Investigation of hydrogen sulfide exposure and lung function, asthma and chronic obstructive pulmonary disease in a geothermal area of New Zealand.

Background: Results have been conflicting whether long-term ambient hydrogen sulfide (H2S) affects lung function or is a risk factor for asthma or chronic obstructive pulmonary disease (COPD). Rotorua city, New Zealand, has the world's largest population exposed to ambient H2S-from geothermal sources.

Objectives: We investigated associations of H2S with lung function, COPD and asthma in this population.

Methods: 1,204 of 1,639 study participants, aged 18-65 years during 2008-2010, provided satisfactory spirometry results. Residences, workplaces and schools over the last 30 years were geocoded. Exposures were estimated from data collected by summer and winter H2S monitoring networks across Rotorua. Four metrics for H2S exposure, representing both current and long-term (last 30 years) exposure, and also time-weighted average and peak exposures, were calculated. Departures from expected values for pre-bronchodilator lung function, calculated from prediction equations, were outcomes for linear regression models using quartiles of the H2S exposure metrics. Separate models examined participants with and without evidence of asthma or COPD, and never- and ever-smokers. Logistic regression was used to investigate associations of COPD (a post-bronchodilator FEV1/FVC < 70% of expected) and asthma (doctor-diagnosed or by FEV1 response to bronchodilator) with H2S exposure quartiles.

Results: None of the exposure metrics produced evidence of lung function decrement. The logistic regression analysis showed no evidence that long-term H2S exposure at Rotorua levels was associated with either increased COPD or asthma risk. Some results suggested that recent ambient H2S exposures were beneficially associated with lung function parameters.

Conclusions: The study found no evidence of reductions in lung function, or increased risk of COPD or asthma, from recent or long-term H2S exposure at the relatively high ambient concentrations found in Rotorua. Suggestions of improved lung function associated with recent ambient H2S exposures require confirmation in other studies.