes at baseline.

CONCLUSIONS

Our results suggest a modest cross-sectional association of arsenic exposure biomarkers with blood pressure, and possible non-linear effects on incident hypertension.

The role of autophagy in metal-induced urogenital carcinogenesis

Environmental and/or occupational exposure to metals such as Arsenic (As), Cadmium (Cd), and Chromium (Cr) have been shown to induce carcinogenesis in various organs, including the urogenital system. However, the mechanisms responsible for metal-induced carcinogenesis remain elusive. We and others have shown that metals are potent inducers of autophagy, which has been suggested to be an adaptive stress response to allow metal-exposed cells to survive in hostile environments. Albeit few, recent experimental studies have shown that As and Cd promote tumorigenesis via autophagy and that inhibition of autophagic signaling suppressed metal-induced carcinogenesis. In light of the newly emerging role of autophagic involvement in metal-induced carcinogenesis, the present review focuses explicitly on the mechanistic role of autophagy and potential signaling pathways involved in As-, Cd-, and Cr-induced urogenital carcinogenesis.

Blood donation and heavy metal poisoning in developing nations: Any link?

Long term health effects of heavy metal exposure from both occupational and environmental settings involve multi-organ toxicities including but not limited to disturbances of neurological, cognitive, and metabolic processes, immune system dysregulation, carcinogenesis and sometimes permanent disabilities. Humans are exposed to toxic metals through various sources and routes of entry. The risk of heavy metal poisoning from donor blood has been the subject of many scientific investigations. In this review we highlight how the access to a safe and adequate blood transfusion with minimal risk of toxic metals to recipients is a public health challenge, especially in developing nations. For quality assurance purposes, blood donors are screened for various blood-borne pathogens, but screening for toxic metal levels is not routine. Evidence from scientific studies used in this review lends credence to the risk of heavy metal poisoning from donors with high blood concentrations of these heavy metals. The risk of toxicity is exceptionally high in vulnerable populations such as neonates and preterm infants, as well as in pregnant women and other individuals with conditions requiring multiple blood transfusions. This is worse in developing countries where some members of the population engage in illegal refining and artisanal mining activities. In order to reduce toxic metal exposure in vulnerable populations, blood meant for transfusion in vulnerable subjects, e.g. children, should be routinely screened for heavy metal concentrations. Patients receiving multiple blood transfusions should also be monitored for iron overload and its attendant toxicities.

ROS-mediated genotoxic stress is involved in NaAsO2-induced cell cycle arrest, stemness enhancement and chemoresistance of prostate cancer cells in a p53-independent manner

Several epidemiological studies reported that chronic arsenic exposure increased risk of prostate cancer. This study aimed to investigate whether chronic NaAsO₂ exposure elevates stemness and chemoresistance in prostate cancer cells. DU145 (wild-type p53) and PC-3 (p53-null) cells were exposed to NaAsO₂ (2 μmol/L) for 30 generations. IC50s to docetaxel and cisplatin were increased in NaAsO₂-exposed DU145 and PC-3 cells. The number of tumor spheres was elevated in NaAsO₂-exposed DU145 and PC-3 cells. Nanog, SOX-2 and ALDH1A1, three markers of cancer stemness, were upregulated in NaAsO₂-exposed PC-3 spheres. Moreover, NaAsO₂-exposed DU145 and PC-3 cells were arrested in G2/M phase. Histone H2AX phosphorylation on Ser139, an indicator for DNA double-strand break, was upregulated in NaAsO₂-exposed DU145 and PC-3 cells. ATM phosphorylation on Ser1981, a key sensor of genotoxic stress, was rapidly elevated in NaAsO₂-exposed DU145 cells. Phosphor-p53, a downstream molecule of ATM signaling, and p21, a direct target of p53, were upregulated in NaAsO₂-exposed DU145 cells. Unexpectedly, p21 was also elevated in NaAsO₂-exposed p53-null PC-3 cells. Antioxidant NAC alleviated NaAsO₂-induced ATM phosphorylation, cell cycle arrest, and subsequent stemness enhancement and chemoresistance in both DU145 and PC-3 cells. These results suggest that ROS-mediated genotoxic stress is involved in NaAsO₂-induced cell cycle arrest, stemness enhancement and chemoresistance of prostate cancer cells in a p53-independent manner.

A review of lifestyle and environment risk factors for pancreatic cancer

Pancreatic cancer (PaCa) is one of the deadliest cancers known and its incidence is increasing in the developed countries. Because of the lack of biomarkers that allow early detection and the tendency of the disease to be asymptomatic, the diagnosis comes often too late for effective surgical or chemotherapy intervention. Lifestyle factors, that may cause common genetic modifications occurring in the disease, interfere with pancreatic physiology or function, and play a role in PaCa development, have been of concern recently, since a strategy to prevent this severe cancer is needed. This review identifies the latest evidences related to increased risk of developing PaCa due to dietary habits such as high alcohol, fructose and red or processed meat intake, and pathological conditions such as diabetes, obesity and infections in addition to stress and smoking behaviour. It aims to highlight the importance of intervening on modifiable risk factors: the action on these factors could prevent a considerable number of new cases of PaCa.

Thoughts on a Unified Theory of Disease

Humans suffer the highest burden of chronic disease in every age group ever in human history. Why? While many theories have been proposed, presented here are thoughts on a unified theory of disease to understand causes and provide guidance for health restoration and disease prevention. My thesis is that the combination of high and increasing body load of heavy metals, meta-metals and persistent and non-persistent environmental chemicals; multiple nutrient deficiencies and insufficiencies and loss of "unimportant" molecules from the food supply; dis-synchronization with the environment; and genetic susceptibility combine to disrupt physiology and cause disease.

Association between rice consumption and risk of cancer incidence in the California Teachers Study

PURPOSE

We evaluated the contribution of rice intake, a source of dietary arsenic, to cancer risk in a population of women with likely low arsenic exposure from drinking water and variable rice intake who participated in the California Teachers Study.

METHODS

Rice consumption was categorized into quartiles (< 9.6, 9.7-15.6, 15.7-42.7, and ≥ 42.8 g/day). Multivariable-adjusted hazard ratios and 95% confidence intervals (95% CI) for incident cancer were estimated comparing rice consumption categories with bladder, breast, kidney, lung, and pancreatic cancer, with progressive adjustment for age, total calories, BMI, race, smoking status, physical activity, and cancer-specific covariates.

RESULTS

The number of breast, lung, pancreatic, bladder, and kidney cancer cases was 7,351; 1,100; 411; 344; and 238, respectively. The adjusted hazard ratios (95% CI) comparing the highest versus lowest rice intake quartiles were 1.07 (1.00-1.15); 0.87 (0.72-1.04); 0.95 (0.66-1.37); 1.11 (0.81-1.52) and 1.07 (0.72-1.59) for breast, lung, pancreatic, bladder, and kidney cancers, respectively. Results were consistent when rice was modeled as a continuous variable and in analyses stratified by smoking status.

