Does residential radon cause lung cancer?

Question

Radon causes lung cancer; a typical statement is this:

The U.S. Environmental Protection Agency (EPA) has identified radon as the second leading cause of lung cancer in the United States. Many homes contain radon concentrations that are high enough to give their occupants lifetime exposures that could increase their risk of developing lung cancer.

While researching this (disclosure: because I'm in the process of purchasing a house that came back with a somewhat high radon measurement), I came across an article that claims that:

To be clear: There are NO valid studies that have conclusively demonstrated that typical residential exposures to radon increase the risk of cancer at all. In fact, all of the valid studies performed thus far show one of two things: 1) No risk and/or 2) a decreasing risk of cancer.

Also that the US Department of Energy says that:

Currently there is very little information about...the health effects associated with exposures to radon at levels believed to be commonly encountered by the public. The only human data available for predicting the risks to the public are studies examining the health effects of exposure to radon and its progeny in underground miners. This information would be appropriate for predicting the risks to the public if everyone was a miner, everyone lived in mines, and a large fraction of the general population smoked cigarettes.

And that:

The uncertainty for attempting to extrapolate the yearly radon concentration from a three to seven day sample, such as that probably used for the vast majority of “radon tests” is huge: about +/- 90% (at the 90% confidence level)

---

This was written by a Forensic Industrial Hygienist named Caoimhín P. Connell, who seems to be in private practice as "providing state-of-the-art industrial hygiene and occupational and environmental assessment service" reference. I can't find anything about his educational background, if that matters.

---

I am not an environmental scientist, but it sounds like he's saying that:

1. Radon levels of the kind you find in a home may not really cause cancer.
2. The reason we think so is based on invalid extrapolation from the exposure of miners, who are exposed to a LOT MORE radon, as well as to many other harmful substances.
3. The actual measurement of radon is wildly inaccurate, so taking action (or even just worrying) based on the measurement is quite possibly pointless

So, is he right and does it follow that radon mitigation is unnecessary?

Answer 1

Key assertions here are, at best, out of date. According to a 1997 study:

Until ongoing case-control studies of indoor radon are completed and the data are pooled and analyzed, the studies of underground miners remain the best source of data to use to assess risk from indoor radon. This meta-analysis provides support for their general validity.

More effort at pooling and analyzing case-control studies has since taken place. Here's an example from 2004:

Collectively, though not separately, these [13 case-control] studies show appreciable hazards from residential radon, particularly for smokers and recent ex-smokers, and indicate that it is responsible for about 2% of all deaths from cancer in Europe.

A similar paper based on North American case-control studies and published the following year also provides "direct evidence of an association between residential radon and lung cancer risk."