The International Volcanic Health Hazard Network (IVHHN; www.ivhhn.org) is an interdisciplinary organization which coordinates research and provides advice on volcanic health hazards and impacts.

The field of research on the human health hazards and impacts of volcanic eruptions dates to 1980 with the eruption of Mount St. Helens (Baxter et al., 1981; Buist and Bernstein, 1986; Horwell and Baxter, 2006). The principal concerns revolved around the respirable crystalline silica (RCS) content of volcanic ash, which blanketed a vast swath of the north-western United States, and its potential to cause the fibrotic lung disease silicosis in exposed communities. A well-known occupational hazard for mine and quarry workers exposed to natural mineral dusts, the consequences of 24-h exposure to the airborne ash, for children and the public, in general, required urgent appraisal to allay panic amongst the million people living and working in the affected areas.

State and federal agencies were immediately mobilised to respond to the emergency and the later recovery phases of the disaster, in collaboration with academic and other research groups. The public health component of this vast undertaking involved many disciplines and was summarised in a volume edited by Buist and Bernstein (1986). The research at Mount St. Helens was reassuring in resolving the health concerns at the time, but also highlighted the future need to systematically identify and quantify the hazards and provide informed advice on mitigation measures because the mineralogy of volcanic ash, along with its respiratory hazard, varies with every eruption.

The Mount St. Helens response was, without doubt, enabled by the financial resources and expertise in the United States. Indeed, the next eruptions to receive a concerted (or any) health response were related to other high-income countries: Sakurajima volcano, Japan, starting in the 1980s (reviewed by Hillman et al., 2012), and Soufrière Hills volcano, Montserrat, a British Overseas Territory, in the late 1990s (reviewed by Baxter et al., 2014), where RCS concentrations were substantially higher than at Mount St. Helens, presenting a significant silicosis risk for the islanders that required special mitigation measures (Hincks et al., 2006). The UK government had the legal responsibility for the health and safety of the Montserrat population and funded the health research as well as supporting the island’s disaster management. Apart from these events, individual research studies have been conducted at various volcanoes (reviewed in Horwell and Baxter, 2006; Mueller et al., 2020b; Stewart et al., 2022), but coordinated, interdisciplinary health responses have been rare, leaving communities both proximal and distal to volcanically active areas uninformed about exposure to airborne gas and ash emissions - and other volcanic hazards - and at risk.

Interdisciplinary responses that inform hazard assessments are essential because critical public health decisions need to be made early in the exposure timeframe. Rapid geochemical and toxicological assessments can identify hazardous characteristics of volcanic ash (Horwell et al., 2013) that could otherwise take years or decades to manifest as respiratory or other chronic diseases. Immediate exposure assessment through ambient air quality monitoring of particles and gases can provide essential data for epidemiological and clinical studies, linking acute symptoms and future diseases to the correct exposure source (Mueller et al., 2020b; Whitty et al., 2020). Personal monitoring of high-risk individuals, such as outdoor workers, can justify implementation of mitigating measures to reduce exposures. Yet, often, experts in these different areas of environmental health sciences are not working together routinely prior to an eruption. Additionally, these experts may be inexperienced in the collection and analysis of volcanic materials.

IVHHN was launched 20 years ago, in February 2003, via a Leverhulme Trust grant (led by authors Sparks & Horwell), to bring together scientists and practitioners who were working globally to protect the health of communities during volcanic eruptions (Pickrell, 2003). Offering a forum for discussion and collaboration, IVHHN included volcanologists, clinicians, public and environmental health specialists, epidemiologists, toxicologists, and exposure scientists. A launch workshop at the third Cities on Volcanoes Conference in Hawaii (July 2003) brought together the members for the first time.

By late 2003, IVHHN expanded its remit to provide public information and scientific protocols for use during eruption crises, with a focus on the health impact of volcanic airborne emissions. In the context of the UK government, requiring evidence-based information and standardized methods for ash analysis during the Soufrière Hills eruption, a workshop was held in November 2003, led by Horwell, Baxter, and Sparks and attended by UK experts in ash and RCS analysis and exposure assessment. The workshop instigated production of two pamphlets on preparedness for ashfall and the health impacts of volcanic ash (https://www.ivhhn.org/ash-pamphlets) (Figure 1), which were translated into several languages. Protocols were also produced on how to collect ash for analyses and methods for particle size analysis (https://www.ivhhn.org/guidelines#ash-collection). The IVHHN website was developed to inform researchers, agencies, and the public about the availability of these products and encourage global use.

Since 2003, IVHHN has evolved into an international organization that provides public information and advises governments on preparing for, and responding to, the many health-related consequences of eruptions (see review in Baxter and Horwell, 2015). As a Commission of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), IVHHN took on a management structure, with Co-Directors (Elias, Stewart, and Damby from 2017 and, in 2021, Ilyinskaya) and an early career representative (Tomašek from 2021) with Horwell as Director of IVHHN since its inception. Regular meetings and workshops identify knowledge gaps, discuss real-world experiences, and set goals and targets for progress, notably protocols and analytical methods and educational materials that enable local agencies and the public to prepare to mitigate health risks.

Reflecting on 20 years of progress, much has been done to grow IVHHN as an internationally respected organization. IVHHN now has five primary focus areas: 1) develop and implement standardized physicochemical and epidemiological protocols for use during eruptions; 2) prepare for and help coordinate health responses in advance of, and during, eruption crises; 3) compile and distil existing knowledge on volcanic crisis health management; 4) foster health hazard and risk communication, including production of public-facing audio-visual and printable informational products; 5) support the exchange of information on the health impacts of volcanic emissions including convening conference sessions and workshops. Critically, all products and advice are evidence-based, with information derived from scientific research and past eruption-response experiences.

IVHHN’s existence has helped to identify critical gaps in knowledge and highlight the rarity of volcanic emissions health impact assessments (Mueller et al., 2020b). As such, IVHHN has followed a precautionary approach, emphasizing preparedness and communication, while providing tools to build a robust evidence base of hazards and impacts from eruptions globally. Despite the constraints of being a largely unfunded endeavour (since 2006), we remain committed to addressing these challenges through worldwide, interdisciplinary, operational, and research collaborations.