You can't see radon. You can measure it.

INDOOR AIR  ·  RADON

You can't see radon. You can measure it.

An odorless gas rises out of the ground and collects indoors. Pooled European data ties higher home levels to more lung cancer — and for smokers, the effect climbs sharply.

Radon is a radioactive gas that comes up through soil and rock and builds up inside homes. You can't see it, smell it, or taste it, so it's easy to leave off the list of things you worry about. The largest pooled study of home radon in Europe puts a number on what it does, and the number is not small.

What the pooled data shows

Darby and colleagues, writing in the BMJ (2005), combined individual records from 13 case-control studies across 9 European countries: 7,148 people with lung cancer and 14,208 without. For each person, radon was measured in the homes they had lived in over the previous 5 to 34 years, then compared against whether they developed lung cancer.

Each 100 Bq/m³ of radon raised lung-cancer risk by about 8.4% as measured. After correcting for the ordinary errors in measuring radon over decades, that works out to roughly 16% per 100 Bq/m³. The relationship was a straight line with no safe floor, and it still held in homes measuring under 200 Bq/m³.

16% (95% CI 5–31%)
Increase in lung-cancer risk per 100 Bq/m³ of usual home radon, corrected for measurement error (Darby et al., 2005).

Why smoking changes the math

The percentage increase was about the same whether you smoked or not. What differs is the starting point. A smoker's baseline lung-cancer risk runs roughly 25 times a lifelong non-smoker's, so the same radon adds far more real risk on top.

The authors modeled it out to age 75. For a lifelong non-smoker, the risk of dying from lung cancer runs about 0.4%, 0.5%, and 0.7% at usual radon levels of 0, 100, and 400 Bq/m³. For a lifelong smoker, the same three levels give about 10%, 12%, and 16%.

10% → 16%
A lifelong smoker's modeled lung-cancer risk by age 75, going from 0 to 400 Bq/m³ of home radon. For a non-smoker, the same jump is 0.4% to 0.7% (Darby et al., 2005).

Across the whole population, the authors estimate home radon is behind about 2% of all cancer deaths in Europe. It sits second only to smoking as a cause of lung cancer, and the two together are worse than either alone.

What this means for your home

Radon varies house to house, even between neighbors on the same street, because it depends on the ground underneath and how the building sits on it. The only way to know your level is to measure it. A test costs little and runs on its own for a few days to a few months.

For reference, the World Health Organization suggests acting at 100 Bq/m³, and the US EPA sets its action level at 4 pCi/L (about 148 Bq/m³). If a test comes back high, mitigation is a well-established fix: a vent pipe and fan that pull radon from under the slab and send it above the roof, usually for a few thousand dollars.

A note on certainty: this is pooled observational work, not a randomized trial, so it shows association rather than proof for any one person. The 16% figure is corrected for measurement error, which widens the confidence interval (5–31%). The absolute risks by age 75 are modeled using US non-smoker baselines, and the studies were European, so your home's ground, construction, and ventilation all matter. What the evidence does support, consistently, is that lower home radon means lower risk — and that you can't manage a level you've never measured.

Can't smell it? You can still test for it.

illumenair measures radon alongside moisture and mold, then gives you a plain-language report and a prioritized action plan for the Portland–Vancouver area.

971-363-5626   ·   info@illumenair.com   ·   www.illumenair.com

Sources: Darby S, Hill D, Auvinen A, et al. “Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies.” BMJ 2005;330(7485):223.   ·   World Health Organization. WHO Handbook on Indoor Radon: A Public Health Perspective, 2009.   ·   US Environmental Protection Agency, radon action level (4 pCi/L).