https://en.wikipedia.org/wiki/Radon
http://www.conservation.ca.gov/cgs/minerals/hazardous_minerals/radon/Documents/SR182Map.pdf
Have patience with the pdf map, it loads very slowly.
The meltdown at the Santa Susana Field Labs happened in the 50s. Downhill from the field labs is The Chatsworth Lake area in the San Fernando Valley where they are still building homes. Many of the homes were cabins in the 30s thru 50s. Same thing with the Santa Susana Knolls area in Simi Valley.
The Santa Susan Knolls had reports of cancer clusters in the 80s and Rocketdyne spent many years hauling away the top soil.
Radon is the second largest cause of lung cancer and is shown on the map I linked to. There is a large concentration of radon in the north hills of Simi Valley where very few homes are. There is also a large concentration of radon in the hills south of the San Fernando Valley known as south of the blvd. These are very expensive homes.
There are radon test kits you can buy. Radon is not tested for when buying or selling a home, but in my opinion it should be. A raised foundation allows the radon to be exhausted and dispersed away from the living area of a home. Providing a plastic membrane under the foundation during construction also works for dispersing radon.
The government will help low income homeowners insulate a home and will go thru great lengths to get rid of all drafts. They do it for free, it is a surcharge on our energy bills. But with a closed home, radon can build up in the living area. Radon can also be found in granite counter tops.
The gas leak is in the hills north of the San Fernando Valley about 5 miles northeast from the Rocketyne Field Labs. The homes in the neighborhood below are being offered extended stay in hotels and rentals until the leak can be capped next month. I don’t think there is any relation with the Rocketdyne Field Labs, they are on different mountain ranges.
Back in the 1970s we had a gas fire very near to today’s leak and had Red Adair come extinguish it.
The camera view that shows the plume of smoke uses filters to show the gas, it is invisible to the naked eye and I have not smelled it driving downwind of it. But if that camera view were not clipped, it would show you flares on the backside of that mountain off of hwy 126. I drove it last weekend at night.
Again, Radon rears it’s ugly head.
Big deal.
Look at the radon decay chain. The real isotope of concern is Polonium. It is particulate, not gas. Strangely enough, Polonium is the isotope of concern for smokers.
These same people that will worry and sweat and whine about Radon will sit in that same home puffing away, getting up to 2 Rem or more, per year, of alpha exposure to their lungs.
Big deal about nothing, go ahead, spend all that money for test kits and remediation.