RADON: THE INVISIBLE KILLER Radon: The Invisible Killer

RADON: THE INVISIBLE KILLER Euroweek 2009

Presentation

DESCRIPTION

Date

11.5.2009

Author(s)

Désiré Nzengou (Team leader),

Aki Galand, Tuire Tapanen

Name of the bachelor's thesis

Radon: The Invisible Killer

Abstract This article’s purpose is to examine the current state of knowledge of the indoor radon problem. Its starts by the fundamentals: the

physical behavior of radon and radon decay products in indoor air followed by the location of radon in Belgium and Finland. Then we

see what is about the legal aspect of radon at European level, and this study ends by a case study using the European Commission Radon

Software (ECRS) provided by the professor in charge of the Nuclear physic department at ISIB (Industrial Engineering school).

Introduction

For a while, the society’s perception of the importance of indoor radon has changed radically. Subsequent events, as measurement

campaigns in several countries, transformed that common idea in the 70s that elevated indoor radon concentration was an isolated

concern, to the now widely understanding of the health risk of the inhalation of radon decay products indoors, even higher than any other

environmental carcinogens. Furthermore, radon concentrations ten, hundred or even more times the average are observed with startling

frequency, even in buildings that are otherwise quite ordinary. Long-term exposure to such concentrations lead to individuals risks of

lung cancer that are so high as to be unacceptable by almost any standard.

As a major environmental concern, radon has drawn considerable attention in many European countries, Canada, USA, etc. Formerly

known only as an element residing in an obscure corner of the periodic table, radon has been propelled into a topic of people discussion,

consequence of public awareness.

Studies of radon can have important implications for studies of other indoor pollutants, and vice versa. Indeed, on the one hand, the

detailed studies of the behavior of other airborne pollutants in the outdoor atmosphere provide a model approach and results that directly

apply to the understanding of radon. On the other hand, the study of the radon’s behavior in the indoor environment can give some

generally useful information on the dynamics of indoor atmospheres. An additional important aspect of radon is that it represents a

relatively simple carcinogenic agent when compared with tobacco smoke, for example. Consequently, our understanding of

carcinogenesis could be advanced by focusing efforts on radon as a model agent.

Subject headings, (keywords)

radon,

Pages Language

7 p. English

1

1 THE PHYSICS OF AIRBORN RADON (1)

Radon is a rare radioactive gas of natural origin. It is odourless and colourless. It

emanates from the soil and, in smaller quantities, from construction materials. Radon

is an intermediate stage in the transformation of an instable radioactive substance,

uranium 238, into a stable element (lead). Formed by the disintegration of radium,

222Rn is the most stable isotope, which has a half-life of 3.8 days. An inert gas, radon

is also the heaviest of the rare gases.

This gas generally dilutes rapidly in the atmosphere, where it is usually present at a

very low concentration – except in rare situations of a very calm atmosphere. Of all

the natural radiations humans receive – cosmic, from soils, water and food – radon is

by far the most significant. It is often referred to as “invisible” or “silent” because

despite the fact that it represents more than a third of the radiation that Belgians are

exposed to in everyday life, it remains relatively ignored in public discourse. It is

estimated that radon makes up 32 to 40 percent of total radiation exposure for the

average Belgian. This is almost at the same level as medical exposure. In certain areas

in the south of Belgium, it is the principle source of radiation, representing in some

cases more than 50 percent. In indoor spaces the dilution of radon in the air is less

effective, its concentration reaching, at a certain time, levels high enough to cause

some concern.

Radon itself is not very dangerous; a noble gas, it is not metabolized and does not

deposit in the respiratory system. Its disintegration does, however, create other

radioactive elements present in suspension in the air: Po-218, Pb-214, Bi-214, Po-

214… These elements are solids that deposit almost totally in the respiratory system,

where they remain until their disintegration. Each atom of these radon progeny

trapped in the respiratory system is a source of radiation and a possible cause of (lung)

cancer.

2 WHERE CAN RADON BE FOUND IN BELGIUM? (2)

The basement rocks of radon producers are mainly located in Wallonia, especially in

the Ardennes: counties of Bastogne, Neufchâteau and Verviers. The additional ones

are Condroz, the Sambre and Meuse, some municipalities in Walloon Brabant along

the Dyle and Visé. Flanders and Brussels have both, on the one hand, soils low in

uranium and are thus spared. On the other hand, in case of normal soil concentrations

of uranium, the permeability is too low to pass up radon.