CONCLUSION

Rice consumption was not associated with risk of kidney, lung or pancreatic cancer, except maybe a small excess risk for breast cancer and a small non-significant excess risk for bladder cancer, comparing the highest versus lowest quartile of rice intake. Due to lower consumption patterns in this cohort, future studies should involve populations for which rice is a staple food and use of an arsenic biomarker.

Understanding the Relationship between Environmental Arsenic and Prostate Cancer Aggressiveness among African-American and European-American Men in North Carolina

High-level exposure to arsenic, a known carcinogen and endocrine disruptor, is associated with prostate cancer (PCa) mortality. Whether low-level exposure is associated with PCa aggressiveness remains unknown. We examined the association between urinary arsenic and PCa aggressiveness among men in North Carolina. This cross-sectional study included 463 African-American and 491 European-American men with newly diagnosed, histologically confirmed prostate adenocarcinoma. PCa aggressiveness was defined as low aggressive (Gleason score < 7, stage = cT1–cT2, and PSA < 10 ng/mL) versus intermediate/high aggressive (all other cases). Total arsenic and arsenical species (inorganic arsenic (iAs^III + iAs^V), arsenobetaine, monomethyl arsenic, and dimethyl arsenic)) and specific gravity were measured in spot urine samples obtained an average of 23.7 weeks after diagnosis. Multivariable logistic regression was used to estimate the covariate-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for PCa aggressiveness in association with arsenic tertiles/quantiles overall and by race. The highest (vs. lowest) tertile of total arsenic was associated with PCa aggressiveness ORs of 1.77 (95% CI = 1.05–2.98) among European-American men, and 0.94 (95% CI = 0.57–1.56) among African-American men (P_Interaction = 0.04). In contrast, total arsenic and arsenical species were not associated with PCa aggressiveness in unstratified models. Low-level arsenic exposure may be associated with PCa aggressiveness among European-Americans, but not among African-Americans.

Use of study-specific MOE-like estimates to prioritize health effects from chemical exposure for analysis in human health assessments

There are unique challenges in estimating dose-response with chemicals that are associated with multiple health outcomes and numerous studies. Some studies are more suitable than others for quantitative dose-response analyses. For such chemicals, an efficient method of screening studies and endpoints to identify suitable studies and potentially important health effects for dose-response modeling is valuable. Using inorganic arsenic as a test case, we developed a tiered approach that involves estimating study-specific margin of exposure (MOE)-like unitless ratios for two hypothetical scenarios. These study-specific unitless ratios are derived by dividing the exposure estimated to result in a 20% increase in relative risk over the background exposure (RRE20) by the background exposure, as estimated in two different ways. In our case study illustration, separate study-specific ratios are derived using estimates of United States population background exposure (RRB-US) and the mean study population reference group background exposure (RRB-SP). Systematic review methods were used to identify and evaluate epidemiologic studies, which were categorized based on study design (case-control, cohort, cross-sectional), various study quality criteria specific to dose-response analysis (number of dose groups, exposure ascertainment, exposure uncertainty), and availability of necessary dose-response data. Both case-control and cohort studies were included in the RRB analysis. The RRE20 estimates were derived by modeling effective counts of cases and controls estimated from study-reported adjusted odds ratios and relative risks. Using a broad (but not necessarily comprehensive) set of epidemiologic studies of multiple health outcomes selected for the purposes of illustrating the RRB approach, this test case analysis would suggest that diseases of the circulatory system, bladder cancer, and lung cancer may be arsenic health outcomes that warrant further analysis. This is suggested by the number of datasets from adequate dose-response studies demonstrating an effect with RRBs close to 1 (i.e., RRE20 values close to estimated background arsenic exposure levels).

Arsenic pollution in Quaternary sediments and water near a former gold mine

Contamination of water and sediments with arsenic and heavy metals is a global issue affecting human health. Regions covered with Quaternary deposits have received little attention from the point of view of the flux of arsenic and heavy metals from sediments to surface water. This study aims to determine the flux of arsenic and other heavy metals from Quaternary sediments to surface waters in an area affected by the former Złoty Stok gold and arsenic mine. Contamination in surface waters and sediments was caused by arsenic, whereas concentrations of metals were usually within water quality standards. Arsenic contamination of surface water increased in the lower part of the basin covered by Quaternary sediments, and exceeded water quality standards by 2 orders of magnitude. Arsenic mass flux exceeded 8 kg/day near the confluence of the Trująca River with the Nysa Kłodzka, a main tributary of the Oder River. An increase in arsenic concentration in the lower part of the basin is related to mine tailings and preferential flow of groundwater through Quaternary sediments. In future, water resources scarcity may lead to an increase in arsenic contamination in surface and groundwater.

Inorganic arsenic promotes luminal to basal transition and metastasis of breast cancer

Inorganic arsenic (iAs/As₂ O₃ ^2- ) is an environmental toxicant found in watersheds around the world including in densely populated areas. iAs is a class I carcinogen known to target the skin, lungs, bladder, and digestive organs, but its role as a primary breast carcinogen remains controversial. Here, we examined a different possibility: that exposure to iAs promotes the transition of well-differentiated epithelial breast cancer cells characterized by estrogen and progesterone receptor expression (ER+/PR+), to more basal phenotypes characterized by active proliferation, and propensity to metastasis in vivo. Our results indicate two clear phenotypic responses to low-level iAs that depend on the duration of the exposure. Short-term pulses of iAs activate ER signaling, consistent with its reported pseudo-estrogen activity, but longer-term, chronic treatments for over 6 months suppresses both ER and PR expression and signaling. In fact, washout of these chronically exposed cells for up to 1 month failed to fully reverse the transcriptional and phenotypic effects of prolonged treatments, indicating durable changes in cellular physiologic identity. RNA-seq studies found that chronic iAs drives the transition toward more basal phenotypes characterized by impaired hormone receptor signaling despite the conservation of estrogen receptor expression. Because treatments for breast cancer patients are largely designed based on the detection of hormone receptor expression, our results suggest greater scrutiny of ER+ cancers in patients exposed to iAs, because these tumors may spawn more aggressive phenotypes than unexposed ER+ tumors, in particular, basal subtypes that tend to develop therapy resistance and metastasis.

Statistical Assessment of Toxic and Essential Metals in the Serum of Female Patients with Lung Carcinoma from Pakistan

Lung cancer (LC) is the number one cancer killer of women both in the USA and around the world. Besides cigarette smoking, an important feature in the etiology of LC is its strong association with exposure of toxic metals. The primary objective of the present investigation was to assess the concentrations of toxic/essential elements (Ni, Ca, Se, Zn, Co, K, Cr, As, Cu, Na, Fe, Hg, Cd, Mg, Mn, and Pb) in the serum samples of LC female patients with female controls by atomic absorption spectrometry after wet-acid digestion procedure. Carcinoembryonic antigen (CEA) was also measured in the serum of the patients using immunoradiometric method. Comparative appraisal of the data revealed that concentrations of Cr, Mg, Cd, Pb, Hg, As, and Ni were noted to be high significantly in serum of LC female patients, while the average Fe, Co, Mn, Na, K, Zn, Ca, and Se were observed at higher levels in female controls (p < 0.05). The correlation study revealed significantly different mutual associations among the elements in the both donor groups. Markedly, variations in the elemental levels were also noted for different types (non-small cell lung cancer and small cell lung cancer) and stages (I, II, III, & IV) of LC patients. Multivariate analyses showed substantially diverse apportionment of the metals in the female patients and female controls. Hence, present findings suggest that the toxic and essential metals accumulated in the body may pose a high risk for LC progression in Pakistani females.

