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Table 1 Radon levels in homes throughout the world

From: Indoor radon exposure and lung cancer: a review of ecological studies

Country Period[ref] Area No. of dwellings 222Rn (Bq/m3)
AM(SD) GM(SD) Median (Min, Max) Excessive rate (%) Recommended level
USA 1989–1990 [12, 42] Nationwide (sample size) 5,694 1.25(0.12) 0.68(0.08) - 6.0 4pCi/L (USA unit is pCi/L)
1991 [43] Texas 2,890 1.0 0.5 0.6 3.6
2003–2004 [44] Illinois 22,082 - 5.16(3.47) 3.6 (0.4, 178.9) 46.0
2010 [45] Ohio 159,340 - 3.99 -(-, 927.6) 32.64
−2014 [46] Kansas 73,959 5.1 - -(-, 1,121.6) 42.6
−2014 [47] New York 73,519 6.24 2.72(3.52) -(-, 522.1) -
−2015.6 [48] Nevada 17,255 3.68 - - 26.4
Canada 2007 [49] Ottawa 93 110(168) 74(2.26) -(8,1525) 12.0 200
2008 [50] Winnipeg 116 143(101) 112(2.07) -(20, 483) 20.0
2010 [51] Fredericton 45 138(213) 82(2.56) -(16, 1374) 18.0
2010 [51] Halifax 64 259(475) 107(3.67) -(4, 2341) 32.0
UK 1986–1987 [52] Nationwide (sample size) 2,093 20.5 15(2.2) - 0.5 200
−2009 [52] England 465,000 99 53 - 11.3
−2009 [52] Wales 16,800 91 51 - 10.7
−2008 [54] Scotland 19,100 37 20 -(-, 4,600) 1.9
−2009 [55] Northern Ireland 24,000 70 46 -(-, 4,900) 5.0
Denmark 1985–1986 [56] Nationwide 496 47 29(2.2) - 2.2 200
1995–1996 [57] Nationwide 3,019 - - -(2, 590)  
-[58] Newly constructed 200 - - 36.8 (9.0, 118) 7.0 100 (New homes)
Finland 1990–1991 [56] Nationwide 3,074 123 84(2.1) - 3.6 (Above 200 12.3) 400
−1996 [59, 60] Nationwide 51,443 248 - -(-, 32,700) 13.0 (Above 200 33.0)
Germany 1978–1984 Nationwide 7,500 50 40 - 1.5-2.5 (Above 200) 100
1991–1993 [56]
Hungary 1994–2006 [61] Nationwide 6,154 174(139) - -(-, 1,841) 29.0 200
Ireland 1992–1999 [62] Nationwide 11,319 89 57(2.40) -(10, 1,924) 8.8 200
Japan 1993–1996 [63] Nationwide 899 15.5(13.5) 12.7(1.78) 11.7 (-, 208) - -
-[64] Hokkaido, Hiroshima, Kochi 6,645 21.3(18.8) 17.3(1.83) 16.4 (-) 0.4 (Above 148)
China 1984–1990 [65] Nationwide 10,811 22.5 19.6 - -  
1994–1998 [66] Shenyang 608 115.7 91.2(1.93) 122.4 (-) 17.4 (Above 148)  
Gansu 2,394 222.9 176.2(2.08) 227.8 65.7 (Above 148)  
  1. AM arithmetic mean, SD standard deviation, GM geometric mean, Min minimum, Max maximum