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Journal articles: various topics (Part 2) + WHO report + news article

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  • dr_sara_bennett
    ... http://highwire.stanford.edu/cgi/medline/pmid;15276403 Chronic health effects in people exposed to arsenic via the drinking water: dose-response
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      Chronic health effects in people exposed to arsenic via the drinking
      water: dose-response relationships in review. T Yoshida, H
      Yamauchi, and G Fan Sun. Toxicol Appl Pharmacol 1 Aug 2004 198(3):
      p. 243.

      Abstract: Chronic arsenic (As) poisoning has become a worldwide
      public health issue. Most human As exposure occurs from consumption
      of drinking water containing high amounts of inorganic As (iAs). In
      this paper, epidemiological studies conducted on the dose-response
      relationships between iAs exposure via the drinking water and
      related adverse health effects are reviewed. Before the review, the
      methods for evaluation of the individual As exposure are summarized
      and classified into two types, that is, the methods depending on As
      concentration of the drinking water and the methods depending on
      biological monitoring for As exposure; certain methods may be
      applied as optimum As exposure indexes to study dose-response
      relationship based on various As exposure situation. Chronic effects
      of iAs exposure via drinking water include skin lesions,
      neurological effects, hypertension, peripheral vascular disease,
      cardiovascular disease, respiratory disease, diabetes mellitus, and
      malignancies including skin cancer. The skin is quite sensitive to
      arsenic, and skin lesions are some of the most common and earliest
      nonmalignant effects related to chronic As exposure. The increase of
      prevalence in the skin lesions has been observed even at the
      exposure levels in the range of 0.005-0.01 mg/l As in drinking
      waters. Skin, lung, bladder, kidney, liver, and uterus are
      considered as sites As-induced malignancies, and the skin is though
      to be perhaps the most sensitive site. Prospective studies in large
      area of endemic As poisoning, like Bangladesh or China, where the
      rate of malignancies is expected to increase within the next several
      decades, will help to clarify the dose-response relationship between
      As exposure levels and adverse health effects with enhanced accuracy.


      Evidence that arsenite acts as a cocarcinogen in skin cancer. TG
      Rossman, AN Uddin, and FJ Burns. Toxicol Appl Pharmacol 1 Aug 2004
      198(3): p. 394.

      Abstract: Inorganic arsenic (arsenite and arsenate) in drinking
      water has been associated with skin cancers in several countries
      such as Taiwan, Chile, Argentina, Bangladesh, and Mexico. This
      association has not been established in the United States. In
      addition, inorganic arsenic alone in drinking water does not cause
      skin cancers in animals. We recently showed that concentrations as
      low as 1.25 mg/l sodium arsenite were able to enhance the
      tumorigenicity of solar UV irradiation in mice. The tumors were
      almost all squamous cell carcinomas (SCCs). These data suggest that
      arsenic in drinking water may need a carcinogenic partner, such as
      sunlight, in the induction of skin cancers. Arsenite may enhance
      tumorigenicity via effects on DNA repair and DNA damage-induced cell
      cycle effects, leading to genomic instability. Others have found
      that dimethlyarsinic acid (DMA), a metabolite of arsenite, can
      induce bladder cancers at high concentrations in drinking water. In
      those experiments, skin cancers were not produced. Taken together,
      these data suggest that arsenite (or possibly an earlier
      metabolite), and not DMA, is responsible for the skin cancers, but a
      second genotoxic agent may be a requirement. The differences between
      the US and the other arsenic-exposed populations with regard to skin
      cancers might be explained by the lower levels of arsenic in the US,
      less sun exposure, better nutrition, or perhaps genetic
      susceptibility differences.


      Oxidative stress and apoptosis in metal ion-induced carcinogenesis.
      H Shi, LG Hudson, and KJ Liu. Free Radic Biol Med 1 Sep 2004 37(5):
      p. 582.

      Abstract: Epidemiological evidence suggests that exposure to
      certain metals causes carcinogenesis. The mechanisms of metal-
      induced carcinogenesis have been pursued in chemical, biochemical,
      cellular, and animal models. Significant evidence has accumulated
      that oxidative stress may be a common pathway in cellular responses
      to exposure to different metals. For example, in the last few years
      evidence in support of a correlation between the generation of
      reactive oxygen species, DNA damage, tumor promotion, and arsenic
      exposure has strengthened. This article summarizes the current
      literature on metal-mediated oxidative stress, apoptosis, and their
      relation to metal-mediated carcinogenesis, concentrating on arsenic
      and chromium.


      Chronic inorganic arsenic exposure induces hepatic global and
      individual gene hypomethylation: implications for arsenic
      hepatocarcinogenesis. Hua Chen, ShuanFang Li, Jie Liu, Bhalchandra
      A. Diwan, J. Carl Barrett and Michael P. Waalkes. Carcinogenesis
      2004 25(9):1779-1786.