Locus-Specific Differential DNA Methylation and Urinary Arsenic: An Epigenome-Wide Association Study in Blood among Adults with Low-to-Moderate Arsenic Exposure

BACKGROUND

Chronic exposure to arsenic (As), a human toxicant and carcinogen, remains a global public health problem. Health risks persist after As exposure has ended, suggesting epigenetic dysregulation as a mechanistic link between exposure and health outcomes.

OBJECTIVES

We investigated the association between total urinary As and locus-specific DNA methylation in the Strong Heart Study, a cohort of American Indian adults with low-to-moderate As exposure [total urinary As, mean  ( ± SD )  μ g / g creatinine: 11.7 (10.6)].

METHODS

DNA methylation was measured in 2,325 participants using the Illumina MethylationEPIC array. We implemented linear models to test differentially methylated positions (DMPs) and the DMRcate method to identify regions (DMRs) and conducted gene ontology enrichment analysis. Models were adjusted for estimated cell type proportions, age, sex, body mass index, smoking, education, estimated glomerular filtration rate, and study center. Arsenic was measured in urine as the sum of inorganic and methylated species.

RESULTS

In adjusted models, methylation at 20 CpGs was associated with urinary As after false discovery rate (FDR) correction (FDR <   0.05 ). After Bonferroni correction, 5 CpGs remained associated with total urinary As (p Bonferroni < 0.05 ), located in SLC7A11, ANKS3, LINGO3, CSNK1D, ADAMTSL4. We identified one DMR on chromosome 11 (chr11:2,322,050-2,323,247), annotated to C11orf2; TSPAN32 genes.

DISCUSSION

This is one of the first epigenome-wide association studies to investigate As exposure and locus-specific DNA methylation using the Illumina MethylationEPIC array and the largest epigenome-wide study of As exposure. The top DMP was located in SLC7A11A, a gene involved in cystine/glutamate transport and the biosynthesis of glutathione, an antioxidant that may protect against As-induced oxidative stress. Additional DMPs were located in genes associated with tumor development and glucose metabolism. Further research is needed, including research in more diverse populations, to investigate whether As-related DNA methylation signatures are associated with gene expression or may serve as biomarkers of disease development. https://doi.org/10.1289/EHP6263.

Inorganic arsenic methylation capacity and breast cancer by immunohistochemical subtypes in northern Mexican women

BACKGROUND

Previously we reported that inorganic arsenic (iAs) methylation capacity was associated with breast cancer (BC). BC risk factors may vary according to immunohistochemical subtype. Here we explored the relationships between the capacity to methylate iAs and the risk of BC by subtype.

METHODS

A population-based case-control study was performed in northern Mexico. Patients with available information about BC subtypes (n = 499) were age-matched with healthy controls. Sociodemographic, reproductive, and lifestyle characteristics were obtained. Tumor marker information was obtained from medical records. Cases were classified as HR+ [estrogen receptor (ER+) and/or progesterone (PR+), and human epidermal growth factor receptor 2 (HER2-)], HER2+, or triple negative (TN). Urinary arsenic species were determined by high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS), and methylation capacity parameters calculated. Conditional logistic regression models were used to estimate BC risk by subtypes.

RESULTS

Urinary total arsenic varied from 0.60 to 303.29 μg/L. A significant positive association was found between % monomethylarsonic acid (%MMA) and HR + BC: one percent increase resulted in OR_{%MMA continuous} = 2.73, 95% CI: 1.48, 5.05), and this association remained even when %iAs or % dimethylarsinic acid (%DMA) were added to the models with %MMA. MMA/iAs was positively associated with HR + BC (OR_{MMA/iAs continuous} = 2.03, 95% CI: 1.33-3.10). A significant negative association was observed between DMA/MMA and HR + BC (OR_{DMA/MMA continuous} = 0.43, 95% CI: 0.26, 0.71). MMA/iAs was positively associated with TN BC (OR _{MMA/iAs continuous} = 4.05; 95% CI: 1.63, 10.04).

CONCLUSION

Altered iAs methylation capacity resulting in higher %MMA was associated with HR+ and TN BC but not with HER2+. MMA is the iAs metabolite more likely to be related to BC. Further research is needed to confirm these results and elucidate the underlying biological mechanisms.

KRAS-retroviral fusion transcripts and gene amplification in arsenic-transformed, human prostate CAsE-PE cancer cells

CAsE-PE cells are an arsenic-transformed, human prostate epithelial line containing oncogenic mutations in KRAS compared to immortalized, normal KRAS parent cells, RWPE-1. We previously reported increased copy number of mutated KRAS in CAsE-PE cells, suggesting gene amplification. Here, KRAS flanking genomic and transcriptomic regions were sequenced in CAsE-PE cells for insight into KRAS amplification. Comparison of DNA-Seq and RNA-Seq showed increased reads from background aligning to all KRAS exons in CAsE-PE cells, while a uniform DNA-Seq read distribution occurred in RWPE-1 cells with normal transcript expression. We searched for KRAS fusions in DNA and RNA sequencing data finding a portion of reads aligning to KRAS and viral sequence. After generation of cDNA from total RNA, short and long KRAS probes were generated to hybridize cDNA and KRAS enriched fragments were PacBio sequenced. More KRAS reads were captured from CAsE-PE cDNA versus RWPE-1 by each probe set. Only CAsE-PE cDNA showed KRAS viral fusion transcripts, primarily mapping to LTR and endogenous retrovirus sequences on either 5'- or 3'-ends of KRAS. Most KRAS viral fusion transcripts contained 4 to 6 exons but some PacBio sequences were in unusual orientations, suggesting viral insertions within the gene body. Additionally, conditioned media was extracted for potential retroviral particles. RNA-Seq of culture media isolates identified KRAS retroviral fusion transcripts in CAsE-PE media only. Truncated KRAS transcripts suggested multiple retroviral integration sites occurred within the KRAS gene producing KRAS retroviral fusions of various lengths. Findings suggest activation of endogenous retroviruses in arsenic carcinogenesis should be explored.

