BOX 3-1ODOR THRESHOLD FOR SULFUR MUSTARD AND LEWISITE: COMPARISON WITH TISSUE DAMAGE THRESHOLDS

Even when enough agent had broken through their gas mask canisters to produce symptoms, chamber test subjects may not have noticed it, at least by odor. The odor threshold for sulfur mustard is reported to be about 0.6 mg/m³, and the median concentration of Lewisite detectable by odor is reported to be 14 to 23 mg/m³ (OSRD, 1946). However, both agents have effects on the eye and respiratory tract at lower concentrations (Papirmeister et al., 1991; Urbanetti, 1987). For example, sulfur mustard exposure at a concentration of 0.5 mg/m³ for 30 minutes (15 Ct) would result in both respiratory and eye symptoms (see Table 3-4). For Lewisite, such irritating effects are reported to be noticeable at concentrations estimated to be as low as 6 to 8 mg/m³ (Papirmeister et al., 1991; Urbanetti, 1987). Thus, for sulfur mustard exposures at 0.5 mg/m³, an exposure of only about 25 minutes (12.5 Ct) could be expected to cause eye and respiratory tract symptoms without the subject being aware of the exposure, at least by odor.