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Re: Inhaling volcanic ash on Montserrat

Dear Editor

I have only recently had an opportunity to see the OEM online abstract of this paper[1] but I did see the unpublished original version in the Health Department archives whilst I was Chief Medical Officer on Montserrat from late 1998 to late 2000.

My first comment is that this survey of schoolchildren was carried out in February 1998 and yet it has only now been published in a scientific journal more than 5 years later. This is of some relevance since the highlights of the paper published in the BMJ on 12 April 2003 [2] comment that since the time of the first eruption in 1995 the children “have had an excess of respiratory illness” and that “few were receiving recommended appropriate treatment”. This statement is misleading. It may well have been true up until 1998 but it is certainly not true for the period beyond that time. The reality of children more heavily exposed to heavy ash falls experiencing more wheeze and asthma than those less exposed has been convincingly demonstrated in the paper. However most of the children living on Montserrat since 1998 have been in the north of the island and only intermittently exposed to relatively lighter falls of ash.

My own clinical experience and that of visiting paediatricians is that the prevalence of asthma and asthma like symptoms is no higher than other parts of the Caribbean and may even be lower. A survey carried out by the Health Department of resident children in June 2000 [3] found the prevalence of “wheeze ever” in all schoolchildren to be 22.7% (compared with 27.7% in all children in the 1998 survey). This survey also found the prevalence of “asthma ever” to be 13.8% compared with 9.8% in the 1998 survey. The 2000 survey found no association with exposure to higher ash levels but it must be recognised that in 2000 very few children were exposed to anything like the levels experienced between 1995 and 1998.The treatment that has been given to children experiencing asthma has been along conventional lines as recommended by paediatricians in the United Kingdom.

Further evidence of the lack of any continuing serious adverse effects of volcanic ash on respiratory health comes from a one year survey of all clinic attendances by all age groups on Montserrat during 1999.. This survey found no correlation between weekly clinic attendances for respiratory symptoms and episodes of ash venting or increased ground ash levels. A further study by the Institute of Occupational Health in Edinburgh [4] carried out in October 2000 found a prevalence of asthma of 8.1% and of chronic bronchitis of 6.7% in a group of 421 workers on Montserrat occupationally exposed to high levels of ash. A subsequent survey of 440 Montserratians relocated to the United Kingdom [5] found a prevalence of 14.2% for asthma and 14.0% for chronic bronchitis.

My second and most important comment is that by far the most important adverse effects of the volcanic eruptions relate to the social and economic disruption and its effect on the life and health of the people. In my paper in the West Indian Medical Journal [3] I have described a change in population demographics with a fall in the productive group and a rise in more dependent people, loss of older female family providers, more elderly people becoming dependant on the state, increases in anxiety and depression in the elderly, changes in the diet and increasing obesity in children and increases in domestic violence.

One of my concerns whilst on Montserrat was that most of the academic input following the disaster was put into vulcanology and respiratory health. Some valuable findings have come out of this work but no formal academic input was made into other more serious matters, especially on the health side.

Fortunately the outstanding health problems of Montserat have been addressed by the health department with the help of the UK Department for International Development and the Pan American Health Organisation but much remains to be done. The importance of this was dramatically emphasised with the reports of a massive dome collapse on 12/13th July and ash venting which uncharacteristically smothered the inhabited north of the island. Such a big eruption could easily demoralise some of those not already traumatised. However we can expect the resilience of the remaining population of around 4500 people to carry them through yet again in spite of all the social and economic disruption which has had a far more profound influence on their health than the purely physical effect of the ash.

References

(1) L Forbes, D Jarvis, J Potts, and P J Baxter. Volcanic ash and respiratory symptoms in children on the island of Montserrat, British West Indies. Occup Environ Med 2003;60:207-211.

(2) BMJ family highlights. Inhaling volcanic ash effects breathing. BMJ2003;326:785.

(3) Avery JG The Aftermath of a Disaster. Recovery Following the Volcanic Eruptions in Montserrat, West Indies. West Indian Medical Journal; in press.

(4) Cowie HA, Searl A, Ritchie PJ, Graham MK, Swales C et al. A health Survey of Workers on the Island of Montserrat. Research Report.TM/02/02. Edinburgh: Institute of Occupational Medicine; 2002

(5) Cowie HA, Searl A, Ritchie PJ, Graham MK, Hutchison PA, Pilkington A. A Health Survey of Montserratians Relocated to the United Kingdom. Research Report TM 01/07. Edinburgh: Institute of Occupational Medicine; 2001.