Chronic exposure to arsenite enhances influenza virus infection in cultured cells

Arsenic is a ubiquitous environmental toxicant that has been associated with human respiratory diseases. In humans, arsenic exposure has been associated with increased risk of respiratory infection. Considering the existing epidemiological evidence and the well-established impact of arsenic on epithelial cell biology, we posited that the effect of arsenic exposure in epithelial cells could enhance viral infection. In this study, we characterized influenza virus A/WSN/33 (H1N1) infection in Madin-Darby Canine Kidney (MDCK) cells chronically exposed to low levels of sodium arsenite (75 ppb). We observed a 27.3-fold increase in viral matrix (M2) protein (24 hours postinfection [p.i.]), a 1.35-fold increase in viral mRNA levels, and a 126% increase in plaque area in arsenite-exposed MDCK cells (48 hours p.i.). Arsenite exposure resulted in 114% increase in virus attachment-positive cells (2 hours p.i.) and 224% increase in α-2,3 sialic acid-positive cells. Interestingly, chronic exposure to arsenite reduced the effect of the antiviral drug, oseltamivir in MDCK cells. We also found that exposure to sodium arsenite resulted in a 4.4-fold increase in viral mRNA levels and significantly increased cytotoxicity in influenza A/Udorn/72 (H3N2) infected BEAS-2B cells. This study suggests that chronic arsenite exposure could result in enhanced influenza infection in epithelial cells, and that this may be mediated through increased sialic acid binding. Finally, the decreased effectiveness of the anti-influenza drug, oseltamivir, in arsenite-exposed cells raises substantial public health concerns if this effect translates to arsenic-exposed, influenza-infected people.

Toxic Metal Implications on Agricultural Soils, Plants, Animals, Aquatic life and Human Health

The problem of environmental pollution is a global concern as it affects the entire ecosystem. There is a cyclic revolution of pollutants from industrial waste or anthropogenic sources into the environment, farmlands, plants, livestock and subsequently humans through the food chain. Most of the toxic metal cases in Africa and other developing nations are a result of industrialization coupled with poor effluent disposal and management. Due to widespread mining activities in South Africa, pollution is a common site with devastating consequences on the health of animals and humans likewise. In recent years, talks on toxic metal pollution had taken center stage in most scientific symposiums as a serious health concern. Very high levels of toxic metals have been reported in most parts of South African soils, plants, animals and water bodies due to pollution. Toxic metals such as Zinc (Zn), Lead (Pb), Aluminium (Al), Cadmium (Cd), Nickel (Ni), Iron (Fe), Manganese (Mn) and Arsenic (As) are major mining effluents from tailings which contaminate both the surface and underground water, soil and food, thus affecting biological function, endocrine systems and growth. Environmental toxicity in livestock is traceable to pesticides, agrochemicals and toxic metals. In this review, concerted efforts were made to condense the information contained in literature regarding toxic metal pollution and its implications in soil, water, plants, animals, marine life and human health.

Prostate Cancer Incidence in U.S. Counties and Low Levels of Arsenic in Drinking Water

Background: Although inorganic arsenic in drinking water at high levels (100s–1000s μg/L [ppb]) increases cancer risk (skin, bladder, lung, and possibly prostate), the evidence at lower levels is limited. Methods: We conducted an ecologic analysis of the dose-response relationship between prostate cancer incidence and low arsenic levels in drinking water in a large study of U.S. counties (N = 710). County arsenic levels were <200 ug/L with median <100 ug/L and dependency greater than 10%. Groundwater well usage, water arsenic levels, prostate cancer incidence rates (2009–2013), and co-variate data were obtained from various U.S. governmental agencies. Poisson and negative-binomial regression analyses and stratified analysis were performed. Results: The best fitting polynomial analysis yielded a J-shaped linear-quadratic model. Linear and quadratic terms were significant (p < 0.001) in the Poisson model, and the quadratic term was significant (p < 0.05) in the negative binomial model. This model indicated a decreasing risk of prostate cancer with increasing arsenic level in the low range and increasing risk above. Conclusions: This study of prostate cancer incidence in US counties with low levels of arsenic in their well-water arsenic levels finds a j-shaped model with decreasing risk at very low levels and increasing risk at higher levels.

Understanding the mechanistic insight of arsenic exposure and decoding the histone cipher

BACKGROUND

The study of heritable epigenetic changes in arsenic exposure has intensified over the last decade. Groundwater arsenic contamination causes a great threat to humans and, to date, no accurate measure has been formulated for remediation. The fascinating possibilities of epi-therapeutics identify the need for an in-depth mechanistic understanding of the epigenetic landscape.

OBJECTIVE

In this comprehensive review, we have set to analyze major studies pertaining to histone post-translational modifications in arsenic-mediated disease development and carcinogenesis during last ten years (2008-2018).

RESULTS

The role of the specific histone marks in arsenic toxicity has been detailed. A comprehensive list that includes major arsenic-induced histone modifications identified for the last 10 years has been documented and details of different states of arsenic, organisms, exposure type, study platform, and findings were provided. An arsenic signature panel was suggested to help in early prognosis. An attempt has been made to identify the grey areas of research.

PROSPECTS

Future prospective multi-target analyses of the inter-molecular crosstalk among different histone marks are needed to be explored further in order to understand the mechanism of arsenic toxicity and carcinogenicity and to confirm the suitability of these epi-marks as prognostic markers.

Association between serum heavy metals and prostate cancer risk - A multiple metal analysis

BACKGROUND

Prostate cancer is one of the most prevalent cancers in men. Exposure to heavy metals and their association with prostate cancer risk has been studied extensively, but combined effects remain largely inconclusive.

OBJECTIVES

To elucidate the association between serum concentrations of heavy metals and prostate cancer risk.

METHODS

Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the concentrations of a panel of 10 heavy metals (Mn, Cu, Zn, As, Se, Sb, Co, Cu, Cd and Pb) in serum samples of 141 cases and 114 controls in the Singapore Prostate Cancer Study. Linear probit regression models were used to estimate risk differences (RDs) and 95% confidence intervals (CIs) for the associations between log-centered serum metal concentrations and prostate cancer risk with adjustment for potential confounders. Bayesian kernel machine regression (BKMR) models were used to account for nonlinear, interactive, and joint metal effects.

RESULTS

Using probit regression, four heavy metals (As, Zn, Mn, Sb) were significantly and positively associated with prostate cancer risk in the unadjusted models. Using BKMR analysis, both As and Zn had positive risk differences on prostate cancer risk when all other metals were held fixed at the 25th and 50th percentiles (RD, 25th percentile: As: 0.15, Zn: 0.19, RD, 50th percentile: As: 0.45, Zn: 0.37). In addition, the overall mixture risk difference was positive and the 95% credible intervals did not include 0 when all metals in the mixture were jointly above their 55th percentile, as compared to when all metals were below their median values.

CONCLUSIONS

In summary, we found positive associations between the serum levels of As and Zn and prostate cancer risk on the risk difference scale using BKMR models. The overall mixture effect was also associated with increased prostate cancer risk. Future studies are warranted to validate these findings in prospective studies.

Time to Change Standard of Care to Include Screening for Common Disease-Inducing Toxicants

Foundational to the standard of care is diagnosis of overt disease as well as testing for early predictors of future disease. Obvious examples of the later include measurement of blood pressure and cholesterol. The time has come to add to this thinking early detection of the environmental causes of disease. Substantial research now shows that metal and chemical contamination of the environment has resulted in body loads of these toxicants at high enough levels to induce disease. The time has come to add screening for toxicant load to the standard of care.

