Sensitivity Analysis of U.S. EPA's Estimates of Skin Cancer Risk from Inorganic Arsenic in Drinking Water

The current U.S. Environmental Protection Agency's (USEPA's) risk analysis on the Integrated Risk Information System (IRIS) for arsenic in drinking water is based on an epidemiological study of skin cancer in Taiwan. Assumptions used in the USEPA application of the multistage-Weibull model for risk estimation were varied to assess the effect on predicted risk of skin cancer to the U.S. population at arsenic concentrations of 1 to 50?µg/L in drinking water. Among the assumptions tested, the only notable change in risk estimates was a reduction when the arsenic concentration used as representative for Taiwan villages in the low range (<300?µg/L) was increased to the 75th percentile (245?µg/L) in place of the mean used in the USEPA analysis (170?µg/L), but the representative value for Taiwan villages in the high range (≥600?µg/L) was not increased simultaneously to the 75th percentile. Additionally, a simulation study was conducted using records of arsenic measurements in wells from the same period and region of Taiwan as the original study. The exposure-response curve estimated from 60 villages (60 data points) differed only marginally from the outcome when data were summarized into four data points (as in the USEPA skin cancer analysis). Briefly discussed are differences between the study area of Taiwan and the U.S. in nutritional status and consumption of inorganic arsenic in food that might bias predicted U.S. skin cancer risks.     

Arsenic Removal Technologies for Drinking Water Treatment

Arsenic contamination as a consequence of human activities such as mining and pesticide use is affecting the water resource quality worldwide. Because of the high risk of arsenic exposure, specific water treatment processes are required to meet the anticipated more severe water quality standards. Better understanding of presently available processes is necessary to develop economic, efficient and effective methods for arsenic removal. Arsenic could either be coagulated, adsorbed using a wide range of materials both mineral and organic or could be directly rejected by membrane processes such as reverse osmosis and nanofiltration. The recent development of submerged hybrid membrane systems, such as membrane bioreactor in wastewater treatment, offers alternative technologies for arsenic treatment. The membrane in hybrid systems allows a better phase separation between the particles binding the arsenic and the treated water. The effect of pH and contact time, and the existence of other ionic compounds must be taken into account when designing the system for optimum arsenic rejection. Further research on both hydraulic and removal performances of hybrid adsorption/membrane technology is still required to assess the full potential of this technology for arsenic removal.     

Estimation of Dietary Intake of Inorganic Arsenic in U.S. Children

Arsenic is a natural component of the environment and is ubiquitous in soils, water, and the diet. Because dietary intake can be a significant source of background exposure to inorganic arsenic (the most toxicologically significant form), accurate intake estimates are needed to provide a context for risk management of arsenic exposure. Intake of inorganic arsenic by adults is fairly well characterized, but previous estimates of childhood intake were based on inorganic arsenic analyses in a limited number of foods (13 food types). This article estimates dietary intake for U.S. children (1 to 6 years of age) based on reported inorganic arsenic concentrations in 38 foods and in water used in cooking those foods (inorganic arsenic concentration of 0.8 μg/L), and U.S. Department of Agriculture food consumption data. This information is combined using a probabilistic software model to extract food consumption patterns and compute exposure distributions. The mean childhood dietary intake estimate for inorganic arsenic was 3.2 μg/day with a range of 1.6 to 6.2 μg/day for the 10th and 95th percentiles, respectively. For both the mean and 95th percentile inorganic arsenic intake rates, intake was predominantly contributed by grain and grain products, fruits and fruit juices, rice and rice products, and milk.     

Assessing Risk of Inorganic Arsenic in Drinking Water in the United States

Limitations of the current EPA risk assessment for inorganic arsenic in drinking water in the U.S. are discussed. An empirical approach is suggested that would sample survey the populations in regions with the highest arsenic levels in drinking water for signs of arsenicism, which has been much more prevalent and appeared much earlier in exposed populations than cancer (e.g., of the skin). Biomarkers of exposure, such as arsenic content in urine, nails, hair, and skin scales, may provide even earlier indications of subpopulations with excessive arsenic exposure and identify individuals at risk. Further study is needed to evaluate fully the potential for use of biomarkers, focusing on the accuracy and reliability of analytical methods, the utility of biomarkers as indicators of short-term and long-term exposure and as precursors to clinical signs of arsenicism, and the use of “normal” ranges of biomarkers for interpretation of field observations.     

