http://ec.europa.eu/energy/nuclear/consultations/doc/2009_04_20_natural_radiation_sources.pdf

You can find all the action levels for the EC

Dear Sir,

      As you probably know, radon is the decay daughter of long-lived radium (which is everywhere- rocks, soil, etc).  Over 35 years ago a Princeton professor worried about the high radium content in the black sands around Princeton.  He did a simple measurement and determined the radon concentration in his sealed basement was 10000 ppm.  Our illustrious and dumb EPA has decided that it should be 7 ppm.  They refuse to divulge where that number comes from, but I am guessing that it is pulled out of the air.  If you utilize radiation doses to the lungs, the number is more properly between 500 and 1000 ppm.  Radon is very short lived.  The cure for buildings is simple-  just keep a bit of air flowing  (a very small fan).  I actually had a person call me several years ago worried about 9 ppm.  I think the survivors from Hiroshima got about a million times greater dose and they lived longer than the average Japanese citizen.

     I hope this helps.  Dennis Moltz

Thank you Dr. Kostas C. Stamoulis and Dr . Dennis M. Maltz.  for your answers and attachment.

Best Regards

Salam Dr. Abd Elmoniem,

The U.S. Environmental Protection Agency (EPA) sets the action level for radon in indoor air at 4 pCi/L. That is if the air concentration in residences, schools, or offices is 4 picoCurie/litter or more, it is recommended to install a mitigation system. In water the action level is 300 pCi/L. Please check the website below for more details.

http://water.epa.gov/lawsregs/rulesregs/sdwa/radon/regulations.cfm

As far as radium, the EPA standard for drinking water are 5 pCi/L for Ra-226 and Ra-228, and 15 pCi/l for Ra-224. For additional information check the website below.

http://www.epa.gov/radiation/radionuclides/radium.html

Take care,

Ilham