Cytotoxic and genotoxic effects of arsenic on erythrocytes of Oryzias latipes: Bioremediation using Spirulina platensis

BACKGROUND

Exposure to the environmental pollutants poses a serious threat to aquatic organism. The arsenic exposure in fish increases the risk of developing serious alterations from embryo to adult.

OBJECTIVES

The present investigation was done to study the toxic effects of heavy metal arsenic [As(III)] on medaka (Oryzias latipes). Morphological alterations, apoptosis, nuclear abnormalities, and genotoxic biomarkers in erythrocytes were used to determine the stress caused by arsenic (As) exposure.

METHODS

Medaka was exposed to As for 15 days at two toxic sublethal concentrations (7 ppm and 10 ppm) in combination with Spirulina platensis (SP) treatment as antioxidant algae at 200 mg/L.

RESULTS

Results were consistent with a previous study results on tilapia. Exposure of medaka to As resulted in a dose-dependent increase in most the biomarkers used in the current study. Fish exposed to10 ppm As showed highest level of DNA damage. For the first time to our knowledge, using SP to counter the As toxicity in medaka, DNA damage restored to control levels.

CONCLUSION

Accordingly, those results suggests that SP can protect medaka in aquaculture against As-induced damage by its ability as reactive oxygen species (ROS) reducer, antioxidant role, and DNA damage scavenger.

Low-Level Exposure to Arsenic in Drinking Water and Risk of Lung and Bladder Cancer: A Systematic Review and Dose-Response Meta-Analysis

BACKGROUND

Exposure to high levels of arsenic in drinking water has been associated with an increased risk of lung and bladder cancer, but the presence of an increased risk at low levels is questionable.

METHODS

A systematic review and a dose-response meta-analysis were conducted on risk estimates of lung and bladder cancer for exposure to arsenic in drinking water up to 150 µg/L, using a 2-stage approach based on a random-effects model.

RESULTS

Five studies of lung cancer were identified; the meta-relative risk (RR) for an increase of 10 µg/L arsenic level was 1.03 (95% confidence interval [CI]: 0.99-1.06; P heterogeneity = .05). The meta-analysis of bladder cancer included 8 studies; the meta-RR for an increase of 10 µg/L arsenic level was 1.02 (95% CI: 0.97-1.07, P heterogeneity = .01). Sensitivity analyses, including a 1-stage meta-regression, confirmed the main findings.

CONCLUSION

This systematic review and meta-analysis provided evidence of a lack of an increased risk of lung and bladder cancer for exposure to arsenic in drinking water up to 150 µg/L, the highest concentration studied.

Hormetic Dose Response of NaAsO2 on Cell Proliferation of Prostate Cells in Vitro: Implications for Prostate Cancer Initiation and Therapy

Sodium meta-arsenite (NaAsO₂) has been suggested to play a role both in initiation/progression of prostate cancer and as a future antiprostate cancer drug. We have studied the effects of NaAsO₂ on cell proliferation of prostate cancer and noncancer cells, breast cancer cells, and adrenocortical carcinoma cells in vitro. Further, we have investigated the effect of NaAsO₂ on the androgen receptor. We report that NaAsO₂ alters the cell proliferation of prostate cells, in a hormetic manner, by increasing cell proliferation at low concentrations and decreasing the cell proliferation at high concentrations. No activation of the androgen receptor was detected. We conclude that NaAsO₂ is able to increase cell proliferation of prostate cells in vitro at low concentrations, while it decreases cell viability at high concentrations. This novel finding has to be further addressed if NaAsO₂ should be developed into an antiprostate cancer drug.

Arsenite malignantly transforms human prostate epithelial cells in vitro by gene amplification of mutated KRAS

Inorganic arsenic is an environmental human carcinogen of several organs including the urinary tract. RWPE-1 cells are immortalized, non-tumorigenic, human prostate epithelia that become malignantly transformed into the CAsE-PE line after continuous in vitro exposure to 5μM arsenite over a period of months. For insight into in vitro arsenite transformation, we performed RNA-seq for differential gene expression and targeted sequencing of KRAS. We report >7,000 differentially expressed transcripts in CAsE-PE cells compared to RWPE-1 cells at >2-fold change, q<0.05 by RNA-seq. Notably, KRAS expression was highly elevated in CAsE-PE cells, with pathway analysis supporting increased cell proliferation, cell motility, survival and cancer pathways. Targeted DNA sequencing of KRAS revealed a mutant specific allelic imbalance, ‘MASI’, frequently found in primary clinical tumors. We found high expression of a mutated KRAS transcript carrying oncogenic mutations at codons 12 and 59 and many silent mutations, accompanied by lower expression of a wild-type allele. Parallel cultures of RWPE-1 cells retained a wild-type KRAS genotype. Copy number analysis and sequencing showed amplification of the mutant KRAS allele. KRAS is expressed as two splice variants, KRAS4a and KRAS4b, where variant 4b is more prevalent in normal cells compared to greater levels of variant 4a seen in tumor cells. 454 Roche sequencing measured KRAS variants in each cell type. We found KRAS4a as the predominant transcript variant in CAsE-PE cells compared to KRAS4b, the variant expressed primarily in RWPE-1 cells and in normal prostate, early passage, primary epithelial cells. Overall, gene expression data were consistent with KRAS-driven proliferation pathways found in spontaneous tumors and malignantly transformed cell lines. Arsenite is recognized as an important environmental carcinogen, but it is not a direct mutagen. Further investigations into this in vitro transformation model will focus on genomic events that cause arsenite-mediated mutation and overexpression of KRAS in CAsE-PE cells.

Population-based mortality data suggests remediation is modestly effective in two Montana Superfund counties

The health effects of living in proximity to Superfund sites with ongoing remediation were evaluated for residents of two contiguous Montana counties, Deer Lodge and Silver Bow. Deer Lodge and Silver Bow are home to the Anaconda Smelter and Silver Bow Creek/Butte Area Superfund sites, respectively. Established by the Environmental Protection Agency in 1983, both sites have had ongoing remediation for decades. Employing county level death certificate data obtained from the Centers for Disease Control and Prevention WONDER site, sex and age-adjusted standardized mortality ratios (SMRs) for composite targeted causes of death were calculated using observed versus expected mortality for both counties, and compared to the expected mortality from the remaining Montana counties. Cancers, cerebro- and cardiovascular diseases (CCVD), and organ failure were elevated for the two counties during the study period, 2000-2016, with SMRs of 1.19 (95% CI 1.10, 1.29); 1.36 (95% CI 1.29, 1.43); and 1.24 (95% CI 1.10, 1.38), respectively. Neurological conditions were not elevated for the two counties (SMR = 1.01; 95% CI 0.89, 1.14). Time trend analyses performed using Cox regression models indicate that deaths from cancers (HR = 0.97; p = 0.0004), CCVDs (HR = 0.95; p ≤ 0.0001), and neurological conditions (HR = 0.97; p = 0.01) decreased over the study period. While the ecological approach applied limits the interpretation of our results, our study suggests that while mortality is elevated, it is also decreasing over time for these two Superfund sites.

