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Water quality improvement is the most efficient way to prevent arsenic exposure. After the cessation of arsenic ingestion, arsenic methylation capacity of the exposed population can change significantly. The factors associated with these changes remain poorly understood. Therefore, arsenic methylation capacity in a study cohort was estimated before and after water quality improvement in the present study. Results indicated that urinary content of the arsenic species in the study cohort significantly decreased after water quality improvement. In addition, the proportions of inorganic arsenic (%iAs) and monomethyl arsenic acid (%MMA) were significantly decreased, while proportions of dimethyl arsenic (%DMA) increased. The primary methylation index (PMI) and secondary methylation index (SMI) increased from 0.85 to 0.92 and 0.82 to 0.84, respectively. Arsenic species urinary content and arsenic methylation index varied slightly between the study cohort after water quality improvement and the control cohort. The rate of increase in PMI was higher than that in SMI. The study group aged 31-50 years had the highest increase in PMI. Logistic regression revealed that %DMA before water quality improvement was negatively associated with the increase in PMI, while %iAs were positively related, and %MMA were positively associated with the increase in SMI. It is concluded that urinary arsenic species content and arsenic methylation capacity increased to the levels of the control cohort after water quality improvement. An increase in primary arsenic methylation capacity may be a burden on the secondary arsenic methylation capacity. The main role of arsenic methylation capacity recovery may be the cessation of arsenic exposure.

Few studies have been conducted to compare arsenic exposure, metabolism, and methylation in populations exposed to arsenic in drinking water and from coal combustion. Therefore, arsenic concentrations in the environment and arsenic speciation in the urine of subjects exposed to arsenic as a consequence of coal combustion in a rural area in Shaanxi province (CCA) and in drinking water in a rural area in Inner Mongolia (DWA) were investigated. The mean arsenic concentrations in drinking water, indoor air, and soil in CCA were 4.52 μg/L, 0.03 mg/m 3 , and 14.93 mg/kg, respectively. The mean arsenic concentrations in drinking water and soil in DWA were 144.71 μg/L and 10.19 mg/kg, respectively, while the level in indoor air was lower than the limit of detection. The total daily intakes of arsenic in DWA and CCA were 4.47 and 3.13 μg/day·kg, respectively. The mean urinary concentrations of inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and total arsenic (TAs) for subjects with skin lesions in DWA were 50.41, 47.01, 202.66, and 300.08 μg/L. The concentrations for subjects without skin lesions were 49.76, 44.20, 195.60, and 289.56 μg/L, respectively. The %iAs, %MMA, and %DMA in the TAs in the urine of subjects from CCA were 12.24, 14.73, and 73.03%, while the corresponding values from DWA were 17.54, 15.57, and 66.89%, respectively. The subjects in DWA typically had a higher %iAs and %MMA, and a lower %DMA, and primary and secondary methylation index (PMI and SMI) than the subjects in CCA. It was concluded that the arsenic methylation efficiency of subjects in DWA and CCA was significantly influenced by chronic exposure to high levels of arsenic in the environment. The lower PMI and SMI values in DWA revealed lower arsenic methylation capacity due to ingestion of arsenic in drinking water. However, it remained unclear if the differences in arsenic metabolism between the two groups were due to differences in exposure levels or in exposure route.

In order to figure out the prevalence of skin lesions and methylation capacity for migrant and native adult women in an endemic area for arsenic poisoning in Inner Mongolia, China, 207 adult women were selected for study subjects. The results showed that the prevalence of skin lesions for the external group, provincial group and native group was 36.54, 26.15 and 35.56 %, respectively. The nail content of arsenic and urinary concentrations of dimethylarsenic (DMA), monomethylarsenic (MMA) and inorganic arsenic (iAs) were significantly higher in women with skin lesions than in those without skin lesions. The highest urinary concentrations of DMA, MMA and iAs were 213.93, 45.72 and 45.01 μg/L in the native group. The arsenic methylation capacity index revealed that the external group had the greatest capacity, while the native group had the lowest. The odds ratios of skin lesions in relation to arsenic metabolites and arsenic methylation capacity varied widely among the three groups. Urinary MMA and iAs concentrations were positively associated with risk of skin lesions in the three groups of adult women, while primary and secondary methylation capacities were negatively related to risk of skin lesions in native and provincial groups. The external group might be more susceptible to MMA and iAs, while the provincial and native groups were more tolerance to MMA and iAs. Lower primary and secondary arsenic methylation capacities increased the risk of skin lesions in native and provincial groups. Moreover, higher nail arsenic concentration increased the risk of skin lesions of adult women.

