ARSENIC INDUCED HEALTH EFFECTS, GENETIC SUSCEPTIBILITY AND THE ROLE OF BACTERIA IN GROUND WATER ARSENIC CONTAMINATION
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
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| Title |
ARSENIC INDUCED HEALTH EFFECTS, GENETIC SUSCEPTIBILITY AND THE ROLE OF BACTERIA IN GROUND WATER ARSENIC CONTAMINATION
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| Creator |
Das, Nandana
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| Subject |
Molecular & Human Genetics
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| Description |
More than 150 million people throughout the world are exposed to arsenic through either drinking water or other sources. It is an exclusive human carcinogen and has no carcinogenic effect on other animals. Six states of India are majorly contaminated by this deadly toxin. In West Bengal, ground water of 9 out of 16 districts are contaminated with arsenic and over 26 million individuals are at health risk. The arsenic-induced adverse health effects, genetic damage and susceptibility to arsenicosis were evaluated in this dissertation. Attempts have also been made to evaluate the seasonal variations in the ground water arsenic contamination in different parts of India and the role of bacteria in ground water arsenic contamination. We selected individuals from Murshidabad district of West Bengal as our arsenic exposed population, where water analysis showed significantly high levels of arsenic concentrations than the maximum permissible limit of 10μg/L as set by World Health Organization (WHO) and United States Environmental Protection Agency (USEPA). Individuals from East Midnapur district was selected as our control population since there is no arsenic contamination in their drinking water. For the investigation of seasonal changes of ground water arsenic content and the role of bacteria in arsenic contamination of drinking water, samples were collected from four highly contaminated regions of India along the Ganga-Brahmaputra-Barak basin (Nadia and Murshidabad districts of the lower Ganga fluvial plains, Ara district of the middle Ganga plain, and the Cachar district of Brahmaputra-Barak plain).
Epidemiological studies show a wide range of adverse health disorders including skin pigmentations, keratosis, peripheral neuropathy, conjunctivitis, respiratory diseases, liver and cardiovascular problems along with cancers of skin and different internal organs. Although a large number of individuals are exposed to arsenic through drinking water but only about 10-15% exposed individuals showed arsenic induced skin lesions which suggests that susceptibility to arsenic is distinctly different among individuals. Thus, the exposed study group was divided into two broad categories - individuals manifesting the characteristic arsenic induced skin lesions (symptomatic) and those who do not develop them (asymptomatic). To further explore the impact of arsenic exposure on health status, we examined the prevalence of three most frequently encountered disorders like peripheral neuropathy, respiratory illness band eye problems within the arsenic exposed population (with and without skin lesions) and compared with the control group. The risk of developing liver and cardiovascular diseases on exposure to arsenic was also investigated. Arsenic induced cytogenetic damage was assessed along with genetic variants that may have an association with arsenic susceptibility.
A total of 535 arsenic-exposed individuals (277 with skin lesions and 258 without skin lesions) and 107 arsenic unexposed participants were recruited for our study. It was observed that peripheral neuropathy, respiratory diseases and eye problems are prevalent at a significantly higher rate in individuals exposed to arsenic compared to the unexposed group. Exposed individuals with skin lesions had much higher occurrence of all three diseases, indicating that people who are highly susceptible to arsenic toxicity are also more likely to develop these non-dermatological health problems.
Towards the aim of predicting the extent of liver and cardiovascular disease risk in the arsenic exposed population, we assessed bioindicators of hepatocellular injury as indicated by the serum levels of liver enzymes, determined the autoimmune status as indicated by the amounts of serum ANA and anti-dsDNA and measured circulating inflammatory cytokines related to cardiovascular diseases. The results were compared with levels of these parameters in the arsenic unexposed group. Various tests are performed to detect specific liver activities ensuing proper functioning of the liver. Among all parameters, serum bilirubin is the indicator that marks liver’s capacity of organic anion transport and drug metabolism, while aminotransferase (ALT, AST), alkaline phosphatase (ALP) and aminopeptidase levels suggest injury to hepatocytes. Elevated or abnormal levels of these liver function test parameters in an individual indicate underlying liver diseases. In our study we have found significantly increased serum levels of bilirubin, ALT, AST, and ALP in the arsenic exposed population compared to unexposed individuals.
Cytokines play key roles in systemic inflammation leading to cardiovascular diseases. We observed significantly increased circulating levels of cardiovascular disease associated inflammatory cytokines IL6 and IL8 in the arsenic exposed population compared to the control. We have also found a significant increase in the serum levels of autoimmune biomarkers antinuclear antibody (ANA) and anti-double stranded DNA (anti-dsDNA) in arsenic exposed population, indicating that arsenic exposure also induces autoimmune diseases. Both autoimmune and liver diseases are risk factors for cardiovascular ailments. Thus, the arsenic exposure induced hepatic injury and systemic inflammatory diseases most likely contributes to the increased cardiovascular disease risk observed in our arsenic exposed populations (Das et. al., 2012).
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| Date |
2015
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| Type |
Thesis
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/2579/1/THESIS_COMPILED_22.8.15_PRINT.pdf
Das, Nandana (2015) ARSENIC INDUCED HEALTH EFFECTS, GENETIC SUSCEPTIBILITY AND THE ROLE OF BACTERIA IN GROUND WATER ARSENIC CONTAMINATION. PhD thesis, Jadavpur University. |
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| Relation |
http://www.eprints.iicb.res.in/2579/
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