Ethnic, geographic and dietary differences in arsenic exposure in the multi-ethnic study of atherosclerosis (MESA)

Differences in residential location as well as race/ethnicity and dietary habits may result in differences in inorganic arsenic (iAs) exposure. We investigated the association of exposure to iAs with race/ethnicity, geography, and dietary intake in a random sample of 310 White, Black, Hispanic, and Chinese adults in the Multi-Ethnic Study of Atherosclerosis from 6 US cities with inorganic and methylated arsenic (ΣAs) measured in urine. Dietary intake was assessed by food-frequency questionnaire. Chinese and Hispanic race/ethnicity was associated with 82% (95% CI: 46%, 126%) and 37% (95% CI: 10%, 70%) higher urine arsenic concentrations, respectively, compared to White participants. No differences were observed for Black participants compared to Whites. Urine arsenic concentrations were higher for participants in Los Angeles, Chicago, and New York compared to other sites. Participants that ate rice ≥2 times/week had 31% higher urine arsenic compared to those that rarely/never consumed rice. Participants that drank wine ≥2 times/week had 23% higher urine arsenic compared to rare/never wine drinkers. Intake of poultry or non-rice grains was not associated with urinary arsenic concentrations. At the low-moderate levels typical of the US population, exposure to iAs differed by race/ethnicity, geographic location, and frequency of rice and wine intake.

A missense variant in FTCD is associated with arsenic metabolism and toxicity phenotypes in Bangladesh

Inorganic arsenic (iAs) is a carcinogen, and exposure to iAs via food and water is a global public health problem. iAs-contaminated drinking water alone affects >100 million people worldwide, including ~50 million in Bangladesh. Once absorbed into the blood stream, most iAs is converted to mono-methylated (MMA) and then di-methylated (DMA) forms, facilitating excretion in urine. Arsenic metabolism efficiency varies among individuals, in part due to genetic variation near AS3MT (arsenite methyltransferase; 10q24.32). To identify additional arsenic metabolism loci, we measured protein-coding variants across the human exome for 1,660 Bangladeshi individuals participating in the Health Effects of Arsenic Longitudinal Study (HEALS). Among the 19,992 coding variants analyzed exome-wide, the minor allele (A) of rs61735836 (p.Val101Met) in exon 3 of FTCD (formiminotransferase cyclodeaminase) was associated with increased urinary iAs% (P = 8x10-13), increased MMA% (P = 2x10-16) and decreased DMA% (P = 6x10-23). Among 2,401 individuals with arsenic-induced skin lesions (an indicator of arsenic toxicity and cancer risk) and 2,472 controls, carrying the low-efficiency A allele (frequency = 7%) was associated with increased skin lesion risk (odds ratio = 1.35; P = 1x10-5). rs61735836 is in weak linkage disequilibrium with all nearby variants. The high-efficiency/major allele (G/Valine) is human-specific and eliminates a start codon at the first 5´-proximal Kozak sequence in FTCD, suggesting selection against an alternative translation start site. FTCD is critical for catabolism of histidine, a process that generates one-carbon units that can enter the one-carbon/folate cycle, which provides methyl groups for arsenic metabolism. In our study population, FTCD and AS3MT SNPs together explain ~10% of the variation in DMA% and support a causal effect of arsenic metabolism efficiency on arsenic toxicity (i.e., skin lesions). In summary, this work identifies a coding variant in FTCD associated with arsenic metabolism efficiency, providing new evidence supporting the established link between one-carbon/folate metabolism and arsenic toxicity.

Cellular and Molecular Effects of Prolonged Low-Level Sodium Arsenite Exposure on Human Hepatic HepaRG Cells

Inorganic arsenic is a human carcinogen associated with several types of cancers, including liver cancer. Inorganic arsenic has been postulated to target stem cells, causing their oncogenic transformation. This is proposed to be one of the key events in arsenic-associated carcinogenesis; however, the underlying mechanisms for this process remain largely unknown. To address this question, human hepatic HepaRG cells, at progenitor and differentiated states, were continuously treated with a noncytotoxic concentration of 1 μM sodium arsenite (NaAsO2). The HepaRG cells demonstrated active intracellular arsenite metabolism that shared important characteristic with primary human hepatocytes. Treatment of proliferating progenitor-like HepaRG cells with NaAsO2 inhibited their differentiation into mature hepatocyte-like cells, up-regulated genes involved in cell growth, proliferation, and survival, and down-regulated genes involved in cell death. In contrast, treatment of differentiated hepatocyte-like HepaRG cells with NaAsO2 resulted in enhanced cell death of mature hepatocyte-like cells, overexpression of cell death-related genes, and down-regulation of genes in the cell proliferation pathway, while biliary-like cells remained largely unaffected. Mechanistically, the cytotoxic effect of arsenic on mature hepatocyte-like HepaRG cells may be attributed to arsenic-induced dysregulation of cellular iron metabolism. The inhibitory effect of NaAsO2 on the differentiation of progenitor cells, the resistance of biliary-like cells to cell death, and the enhanced cell death of functional hepatocyte-like cells resulted in stem-cell activation. These effects favored the proliferation of liver progenitor cells that can serve as a source of initiation and driving force of arsenic-mediated liver carcinogenesis.

The Strong Heart Water Study: Informing and designing a multi-level intervention to reduce arsenic exposure among private well users in Great Plains Indian Nations

Elevated arsenic exposure from drinking water is associated with an increased risk of cardiovascular disease, diabetes, kidney disease, and skin, lung, and bladder cancer. Arsenic contamination in groundwater supplies disproportionately affects rural populations using private wells. Arsenic mitigation programs for American Indian communities are limited. There is an urgent need for targeted approaches to reduce arsenic exposure for at-risk communities using private wells. Formative research was conducted to inform and design a community-based arsenic mitigation intervention for Lakota and Dakota Nations in the Great Plains Area of the United States, where, in some communities, one-quarter of private wells are estimated to have elevated arsenic. Formative research included semi-structured interviews, a community workshop, intervention-planning workshops, and a pilot study of the developed intervention. Community members prioritize aesthetic qualities of water (e.g. taste, color), safety, and other situational factors (e.g. cost) when considering their drinking and cooking water. Although water safety is a concern, awareness and concern for arsenic vary substantially within communities. To reduce arsenic exposure, community members recommended communication of water test results, home visits for intervention delivery, and reminders to use arsenic-safe water. Findings informed the development of an intervention to prevent arsenic exposure through drinking water and cooking, including health promotion messages and household items to facilitate use of an arsenic removal device (e.g. tankards to store filtered water). The pilot study indicated promising acceptability and operability of the developed intervention. This research provides a model for the development of environmental health interventions in partnership with American Indian and other private well-using communities.

