A tiny amount of radiation emanating from the tsunami-damaged nuclear power plants in Japan has reached Colorado (9News), but in fact, plenty of radioactivity had already been occurring in our state: A large bed of uranium lies underneath Colorado—as well as the other Four Corners states—and our higher altitude provides less atmospheric protection, as The Atlantic‘s Alexis Madrigal explains in a video on “how to think about how much radiation we should worry about.” Indeed, Coloradans could be naturally exposed to three to four times the dose of natural radiation as Delaware.

The difference in background radiation between the two states can serve as a guide, but just because Colorado’s is higher than the rest of the country’s doesn’t mean it’s a threat to your health, says Jeff King, a nuclear engineering professor at the Colorado School of Mines (Colorado Public Radio).

Meanwhile, mining our big bed of uranium is under public scrutiny, and the Environmental Protection Agency is taking additional public comment on the proposed Piñon Ridge uranium mill in southwestern Colorado as a result (Telluride Daily Planet).