According to RadonSeal, although radon in homes has been declared a national health problem, there are no federal or state standards. The Radon Act 51 passed by the US Congress set the natural outdoor level which averages 0.4 pCi/L as the target radon level for homes which unfortunately most homes (two thirds) exceed.

The Environment Protection Agency was given the task of developing practical guidelines. Considering the high cost of mitigation methods available to homeowners in 1980s (averaging $1,200 but up to $2,500), EPA issued its recommendations:

• 4 pCi/L ... the "action" limit (fix your home)
• 2 pCi/L ... the "consider action" limit (consider fixing your home)

EPA did not want to force homeowners to install costly radon mitigation systems, leaving the decision up to each homeowner. But at the same time, EPA has made it clear that the 4 pCi/L action limit is not a "safe" level and warned the public:

Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family's risk of lung cancer.

Unlike radon levels in homes, occupational radon limits are governed by law and regulations.

The Miners Safety and Health Act (MSHA) covers underground miners. Their annual exposure is limited to less than 4 WLM (Working Level Months), equivalent to 33 pCi/L during their working hours. The Occupational Safety and Health Act (OSHA) limits cumulative radon exposure in the workplace to 30 pCi/L based on 40 working hours per week. Assuming the highest radon level in modern mines, the average person receives in his home at 4 pCi/L over 12 years the same radiation dose as if he/she worked for 5 years in a uranium mine.

There are no hard facts. There is no study that shows a level of lung cancer hazard for radon.

Joseph L Alvarez I have read some of the research and it seems unclear as you are writing. Thank you for your input.

I disagree with Joseph Alvarez, he knows it.

I can only repeat what I recently wrote in another discussion:

The European pooled study of lung cancer due to residential radon by Darby et al. (2005) was summarized in the WHO radon handbook, as follows:

" In the European pooling study, the exposure-response relationship appeared to be approximately linear with no evidence for a threshold below which there was no risk.In particular, the results were incompatible with a threshold above 150 Bq/m3 (i.e.150 Bq/m3 was the 95% upper confidence limit for any threshold). Furthermore, the investigators found a statistically significant association between radon concentration and lung cancer, even when the analysis was restricted to people in homes with measured radon concentrations below 200 Bq/m3. The risk of lung cancer was 20% higher (95% confidence interval 3-30%) for those individuals with measured radon concentrations 100-199 Bq/m3 (mean: 136 Bq/m3) when compared to those with measured radon concentrations under 100 Bq/m3 (mean: 52 Bq/m3)."

This is for living space. As we spend, during our lifetime, much less time at work than at home, higher levels can be admitted at work than at home.

However, the fact that a risk was established above 100 Bq/m3 at home does not mean that a corrective action is justified. A cost-benefit analysis should be undertaken, which is not very clear because of a lack of consensus about the cost of a cancer death, and because of the uncertainties about the risk factor. Moreover, this analysis can differ according to age and to smoking habits. Very roughly, an action is often justified, let us say above 200 Bq/m3, for young smokers or young children exposed to tobacco smoke, but only cheap actions can be justified, even at 1000 Bq/m3, for old non-smoking people.

François Tondeur Thank you for a clear answer. This was very helpful.

According to Radon.com, A safe level of radon gas is no radon gas. The radon level at living space and work place depends on your geographical location. The radon levels of the air you breathe outside of your home may be as high as 0.75 pCi/L. But the national average of outside radon levels is 0.4 pCi/L which was passed by the Congress (Radon Act 51) as the target radon level for indoor radon level.

Each country sets their own guidance values of acceptable radon concentrations for work and living places. In Australia it is 200 Bq/m3 for dwellings and 1000 Bq/m3 for workplaces. Understand that the risk estimates have large uncertainties and limits for dwellings are suggested to be somewhere between 100 - 300 Bq/m3. ICRP 126 Radiological Protection against Radon Exposure is a good place to start. Overall advice above by François Tondeur is good.

There is no evidence until now about the critical level for radon an living or working place and no clear correlation between Radon levels and lung cancer hazard. This is because immunity has an important rule in this regard and need huge data to study effects of radon taking into consideration all health parameters that may increase radon hazard as well as environmental parameters.

Amal Alsayaheen Thank you for the input.

J. García-Tobar

According to WHO:

• Radon is a naturally occurring radioactive gas that may be found in indoor environments such as homes, schools, and workplaces.
• Radon is the most important cause of lung cancer after smoking.
• Radon is estimated to cause between 3–14% of all lung cancers in a country, depending on the national average radon level and smoking prevalence. An increased rate of lung cancer was first seen in uranium miners exposed to high concentrations of radon. In addition, studies in Europe, North America, and China have confirmed that even low concentrations of radon – such as those found in homes – also confer health risks and contribute significantly to the occurrence of lung cancers worldwide.
• The lower the radon concentration in a home, the lower the risk of lung cancer as there is no known threshold below which radon exposure carries no risk.
• The risk of lung cancer increases by 16% per 100 Bq/m3 increase in a long time average radon concentration. The dose-response relation is linear – for example, the risk of lung cancer increases proportionally with increasing radon exposure.
• Well-tested, durable, and cost-efficient methods exist for preventing radon in new houses and reducing radon in existing dwellings.

Radon is much more likely to cause lung cancer in people who smoke. In fact, smokers are estimated to be 25 times more at risk from radon than non-smokers. To date, no other cancer risks have been established.

In many countries, drinking water is obtained from groundwater sources such as springs, wells, and boreholes. These sources of water normally have higher concentrations of radon than surface water from reservoirs, rivers, or lakes.

To date, epidemiological studies have not found an association between consumption of drinking-water containing radon and an increased risk of stomach cancer. Radon dissolved in drinking-water can be released into indoor air. Normally, a higher radon dose is received from inhaling radon compared with ingestion. In circumstances where high radon concentrations might be expected in drinking-water, it is prudent to measure radon concentrations. Straightforward and effective techniques exist to reduce the concentration of radon in drinking-water supplies by aeration or using granular activated carbon filters.

Jorge Morales Pedraza Thank you for a long and interesting answer.

You’re welcome

@ J. García-Tobar It is not clear that teleworking from home increases radon exposition. It will depend on each case and would have to be measured. Regards

Héctor Rodríguez-Solano Suárez Thank you for this additional input.

I agree with Jorge Morales Pedraza .

Mohamad Abdulhai Thank you for your input.

Thank you for your comprehensive answer Jorge Morales Pedraza

Dear Kjartan Skogly Kversøy . radon is present above the defined level of 300 Bq/m3 (as an annual average) and employers are required to take action to restrict resulting exposures. See the link: https://www.hse.gov.uk/radiation/ionising/radon.htm

Kindly see also the following useful link: https://www.ukradon.org/information/workplace

Also check please the following useful link: http://www.hsa.ie/eng/Topics/Radon/

Aref Wazwaz Thank you for your interesting input.

You are most welcome dear Kjartan Skogly Kversøy

Wish you the best always.