"Overblown" and "discredited" would apply to the carelessly and perhaps cynically promoted use of x-ray fluorescence (XRF) spectroscopy as a magic bullet to discern tainted drywall. The theory was that any board with a strontium level higher than 1200 ppm (or mg/kg) would be tainted, and given the ease of using an XRF gun to make this measurement, XRF would be the way to go.
Then, the drywall test results from Lawrence Berkeley National Labs came in...
One sample, from Taian Taishan put out 185.14µg/m2/hr of hydrogen sulfide, and was rated as the second worst tested. But, its strontium content was a mere 273 mg/kg. Then there's a super-clean American board with no measurable hydrogen sulfide, with strontium at an eye-popping 2580 mg/kg.
How about one of the lowest emitting Chinese samples tested, with virtually unmeasurable sulfide emissions, and an astounding 5890 mg/kg of strontium?
Strontium APPEARED to be a marker for high sulfide, based on preliminary work, but it now seems as if the deck was stacked. Perhaps, board from particular mines with high strontium and high sulfur just happened to occur in many of the first homes tested.
I'm also inclined to believe that negative findings were suppressed. I wonder how long it will take for XRF instrument manufacturers to remove tainted drywall references from their websites—or at least acknowledge that XRF alone is not definitive?
Keep track right here:
Right now, the best inspection method is still non-destructive evaluation, looking for signs of tainted drywall (corrosion to wires and HVAC components, usually accompanied by odor).Read the complete article.