I was recently asked which counties are covered under the Radiation Exposure Compensation Act (RECA) for downwinder claims. I found this list on the Department of Justice RECA website:
Downwind, Counties and other: in the State of Utah, the counties of Beaver, Garfield, Iron, Kane, Millard, Piute, San Juan, Sevier, Washington, and Wayne; in the State of Nevada, the counties of Eureka, Lander, Lincoln, Nye, White Pine, and that portion of Clark County that consists of townships 13 through 16 at ranges 63 through 71; and in the State of Arizona, the counties of Apache, Coconino, Gila, Navajo, Yavapai, and that part of Arizona that is north of the Grand Canyon.
See http://www.justice.gov/civil/common/reca.html (last accessed November 20, 2011).