To investigate the interaction between skin lesion status and arsenic methylation profiles, the concentrations and proportions of arsenic metabolites in urine and arsenic methylation capacities of study subjects were determined. The results showed that the mean urinary concentrations of iAs (inorganic arsenic), MMA (monomethylarsonic acid), DMA (dimethylarsinic acid), and TAs (total arsenic) were 75.65, 68.78, 265.81, and 410.24 μg/L, respectively, in the skin lesions subjects. The highest values were observed in the multiple skin lesions subjects. Higher %iAs and %MMA, and lower %DMA, PMI (primary methylation index), and SMI (secondary methylation index) were found in skin lesions subjects. The multiple skin lesions subjects had highest %iAs and %MMA, and lowest %DMA, PMI, and SMI. The prevalence of skin lesions strongly, positively correlated with arsenic levels in drinking water. The elder persons also had higher frequency of skin lesions compared with younger persons. It can be concluded that arsenic levels in drinking water significantly affected the prevalence of skin lesions. Male subjects usually had higher proportions of skin lesions when compared with female subjects. Moreover, it may be concluded that MMA was significantly related to single skin lesion, whereas DMA and iAs were associated with multiple skin lesions. It seemed that MMA had greater toxicity to hyperkeratosis, whereas DMA and iAs had higher toxicity to depigmentation or pigmentation. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 28-36, 2017., (© 2015 Wiley Periodicals, Inc.)

Objective: To study the effect on endocrine system of SD rats exposed to low-dose arsenic., Methods: A subchronic test on rats which were divided into five groups randomly( the control group, 0. 05, 0. 1, 0. 2, 0. 4 μg / m L), 20 rats each group, half male and female. A total of 200 rats were allowed to acclimate for 1 week and their hormones level were measured by RIA method after 110 and 194 days., Results: The hormones level of rats was disordered in different groups. The T level of male rats exposedto arsenic for 110 days were( 4. 80 ± 4. 26), ( 4. 54 ± 3. 31), ( 1. 27 ± 1. 51), ( 1. 93 ±2. 23) and( 4. 83 ± 2. 31) ng / m L( P = 0. 05), respectively. The T4 level of each female group were( 40. 20 ± 7. 10), ( 40. 85 ± 8. 66), ( 46. 49 ± 8. 52), ( 44. 66 ± 11. 83) and( 26. 80 ± 8. 12) ng /m L, compared with control group, 0. 4 μg /m L group decreased obviously( P < 0. 05). Meanwhile, their Cort level of each group were( 312. 10 ±10. 61), ( 333. 15 ± 15. 73), ( 341. 13 ± 19. 25), ( 342. 59 ± 25. 96) and( 314. 84 ±16. 76) ng / m L, and the 0. 05, 0. 1 and 0. 2 μg / m L groups were significantly increased( P < 0. 05). Furthermore, the T4 level of male groups exposed to arsenic for 194 days were( 23. 06 ± 5. 54), ( 33. 18 ± 5. 29), ( 34. 23 ± 4. 15), ( 37. 19 ± 4. 13) and( 39. 92± 6. 27) ng / m L, respectively. Compared with control group, all experimental group significantly increased( all P < 0. 05). Additionally, the T3 level of female group were( 0. 84 ± 0. 12), ( 0. 89 ± 0. 14), ( 0. 83 ± 0. 15), ( 0. 96 ± 0. 16) and( 0. 75 ± 0. 11)ng / m L, and 0. 2 μg / m L group obviously increased( P < 0. 05). Obvious change of hormone had not been found in other group exposed to subchronic low-dose arsenic( all P> 0. 05)., Conclusion: Subchronic low-dose arsenic exposure have slight endocrine effects on SD rats.

More than 0.3 million individuals are subject to chronic exposure to arsenic via their drinking water in Inner Mongolia, China. To determine arsenic methylation capacity profiles for such individuals, concentrations of urinary arsenic metabolites were measured for 548 subjects using high-performance liquid chromatography and a hydride generator combined with inductively coupled plasma-mass spectrometry. Mean urinary concentrations of dimethylarsonic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenic (iAs), and total arsenic (TAs) were 200.50, 46.71, 52.96, and 300.17 μg/L, respectively. The %iAs, %DMA, and %MMA were 15.98, 69.72, and 14.29%. Mean urinary %iAs and %MMA were higher in males, while urinary %DMA was higher in females. There was a strong positive correlation between %iAs and %MMA, with negative correlations between %iAs and %DMA, and %iAs and %MMA. In addition, %iAs and %MMA were positively associated with total arsenic in drinking water (WAs), while %DMA was negatively related with WAs. Regression analysis indicated that the primary methylation index (PMI) and secondary methylation index (SMI) generally decreased with increasing WAs. Females had a higher arsenic methylation capacity compared to males. Younger subjects had lower primary arsenic methylation capacity. However, the secondary arsenic methylation capacity was hardly affected by age. Moreover, both primary and secondary arsenic methylation capacities were negatively related to WAs.