Arsenic‑induced BRCA1 CpG promoter methylation is associated with the downregulation of ERα and resistance to tamoxifen in MCF7 breast cancer cells and mouse mammary tumor xenografts

A significant percentage (~30%) of estrogen receptor-α (ERα)-positive tumors become refractory to endocrine therapies; however, the mechanisms responsible for this resistance remain largely unknown. Chronic exposure to arsenic through foods and contaminated water has been linked to an increased incidence of several tumors and long-term health complications. Preclinical and population studies have indicated that arsenic exposure may interfere with endocrine regulation and increase the risk of breast tumorigenesis. In this study, we examined the effects of sodium arsenite (NaAs^III) exposure in ERα-positive breast cancer cells in vitro and in mammary tumor xenografts. The results revealed that acute (within 4 days) and long-term (10 days to 7 weeks) in vitro exposure to environmentally relevant doses reduced breast cancer 1 (BRCA1) and ERα expression associated with the gain of cyclin D1 (CCND1) and folate receptor 1 (FOLR1), and the loss of methylenetetrahydrofolate reductase (MTHFR) expression. Furthermore, long-term exposure to NaAs^III induced the proliferation and compromised the response of MCF7 cells to tamoxifen (TAM). The in vitro exposure to NaAs^III induced BRCA1 CpG methylation associated with the increased recruitment of DNA methyltransferase 1 (DNMT1) and the loss of RNA polymerase II (PolII) at the BRCA1 gene. Xenografts of NaAs^III-preconditioned MCF7 cells (MCF7NaAs^III) into the mammary fat pads of nude mice produced a larger tumor volume compared to tumors from control MCF7 cells and were more refractory to TAM in association with the reduced expression of BRCA1 and ERα, CpG hypermethylation of estrogen receptor 1 (ESR1) and BRCA1, and the increased expression of FOLR1. These cumulative data support the hypothesis that exposure to As^III may contribute to reducing the efficacy of endocrine therapy against ERα-positive breast tumors by hampering the expression of ERα and BRCA1 via CpG methylation, respectively of ESR1 and BRCA1.

Biomonitoring of metals and trace elements in urine of central Ethiopian populations

Biomonitoring of chemical concentrations in humans is important for detecting, monitoring, and addressing a wide range of health threats. However, it is virtually absent across many African nations, including Ethiopia. This study aims to determine urinary concentrations for metals and trace elements in populations living in the central Ethiopian Rift Valley. The region is unindustralized, rural, and characterized by unique geologic rifting and volcanic activities that have produced vast pyroclastic materials, forming its aquifer and fertile agricultural soils. Millions of people in the region rely on wells for drinking water and are engaged in cereal-based subsistence agriculture. We enrolled a total of 386 residents aged 10-50 years old (201 females and 185 males). The levels of 23 elements except F^─ were quantified in water and urine samples by ICP-MS. Mean concentrations of B, F^─, Ca, and Mg were measured in mg/L levels, while concentrations of Mo, Zn, Sr, Rb, and Li ranged between 100 and 700 μg/L. Mean concentrations between 5 and 15 μg/L were found for Ni, Cu, and Mn, while Ag, Be, Cd, Co, Pb, Sb, Th, TI, and U were all below 5 μg/L. Arsenic and Al had mean concentrations between 30 and 50 μg/L. Mean urinary concentrations of Ca, Cu, Mg, Pb, Sr, and Zn were significantly higher in males than females, whereas Co and Mn were higher in females. Finally, younger individuals (10-30 years) had significantly higher mean concentrations of B, Cd, Co, Mg, Mo, and Pb than those between 31 and 50 years, whereas only Ca was higher in the older age group. The concentration ranges of B, Mo, Mn, TI, Li, Zn, and in particular F^─ (0.44-44.6 mg/L) and As (2.2-164 μg/L) in urine were higher than the reference ranges reported in healthy unexposed North American and European populations, while those for the remaining 16 elements were comparable to published reference ranges from such settings. The established concentration ranges are important to monitor future changes in exposure, and risk factors for disease, that might stem from the economic growth and industrialization that is currently underway in the region.

Targeted metabolomics to understand the association between arsenic metabolism and diabetes-related outcomes: Preliminary evidence from the Strong Heart Family Study

BACKGROUND

Inorganic arsenic exposure is ubiquitous and both exposure and inter-individual differences in its metabolism have been associated with cardiometabolic risk. A more efficient arsenic metabolism profile (lower MMA%, higher DMA%) has been associated with reduced risk for arsenic-related health outcomes. This profile, however, has also been associated with increased risk for diabetes-related outcomes.

OBJECTIVES

The mechanism behind these conflicting associations is unclear; we hypothesized the one-carbon metabolism (OCM) pathway may play a role.

METHODS

We evaluated the influence of OCM on the relationship between arsenic metabolism and diabetes-related outcomes (HOMA2-IR, waist circumference, fasting plasma glucose) using metabolomic data from an OCM-specific and P180 metabolite panel measured in plasma, arsenic metabolism measured in urine, and HOMA2-IR and FPG measured in fasting plasma. Samples were drawn from baseline visits (2001-2003) in 59 participants from the Strong Heart Family Study, a family-based cohort study of American Indians aged ≥14 years from Arizona, Oklahoma, and North/South Dakota.

RESULTS

In unadjusted analyses, a 5% increase in DMA% was associated with higher HOMA2-IR (geometric mean ratio (GMR)= 1.13 (95% CI: 1.03, 1.25)) and waist circumference (mean difference=3.66 (0.95, 6.38). MMA% was significantly associated with lower HOMA2-IR and waist circumference. After adjustment for OCM-related metabolites (SAM, SAH, cysteine, glutamate, lysophosphatidylcholine 18.2, and three phosphatidlycholines), associations were attenuated and no longer significant.

CONCLUSIONS

These preliminary results indicate that the association of lower MMA% and higher DMA% with diabetes-related outcomes may be influenced by OCM status, either through confounding, reverse causality, or mediation.

A meta-analysis of the distribution, sources and health risks of arsenic-contaminated groundwater in Pakistan

Globally, millions of people who rely on groundwater for potable purposes and agriculture have been inadvertently exposed to toxic arsenic (As) because of its natural occurrence in groundwater in several countries of Asia, Europe and America. While the presence of As in groundwater and its impacts on human health have been documented in many countries, there is little information on As contamination in Pakistan. This review highlights, for the first time, the extent and severity of As-induced problems in Pakistan based on relevant published papers; discusses possible sources of As contamination of aquifers; and estimates As-induced potential health hazards in the country in relation to global data. Data from 43 studies (>9882 groundwater samples) were used to describe As variability in groundwater of Pakistan and for comparison with global data. The mean groundwater As content reported in these studies was 120 μg/L (range: 0.1-2090 μg/L; SD: ±307). About 73% of the values for mean As contents in the 43 studies were higher than the World Health Organization (WHO) permissible limit (10 μg/L) for drinking water, while 41% were higher than the permissible limit of As in Pakistan (50 μg/L). It was observed that groundwater samples in some areas of Punjab and Sindh provinces contained high As concentrations which were almost equal to concentrations reported in the most contaminated areas of the world. We predicted that the mean values of ADD, HQ and CR were 4.4 μg kg^-1day^-1 (range: 0-77 μg kg^-1day^-1), 14.7 (range: 0-256) and 0.0029 (range: 0-0.0512), respectively, based on mean As concentrations reported in Pakistan. In addition, this article proposes some integrated sustainable solutions and future perspectives keeping in view the regional and global context, as well as the on-ground reality of the population drinking As-contaminated water, planning issues, awareness among civil society and role of the government bodies. Based on available data, it is predicted that almost 47 million people in Pakistan are residing in areas where more than 50% of groundwater wells contain As concentrations above the WHO recommended limit of As in drinking water.

