The city of Rotorua, New Zealand is the only city in the world that is sited on an active geothermal field. At various points in the city can be found geysers, boiling mud pools, and steaming, near-boiling water pools. The Maori people, who lived here for centuries before the Europeans came to New Zealand, used the hot pools for cooking. The smell of hydrogen sulfide (H2S) gas, emitted from geothermal vents in the ground, is usually apparent to people approaching the city. However, awareness of the smell rapidly fades as people get used to it.
Rotorua now has the largest population in the world continuously exposed to levels of H2S gas. However, exposure to H2S in Rotorua is not uniform. Some areas receive much more H2S exposure than others and an individual person's actual exposure will depend on where they have lived, where they have worked or studied, and their movement patterns.
H2S is well-known to be highly toxic at high exposures, but it is unknown whether long-term, low-level exposures to this gas (as in Rotorua) cause any health effects. Around the world, many communities living near paper mills, animal processing facilities, oil or gas refineries, and sewage or wastewater treatment plants are substantially exposed to H2S, and there is uncertainty about the most appropriate air quality standards for this gas. Rotorua, because of its relatively large population and relatively high H2S exposures is widely regarded as the most appropriate place to investigate this important issue. Our study is taking advantage of this "natural experiment" to obtain information that will be very important both to Rotorua and to the other H2S-exposed communities throughout the world.
This is an international collaborative study being carried out by investigators from the University of Otago's Wellington School of Medicine and Health Sciences and from the University of California and Stanford University in the United States.
Over the course of 3 years, 1,800 Rotorua residents, aged 18-65, will participate in our study. Each participant will answer questions in a questionnaire and undergo a series of tests to check the functioning of their eyes, their lungs, and their nervous system. We will also check for evidence of diabetes and whether participants have allergic reactions to several common substances.
As well as testing study participants, we will be mapping in some detail the distribution of hydrogen sulfide concentrations across the geothermal field and how these concentrations vary seasonally and across the course of a day. We will link this information with the other details obtained from participants by questionnaire on places where they have lived, worked and studied in Rotorua. That way, we will be able to create a longitudinal H2S exposure profile for each resident.
In the final step, we will carry out complex statistical analyses of the health information we obtain from participants to find out whether the functioning of their eyes, lungs, or nervous systems appears to be affected by their H2S exposures. Results of the study will eventually be published in peer-reviewed scientific and medical journals. However, all results will be presented as statistical summaries so that no individual participant can in any way be identified.