| Abstract: | Follow-up tests were performed in 25 complaint homes previously investigated by the Wisconsin Division of Health to determine ambient formaldehyde concentrations. Four collection methods were compared in each home: (1) midget impingers containing double-distilled water and immersed in ice baths, (2) midget impingers containing 1% sodium bisulfite solution and immersed in ice baths, (3) midget impingers containing cold 1% sodium bisulfite solution (temperature not maintained with an ice bath), and (4) a refrigerated, complete sampling unit developed at Lawrence Berkley Laboratory which utilized double-distilled water as a collection medium. Air was drawn through the midget impingers using personal sampling pumps. All four types of sampling trains were operated simultaneously in a bedroom, collecting specimens within an area of about 4 ft2, while in the kitchen or living room, all sampling trains except for the impingers containing 1% sodium bisulfite solution and immersed in ice baths were operated together. Analysis of variance indicated that the three samples collected using midget impingers and personal sampling pumps gave similar results. All specimens collected in water were analyzed using both the chromotropic acid and pararosaniline analytical methods. Quality control specimens prepared in the laboratory showed excellent agreement between the two methods; however, field specimens through which air had been drawn were assigned lower values using the pararosaniline method. Special precautions were taken to ensure that specimens collected in water were not contaminated with sodium bisulfite, a serious interference for the pararosaniline test. To rule out the possibility that specimens deteriorated between analysis, test results from each method were confirmed by repeating each method for selected sets of specimens for a period of several days. It was hypothesized that some source of interference was present in the field specimens which affected the pararosaniline analysis. Statistical tests were applied to determine whether the observed discrepancy between the analytical methods was consistent and a regression model was employed to determine whether any of the other environmental parameters measured during sample collection was associated with the discrepancy. |