      Abstract: Inorganic arsenic is a human carcinogen that can target
      the liver, but its carcinogenic mechanisms are still unknown. Global
      DNA hypomethylation occurs during arsenic-induced malignant
      transformation in rodent liver cells. DNA hypomethylation can
      increase gene expression, particularly when occurring in the
      promoter region CpG sites, and may be a non-genotoxic mechanism of
      carcinogenesis. Thus, in the present study liver samples of male
      mice exposed to 0 (control) or 45 p.p.m. arsenic (as NaAsO2) in the
      drinking water for 48 weeks were analyzed for gene expression and
      DNA methylation. Chronic arsenic exposure caused hepatic steatosis,
      a lesion also linked to consumption of methyl-deficient diets.
      Microarray analysis of liver samples showed arsenic induced aberrant
      gene expression including steroid-related genes, cytokines,
      apoptosis-related genes and cell cycle-related genes. In particular,
      the expression of the estrogen receptor- (ER-), and cyclin D1 genes
      were markedly increased. RT-PCR and immunohistochemistry confirmed
      arsenic-induced increases in hepatic ER- and cyclin D1 transcription
      and translation products, respectively. Arsenic induced hepatic
      global DNA hypomethylation, as evidenced by 5-methylcytosine content
      of DNA and by the methyl acceptance assay. Arsenic also markedly
      reduced the methylation within the ER- gene promoter region, as
      assessed by methylation-specific PCR, and this reduction was
      statistically significant in 8 of 13 CpG sites within the promoter
      region. Overall, in controls 28.3% of the ER- promoter region CpG
      sites were methylated, but only 2.9% were methylated after chronic
      arsenic exposure. Thus, long-term exposure of mice to arsenic in the
      drinking water can induce aberrant gene expression, global DNA
      hypomethylation, and the hypomethylation of the ER- gene promoter,
      all of which could potentially contribute to arsenic


      Occurrence of cyanobacterial toxins (mycrocystins) in surface water
      of rural Bangladesh: pilot study. By M. Welker, I. Chorus and J.
      Fastner, Federal Environmental Agency, Germany. WHO/SDE/WSH/04.06.
      World Health Organization 2004.

      Report Summary [full text available online free of charge]: In
      Bangladesh the exposure of millions of inhabitants to water from
      (shallow) tube wells contaminated with high geogenic loads of
      arsenic is a major concern. As an alternative to the costly drilling
      of deep wells, the return to the use of surface water as source of
      drinking water is being considered.

      In addition to the well-known hazards of water borne infectious
      diseases associated with the use of surface water, recently the
      potential public health implications of toxic cyanobacteria have
      been recognized. As a first step towards a risk assessment for
      cyanotoxins in Bangladesh surface waters, seston [defined as "all
      particulate matter in suspension in water" – Mod.] samples of 79
      ponds were analysed in late summer of 2002 for the presence of
      cyanobacteria and microcystins, the most frequently detected
      cyanobacterial toxins worldwide. Microcystins were detected in 39
      ponds, mostly together with varying abundance of potentially
      microcystin-producing genera such as Microcystis, Planktothrix and
      Anabaena. Total microcystin concentrations ranged between < 0.1 and
      up to >1000 ug/l, and more than half of the positive samples
      contained high concentrations of more than 10 ug/l. The results
      clearly show that concentration of microcystins well above the WHO
      provisional guideline value of 1 ug/l microcystin-LR can be
      frequently detected in Bangladesh ponds. Thus, an increasing use of
      surface water for human consumption would introduce a risk of
      replacing one health hazard by another and therefore needs to be
      accompanied by cyanotoxin hazard assessments.


      Arsenic-Tainted Water. Joan Stephenson. JAMA. 2004;292:794.

      [First 150 words of full text – no abstract available:] High levels
      of arsenic in large parts of the Ganges Delta have poisoned millions
      of people during the last 2 decades and the risk of contamination of
      drinking and irrigation water with arsenic continues to pose a
      threat to the lives of millions worldwide (Bull World Health Organ.
      2000; 78:1093-1103). But the mechanisms underlying the release of
      arsenic from sediments into ground waters are poorly understood.
      Now, scientists from England and India report evidence from
      laboratory studies that anaerobic iron-reducing bacteria (from a
      contaminated aquifer in India) thrive under conditions that favor
      the release of a toxic form of arsenic (Nature. 2004;430:68-71).
      Because the bacteria require organic carbon to grow, the researchers
      suggest that their findings support theories that the introduction
      of organic carbon through agricultural practices (such as
      irrigation) is a factor in mobilizing arsenic from sediment into the
      water supply. If . . .


      Mental health burden amongst inhabitants of an arsenic-affected area
      in Inner Mongolia, China. Y Fujino, X Guo, J Liu, L You, M
      Miyatake, T Yoshimura, and Japan Inner Mongolia Arsenic Pollution
      (JIAMP) Study Group. Soc Sci Med, November 1, 2004; 59(9): 1969-73.

