Average Airborne Gross Beta Concentrations (n)

Year

5 States (18 Sites)

5 States (10 Sites)

Other U.S.

March 15-April 30

2010

0.005112 (190)

0.005130 (132)

0.008527 (401)

2011

0.033016 (225)

0.029563 (138)

0.020204 (378)

2011/2010 Ratio**

7.345

5.253

2.397

Other Dates January 1-October 4

2010

0.006027 (853)

0.006184 (660)

0.009573 (1810)

2011

0.005526 (858)

0.005550 (564)

0.009670 (1679)

2011/2010 Ratio**

0.983

0.0889

1.018

3/15-4/30 ratio/

7.472

5.909

2.355

Other Dates ratio