Arsenic pollutes groundwater in 70 countries worldwide, including the U.S., Canada and Mexico. The B-vitamin folic acid reduced blood levels of arsenic in 130 Bangladeshi adults who had high arsenic blood levels and low blood-plasma levels of folate, the food form of folic acid. Researchers measured blood levels of arsenic before and after a 12-week period when participants took 400 mcg of folic acid per day or a placebo and found that those who had taken folic acid had 22.24% lower blood levels of a certain type of arsenic (monomethylarsonic or MMA) compared to 1.24% less for placebo. MMA tends to stay in the bloodstream, but folate binds with MMA, permitting the body to excrete the arsenic through the urine. Compared to placebo, those who took folic acid also excreted more of a second type of arsenic, called dimethylarsenic or DMA. Overall, the folic acid group had 13.26% less total arsenic in the blood compared to 2.49% less for placebo.