2

3 OCCURRENCE OF RADON IN FINLAND

Radon is a quite common problem in Finland and is checked whenever buildings are

being built. On average, Finnish people are exposed to 3,7 mSv of radiation annually.

The radiation portion of radon is 2 mSv (80 Bq/m3), thus making it the largest single

factor for radiation exposure.

Occurrence of radon depends on two key factors. Firstly there has to be Uranium in

the soil as radon is the product of radioactive decay of uranium. Second factor is the

quality of soil. The soil has to be porous enough to allow the flow of gas to the

surface. The soil has an effect on occurrence of radon because of its half-life (3.8

days). Hence, if the gas cannot move fast enough in the soil it has decayed to harmless

compounds before being a health hazard to people. This is why the highest radon

values in Finland have been measured in esker and rocky areas.

In addition of radon affecting the indoors air, it can be problem in water from drilled

wells. Especially in the rural areas where people use private wells instead of the

municipalities’ water network. Radon in water can cause stomach cancer instead of

lung cancer as the radiation occurs in stomach after drinking water instead of

breathing it. Though, radon in water affects lungs as well due to inhaling it in shower

or while washing dishes when radon has been released from water into the air.

In addition, the amount of radon is approximately 15 % higher in the air in the winter

than in the summer, the annual average has been calculated with that in mind.

4 LEGAL ASPECT AT EUROPEAN LEVEL

4.1 About the recommendation (3)

The European commission recommends:

For the existing dwellings:

- That measures of lowering of the radon level are considered beyond the reference

level fixed at an average annual radon concentration of 400 Bq/m3.

- That the urgency of the implementation of the corrective actions heeds the extent of

the exceeding of the reference level.

- That the population is informed of the radon levels to which it is exposed and the

solutions allowing to reduce them.

3

For the new dwellings:

- The reference level fixed at an average annual radon concentration of 200 Bq/m3.

- That informations are provided to the possible levels of exposure of radon and to the

precautionary measures being able to be taken.

4.2 About the directive (4)

According to the Directive of 1996, Title VII: Increase in exposure due to natural

radioation sources, each member state shall ensure through surveys or others

appropriate means that work activities which may be affected are identified. These

include: (a) work activities where workers and public are exposed to thoron or radon

progeny, gamma rays or any other radiations in workplace such as mines,

underground workplaces and workplaces on the surface in selected areas; (b) work

activities involving the use or storage of materials not usually regarded as radioactive

but which contain naturally occuring radionuclides; (c) work activities involving the

production of residue not usually regarded as radioactive but which contain naturally

occuring radionuclides; (d) aircraft operation.

Article 41: protection against exposure to natural sources of terrestrial radiation says

that for each activity declared by the concerned member states, the appropriate means

for monitoring exposure are: (a) the implementation of corrective measures to reduce

exposure as stipulate in Title IX; (b) the application of protective measures against

radiation according to Title III,IV,V,VI and VIII.

Article 42: protection of air crew says that each member states shall take the

necessary arrangements in order for undertakings operating aircraft to take account of

crew exposure to cosmic radiation succeptible to be more than 1 mSv per year.

5 IN PRACTICE: COSTS AND BENEFITS ANALYSIS

Software exercise realized in the laboratory of ISIB (Industrial Engineering

School of Brussels): indoor radon risk evaluation and justification of mitigation

By this practice, we approach the various parameters that influence the health risk

associated to radon and, thus, the justification of mitigation actions.

We have at our disposal the European Commission Radon Software ECRS, a tool for

risk calculation and evaluation of countermeasures based on three main kinds of data:

- The exposition data provided by the user, complemented by additional

information on exposed people (such as the age, smoking habits, etc.);

4

- Two risk evaluation models: one derived from the direct epidemiological

follow-up of groups subject to high radon exposures, and the other from

traditional dosimetric models for internal contamination.

- Statistical data on the population of the country being exposed.

5.1 Collective calculation and mitigation

We realize a collective calculation using only the age-duration epidemiologic risk

model (ADM) and considering one measurement per typical house, season adjusted.

