Is Ambient Hydrogen Sulfide a Risk to Human Health?

Abstract

Hydrogen sulfide gas (H 2 S) has an obnoxious odor at very low concentrations and is thus responsible for considerable annoyance and concern in communities near H 2 S sources such as wastewater treatment plants. Human health data, however, do not clearly indicate that ambient concentrations (less than 1 ppm) are hazardous. Several regulatory or scientific organizations have derived standards or guidelines for H 2 S exposure for different populations, and these values vary considerably. We examine here some of the reasons for the differences, and suggest that community exposures may best be evaluated in light of the acute minimal risk level of 70 ppb derived by the Agency for Toxic Substances and Disease Registry (ATSDR).

Use of Nasal Pathology in the Derivation of Inhalation Toxicity Values for Hydrogen Sulfide

“…The RfC of 1.5 ppb (2.1 µg/m 3 ) was subsequently determined by applying an aggregate uncertainty factor of 300 (representing a factor of 3 for interspecies extrapolation, 10 for interhuman variability, and 10 for subchronic exposure) to the NOAEL HEC . 19 Some individuals 20 have criticized the US EPA derivation of the RfC questioning whether effects seen by Brenneman et al 16 at the LOAEL should be considered adverse, since the effects seen in this study were likely reversible. H 2 S-induced olfactory neuron loss in rodents has been considered an adverse effect by other organizations, including the US National Academies in their derivation of occupational exposure limits for submariners.…”

“…Additional concerns regarding the appropriateness of the time and dosimetric adjustments used by the agency have also been raised by critics of the RfC. 20…”