Pam - years ago I recall a NY non-profit (which I think still operates) had a mitigator(s) that charged full price to those that could afford it and used those profits to supplement the low income mitigations. Funding for low income housing has always been an issue, I can't remember how many times I heard 'what is the purpose of measuring low income housing if it is not going to be fixed'

All great comments. While soil-gas is the likely suspect, if the home uses WELL water, then that could be the problem (measure a shower/bath room). Lastly, slate is metamorphized from shale, which is known to contain much more radium (Ra-226) than granite, and they have equivalent emanating factors. If you use an inverted bowl/box to measure flux from the slate, also measure something like ceramic tiles or maybe concrete for a "background" since some radon WILL be coming off the slate and you have to have context.

Tobacco contains RDPs, of which polonium (half life = 138 days) is most important, since it is a high energy alpha emitter and volatile (vaporizes) at cigarette temperatures. Tobacco leaves are very sticky thus particulates (dust and RDPs) stick. So, plants can remove 'radon' but is it not significant compared to what's in the air.

Jeff - Many years ago I received a couple of SIRG grants to provide (through the hospital) radon info and test kit to new parents that lived in Zone 1 counties. Although I am now not involved in the program, I am glad to say the program is still continued by the radon section of the NY State Health Dept. (as evidenced by the packages that my new grandchildren brought home from the hospital). - Mike Kitto

Is urethane less permeable to radon penetration than silicone?