The FDA tested rice samples from all the rice growing region in China. They all exceeded the USA standards for allowable arsenic levels.
Stay away from food from China is my recommendation.
They also put melamine in their baby formula. Chinese living all over the world routinely ship baby food to China. The UK passed laws to put some limit on this practice a few years ago.
Rice is not the only source of niacin. It’s not even the highest source of niacin. A cup of potato flakes has 3 times the niacin of a cup of dry rice*. A cup of buckwheat has almost 4 times as much. A cup of corn flour has roughly the same niacin as rice, but make it hominy and the niacin becomes more bioavailable.
(*I’m using potato flakes for this comparison rather than a fresh or cooked potato, because the water content changes depending on how it was cooked. And dry flakes are closer in moisture content to dry rice, making for a more accurate comparison.)