Radon and radioactivity

RADON

Radon is a radioactive gas, heavier than air, particularly abundant in some areas of Italy, coming from underground and/or building materials. It accumulates in basements and in lower stories of the building, often together with other gases (carbon dioxide, hydrogen sulfide, etc.).
It is a colourless, odourless and tasteless gas, so it’s impossible to feel its presence in the air, water or food without proper equipment. It comes mainly from soils with an high content of Uranium/Radium such as tuff, pozzolan, some granites and volcanic rocks. Radon 222, the main isotope of this gas, is the product of the decay of Uranium 238. While the other element of the radioactive series are solid, Radon is a gas so it can seep through cracks, pass through porous materials, dissolve into water and penetrate this way into the buildings also through water pipes. Once it’s accumulated, Radon can be breathed and can continue the radioactive serie inside the body, damaging health and increasing the risk of developing lung cancer. Epidemiological studies released by World Health Organization (OMS) and the International Agency for Research on Cancer (IARC) have scientifically established the carcinogenicity of this gas.

BfS Radon comparison Certificate

CURRENT LAWS

The regulations on radioactivity in all European Union countries is based on the European Commission Recommendation of 8 June 2000, n. 2000/473/Euratom that establishes that art. 36 of Euratom pact regarding the control of the environmental radioactivity degree to measure population exposure is respected (G.U.C.E. series L, 27 July 2000, n.191).

Italian law establishes with D.Lgs. 17 March1995, n. 230 (ordinary supplement n. 74, to Gazzetta Ufficiale n. 136, 13 June) the respect of Euratom rules 80/836, 84/467, 84/466, 89/618, 90/641 and 92/3 on ionizing radiations.

Regarding risk arising from Radon exposure, italian law protects only workplaces (D.Lgs. 26 May 2000, n. 241), while on homes the European Community recommendations apply. In this situation the recommendations give “suggested values”, or values of Radon concentration that shouldn’t be exceeded. Below the “suggested values” the situation is considered acceptable. Recently the acceptable Radon levels have been reduced by the WHO.

RADIOACTIVITY MEASUREMENT

There are many instruments capable of measuring radioactivity and evaluating radioactive pollution or to measure Radon gas. They work basically on the effects that radioactivity has on some substances, such as the impression of photographic solutions, the excitation of luminescent substances of the ionization of gases, liquids or crystals in presence of radiations.

These instruments are used to:

– keep the dose of radiations absorbed by each individual under control;

– measure the levels of irradiation or radioactive contamination in the environment, in things and in human bodies;

– keep constantly under control the levels of irradiation or radioactive contamination in the environment and in things, with the possibility to record the measured data;

– give detailed informations on the type of radioactive source and the level of radioactive pollution.

The measuring unit for radioactivity is the becquerel (Bq) .

A sample containing radioisotopes is characterized by its radioactivity level, expressed as number of decays of radioactive nuclei for time unit:

1 becquerel = 1 Bq = 1 decay per second.

Measuring unit for Radon gas

When measuring Radon and its radioactivity in air it is generally measured as Bequerel per square meter (Bq/m³): a Bq/m³ is equal to the decay of one atom of Radon in a square meter of air every second, producing another radioactive atom (in the case of Radon 222 it’s Polonium 218) and one alpha particle (alpha radiation). In the anglosaxon system the Picocurie/liter (pCi/L) is still used, and it’s the measuring unit for Radon in the USA.

INSTRUMENTS

Counters are the instruments used to detect and measure radioactivity in the environment, in things and in people. There are two kinds of counters: the scintillation and the ionization kinds. The scintillation ones work on the luminescence produced by radiations that hit specific mineral compounds. The ionization ones work because there is a different electric conductivity in a gas when it is ionized by a radiation.

For the measurement of Radon dosimeters are used (trace dosimeter, scintillation dosimeter, etc.) that must be left in the environment for periods of time ranging from a few hours to a year. Since Radon emission is very variable, due to climatic and seasonal factors, short detections should be avoided. These detections, in fact, usually give bad representation of the average annual levels and can lead to insufficient or inappropriate countermeasures. Measurement with inappropriate instruments, such as Geiger-Muller counters (that measure beta and gamma radiations but not alpha) should be avoided. Measurement longer than 1 month must be performed with passive dosimeters that allow to evaluate with certainty the presence of Radon gas and the average level of radioactivity it generates. In case the presence of gas in the building is confirmed, other investigations are needed to find the source of the gas (basement or building material) before beginning mitigation and remediation.

Radon is present in Italy with an average concentration in buildings of 77 Bq/m³. Limit values are:

• 148 Bq/m³ maximum level advised by EPA (U.S. Environmental Protection Agency) over which remediation is necessary;
• 200 Bq/m³ maximum level advised by EU for new buildings;
• 400 Bq/m³ maximum level advised by EU for old buildings over which remediation is necessary;
• 500 Bq/m³ maximum level on workplaces (D.L. 241/2000)

Over those values it is necessary to proceed to remediation.