Determination of Arsenic Scalp Hair of Pakistani Children and Drinking Water for Environmental Risk Assessment

This cross-sectional study measured the arsenic level in scalp hair samples of children from two age groups exposed to contaminated underground water in Pakistan. The As concentrations in water and scalp hair samples were analyzed by electrothermal atomic absorption spectrometry. The studied areas were divided into three regions based on concentration of As in water and scalp hair of children who had been exposed to different levels of As through drinking water. The average As concentrations in underground water samples of sub-districts Faiz Ganj, Thari Mirwah, and Gambat were observed to be 15.2, 28.5, and 98.3 μg/L, respectively, which were marked as less, medium, and highly contaminated areas, respectively. The proportion of the children with lower body mass index significantly increased with increasing As exposure level; the dose–response relationship was consistently observed among the subgroups. The range of As concentrations in scalp hair samples of children of age 1–5 and 6–10 years was 0.21–3.88 and 0.32–3.63 μg/g, respectively. Thus, it is likely that children in our study areas are chronically exposed to As through drinking groundwater, suggesting that there is an urgent need to take immediate solution, especially in the Gambat sub-district.     

The Association of Body Weight,Dietary Intake,and Energy Expenditure with Dietary Restraint and Disinhibition

LAWSON, OLGA J, DONALD A WILLIAMSON, CATHERINE M CHAMPAGNE, JAMES P DELANY, ELLEN R BROOKS, PAULA M HOWAT, PATRICIA J WOZNIAK, GEORGE A BRAY AND DONNA H RYAN. The association of body weight, dietary intake, and energy expenditure with dietary restraint and disinhibition. Obes Res. 1995;3:153–161. The hypotheses that dieting and/or overeating are associated with adiposity, eating disturbances, and lowered energy expenditure were tested in this study. A sample of 44 premenopausal women scoring high and low on measures of dietary restraint and disinhibition of dietary control, as measured by the Three Factor Eating Questionnaire, was studied. A 2 × 2 factorial design was employed (High/Low Restraint x High/Low Disinhibition). Dependent variables were: body composition, dietary intake, activity, resting metabolic rate, and thermic effect of food. Unrestrained overeaters (Low Restraint/High Disinhibition group) were very obese. High Dietary Restraint was associated with intent to diet and controlled eating. High scores on the Disinhibition Scale were associated with episodic overeating. Groups did not differ in resting metabolic rate (controlled for fat-free mass). Lower thermic effect of food was found to be associated with the obesity found in High Disinhibition subjects. Thus, Dietary Restraint was not associated with significant adverse effects upon physical or psychological health. High Disinhibition, however, was associated with adiposity and significant disturbances of eating.     

Arsenic in Seafood: Speciation Issues for Human Health Risk Assessment

Major sources of arsenic exposure for humans are foods, particularly aquatic organisms, which are called seafood in this report. Although seafood contains a variety of arsenicals, including inorganic arsenic, which is toxic and carcinogenic, and arsenobetaine, which is considered nontoxic, the arsenic content of seafood commonly is reported only as total arsenic. A goal of this literature survey is to determine if generalizable values can be derived for the percentage of total arsenic in seafood that is inorganic arsenic. Generalizable values for percent inorganic arsenic are needed for use as default values in U.S. human health risk assessments of seafood from arsenic-contaminated sites. Data from the worldwide literature indicate the percent of inorganic arsenic in marine/estuarine finfish does not exceed 7.3% and in shellfish can reach 25% in organisms from presumably uncontaminated areas, with few data available for freshwater organisms. However, percentages can be much higher in organisms from contaminated areas and in seaweed. U.S. site-specific data for marine/estuarine finfish and shellfish are similar to the worldwide data, and for freshwater finfish indicate that the average percent inorganic arsenic is generally < 10%, but ranges up to nearly 30%. Derivation of nationwide defaults for percent inorganic arsenic in fish, shellfish, and seaweed collected from arsenic-contaminated areas in the United States is not supported by the surveyed literature.     

Estimation of Multimedia Inorganic Arsenic Intake in the U.S. Population

Arsenic is widely distributed in the environment by natural and human means. The potential for adverse health effects from inorganic arsenic depends on the level and route of exposure. To estimate potential health risks of inorganic arsenic, the apportionment of exposure among sources of inorganic arsenic is critical. In this study, daily inorganic arsenic intake of U.S. adults from food, water, and soil ingestion and from airborne particle inhalation was estimated. To account for variations in exposure across the U.S., a Monte Carlo approach was taken using simulations for 100,000 individuals representing the age, gender, and county of residence of the U.S. population based on census data. Our analysis found that food is the greatest source of inorganic arsenic intake and that drinking water is the next highest contributor. Inhalation of airborne arsenic-containing particles and ingestion of arsenic-containing soils were negligible contributors. The exposure is best represented by the ranges of inorganic arsenic intake (at the 10^th and 90^th percentiles), which were 1.8 to 11.4 µg/day for males and 1.3 to 9.4 µg/day for females. Regional differences in inorganic arsenic exposure were due mostly to consumption of drinking water containing differing inorganic arsenic content rather than to food preferences.     

