Evaluation of a New Solid Sorbent Sampler for Alveolar Methylene Chloride Used in Tandem with a Bag for Sampling Alveolar Carbon Monoxide

Abstract

A method for sampling and analysis of methylene chloride and carbon monoxide in alveolar air is described. The method employs a three-section bed of charcoal cloth sorbent for the determination of methylene chloride concentrations and a bag downstream of the solid sorbent sampler for determination of carbon monoxide concentrations. The method was evaluated in a study to assess the level of exposure to and uptake of methylene chloride by 14 furniture strippers. Alveolar breath samples obtained from these workers were analyzed for methylene chloride and carbon monoxide. Venous blood samples also were obtained from the furniture strippers and analyzed for methylene chloride and carboxyhemoglobin.

All methylene chloride samples were analyzed by gas chromatography with flame ionization detection. Breath carbon monoxide was analyzed using an electrochemical detector (Ecolyzer). Blood carboxyhemoglobin levels were determined with a CO-Oximeter. The accuracy of the breath sampling and analytical procedure was assessed by comparing the alveolar breath methylene chloride and carbon monoxide concentrations to venous blood concentrations of methylene chloride and carboxyhemoglobin, respectively. Linear regression analysis showed that the blood and breath concentrations of methylene chloride were reasonably correlated (r = 0.87), with a standard error of estimation of 1.37 mg/L (even including two extreme outliers in the data analysis). An in vivo blood:gas partition coefficient of 16.7 for methylene chloride was computed from the blood:breath concentration data (excluding the two extreme outliers). Breath carbon monoxide measurements were not as well correlated with blood carboxyhemoglobin (r = 0.84) as historically expected, primarily due to two outlying data points. The standard error of the estimate was also relatively large—1.89 percent carboxyhemoglobin. However, the slope of the linear regression equation relating blood carboxyhemoglobin to breath carbon monoxide was comparable to previously reported results. This study has demonstrated that monitoring of these analytes in alveolar breath may be a useful alternative to monitoring them in blood. Recommendations for improvements to the breath and blood sampling and analytical procedures are also given.