BIOLOGICAL MARKERS OF EXPOSURE TO SO2 - S-SULFONATES IN NASAL LAVAGE

S-sulfonate levels were measured in the nasal lavage (NAL) fluid of hu mans exposed to sulfur dioxide as a potential biological marker of exp osure. These levels were determined by treating NAL fluid protein with cyanide to cleave the S-S linkage and release the sulfite. The cyanol ytically released sulfite was measured by ion chromatography. In two e xperiments, humans were exposed to air or 1 PPM SO2 for 10 minute, and to air or 7 ppm SO2 for 20 minutes and lavaged immediately after expo sure. Releasable sulfite levels in NAL fluid were 1.06 +/- 0.24 and 2. 61 +/- 0.55 mug SO3=/mg protein, respectively (mean +/- SE, n = 5), fo r the first experiment, and 1.16 +/- 0.37 and 4.91 +/- 0.76 mug SO3=/m g protein, respectively (mean +/- SE, n = 8), for the second. The subj ects in the former study were persons with asthma. In both experiments , S-sulfonate levels were statistically elevated in the exposed group compared with the control groups (p < 0.05, paired t-test). The same i ndividuals in the second experiment received five additional 20-minute exposures to 7 ppm SO2 every other day, for a total of six exposures. NAL fluid taken at the conclusion of the final exposure had releasabl e sulfite levels of 4.99 +/- 1.36 mug SO3=/Mg protein; these levels we re statistically elevated relative to controls bw were not elevated re lative to the 1-day exposure (mean +/- SE, n = 8). The lack of accumul ation of S-sulfonates after 6 days of short-term exposure suggests cle arance of these compounds from the nasal passage within 24 hours. The levels of S-sulfonates observed in NAL fluid in this study are almost three orders of magnitude higher than those measured in plasma followi ng similar SO2 exposures. Measurement of S-sulfonates in the nasal pas sage may be an effective short-term biomarker of exposure to SO2.