Table 2.
Comparison of the Known Effects of H2S Exposure to the Theoretical Equivalent Plasma Sulfide Concentration Assuming Equilibration Across Alveolar Membranes and No Blood or Tissue Metabolism
| Ambient H2S (ppm) | Equivalent total plasma sulfide (μM)a | Effects |
|---|---|---|
| 0.01–0.3 | 0.004–0.1 | Threshold for detection |
| 1–3 | 0.4–1 | Offensive odor, headaches |
| 10 | 4.5 | 8-hour occupational exposure limit in Alberta, Canada |
| 15 | 6.7 | 15 minute exposure limit in Alberta, Canada |
| 20–50 | 9–22 | Eye and lung irritation |
| 100 | 45 | Olfactory paralysis |
| 250–500 | 112–225 | Pulmonary edema |
| 500 | 225 | Sudden unconsciousness (“knockdown”), death within 4- to 8-hours |
| 1000 | 450 | Immediate collapse, breathing ceases within several breaths |
This table shows that the majority of plasma and tissue H2S concentrations reported in the literature (20–300 μM) would range from noxious to fatal and all would be malodorous.
All except equivalent total plasma sulfide column modified from Guidotti (22). Equivalent plasma sulfide is the theoretical sulfide concentration in plasma calculated after Whitfield et al. (76) (supplemental information) with the following assumptions: 1) H2S freely equilibrates across the alveolar membranes (26, 71), 2) Henry's Law constant for H2S at 37°C and 140 mM NaCl is 0.0649 M·atm−1 (12), 3) 20% of total sulfide exists as H2S gas (52), and 4) there is no H2S metabolism in blood or tissues. Table modified from Olson (55), with permission.