The health risks of inhaling volcanic ash are still largely unknown, as is the health benefit of reducing exposure through respiratory protection and other interventions. The lack of evidence is primarily due to the challenges of conducting clinical trials and epidemiological surveys in crisis conditions, as well as the difficulties in following cohorts over decades to determine chronic disease risk. This risk is of particular concern at volcanoes which produce crystalline silica in lava domes [9], where eruptions may continue, in phases, over years or decades.

The HIVE project was aiming to conduct a clinical trial of the benefits of mask wearing, in ashy conditions, for individuals with mild asthma. The study was to be undertaken with communities living around Sakurajima volcano, Japan, which had been erupting several times per day for the previous few years. A challenge in conducting any clinical trial in a natural setting is the variable exposure to the pollutant. In fact, the volcano stopped erupting shortly before the trial started, highlighting a major challenge of trying to conduct natural hazard-based health research.

One way to improve evidence of health impact is to have standardized measurement methodologies so that studies in different volcanic crises can be compared. The HIVE project, in association with the International Volcanic Health Hazard Network (www.ivhhn.org), produced a set of epidemiological protocols to be used in the days and months following onset of an eruption [10].

The first protocol provides a method for a basic study, tallying hospital and clinic visits of respiratory (and potentially other health) outcomes, to be conducted during or immediately following a volcanic eruption. The second protocol is for a more detailed, cross-sectional survey of individuals exposed to volcanic emissions, which may be undertaken if the basic study indicates adverse health effects.

It may also be possible to estimate the health impact of future eruptions, using scenario-based health impact assessments (HIA). The HIVE project also conducted a review of whether such HIA were possible in volcanic environments where, usually, it is hard to gather the exposure and medical data from which to calculate concentration-response functions (CRFs). The study investigated whether it was possible to use urban pollution CRFs in lieu of exposure and health data from volcanic locations, and concluded that this was the best available strategy, although there would be inherent uncertainties in the calculation [11].