Radon

Characteristics of Radon-222

Fate and Transport

Monitoring in the Environment

Measurement

Measurement Methods

Control and Prevention

Harmful Effects

Absorption, Distribution and Organic Sites of Toxicity

Radon Dose

Radon Biomarkers

Risk Assessment

Molecular Action and Genetic Effects


Radon for Skeptics

Radon for Children

Radon for Skeptics

Doubters Gallery

Buddha -“The path to radon is an illusion”
Aristotle - “I see truth. I can’t see radon.Therefore, radon is not truth.”
Descartes -“ I think radon isn’t real, therefore radon isn’t real”
Brunell - “Radon is voodoo”

Doubters Summary

Radon is an illusion
Radon is not truth
Radon isn’t real
Radon is voodoo

Believers Gallery

WHO - Agency for Research on Cancer
NAS - Biologic Effects of Ionizing Radiation IV
Int. Commission on Radiological Protection
National Council on Radiation Protection
EPA - Office of Radiation Programs
Center for Disease Control
American Lung Association
American Medical Association
American Public Health Association

Believers Summary

Radon is a Group A human carcinogen
Radon causes lung cancer
Radon is a significant public health problem

Key Questions

Doubters

1. Is radon real?
2. Does radon do bad things?
3. Does radon do bad things to lots of people?

Believers

1. Hazard identification
2. Biological effects of radon
3. Population health effects of radon

Hazard Identification


Physical Characteristics

  • Can’t see it
  • Can’t smell it
  • Can’t taste it
  • Can’t hear it
  • Can’t feel it

What is it? Radioactive

More about radon-222:

  • Chemically inert, uncharged noble gas
  • Produced from decay of uranium-238
  • Seeps out of rocks and soil
  • Builds up indoors and in mines
  • T1/2 is 3.8 days
    Decays by alpha particle emission
  • Produces short-lived solid alpha-emitters - Polonium 218 and 214

Biological Effects of Radon

  • Radon-222 gas does not cause health effects
  • Solid charged radon progeny attach to airborne particulates (dust)
  • Dust particles are inhaled and can adhere to lung lining
  • Deposited progeny decay by alpha emission
  • Alpha particles impact bronchial epithelium
  • Alpha particles can damage nuclear DNA
  • Damaged DNA can lead to lung cancer

Ionizing Radiation (IR) Review

  • Radioactive atoms are unstable
  • Spontaneous atomic decay produces IR
  • IR breaks chemical bonds and strips electrons
  • IR can damage molecules and living cells
  • IR damage is related to mass, energy and dose

Flavors of Ionizing Radiation

BIG ( Alpha Particles)
Large and positively charged (Helium nucleus)
Short travel distance, rapid energy loss in matter
MEDIUM (Beta Particles)
Positively or negatively charged electrons
Moderate travel distance and energy
SMALL (Gamma Rays)
Photons without charge or mass
Long travel distance and high energy

Health Effects of IR

Non-Stochastic

  • Severity of effect increases as dose increases
  • Short-term, high level, acute exposure
  • Short disease latency - “radiation sickness” - burns, nausea, weakness, hair loss, organ malfunction

Stochastic

  • Probability of effect increases as dose increases
  • Long-term, low level, chronic exposure
  • Long disease latency - Cancer, teratogenic and genetic mutations

Health Effects of Radon Progeny

  • Alpha particles deliver high density of ionizations (high LET)
  • Small number of densely ionizing tracks per cell
  • ~4 alpha tracks deliver 1 Gy of energy vs ~1000 gamma rays
  • Most damage caused by direct ionization of DNA vs hydroxyl radical reaction

Radiation Induced Carcinogenesis Theory

  • Multi-stage
  • Oncogenes induced
  • Tumor-suppressor genes damaged
  • Chromosomal fracture / abnormal repair

Population Health Effects

Animal Studies

US DOE - lung cancer, pulmonary fibrosis, COPD
NAS - resp. tumor rate increased with exposure
NAS - tumor rate increases above 20 WLM
DOE - lifetime lung tumor risk coefficients similar in animals and humans

Radium and NORM’s

Radium-226 Health Effects
Soluble solid in Uranium-238 decay chain
Decays by alpha emission (T 1/2 1,620 years) to Radon-222
Radium watch dial painters - 1920’s
US Radium Corp - “Radium Girls”
8-40 years later - Jaw-bone cancer (radium necrosis)
NORM’s ( naturally occurring radioactive materials)
Mining, coal ash, phosphate, uranium, oil and gas
Uranium, Thorium, Radium, Radon, Carbon, Potassium
Health effects poorly understood

Miners

Underground Miners Studies
20+ epidemiological studies in US, Canada, China, Europe and Australia
Consistent exposure-response relationship
Similar excess RR / WLM estimates
Low exposures over long time periods produce greater lung cancer risk
Increased lung cancer rates observed at low cumulative exposures (20 - 90 WLM)
Increased risk observed after controlling for smoking, silica, diesel, metal dust …
Underground Miners Studies
Population WLM RRC%/WLM N
Czech Uranium 313 1.92 9,403
Ontario Uranium 40-90 1.4 15,984
New Mex Uranium 111.4 1.8 3,469
Swedish Iron 81.4 1.4 1,415
Colorado Uranium 834 0.6 44,127
Eldorado Uranium 20.2 2.6 8,487
Newfoundland 382.2 0.9 1,772

WLM - “Working Level Month” = exposure to radon progeny concentration of 100 pCi / L for 170 hours
RRC% - “relative risk coefficient” = the fractional increase above the baseline lung cancer incidence

Population Health Effects - Residential

Residential Studies - Case Control

New Jersey - 480 / 442, RR increased 3.4% / WLM
Sweden - 210 / 400, borderline increase > 4 pCi/ L
Finland - 291 / 495, no statistical difference
China - 308 / 356, no statistical difference

Case Control Study Limitations

  • Small sample size
  • Low and variable exposure levels
  • Selection bias

Exposure-Response Assessment Model
Human data - underground miners
Similar exposure levels - mines & residential
Mine studies down to radon doses of 20 - 70 WLM
Average cumulative residential dose of 18 WLM
4 pCi / L lifetime cumulative dose of 57 WLMs
Linear dose-response relationship
No evidence for a lower limit risk threshold
Radon and smoking have a multiplicative efffect

Causality Criteria - Radon and Lung Cancer
1. Consistent association -animal, occupational, residential
2. Strong association - linear exposure - response curve
3. Specific association - radon and lung cancer
4. Time Relationships -
5. Congruence - consistent with known radiation effects
6. Sensitivity -
7. Biological Mechanism - alpha particle biological effects
8. Plausibility - not contradicted by other information
9. Research / Experiments - consistent animal data
10. Analogy - radium necrosis


Summary

Radon is real
Radon causes lung cancer
Higher radon exposures cause more lung cancer
Check your home radon level
Stop smoking


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