@flo arsenic is naturally occurring and is present in some foods because of this. Rice and wine are common examples. However, it’s generally only present in small amounts, so you would have to eat a lot of whatever the food item is for harmful effects. That’s why cazzie and Strauss, and maybe others I missed in my quick looking back, are saying the “dosage makes the poison.” Too much of anything is lethal, even necessary and seemingly benign things like water. But it takes a lot of water. Just as it would take a lot of rice. Upshot, we don’t usually need to worry about it.
A year or two ago I remember hearing something on the radio about arsenic levels being higher than normal in rice that year—I can’t remember the reason—but even then, the concern was only for people who ate it every day (or nearly so), and the recommendation was just for them to back off the rice, not stop eating it entirely.
If you’re interested, here’s some of the FDA’s information on arsenic, lead and cadmium, and mercury in food and other consumer products. Although these chemicals are in many different products, the FDA works to make sure that they’re below certain levels and that that we don’t ingest any one chemical in enough quantity for it to be harmful. (You’re in the US, yes? If I got that wrong just refer to the relevant government agency.)
A couple of years ago I heard a story about a man who destroyed his kidneys because he drank too much iced black tea—the oxalic acid had exhausted his kidneys. Turns out “too much” meant around 50 cups a day for 16 years or something like that. At lower levels (read—reasonable levels), the kidneys are able to handle it just fine. But then, the same can be said for how the body can process sugars or fats or salts. Or, to go back to the beginning of my post, water. Everything in moderation.
Basically, it’s not “eat/drink this poison, don’t worry it’s organic”—it’s “there’s not enough of this chemical in the product to poison you, your body will be able to process it just fine, because your body is built to do just that.”