Serum Concentrations of 15 Elements Among Helicobacter Pylori-Infected Residents from Lujiang County with High Gastric Cancer Risk in Eastern China

Helicobacter pylori (H. pylori) infection can interfere with the absorption of most elements, and the variations of some element levels are related to the incidence of gastric cancer. However, there have been conflicting results concerning the influence of H. pylori infection on serum element levels. The present study aimed to compare the serum element concentrations of H. pylori-infected local residents with uninfected residents from Lujiang County with high gastric cancer risk in Eastern China. We used data and serum samples from the H. pylori screening-survey program which was a cross-sectional study. We took 155 samples randomly from the screening survey, identified 74 H. pylori-positive residents and 81 H. pylori-negative residents by a serological test. The serum concentrations of 15 elements (calcium, magnesium, iron, zinc, selenium, copper, molybdenum, chromium, cobalt, nickel, lead, cadmium, mercury, arsenic, and aluminum) were determined using inductively coupled plasma mass spectrometry. Serum cobalt was found at higher levels in the H. pylori-infected residents than the H. pylori-uninfected residents (0.246 vs 0.205 μg/L, P = 0.022), but no statistically significant differences in the serum levels of other elements were found. This is the first study to report the serum concentrations of 15 elements and their relationships with the infection status of H. pylori among local residents from Lujiang County with high gastric cancer risk. Although the International Agency for Research on Cancer has classified cobalt and other soluble cobalt salts as possibly carcinogenic to human beings, our results may provide a clue to the relationships between cobalt, H. pylori, and gastric cancer.

[Association between Arsenic Intake and Cancer-From the Viewpoint of Epidemiological Study]

Arsenic is widely distributed in nature, and humans are exposed to arsenic through air, water, beverages, and food. On the bases of previous studies of highly exposed populations, arsenic is designated as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC), and IARC has established a causal role for arsenic in cancers of the urinary bladder, lung, and skin in humans. However, there are very few epidemiological studies of the association between low-moderate arsenic exposure and cancer. In particular, there is only one study of the association between arsenic intake from food and cancer. Further epidemiological studies are needed.

Association between lung cancer risk and inorganic arsenic concentration in drinking water: a dose-response meta-analysis

High dose arsenic in drinking water (≥100 μg L^-1) is known to induce lung cancer, but lung cancer risks at low to moderate arsenic levels and its dose-response relationship remains inconclusive. We conducted a systematic review of cohort and case-control studies that quantitatively reported the association between arsenic concentrations in drinking water and lung cancer risks by searching the PubMed database till June 14, 2018. Pooled relative risks (RRs) of lung cancer associated with full range (10 μg L^-1-1000 μg L^-1) and low to moderate range (<100 μg L^-1) of water arsenic concentrations were calculated using random-effects models. A dose-response meta-analysis was performed to estimate the pooled associations between restricted cubic splines of log-transformed water arsenic and the lung cancer risks. Fifteen studies (9 case-control and 6 cohort studies) involving a total of 218 481 participants met the inclusion criteria. Meta-analysis identified significantly increased risks of lung cancer on exposure to both full range (RR = 1.21; 95% confidence interval [CI] = 1.05-1.37; heterogeneity I ² = 54.3%) and low to moderate range (RR = 1.18; 95%CI = 1.00-1.35; I ² = 56.3%) of arsenic-containing water. In the dose-response meta-analysis of eight case-control studies, we found no evidence of non-linearity, although statistical power was limited. The corresponding pooled RRs and their 95%CIs for exposure to 10 μg L^-1, 50 μg L^-1, and 100 μg L^-1 water arsenic were 1.02 (1.00-1.03), 1.10 (1.04-1.15), and 1.20 (1.08-1.32), respectively. We provide evidence on the association between increased lung cancer risks and inorganic arsenic in drinking water across low, moderate and high levels. Minimizing arsenic levels in drinking water may be of public health importance.

A review on arsenic carcinogenesis: Epidemiology, metabolism, genotoxicity and epigenetic changes

Long-term exposure to arsenic (inorganic arsenic) is a world-wide environmental health concern. Arsenic is classified as the Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). Epidemiological studies have established a strong association between inorganic arsenic (iAs) exposure in drinking water and an increased incidence of cancer including bladder, liver, lung, prostate, and skin cancer. iAs also increases the risk of other diseases such as cardiovascular disease, hypertension and diabetes. The molecular mechanisms of carcinogenesis of iAs remain poorly defined, several mechanisms have been proposed, including genotoxicity, altered cell proliferation, oxidative stress, changes to the epigenome, disturbances of signal transduction pathways, cytotoxicity and regenerative proliferation. In this article, we will summarize current knowledge on the mechanisms of arsenic carcinogenesis and focus on integrating all these issues to garner a broader perspective.

Do Exposure to Arsenic, Occupation and Diet Have Synergistic Effects on Prostate Cancer Risk?

Background:

Diverse environmental exposures, as well as dietary and lifestyle factors, are associated with prostate cancer (PC) etiology; however little is known about joint interactive influences. The aim of this study was to analyse effects of diet combined with arsenic in drinking water and agricultural occupation on PC risk.

Methods:

A case-control study was conducted in Córdoba, Argentina (period 2008-2015) including 147 cases of PC and 300 controls. All subjects were interviewed about food consumption, socio-demographic and lifestyle characteristics. A sample of drinking water was taken to determine arsenic concentrations. Adherence scores to the Traditional Dietary Pattern were estimated, based on a principal component factor analysis. A two-level logistic regression model was fitted in order to assess effects of the Traditional Pattern, occupation and arsenic exposure on the occurrence of PC (outcome). Family history of PC was considered as a clustering variable.

Results:

PC risk was greatest in subjects with high adherence to the Traditional Pattern (OR 2.18; 95%IC 1.097–4.344). Subjects exposed to arsenic in drinking water above 0.01mg/l who simultaneously performed agricultural activities showed a markedly elevated PC risk (OR 5.07; 95%IC 2.074-12.404). Variance of the random effect of family history of PC was significant.

conclusion:

Diet, arsenic and occupation in agriculture exert significant effects on PC risk. Further efforts are necessary to analyse risk factors integrally, in order to achieve a better understanding of the complex causal network for PC in this multiple-exposure population.