Investigation of health effects of hydrogen sulfide from a geothermal source

Little is known about health effects from chronic exposure to hydrogen sulfide (H2S). The city of Rotorua, New Zealand, is exposed to H2S by virtue of its location over a geothermal field. In this study, the authors classified areas within Rotorua as high-, medium, or low-H2S exposure areas. Using 1993-1996 morbidity data, standardized incidence ratios were calculated for neurological, respiratory, and cardiovascular effects. Poisson regression analysis was used to confirm results. Results showed exposure-response trends, particularly for nervous system diseases, but also for respiratory and cardiovascular diseases. Data on confounders were limited to age, ethnicity, and gender. The H2S exposure assessment had limitations. Assumptions were that recent exposure represented long-term exposure and that an individual's entire exposure was received at home. The results of this study strengthen the suggestion that there are chronic health effects from H2S exposure. Further investigation is warranted.