Objective: To detect ERbeta mRNA expression of subjects exposed to different arsenic drinking water, and to analyze the potential relationship between their abnormal expression and heart injury caused by arsenic in order to study the endocrine disturbing effect of arsenic., Methods: Molecular epidemiological method was used. The study subjects included a total of 273 residents exposed to arsenic via drinking water,and they were divided into four groups according to arsenic concentration, and their blood ERbeta mRNA expression was detected by real-time RT-PCR., Results: The level of ERbeta mRNA expression rose with increasing of water As and urine As (r = 0.159, 0.21, P < 0.05). The prevalence of Q-Tc interval prolongation aggravated with increasing of water As(chi2 = 4.35, P = 0.037), while according with the variation of ERbeta mRNA expression. Tp-Te interval prolonged with increasing of water As (r = 0.199, P = 0.023), as well prolonged with increasing of ERbeta mRNA expression (r = 0.205, P = 0.019). The prevalence of arrhythmia was almost according with the variation of ERbeta mRNA expression., Conclusion: chronic arsenic exposure can potentially disturb ERbeta mRNA expression, as well as there are possible relationship between ERbeta mRNA abnormal expression and Q-Tc interval prolongation and Tp-Te interval prolonged caused by arsenic.

Objective: To study the effect on endocrine system of female rats exposed to chronic arsenic., Methods: 50 female Wistar rats were randomly divided into five groups: control group, 0.05, 0.1, 0.2 and 0.4 microg/ml arsenic groups. The hormone levels were determined by RIA exposing arsenic for 32 weeks., Results: The hormone levels of female rats were disorder in different arsenic groups. E2, P level increased and LH level decreased in arsenic groups compared to controls, but there were no significant differences( P > 0.05). FSH and PRL level increased in low arsenic group and decreased in high arsenic groups (P > 0.05). GnRH and Cort level increased in arsenic groups, and GnRH level obviously increased in 0.4 microg/ml group and Cort level obviously increased in 0.1 and 0.4 microg/ml groups (P < 0.05)., Conclusions: The hormone levels were disordered in rats exposed to chronic arsenic.

Objective: By measure the changes of serumal estadiol and progesterone levels of kunming female mice, which are chronically exposed to different concentrations of arsenic trioxide, discuss the estrogen-like effects of arsenic., Methods: Select the Kunming female mice exposed to different drinking water of arsenic trioxide (0, 0.05, 0.10, 0.20, 0.40 microg/ml) for 20 weeks as the research subjects in this study. Use the method of radioimmunology to measure concentrations of serumal estadiol and progesterone of female adult mice., Results: Compared with the control group, there exists the changes of the concentrations of the serumal estadiol and progesterone of Km female adult mice, which are chronically exposed to the arsenic. Compared to the control group, the differences of the concentrations of the serumal estadiol in the 0.05 microg/ml group and 0.10 microg/ml group have no statistical significance (P > 0.05), the concentrations of estadiol in the 0.20 microg/ml group (P < 0.01) and 0.40 microg/ ml group (P < 0.05) decrease. Compared to the control group, the differences of the concentrations of the serumal progesterone in the 0.05 microg/ml group, 0.20 microg/ml group and 0.40 microg/ml group have no statistical significance (P > 0.05), the concentration of serumal progesterone in the 0.10 microg/ml group (P < 0.01) decrease., Conclusion: Chronically arsenic exposure can interfere the levels of serumal hormones. Arsenic has the estrogen-like effects.

Few studies have been conducted to compare arsenic exposure, metabolism, and methylation in populations exposed to arsenic in drinking water and from coal combustion. Therefore, arsenic concentrations in the environment and arsenic speciation in the urine of subjects exposed to arsenic as a consequence of coal combustion in a rural area in Shaanxi province (CCA) and in drinking water in a rural area in Inner Mongolia (DWA) were investigated. The mean arsenic concentrations in drinking water, indoor air, and soil in CCA were 4.52 μg/L, 0.03 mg/m, and 14.93 mg/kg, respectively. The mean arsenic concentrations in drinking water and soil in DWA were 144.71 μg/L and 10.19 mg/kg, respectively, while the level in indoor air was lower than the limit of detection. The total daily intakes of arsenic in DWA and CCA were 4.47 and 3.13 μg/day·kg, respectively. The mean urinary concentrations of inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and total arsenic (TAs) for subjects with skin lesions in DWA were 50.41, 47.01, 202.66, and 300.08 μg/L. The concentrations for subjects without skin lesions were 49.76, 44.20, 195.60, and 289.56 μg/L, respectively. The %iAs, %MMA, and %DMA in the TAs in the urine of subjects from CCA were 12.24, 14.73, and 73.03%, while the corresponding values from DWA were 17.54, 15.57, and 66.89%, respectively. The subjects in DWA typically had a higher %iAs and %MMA, and a lower %DMA, and primary and secondary methylation index (PMI and SMI) than the subjects in CCA. It was concluded that the arsenic methylation efficiency of subjects in DWA and CCA was significantly influenced by chronic exposure to high levels of arsenic in the environment. The lower PMI and SMI values in DWA revealed lower arsenic methylation capacity due to ingestion of arsenic in drinking water. However, it remained unclear if the differences in arsenic metabolism between the two groups were due to differences in exposure levels or in exposure route. [ABSTRACT FROM AUTHOR]