Arsenic in rice is due to exactly that, pulling naturally occurring arsenic from the water used for irrigation.

I was under the impression that the majority of the arsenic concentration in rice fields is actually an unintented consequence of pesticides used in the 1800's that persist in the soil still today.

Maybe in the US, but in developing countries it often ground water contamination from natural sources.

Not the only source. American rice is grown sometimes on old cotton fields, which were sprayed with arsenic to control boll weevils.

Apparently washing the rice does remove quite a bit.

washing and also soaking for several hours/overnight and/or boiling it with lots of water (and pouring it out) can greatly reduce it iirc

btw, afaik, naturally, brown rice has more has alot, basmati rice seems to have the least

https://sites.dartmouth.edu/arsenicandyou/arsenic-in-rice-an...

The study I saw implied that most of the metals were on the surface as dust, so you could rinse about 60% off. I would expect the bran, containing a lot of the protein and minerals, would have more in it, and also make it more difficult to remove surface contamination.

Incidentally there are also some studies challenging the heavy metals in broadleaf plants link. The newer studies suggest surface contamination is a much bigger factor. That's also another 'pro' in the column for cleaning your vegetables with white vinegar instead of soap. Acids are pretty good at dissolving metal dust, especially from residual contamination near roads from leaded gas. My yard tested high.

  > The study I saw implied that most of the metals were on the surface as dust, so you could rinse about 60% off.

  > The newer studies suggest surface contamination is a much bigger factor.

interesting!

then maybe i dont need to overdo it with rice, sounds good.

  > That's also another 'pro' in the column for cleaning your vegetables with white vinegar instead of soap. 

sounds good, sometimes i skip the rinsing and washing but that is good motivation to keep it up, thanks!