      Abstract: Inner Mongolia, China, is an area with high levels of
      arsenic. The adverse health effects resulting from chronic arsenic
      exposure include skin keratosis, vascular diseases and cancers.
      However, the effects of arsenic exposure on mental health have not
      received much attention. The purpose of this study was to examine
      the effects of arsenic poisoning on the mental health of the
      inhabitants of an arsenic-affected area. We performed a cross-
      sectional study at two villages in Hetao Plain, Inner Mongolia. The
      populations of both villages were similar in age, sex, lifestyle,
      socioeconomic conditions, and geographic location. One hundred and
      thirty four (93.7%) of the 143 inhabitants in the arsenic-affected
      village and 36 (76.6%) of the 47 inhabitants in the arsenic-free
      village participated in the study. Subjects with a 30-item version
      of General Health Questionnaire score of 9 or more were defined as
      having symptoms of distress. The multiple logistic analyses showed
      that the mental health of the subjects in the arsenic-affected
      village was worse than in those in the arsenic-free village (OR=2.5,
      95% CI=1.1-6.0). The effect of arsenic on mental health in arsenic-
      affected areas deserves further investigation. The mental health
      burden in arsenic-affected areas should be considered in the wider
      context of public and community health.


      Bacteria solution to groundwater arsenic - Bangladesh scientist says
      the bugs use arsenic for energy

      Naimul Haq – Daily Star (Dhaka) 14 Aug 2004

      Scientists have identified a special group of bacteria responsible
      for breaking down arsenic in groundwater. This was disclosed by a
      Bangladeshi scientist conducting a study in the UK on the cause of
      naturally occurring arsenic release into groundwater table.

      The discovery may provide a possible solution to groundwater arsenic
      contamination that now exposes an estimated eight million people in
      61 districts in Bangladesh to serious health hazards.

      Millions of people, mostly in the rural areas, have developed
      various symptoms of poisoning from drinking arsenic-contaminated
      water from tubewells for decades. The study by Farhana Islam,
      supervised by other researchers, showed the special group of
      bacteria 'gains energy by respiring (breathing), using the metal
      iron and arsenic containing minerals in the earth sediments'.

      The young scientist said, "Our results show that these are the
      special anaerobic bacteria, as they don't need any oxygen to support
      their growth. They are known as metal-reducing bacteria. We are very
      interested in iron-reducing bacteria that use iron as their growth
      substrate, and can also use arsenic when the iron is used up."

      The bacteria cause changes in the mineral structure of the
      sediments, leading to release of arsenic into groundwater, the study

      Farhana, who studies in the Department of Earth Sciences and
      Williamson Research Centre for Molecular Environmental Science at
      the University of Manchester, told The Daily Star, "We are looking
      at how these processes of breaking down the mineral can be reversed
      so that the groundwater is safe to drink."

      She elaborated, "With our results, we found that maximum amount of
      arsenic was released from contaminated sediment into groundwater in
      the absence of oxygen." There were several hypotheses concerning the
      release of arsenic into the groundwater systems of West Bengal in
      India, where the researchers worked. Some suggested a role for
      aerobic bacteria (arsenopyrite oxidation), some suggested a role for
      metal-reducing bacteria while others considered the problem to be
      driven by geochemistry.

      The scientists from Manchester University conducted experiments in
      their laboratory with sediments collected directly from an area of
      West Bengal affected by arsenic.

      "We were the first group to combine geochemical, mineralogical and
      microbiological/molecular biology techniques to study this system,
      and have presented the first direct evidence to support a role for
      metal-reducing bacteria in arsenic release from the sediments. The
      organisms identified as playing a key role are iron reducing
      bacteria that can attack arsenic once they have exhausted iron as a
      growth element," Farhana explained.

      Studies showed that this type of bacteria is unable to use oxygen
      for growth, rather they use different metals to support their
      metabolism. Metal-reducing bacteria 'breathe' metals such as iron to
      get energy from their food, in the same way humans breathe oxygen to
      break down food.

      The iron-reducing bacteria use iron through the electron transport
      system in the anaerobic respiration and gain energy for their growth
      by reducing this iron. This process is known as dissimilatory iron-

      Explaining the process of arsenic contamination, Farhana said
      instead of using oxygen, the anaerobic bacteria gain their energy by
      respiring, (breathing) using iron-containing minerals in the
      sediments, a process called iron reduction. By doing this, the
      bacteria transfer electrons to iron oxide rust coating the
      sediments, causing changes in the characteristics of the minerals.
      And when the iron runs out, the bugs start to utilise other metals,
      such as arsenic, which occurs naturally. The chemistry of the
      arsenic is changed and the reduced arsenic is able to dissolve into
      groundwater, she said.
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