Assessing the biological reactivity of organic compounds on volcanic ash: implications for human health hazard

Exposure to volcanic ash is a long-standing health concern for people living near active volcanoes and in distal urban
areas. During transport and deposition, ash is subjected to various physicochemical processes that may change its surface
composition and, consequently, bioreactivity. One such process is the interaction with anthropogenic pollutants; however,
the potential for adsorbed, deleterious organic compounds to directly impact human health is unknown. We use an in vitro
bioanalytical approach to screen for the presence of organic compounds of toxicological concern on ash surfaces and assess
their biological potency. These compounds include polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzop-
dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dlPCBs). Analysis of ash collected in or
near urbanised areas at five active volcanoes across the world (Etna, Italy; Fuego, Guatemala; Kelud, Indonesia; Sakurajima,
Japan; Tungurahua, Ecuador) using the bioassay inferred the presence of such compounds on all samples. A relatively low
response to PCDD/Fs and the absence of a dlPCBs response in the bioassay suggest that the measured activity is dominated
by PAHs and PAH-like compounds. This study is the first to demonstrate a biological potency of organic pollutants associated
with volcanic ash particles. According to our estimations, they are present in quantities below recommended exposure
limits and likely pose a low direct concern for human health.