Volume 39, Issue 1 (January 2011)
X-Ray Fluorescence in Corrosive Drywall Investigations: Strontium Levels in Several Corrosive and Non-Corrosive Drywalls and Effects of Drywall Finish on XRF Strontium Detection
A U.S. building boom in the 1990s and 2000s resulted in imports of drywall from foreign sources particularly from China. Some of the homeowners began experiencing problems with homes built during this time. A number of investigations found that the problems could be related to imported Chinese drywall. Limited testing indicated the problem drywall contained elevated levels of strontium (Sr) and suggested that portable X-ray fluorescence (XRF) was a useful screening tool to identify potentially corrosive drywall from non-corrosive drywall. Some investigators suggested that XRF could be used to detect corrosive drywall and differentiate between non-corrosive drywall in a residence by measuring strontium levels through the wall finish. The first part of this paper presents selected XRF data obtained from research of certified gypsum standards and various corrosive and non-corrosive drywalls. The second part of this paper presents XRF data obtained from field samples exhibiting different wall finishes. The results show that although strontium levels in corrosive drywalls are typically higher than some of the non-corrosive drywalls, there are number of non-corrosive domestic and imported drywalls that have strontium levels above the 1200 parts per million (ppm) level referenced in the Consumer Product Safety Commission report (Saltzman, L. E., U.S. Consumer Product Safety Commission Staff Summary of Contractor’s Indoor Air Quality Assessment of Homes Containing Chinese Drywall, CPSC Division of Health Sciences, 2009). The results also document some corrosive drywalls with strontium levels below 600 ppm. The results from the evaluation of the impact of the drywall finish indicate that it can reduce the detected strontium value by over 90 %. The combined results indicate that false positives and false negatives can be readily encountered, thus potentially reducing the reliability of these approaches. The results indicate that the investigators should use caution in interpreting the results from the XRF analysis and should seek corroborating data to verify the results.