Arsenic speciation in marine interstitial water. The occurrence of organoarsenicals

Arsenic speciation data are presented for pore waters squeezed from some native and anthropogenically influenced sediments.Ten stations were sampled with a box corer (to 20 cm) at two British Columbia coastal sites that are influenced by mine-tailings discharges. These are Rupert Inlet and Alice Arm as well as their associated systems of Quatsino Sound/Holberg Inlet and Hastings Arm respectively.Total dissolved arsenic concentrations (As _D) usually exhibited subsurface maxima at 5–10 cm and were generally related to solid phase arsenic (As _p) levels, but there was also a dependence on the nature of the substrate. Tailings exhibited both the lowest (Rupert Inlet) and the highest (Alice Arm) As _D values. Inorganic arsenicals, arsenate (AsV) and arsenite (AsIII) constituted the majority (>90%) of the dissolved species butevery sample contained organoarsenicals. This is the first report of mono-, di- and tri-methylated arsenic species in marine interstitial water.A strong positive correlation between the sum of the methylarsenic compounds (MeAs) and the total dissolved arsenic (As _D) was found, indicating in situ microbial methylation similar to that observed in non-aquatic systems. Flux values for arsenic at the sediment-water interface suggest that, at present, there is no significant mobilization of arsenic from these mine-derived sediments into the water column.     

Mechanisms Preserving Insulin Action during High Dietary Fat Intake

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Changes in Serum Adiponectin in Mice Chronically Exposed to Inorganic Arsenic in Drinking Water

Cardiovascular disease and diabetes mellitus are prominent features of glucose and lipid metabolism disorders. Adiponectin is a key adipokine that is largely involved in glucose and lipid metabolism processes. A growing body of evidence suggests that chronic exposure to inorganic arsenic is associated with cardiovascular disease and diabetes mellitus. We hypothesized that arsenic exposure may increase the risk of cardiovascular disease and diabetes mellitus by affecting the level of adiponectin. In this study, we examined serum adiponectin levels, as well as serum levels of metabolic measures (including fasting blood glucose, insulin, total cholesterol, triglyceride, and high-density lipoprotein (HDL)-cholesterol) in C57BL/6 mice exposed to inorganic arsenic in drinking water (5 and 50 ppm NaAsO₂) for 18 weeks. Body mass and adiposity were monitored throughout the study. We found no significant changes in serum insulin and glucose levels in mice treated with arsenic for 18 weeks. However, arsenic exposure decreased serum levels of adiponectin, triglyceride, and HDL-cholesterol. Further, an inverse relationship was observed between urinary concentrations of total arsenic and serum levels of adiponectin. This study suggests that arsenic exposure could disturb the metabolism of lipids and increase the risk of cardiovascular disease by reducing the level of adiponectin.     

Subchronic Arsenic Exposure Through Drinking Water Alters Lipid Profile and Electrolyte Status in Rats

Arsenic is a groundwater pollutant and can cause various cardiovascular disorders in the exposed population. The aim of the present study was to assess whether subchronic arsenic exposure through drinking water can induce vascular dysfunction associated with alteration in plasma electrolytes and lipid profile. Rats were exposed to arsenic as 25, 50, and 100 ppm of sodium arsenite through drinking water for 90 consecutive days. On the 91st day, rats were sacrificed and blood was collected. Lipid profile and the levels of electrolytes (sodium, potassium, and chloride) were assessed in plasma. Arsenic reduced high-density lipoprotein cholesterol (HDL-C) and HDL-C/LDL-C ratio, but increased the levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and electrolytes. The results suggest that the arsenic-mediated dyslipidemia and electrolyte retention could be important mechanisms in the arsenic-induced vascular disorder.     

Genetic Susceptible Locus in NOTCH2 Interacts with Arsenic in Drinking Water on Risk of Type 2 Diabetes

Background

Chronic exposure to arsenic in drinking water is associated with increased risk of type 2 diabetes mellitus (T2DM) but the underlying molecular mechanism remains unclear.

Objectives

This study evaluated the interaction between single nucleotide polymorphisms (SNPs) in genes associated with diabetes and arsenic exposure in drinking water on the risk of developing T2DM.

