Occurrence Health effects of radon

1 occurrence

1.1 concentration units
1.2 natural
1.3 accumulation in dwellings
1.4 jewelry contamination

occurrence

concentration units

pb formed decay of rn. here typical deposition rate of pb observed in japan function of time, due variations in radon concentration.

radon concentration measured in atmosphere in becquerels per cubic meter (bq/m), si derived unit. frame of reference, typical domestic exposures 100 bq/m indoors , 10-20 bq/m outdoors. in us, radon concentrations measured in picocuries per liter (pci/l), 1 pci/l = 37 bq/m.

the mining industry traditionally measures exposure using working level (wl) index, , cumulative exposure in working level months (wlm): 1 wl equals combination of short-lived rn progeny (po, pb, bi, , po) in 1 liter of air releases 1.3 × 10 mev of potential alpha energy; 1 wl equivalent 2.08 × 10 joules per cubic meter of air (j/m). si unit of cumulative exposure expressed in joule-hours per cubic meter (j·h/m). 1 wlm equivalent 3.6 × 10 j·h/m. exposure 1 wl 1 working month (170 hours) equals 1 wlm cumulative exposure.

a cumulative exposure of 1 wlm equivalent living 1 year in atmosphere radon concentration of 230 bq/m.

the radon (rn) released air decays pb , other radioisotopes. levels of pb can measured. rate of deposition of radioisotope dependent on weather.

natural

radon concentration next uranium mine

radon concentrations found in natural environments low detected chemical means: example, 1000 bq/m (relatively high) concentration corresponds 0.17 pico-gram per cubic meter. average concentration of radon in atmosphere 6×10 atoms of radon each molecule in air, or 150 atoms in each ml of air. entire radon activity of earth s atmosphere @ time due tens of grams of radon, consistently replaced decay of larger amounts of radium , uranium. concentrations can vary place place. in open air, ranges 1 100 bq/m, less (0.1 bq/m) above ocean. in caves, aerated mines, or in poorly ventilated dwellings, concentration can climb 20-2,000 bq/m.

in mining contexts, radon concentrations can higher. ventilation regulations try maintain concentrations in uranium mines under working level , , under 3 wl (546 pci rn per liter of air; 20.2 kbq/m measured 1976 1985) 95 percent of time. concentration in air @ (unventilated) gastein healing gallery averages 43 kbq/m (about 1.2 nci/l) maximal value of 160 kbq/m (about 4.3 nci/l).

radon emanates naturally ground , building materials on world, wherever traces of uranium or thorium can found, , particularly in regions soils containing granite or shale, have higher concentration of uranium. every square mile of surface soil, depth of 6 inches (2.6 km depth of 15 cm), contains approximately 1 gram of radium, releases radon in small amounts atmosphere on global scale, estimated 2,400 million curies (91 tbq) of radon released soil annually. not granitic regions prone high emissions of radon. being rare gas, migrates freely through faults , fragmented soils, , may accumulate in caves or water. due small half-life (four days rn), concentration decreases when distance production area increases. atmospheric concentration varies depending on season , conditions. instance, has been shown accumulate in air if there meteorological inversion , little wind.

because atmospheric radon concentrations low, radon-rich water exposed air continually loses radon volatilization. hence, ground water has higher concentrations of rn surface water, because radon continuously produced radioactive decay of ra present in rocks. likewise, saturated zone of soil has higher radon content unsaturated zone because of diffusional losses atmosphere. below-ground source of water, springs—including hot springs—contain significant amounts of radon. towns of boulder, montana; misasa; bad kreuznach, germany; , country of japan have radium-rich springs emit radon. classified radon mineral water, radon concentration must above minimum of 2 nci/l (74 bq/l). activity of radon mineral water reaches 2,000 bq/l in merano , 4,000 bq/l in village of lurisia (ligurian alps, italy).

radon found in petroleum. because radon has similar pressure , temperature curve propane, , oil refineries separate petrochemicals based on boiling points, piping carrying freshly separated propane in oil refineries can become partially radioactive due radon decay particles. residues oil , gas industry contain radium , daughters. sulfate scale oil can radium rich, while water, oil, , gas contains radon. radon decays form solid radioisotopes form coatings on inside of pipework. in oil processing plant, area of plant propane processed 1 of more contaminated areas, because radon has similar boiling point propane.

accumulation in dwellings

typical lognormal radon distribution in dwellings

typical domestic exposures of ≈ 100 bq/m indoors, specifics of construction , ventilation affect levels of accumulation; further complications risk assessment concentrations in single location may differ factor of 2 on hour, , concentrations can vary between 2 adjoining rooms in same structure.

the distribution of radon concentrations tends asymmetrical around average, larger concentrations have disproportionately greater weight. indoor radon concentration assumed follow lognormal distribution on given territory. thus, geometric mean used estimating average radon concentration in area. mean concentration ranges less 10 bq/m on 100 bq/m in european countries. typical geometric standard deviations found in studies range between 2 , 3, meaning (given 68-95-99.7 rule) radon concentration expected more hundred times mean concentration 2 3% of cases.

the so-called watras incident (named after american construction engineer stanley watras), in employee @ u.s. nuclear plant triggered radiation monitors while leaving work on several days—despite fact plant had yet fueled, , despite employee being decontaminated , sent home clean each evening, dramatized radon levels in particular dwellings can orders of magnitude higher typical. implied source of contamination outside plant, turned out radon levels of 100,000 bq/m (2.7 nci/l) in worker s basement. radon became standard homeowner concern, though typical domestic exposures 2 3 orders of magnitude lower (100 bq/m, or 2.5 pci/l), making individual testing essential assessment of radon risk in particular dwelling.

radon exists in every state , approximately 6% of houses have elevated levels. highest average radon concentrations in united states found in iowa , in appalachian mountain areas in southeastern pennsylvania. of highest readings have been recorded in mallow, county cork, ireland. iowa has highest average radon concentrations in united states due significant glaciation ground granitic rocks canadian shield , deposited soils making rich iowa farmland. many cities within state, such iowa city, have passed requirements radon-resistant construction in new homes. in few locations, uranium tailings have been used landfills , subsequently built on, resulting in possible increased exposure radon.

jewelry contamination

in 20th century, pb-contaminated gold, gold seeds used in radiotherapy had held rn, melted down , made small number of jewelry pieces, such rings, in u.s.

wearing such contaminated ring lead skin exposure of 10 100 millirad/day (0.004 0.04 msv/h).