The problem with cooking with more water is that as well as reducing any trace elements such as arsenic, it removes the vitamin content to a large extent. It's a matter of balance. I don't often cook rice these days but I generally rinse rice in a saucepan with cold water at least three times until it runs clear, then once more with warm. It's surprising how cloudy the water is with warm water. This should remove any dust from the grinding process, and any grindstone particles. Add a little salt. This helps the grains fluff up and in the case of long grain rice makes the grains longer. Then bring to the boil with just enough to cover the rice plus a bit more. Cover and simmer until all water has been absorbed. For those who prefer to live dangerously and eat brown rice, the process is similar, but bear in mind that most of the benefits from extra fibre, vitamins, and yes, noxious trace elements, will be concentrated in the husk. The above method was shown to me by my wife who is of South Asian origin and gets through a lot of rice. So far she hasn't shown any ill effects.
From a quick google, rice from India, Pakistan, and California are likely to contain least arsenic. The USA rice from other states surprisingly can have a higher content as the FDA have no guidelines as to maximum acceptable levels of arsenic. The higher levels are due to residue in the soil from older agrochemicals particularly in cotton growing states where they often contained arsenic in decades past. Due to rice needing raised water levels at some stage in its growth it is more susceptible to absorbing dissolved substances that would normally remain in the soil and not be present in other grains. Australian rice also tends to have higher trace levels of arsenic, and presumably other Asian countries that followed Western rather than traditional methods of pest control would too.
It makes you wonder about what you are getting from your average takeaway as well as the origins of the rice you cook yourself. As said before, it's a matter of balance. You would probably need to eat an incredible amount of rice to suffer any measureable side effects, as many other foods such as shellfish also contain traces of arsenic.