Community Medicine With Recent Advances 6th Edition
Nu Alessio
Volcanic air pollution from both explosive and effusive activity can affect large populations as far as thousands of kilometers away from the source, for days to decades or even centuries. Here, we summarize key advances and prospects in the assessment of health hazards, effects, risk, and management. Recent advances include standardized ash assessment methods to characterize the multiple physicochemical characteristics that might influence toxicity; the rise of community-based air quality monitoring networks using low-cost gas and particulate sensors; the development of forecasting methods for ground-level concentrations and associated public advisories; the development of risk and impact assessment methods to explore health consequences of future eruptions; and the development of evidence-based, locally specific measures for health protection. However, it remains problematic that the health effects of many major and sometimes long-duration eruptions near large populations have gone completely unmonitored. Similarly, effects of prolonged degassing on exposed populations have received very little attention relative to explosive eruptions. Furthermore, very few studies have longitudinally followed populations chronically exposed to volcanic emissions; thus, knowledge gaps remain about whether chronic exposures can trigger development of potentially fatal diseases. Instigating such studies will be facilitated by continued co-development of standardized protocols, supporting local study teams and procuring equipment, funding, and ethical permissions. Relationship building between visiting researchers and host country academic, observatory, and agency partners is vital and can, in turn, support the effective communication of health impacts of volcanic air pollution to populations, health practitioners, and emergency managers.
Sulfur gases (in particular SO2), sulfate aerosol, and ash are the most important airborne hazards for population-scale, longer-term impacts and have been shown to affect air quality locally as well as hundreds to thousands of kilometers from source during large fissure or explosive eruptions (e.g., Schmidt et al. 2011, 2015; de Lima et al. 2012; Durant et al. 2012; Eychenne et al. 2015; Ilyinskaya et al. 2017). Many of the volatile trace elements emitted by volcanoes are classified as metal pollutants by environmental and health protection agencies (e.g., lead, zinc, arsenic, cadmium),Footnote 1 and emission rates can reach levels comparable to anthropogenic fluxes from industrialized countries (Ilyinskaya et al. 2021). Near persistently degassing volcanoes, elevated levels of metals have been reported in air, soils, surface waters, and plants (Delmelle 2003), which are common exposure sources for humans (Prss-Ustn et al. 2011), especially in areas where communities consume catchment or surface water and locally grown crops. Persistent degassing is also the source of fluoride contamination of water resources close to certain volcanoes, notably Ambrym and Tanna, Vanuatu (Cronin and Sharp 2002; Allibone et al. 2012; Webb et al. 2021). Acidified rainfall from persistent degassing can leach lead from plumbing fittings or roofing materials into roof catchment rainwater tanks (Macomber 2020). Ash deposition into water supplies can raise concentrations of fluoride and other potentially toxic elements (e.g., copper, manganese) as well as elements that impart an unpleasant taste or color to the water (Stewart et al. 2006, 2020).
In an eruption crisis, it is rare for there to be an immediate assessment of the health impact of exposure to volcanic air pollution. With limited resources, health agencies must prioritize ensuring sanitary conditions for evacuated communities and monitoring these communities for infectious disease outbreaks, as well as dealing with casualties. In lieu of data to directly measure the health impact, the physicochemical characteristics of the emissions, along with exposure concentrations and durations, may be assessed to get a first indication of whether they may be hazardous to human health.
For volcanic ash, characteristics that inform whether ash may cause harm if inhaled or ingested include particle size, particle shape, surface area, and the presence of leachable elements. Additional, specific hazards can vary according to magma composition and eruption dynamics. For lava dome-related or intermediate to felsic explosive ash samples, crystalline silica (quartz and its polymorphs) is important to quantify as it is the mineral of greatest health concern in ash due to its capacity to cause disease in industrial settings (Baxter et al. 1999; Greenberg et al. 2007). For mafic samples, reactive surface iron and associated generation of free radicals, which are implicated in respiratory diseases (Kelly 2003), can be determined (Horwell et al. 2007). Leachate analyses can determine concentrations of readily soluble elements on fresh ash particles relevant to inhalation or ingestion pathways. These methods may require adaptation for ash from hydrothermal system eruptions which typically contain fluoride in slowly soluble forms (Cronin et al. 2014; Stewart et al. 2020). Ash can also scavenge biologically potent organic pollutants from the atmosphere (Tomašek et al. 2021a). Toxicological assays can be used to assess whether the ash can trigger a biological response, which gives an indication of potential pathogenicity for humans (Damby et al. 2016).
