All-Cause Mortality and Hydrogen Sulfide Emission from Geothermal Power Plant: A Population Based Case-Crossover Study

BACKGROUND: To study the association of short-term increases in the traffic related pollutants nitrogen dioxide (NO₂), ozone (O₃), particulate matter (PM₁₀), sulfur dioxide (SO₂), and in particular, the geothermal source specific hydrogen sulfide (H₂S), with mortality.

METHODS: Daily mortality were obtained from the National Cause-of-Death Registry, Statistics Iceland and data on NO₂, O₃, PM₁₀, SO₂, and H₂S concentrations were obtained from the Environment Agency of Iceland for 2003 to 2009. A time‑stratified case‑crossover design was used to estimate the possible effect of short-term exposure of air pollution and mortality. We stratified by season, gender, and age (<80 and 80≥ years).

RESULTS: The inter-quartile range (IQR) of the 24‑hour concentration levels of NO₂, O₃, PM₁₀, SO₂, and H₂S over the study period was 17 μg/m³, 20 μg/m³, 13 μg/m³, 2 μg/m³, 3 μg/m³, respectively. For every IQR increase in 24-hour concentrations of H₂S, a significant association was found with non-accidental mortality during the summer months of May-November at lag 1 and 2 (5.05%, CI: 0.61-9.68% and 5.09%, CI: 0.44-9.97%), among the elderly at lag 0 and 1 (1.94%, CI: 0.12-1.04% and 1.99%, CI: 0.21- 1.04%), and among males at lag 1 (2.26%, CI: 0.23-4.33%). No statistical association was found between H₂S concentration levels and cardiovascular mortality. Other pollutants did not show increase or consistent patterns of ORs.

CONCLUSIONS: The results suggest that ambient H₂S air pollution may increase non-accidental mortality, although multiple comparisons have to be considered in our study. Traffic related pollutants were not associated with mortality in Reykjavik.