Methods

In 2009–2011, we conducted a follow up study of 957 Bangladeshi adults who participated in a case-control study of arsenic-induced skin lesions in 2001–2003. Logistic regression models were used to evaluate the association between 38 SNPs in 18 genes and risk of T2DM measured at follow up. T2DM was defined as having a blood hemoglobin A1C level greater than or equal to 6.5% at follow-up. Arsenic exposure was characterized by drinking water samples collected from participants'' tubewells. False discovery rates were applied in the analysis to control for multiple comparisons.

Results

Median arsenic levels in 2001–2003 were higher among diabetic participants compared with non-diabetic ones (71.6 µg/L vs. 12.5 µg/L, p-value <0.001). Three SNPs in ADAMTS9 were nominally associated with increased risk of T2DM (rs17070905, Odds Ratio (OR)  = 2.30, 95% confidence interval (CI) 1.17–4.50; rs17070967, OR = 2.02, 95%CI 1.00–4.06; rs6766801, OR = 2.33, 95%CI 1.18–4.60), but these associations did not reach the statistical significance after adjusting for multiple comparisons. A significant interaction between arsenic and NOTCH2 (rs699780) was observed which significantly increased the risk of T2DM (p for interaction = 0.003; q-value = 0.021). Further restricted analysis among participants exposed to water arsenic of less than 148 µg/L showed consistent results for interaction between the NOTCH2 variant and arsenic exposure on T2DM (p for interaction  = 0.048; q-value = 0.004).

Conclusions

These findings suggest that genetic variation in NOTCH2 increased susceptibility to T2DM among people exposed to inorganic arsenic. Additionally, genetic variants in ADAMTS9 may increase the risk of T2DM.     

水稻对砷的吸收及代谢机制研究进展

砷（As）是一种广泛存在的致癌的微量元素。环境中日益严重的As污染问题,影响了水稻的生长和品质,并通过食物链进一步威胁着人类健康。为降低食物链中As的污染并提高水稻对As的耐性,需要深入了解水稻对As的吸收及As在水稻体内转运、代谢过程的生理及分子生物学机制。本文就以上几个问题综述了近些年来国内外的研究结果,并对今后深入研究提出建议。     

Dieting Status and Its Relationship to Weight,Dietary Intake,and Physical Activity Changes Over Two Years in a Working Population

The present study prospectively examined changes in dietary intake, physical activity and weight associated with self-reported efforts to lose weight in a cohort of 3671 men and women sampled from the general population. Dieting efforts, dietary intake, physical activity and weight were measured at two points in time, 24 months apart. At baseline, current dieters reported consuming fewer dairy products, sweets, meat, soft drinks and fried potatoes (all p's < .0001), and engaging more frequently in high-intensity physical activity (p < .0001) than those not currently dieting. At follow-up, current dieters reported consuming fewer sweets (p < .0001) and fried potatoes (p < .0008), and engaging more frequently in moderate-intensity physical activity (p < .02) than those not currently dieting. Prospectively, those who initiated weight-loss diets showed the largest decrease in consumption of sweets (p < .0001), soft drinks (p < .0001), and fried potatoes (p < .01), and increase in frequency of high-intensity physical activity (p < .0001) and moderate-intensity physical activity (p < .007). Those initiating weight-loss diets were the only group to lose weight (1 lb.). Those dieting at baseline but not at follow-up gained the most weight (4 lbs.). Self-reports of current dieting correspond to reported changes in dietary intake and physical activity, and to measured changes in weight over the same time period. Individuals who report dieting to lose weight have healthier eating and exercise patterns than those who do not report dieting.     

Reliability of the Circadian Rhythm of Water and Macronutrient-Rich Diets Intake in Dietary Choice

Rats with ad libitum water and the ability to self-select among three macronutrient-rich diets—carbohydrate (CHO), protein (PRO), and lipid (LIP)—show a circadian rhythmicity in their ingestion. The aim of the present study was to determine whether this circadian rhythmicity is reliable from day to day. Eight rats were offered ad libitum water and a choice of three isoenergetic diet rations providing carbohydrate, protein, and lipid. Water and food intake was recorded every 3 h for 7 days. The reliability of the circadian rhythm of water and food intake was assessed by the Intraclass Correlation Coefficient (ICC) and the test-retest reliability using the Pearson's Correlation Coefficient (r). The results showed that the circadian rhythm of water, CHO, and PRO intake are strongly reliable. However, the circadian rhythm of LIP intake is less reproducible. Among the three reliable parameters—water, CHO, and PRO, the circadian rhythm of water intake was the most reproducible over 7 days. This suggests that water intake may be used as a marker of circadian rhythmicity in ingestive behavior.