Arsenic in drinking water or inorganic arsenic is a cause of skin disease, heart disease, lung cancer, bladder and kidney cancers. Do the risk estimates vary with populations where they are studied? In order to address this question, we conducted a meta analysis of the linkage between arsenic distribution and bladder cancer for different populations and compared the risk estimates and population attributable risk percents. 
The purpose of this paper is to present the findings of a meta analysis of all studies published studies on the association between arsenic in drinking water and risk of skin cancer across the five countries and test their variability. We will also estimate the population attributable risk estimate based on the summated findings from the continents to see if the effect estimates vary across regions and what may account for these changes. In doing this, we chart the prevalence and risk estimates of arsenic toxicity as separate subgroup analyses across the Indian subcontinent and the rest of the world. 
We conducted a meta analysis with the following search terms: "arsenic", "toxicity", " cancer", using pubmed and combined database search. We retrieved the full texts of the studies and we also obtained, wherever possible, works in progress or unpublished studies. We then collated the findings of the study in a database and used Stata to conduct meta analysis using stata's metanal command. We further conducted subgroup analysis based on the geographical region of the world where the studies were conducted and plotted the results on a chart. Based on the Odds Ratios or pooled estimates of the association between arsenic and skin cancer, we estimated the population attributable risks for arsenic caused skin cancer (that is, the part of the skin cancer attributable to arsenic alone based on risk estimate and prevalence of arsenic exposure). 
The heatmap suggests that some parts of the world, people are more susceptible to arsenic toxicity and arsenic alone accounts for the skin lesions than other causes. This needs to be investigated.