The International Volcanic Health Hazard Network (IVHHN)Footnote 2 has developed methods and protocols for rapid, standardized screening of ash samples (Le Blond et al. 2009; Horwell 2007; Horwell et al. 2007; Stewart et al. 2020; Tomašek et al. 2021b), which have been applied during various eruption crises. Table 1 presents post-2000 studies that have determined health-relevant characteristics of ash samples and whether they have used IVHHN methods or not. The major challenges associated with ash characterization relate to timely collection of ash samples, prior capacity building and training in suitable laboratories, funding analyses, and shipping of samples, given that transportation is often disrupted during an eruption. In practice, analyses are rarely completed within the days to weeks over which acute exposures may be occurring, so cannot be relied upon to inform decision-making. Thus, in advance of future eruptions, the hazard could be informed by study of archived ash samples from historic eruptions (Hillman et al. 2012; Horwell et al. 2010b, 2017; Damby et al. 2017).
Exposure to volcanic emissions rarely occurs in clean atmospheres, raising concerns about co-exposures of volcanic emissions and existing air pollution, particularly in urban areas. Preliminary work on these combined hazards indicates that the specific mixture may be important, with a heightened pro-inflammatory response (in laboratory in vitro tests) reported for simultaneous exposure to respirable ash and diesel exhaust particles (Tomašek et al. 2016) but not for ash and complete gasoline exhaust (Tomašek et al. 2018).
Real-time monitoring of airborne gas and PM concentrations can be used as a proxy for assessing population exposure during eruptions, for persistent degassing, and for post-eruption ash resuspension episodes (Wilson et al. 2011). Indoor and outdoor measurements may be made via fixed monitors or portable sensors. Ambient air quality limits exist for airborne contaminants common to volcanic emissions such as PM10, PM2.5, and SO2, and monitoring data can be used to help alert both healthy and sensitive populations. However, air quality monitoring equipment is not installed at many volcanic locations, and installing instrumentation following eruption onset can present significant challenges (Felton et al. 2019). This can hinder agencies in making evidence-based decisions on community protection. An additional challenge to characterizing volcanic air pollution is that SO2 and PM concentrations can vary significantly over short distances and durations (Holland et al. 2020). This issue has received significant attention recently with the introduction of low-cost fixed networks and hand-held, portable sensors that augment higher accuracy but costly regulatory air quality monitoring. These low-cost PM and SO2 sensors perform reasonably well for monitoring volcanic air pollution in communities, as demonstrated during the Kīlauea 2018 eruption (Whitty et al. 2020; Crawford et al. 2021) and in Iceland (Gslason et al. 2015). Air quality forecast models can complement ambient air monitoring and now play an important role in informing the public about current and predicted levels of volcanic pollution in some locations (Barsotti 2020; Holland et al. 2020).
Post-2000 clinical and epidemiological studies conducted on communities affected by volcanic emissions are presented in Table 2. Collectively, these studies support pre-2000 findings, from studies conducted predominantly at Mount St. Helens, Soufrire Hills, and Sakurajima, that exposures to airborne volcanic emissions can exacerbate symptoms of pre-existing lung conditions (reviewed in Horwell and Baxter 2006). However, very few of these studies have followed populations longitudinally using the timeframes needed (on the order of decades) for long-latency diseases such as pneumoconioses or cancers to manifest. Further, situations that produce chronic exposure to ash are rare, with the best-documented examples being the 15-year cumulative exposure to ash from Soufrire Hills volcano, Montserrat (Baxter et al. 2014) and the eruption of Sakurajima volcano, Japan, with frequent ash exposures since the 1970s (reviewed by Hillman et al. 2012). Overall, major knowledge gaps remain about whether chronic exposures can trigger development of potentially fatal cardiorespiratory diseases and also whether chronic health effects can result from acute exposures.
The evidence base is weak on which characteristics of volcanic or other air pollution sources are responsible for the observed negative health outcomes. Routine monitoring does not cover all species of concern (e.g., metal pollutants and aerosol acidity). In the past decade, many air pollution studies in cities with traffic-related emissions have shown the importance of fine particulate matter, particularly PM2.5, in the development of certain acute and chronic health conditions (respiratory, including lung cancer, and cardiovascular, in particular) and daily mortality. A future challenge will be to determine whether this applies to volcanic PM, as the World Health Organization has concluded that these outcomes relate to geogenic as well as anthropogenic particulate exposures (World Health Organization 2013).
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