Table 8-1Regulations, Advisories, and Guidelines Applicable to Radon

  IARCCarcinogenicity classificationIARC 2008
  222Rn and its decay productsGroup 1a
  ICRPSummary of values recommended
  Nominal probability coefficient for radon- and radon-progeny-induced lung cancer5×10−4 per WLM (0.14 per J h m−3)ICRP 2010
  Dose conversion convention, effective dose per unit of exposureICRP 1994a
    At home1.1 mSv (mJ h m−3)
    At work1.4 mSv (mJ h m−3)
  Action level (dwellings)
    Radon concentration200–600 (Bq m−3)b
    Annual effective dose3–10 mSv
  Action level (workplace)
    Radon concentration500–1,500 (Bq m−3)b
    Annual effective dose3–10 mSv
  Occupational annual limit on exposure
    Per year, averaged over 5 years14 (mJ h m−3)
    In a single year35 (mJ h m−3)
  WHOAir quality guidelinesWHO 2000
  Risk estimates and recommended action level for radon progeny for exposure to 1 Bq/m3
    Lung cancer excess lifetime risk estimate3–6×10−5
    Recommended level for remedial action in buildings≥100 Bq/m3 (2.7 pCi/L); annual average
Drinking water quality guidelinesWHO 2004
  Radon100 Bq/L (2,700 pCi/L)
Regulations and Guidelines:
a. Air
  ACGIHGuidelines for exposure to ionizing radiationACGIH 2007
  Radon daughters4 WLM/year
  EPAAEGL-1, -2, and -3No dataEPA 2011e
Hazardous air pollutantEPA 2010b
  RadonYes42 USC 7412
  Effective dose equivalent to public from 222Rn not to exceed 10 mrem/yearFrom operating uranium mineEPA 2011i
From a DOE facilityEPA 2011j
  222Rn emissions rate from soil not to exceed 20 pCi/m2-second average for entire sourceFrom a DOE facilityEPA 2011k
From an inactive phosphogypsum stackEPA 2011l
From a non-operational uranium mill tailings pileEPA 2011m
From an existing uranium mill tailings pileEPA 2011n
  Standards for uranium byproduct materials shall apply to thorium byproduct materialsProvisions from soil for 222Rn from uranium byproduct materials are applicable to 220Rn from thorium byproduct materialsEPA 2011h
  210Po (222Rn progeny)Emissions from elemental phosphorus plant <2 Ci/year, or 4.5 Ci/year with scrubbersEPA 2011o
Monitoring of radon in homesEPA 2009a
  No action necessary<4 pCi/L, 0.02 WL
  Take necessary action to decrease indoor radon levels≥4 pCi/L
  MSHAAnnual exposure limitsMSHA 2011a
30 CFR 57.5038
  Radon daughters4 WLM in any calendar year underground
Maximum permissible concentrationMSHA 2011b
  Radon daughters1 WL in active workings underground
  NIOSHREL (10-hour TWA)No data
  OSHAOSHA adopted the 1971 version of USNRC regulatory limits in 10CFR20 Appendix B for exposure to radon in air. Applies to employers. OSHA states that following the current 10CFR20 App B is a de minimis violation.Adult workers: 1×10−7 µCi/mL (100 pCi/L) averaged over 40-hour work week of 7 consecutive daysOSHA 2011
29 CFR
1910.1096; OSHA 1971;
OSHA 2002
Workers under 18 years of age: 3×10−9 µCi/mL (3 pCi/L) averaged over 40-hour work week of 7 consecutive daysOSHA 2011
(c)(2); OSHA 1971,
OSHA 2002
Surveys are required in order to complyOSHA 2011,
Post airborne radioactivity area signs when weekly average exceeds 25% of limit (i.e., 25 pCi/L adults, 0.75 pCi/L child workers)OSHA 2011,
  USNRCALI for occupational exposure (values for oral ingestion)USNRC 2011
10 CFR 20,
Appendix B
  220Rn (with daughters removed)Not listed
  220Rn (with daughters present)Not listed
  222Rn (with daughters removed)Not listed
  222Rn (with daughters present)Not listed
ALI for occupational exposure (values for inhalation)
  220Rn (with daughters removed)20,000 µCi
  220Rn (with daughters present)20 µCi (or 12 WLM)
  222Rn (with daughters removed)10,000 µCi
  222Rn (with daughters present)100 µCi (or 4 WLM)
Derived air concentrations for occupational exposure (values for inhalation)
  220Rn (with daughters removed)7×10−6 µCi/mL
  220Rn (with daughters present)9×10−9 µCi/mL (or 1.0 WL)
  222Rn (with daughters removed)4×10−6 µCi/mL
  222Rn (with daughters present)3×10−8 µCi/mL (or 0.33 WL)
Annual average effluent air concentration (no values provided for effluent water)
  220Rn (with daughters removed)2×10−8 µCi/mL
  220Rn (with daughters present)3×10−11 µCi/mL
  222Rn (with daughters removed)1×10−8 µCi/mL
  222Rn (with daughters present)1×10−10 µCi/mL
b. Water
EPADrinking water standards and health advisories for radon activityNone; EPA proposed an MCL for radon in 1991, withdrew it in 1997, and published the final rule in 2000 without a radon MCLEPA 2011d, EPA 1997
National recommended water quality criteriaNo data
c. FoodNo data
d. Other
  ACGIHCarcinogenicity classificationNo dataACGIH 2007
  EPACarcinogenicity classificationIRIS 2012
  222RnWithdrawn in 1993
  222RnNot established
  222RnNot established
Superfund, emergency planning, and community right-to-knowEPA 2011f
40 CFR 302.4 App B
  Designated CERCLA hazardous substance
    220Rnc0.1 Ci
    222Rnc0.1 Ci
  NTPCarcinogenicity classificationNTP 2011
  Ionizing radiation (includes 220Rn and 222Rn)Known to be a human carcinogen

Group 1: carcinogenic to humans.


Assuming 7,000 hours/year indoors or 2,000 hours/year at work and an equilibrium factor of 0.4.


Designated CERCLA hazardous substance pursuant to Section 112 of the Clean Air Act.

ACGIH = American Conference of Governmental Industrial Hygienists; AEGL = Acute Exposure Guideline Levels; ALI = annual limit on intake; CERCLA = Comprehensive Environmental Response, Compensation, and Liability Act; CFR = Code of Federal Regulations; EPA = Environmental Protection Agency; IARC = International Agency for Research on Cancer; ICRP = International Commission on Radiological Protection; MCL = maximum contaminant level; MSHA = Mine Safety and Health Administration; NAS = National Academy of Sciences; NIOSH = National Institute for Occupational Safety and Health; NTP = National Toxicology Program; OSHA = Occupational Safety and Health Administration; REL = recommended exposure limit; RfC = inhalation reference concentration; RfD = oral reference dose; TWA = time-weighted average; USC = United States Code; USNRC = U.S. Nuclear Regulatory Commission; WHO = World Health Organization; WL = working level; WLM = working level months


Cover of Toxicological Profile for Radon
Toxicological Profile for Radon.
Keith S, Doyle JR, Harper C, et al.

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