Let’s define the family suggesting an extreme case in which we’ll run the program

with one of the proposed remedial countermeasures: ventilation, sealing, sump, under

floor mechanical or natural ventilation.

By the cost calculation, this program give us an idea (in €/year) of the assumed

monetary value of human life, and also the discount rate which express the fact that

the money spent for a remedial action cannot be invested, so the possible interest is

lost. It’s thus basically the interest rate you might obtain. Note that the most relevant

results here are the total discounted cost of countermeasure, the cost of residual

detriment and the total cost (detriment + countermeasure). Here is the case:

two adults (father and mother) aged of 40 years old, both non smoker, parents of two

boys and one girl, aged respectively of 8, 2 and 3 years old. The dose of radon

exposure since the age of 20 till 80 (for parents) equals to 200 Bq/m3. Children are

exposed to the same concentration and will leave the house at 18. The results are:

EC Rdon Software - Result Summary of case: Case House non smoker 200 Bq/m3 ADM

(Collective exposure, Epidemiological risk calculation)

Lung cancer mortality:

Whole life lung cancer mortality No exposure Radon

father

1,70% 2,10%

mother

0,30% 0,40%

daughter

0,30% 0,30%

son1

1,70% 1,70%

son2

1,70% 1,70%

Excess of lung cancer mortality:

Years of life lost if death occurs No exposure Radon

father

2,10%

mother

0,40%

daughter

0,30%

son1

1,70%

son2

1,70%

5

Life expectancy:

Average age at death No exposure Radon

father

76,7 76,6 years

mother

81,8 81,7 years

daughter

80,9 80,9 years

son1

75 75 years

son2

74,9 74,9 years

Life expectancy No exposure Radon

father

36,7 36,6 years

mother

41,8 41,7 years

daughter

77,9 77,9 years

son1

67 67 years

son2

72,9 72,9 years

Loss of life expectancy No exposure Radon

father

0,1 years

mother

0 years

daughter

0 years

son1

0 years

son2

0 years

Costs:

No exposure Radon

Effective implementation duration 41 Years

Number of renewals

4 Discounted cost of countermeasure implementation 750 Euros

Discounted cost of countermeasure use 1 063,30 Euros

Discounted cost of countermeasure renewal 1 023,20 Euros

Total discounted cost of countermeasure 2 836,50 Euros

Cost of residual detriment 2 797,60 Euros

Total cost (Detriment + Countermeasure) 5 634,00 Euros

Let’s examine this table by comparing each parameter for the two cases, with or

without exposure to radon, and see what diagrams we have.

5.1.1 Life expectancy and loss of life expectancy in case of exposure

6

5.1.2 Lung cancer mortality with or without radon exposure

We clearly see that the mortality due to lung cancer is more important in case of

exposure to radon. The rate is higher for every member of the family, especially the

father who has the highest risk (0,8%).

5.1.3 Years of life lost due to radon exposure

7

i

REFERENCES

(1) « Limiter le risque de pollution par le radon », Confort et santé, fiche 30, juin 2007

(2) http://www.fanc.fgov.be/fr/page/bienvenue-sur-le-site-radon-de-l-afcn/646.aspx

(3) Recommendation of the Commission, of February 21st, 1990, relating to the protection of the population against the

dangers resulting from the exposure to radon inside the buildings (90/143/Euratom). Official journal n° L 080 of the

3/27/1990, p. 0026 – 0028.

(4) Directive of the Council, of 1996 (96/29/Euratom). Official journal n° L 159 of the 29/06/1996, p. 0001–0114.

(5) Unit of radiation dosage (such as from X rays) applied to humans. Derived from the phrase Roentgen equivalent man, the

rem is now defined as the dosage in rads that will cause the same amount of biological injury as one rad of X rays or gamma

rays.

(6) http://eur-lex.europa.eu

(7) 90/143/EURATOM. Recommandations de la Commission, du 21 février 1990, relative à la protection de la population

contre les dangers résultant de l’exposition au radon à l’intérieur des bâtiments. Journal officiel no L 080 du 27/03/1990

(8) UNSCEAR 2000. «Sources and Effects of Ionizing Radiation». Rapport to the General Assembly. United Nations. 2000

(9) Personal contribution: cost and benefits analysis. Nzengou Désiré