A meta-analysis by Wang et al1 examined the association of inorganic arsenic (iAs) exposure with type 2 diabetes mellitus (T2DM). Arsenic is ubiquitous and contaminates water through geological and manufacturing processes.2 Arsenic in water is a major public health problem, as it is acutely toxic and a carcinogen and millions of people worldwide are exposed to arsenic by drinking contaminated water.3 Countries where arsenic levels in drinking water have been found to exceed the WHO standard of 10 μg/L include Argentina, Australia, Bangladesh, Chile, China, Hungary, India, Mexico, Peru, Taiwan and the USA.4 Worldwide in 2010 285 million people suffered from T2DM and it is estimated this will increase to 439 million by 2030.5 T2DM is accountable for more than 90–95% of all diabetes with unknown specific aetiology. Important risk factors include genetics, aging and obesity.6

The inclusion criteria for this study included recent and complete articles comprising case-control or cross-sectional studies or cohort studies. The meta-analysis for iAs in drinking water and in urine identified an association of iAs exposure with increased T2DM incidence in iAs-endemic areas. In addition the dose-response analysis suggested T2DM risk increased by 13% for every 100 µg/L increment of iAs in drinking water. In general most of these studies reported that higher levels of iAs increased the risk of T2DM. In previous studies, microvascular and macrovascular disease was found in patients with and without diabetes when comparing iAs between endemic areas with non-endemic areas.7 Furthermore, increased risk of hypertension8 and heart disease9 may occur with high-level arsenic exposure from drinking water. Studies that investigated higher levels of iAs in drinking water and greater duration of exposure also showed a strong association with T2DM.8 ,10 ,11–13 Two …