While stone is generally a healthful and beautiful choice for flooring and decorative accents, it has to be installed using healthy guidelines including investigating for radiation and radon content–as per the New York Times–and using safe stone-sealing products. The authors of the essential non-toxic home standby, Prescriptions for a Healthy House, by John Banta, et al, have recommendations for how to fulfill these health requirements, which they include in their new third edition.

The authors have tested several stone products for radiation and radon content and found a range of readings from very low to high levels. Although uranium content in construction materials is not usually considered to be a serious concern it can contribute significantly to ambient radon levels in a home. They recommend that stone, especially granite, be screened for radon prior to installation, even though the Granite Institute has issued a scientific report concluding that granite countertops do not emit radioactivity into the home. Tests, however, are easily performed by simply holding a radiation detector next to the material.

For lower levels of radiation, measurements of longer duration should be performed. Place at least 1 pound of the material in question in a glass container with an instrument for measuring radioactivity. A useful instrument designed for this purpose is Radalert 100, whose small size allows it to fit easy inside a 1-gallon glass pickle jar along with the material to be tested. Set the meter for total counts and leave it to measure for a timed period of 12-24 hours. As a control, the test must be performed in the same way, in the same location, but with the jar empty. Repeat both tests several times to be sure a radiation-emitting solar flare or short-term cosmic event did not interfere with the results.

Sealers for Stone
Many stone-sealing products contain harmful chemicals and high levels of VOCs. The following finishers are free of petroleum-based solvents and can be used for most stone flooring, shelving, and countertops:

AFM Safecoat MexeSeal: A durable sealer providing water and oil repellency, applied over AFM Safecoat Paver Seal .003, an undersealer for porous materials.
Lithofin: Stone sealers (mostly available in the UK).
Livos Meldos Hard Oil and Livos Bilo Floor Wax: A penetrating oil sealer and a clear, mar-resistant finish wax respectively; can be odorous when first applied and should be carefully tested prior to use by a chemically sensitive individual.
Naturel Cleaner and Sealer: Water-soluble flakes that clean, protect, and finish stone surfaces.

The following concern also must be addressed: In standard construction, stone is often laid over an unacceptable backing such as particleboard, which contains high formaldehyde levels.

Adapted from Prescriptions for a Healthy House, by Paula Baker-Laporte, Erica Elliott, and John Banta (New Society Publishers, third revised edition, 2008).