The two parallel lines across this map from southwest to north central Montana show the path where a large portion of radioactive Iodine-131 fallout was deposited from atomic atmospheric tests at the Nevada Test Site. The concentration in the counties between the lines averaged 10.77 units. Blaine County was 9.1. The nineteen counties in Arizona, Nevada and Utah where "downwinders" could qualify for compensation for diseases related to atomic fallout, averaged 3.8 units.