Summary

Arsenic is highly toxic in many ways and now a new risk of exposure has been uncovered. In a study, a group with type 2 diabetes had 26 percent higher levels of arsenic in their urine compared to those without diabetes. It looks, therefore, as if exposure to arsenic in drinking water could be a risk factor and therefore ought to be minimized.

Introduction

Inorganic arsenic is well known to be highly toxic and carcinogenic. Millions of individuals worldwide are exposed to arsenic from natural mineral deposits through their drinking water. This includes some 13 million individuals in the United States, in locations where the amount of arsenic in the water supply exceeds the 10 microgram per liter upper limit recommended by the US Environmental Protection Agency. Humans may also be exposed to organic arsenic, through consuming seafood.

Arsenic is known to interfere with glucose uptake by cells. In previous studies, high chronic arsenic exposure was linked to diabetes. But it is now known whether exposure to lower arsenic levels is also harmful.

What was done

A team at the Johns Hopkins Bloomberg School of Public Health studied 788 adults aged 20 or more as part of the National Health and Nutrition Examination Survey. They noted who had type 2 diabetes - 7.7 percent of the group - and measured levels of total arsenic and arsenobetaine, an organic form of arsenic found in seafood, in the participants' urine.

What was found

Overall, those with type 2 diabetes had a 26 percent higher level of arsenic in their urine compared to those without the disease. Putting it another way. those in the top one fifth of total urine arsenic levels (16.5 micrograms per liter) had 3.6 times the risk of having type 2 diabetes compared to those in the lowest one fifth (3.0 micrograms per liter). And those in the top one fifth of dimethylarsinate levels had 1.5 times the risk of having diabetes compared to those in the lowest one fifth. Dimethylarsinate is a breakdown product of inorganic arsenic and is therefore a marker for exposure. But arsenobetaine levels did not seem to be an indicator for diabetes, for levels in urine were similar whether a participant had the disease or not.

What this study means

Arsenic is known to affect cells' ability to take up insulin which makes it a potential risk factor for diabetes. This study shows that the diabetes risk is present even at the lower levels to which many are exposed through drinking water. Therefore it would be prudent, for the sake of public health, to reduce arsenic in drinking water to a safer level.