Increased respiratory morbidity associated with exposure to a mature volcanic plume from a large Icelandic fissure eruption

Abstract

The 2014-15 Holuhraun eruption in Iceland was the largest fissure eruption in over 200 years, emitting prodigious amounts of gas and particulate matter into the troposphere. Reykjavík, the capital area of Iceland (250 km from eruption site) was exposed to air pollution events from advection of (i) a relatively young and chemically primitive volcanic plume with a high sulphur dioxide gas (SO₂) to sulphate PM (SO₄^2-) ratio, and (ii) an older and chemically mature volcanic plume with a low SO₂/SO₄^2- ratio. Whereas the advection and air pollution caused by the primitive plume were successfully forecast and forewarned in public advisories, the mature plume was not. Here, we show that exposure to the mature plume is associated with an increase in register-measured health care utilisation for respiratory disease by 23% (95% CI 19.7-27.4%) and for asthma medication dispensing by 19.3% (95% CI 9.6-29.1%). Absence of public advisories is associated with increases in visits to primary care medical doctors and to the hospital emergency department. We recommend that operational response to volcanic air pollution considers both primitive and mature types of plumes.

Fig. 1. Dispersion of primitive and mature plumes.

The ground-level concentrations of (a) SO₂ and (b) SO₄²⁻ (units: µg/m³) from Holuhraun eruption, simulated for 20 September 2014. Wind vectors (black arrows) are used to show the plume transport direction. Black square: eruption site. Blue circle: Reykjavík (area approximate). The primitive plume (high mass ratio of SO₂ to SO₄²⁻) is dispersed predominantly to the south-east of the eruption site. The mature plume (high mass ratio of SO₄²⁻ to SO₂) has returned back from Europe and is inundating the Reykjavík capital area from the south. Figure is modified from Ilyinskaya et al.. See Supplementary Movie 1 for animation.

Fig. 2. Mature plume exposure and respiratory health outcomes.

Associations between mature plume exposure and respiratory health outcomes from regression analysis for (a, d) AMD, n = 48,014 individuals; (b, e) PCMD, n = 110,806 individuals; (c, f) HED, n = 20,725 individuals. a–c Unadjusted results. d–f Results adjusted for SO₂. Results are reported as percent change in RR with error bars showing the 95% confidence intervals. Results are shown for different age groups (all age groups combined; <18 years; 18–64 years; >64 years) for several lag combinations; n of individuals in each age group is shown on the x-axis. Lag 0 = the day of the exposure, lag 1 = one day after the exposure, lag 2 = two days after the exposure, lag 0–2 = mean of lag 0, 1, and 2, lag 2–3 = mean of lag 2 and 3, lag 2–4 = mean of lag 2, 3 and 4. On (c, f) the association between exposure and HED visits are shown for combinations of lag 2–4 in adults and elderly; in children, combinations of lag 0–2 are shown as there was no significant change for other age groups.

Fig. 3. Comparison of mature and primitive plumes.

Associations at different time lag between exposure to mature and primitive plumes (where lag 0 is the day of the exposure, lag 1 is one day after the exposure, and so on) for (a) AMD (n = 48,014 individuals with dispensings), and (b–d) respiratory diagnosis categories in PCMD (ICD codes and n of individuals in brackets). b Infectious respiratory diseases (J00–J22, n = 89,406 individuals); c Chronic bronchitis and sinusitis (J30–J39, n = 8706 individuals); d Asthma/chronic obstructive pulmonary disease (COPD) (J44–45, n = 8065 individuals). Results reported as percent change in RR with error bars showing 95% confidence intervals from a two-pollutant distributed lag regression model.

Fig. 4. Mature plume exposure and respiratory health outcomes on no-advisory days.

Associations between mature plume exposure and respiratory health outcomes from regression models on days when no public advisories were issued for (a) AMD, n = 48,014 individuals; b PCMD, n = 110,806 individuals; c HED, n = 20,725 individuals. Results are reported as percent change in RR with error bars showing the 95% confidence intervals. Results are shown for different age groups (all age groups combined; <18 years; 18–64 years; >64 years) for several lag combinations; n of individuals in each age group is shown on the x-axis. Lag 0 = the day of the exposure, Lag 1 = one day after the exposure, Lag 0 = the day of the exposure, lag 1 = one day after the exposure, lag 2 = two days after the exposure, lag 0–2 = mean of lag 0, 1, and 2, lag 2–3 = mean of lag 2 and 3, lag 2–4 = mean of lag 2, 3 and 4. On (c), the association between exposure and HED visits are shown for combinations of lag 2–4 in adults and elderly; in children, combinations of lag 0–2 are shown as there was no significant change for other age groups.

Fig. 5. Self-reported symptoms in Reykjavík.

The figure shows the cumulative number of responses to the IMO online questionnaire. The responses are separated into those recorded on days impacted by a primitive plume (always associated with a public advisory), by a mature plume associated with public advisories, and by a mature plume not associated with a public advisory. ‘Other symptoms’ were recorded in free-form text box and included, e.g., headaches and increased asthma symptoms.