There are tests that show that soaking rice in 6 cups of water before you cook it reduces the amount of arsenic in the rice.
A leading arsenic researcher did experiments and found that when they cooked rice at a ratio of 5:1, 5 cups of water for every cup of rice, they could lower the levels to 43% of the arsenic level of the original rice. When they soaked the rice overnight and then used the 5:1 cooking method, only 18% was left. This is because arsenic is water soluble, and is soaked out of the grains when left to soak in water. Of course, after soaking the rice you need to drain and rinse the rice with fresh water. If you soak it overnight, you can cook it and then rinse it one last time in boiling water to get rid of the remainder.