Send letter to journal:
Re: Respiratory effects of volcanic emissions

Dear Editor

Although at least 455 million people worldwide live within potential exposure range of a volcano active within recorded history,[1] surprisingly little primary epidemiological research on health effects of volcanic emissions has been published. The research by Forbes et al.[2] on the respiratory effects of the eruptions in Montserrat is therefore very welcome. However, more studies are needed to determine the transferability of results to volcanic emissions elsewhere. There may be important differences between volcanoes and between events from the same volcano in terms of eruption pattern, gaseous emissions, base composition of ash (e.g. cristobalite concentrations), compounds adsorbed onto ash particles (which may be volcanic in origin or derived from other pollution sources), the percentage of particles small enough to be respirable and toxicological activity.[3] For example, most respirable ash in Montserrat has originated from pyroclastic flows, with cristobalite concentrations measured at 20.1%, but Montserrat ash derived from phreatic explosions has lower cristobalite concentrations (8.6%)[4] and these are higher than the 4.2% quoted for ash from the United States Mount St Helens eruptions in 1980.[5] The Soufriere Hills volcano in Montserrat has produced unusually frequent pyroclastic flows, resulting in high exposures to fine ash even in residential areas distant from the volcano but population exposure to volcanic gases such as sulphur dioxide has been low. This contrasts with volcanoes such as Sakurajima, Japan where frequent ashfalls have been accompanied by SO2 emissions[6] or Kilauea, Hawaii where emissions are predominantly SO2.[7]

Studies of health effects of volcanic ash exposure may help elucidate mechanisms relevant to action of anthropogenic pollution. For example, it remains unclear whether concentration or composition of anthropogenic particulate air pollution is more important for respiratory health effects.[8] Montserrat children demonstrated increased levels of wheeze and bronchial hyperreactivity following repeated exposures to high concentrations of respirable dust, with elevated cristobalite content but low soluble acid content and low in vitro[9] and in vivo[4] bioreactivity in toxicological studies. Long-term exposure to high levels of cristobalite might be expected to be associated with reductions in lung volumes, not presented in this study, rather than with increased bronchial reactivity. This raises the possibility that the effect of Montserrat ash on bronchial reactivity may have been related to the quantity rather than the quality of the particulates.

Finally, it is unclear whether a peak flow meter or hand-held spirometer was used in the Montserrat study. A hand-held spirometer is suggested as the ideal measuring tool for field investigations into respiratory effects of volcanic emissions in children. It can be used reliably in children as young as 5 years, gives a range of readings including FEV1, which has better baseline reproducibility than peak flow[10] and lung volumes, which may be particularly useful if follow-up studies into long-term effects are planned.

References

(1) Small D, Naumann T. The global distribution of human population and recent volcanism. Environmental Hazards 2001; 3:93-109.

[2] Forbes L, Jarvis D, Potts J, Baxter PJ. Volcanic ash and respiratory symptoms in children in the island of Montserrat, British West Indies. Occup Environ Med 2003; 60:207-211.

[3] Vallyathan V, Robinson V. Comparative in vitro cytotoxicity of volcanic ashes from Mount St. Helens, El Chichón, and Galunggung. Journal of Toxicology and Environmental Health 1984; 14:641-654.

[4] Housley DG, Berube KA, Jones TP et al. Pulmonary epithelial response in the rat lung to instilled Montserrat respirable dusts and their major mineral components. Occup Environ Med 2002; 59(7):466-472.

[5] Baxter PJ, Bonadonna C, Dupree R et al. Cristobalite in volcanic ash of the Soufriere Hills Volcano, Montserrat, British West Indies. Science 1999; 283:1142-1145.

[6] Uda H, Akiba S, Hatano H, Shinkura R. Asthma-Like Disease in the Children Living in the Neighborhood of Mt. Sakurajima. Journal of Epidemiology 1999; 9(1):27-31.

[7] Mannino DM, Ruben S, Holschuh FC et al. Emergency Department Visits and Hospitalizations for Respiratory Disease on the Island of Hawaii, 1981 to 1991. Hawaii Medical Journal 1996; 55(March):48-54.

[8] Peden DB. Pollutants and asthma: role of air toxics. Environ Health Persp 2002; 110(Suppl 4):565-568.

[9] Wilson MR, Stone V, Cullen RT et al. In vitro toxicology of respirable Montserrat volcanic ash. Occup Environ Med 2000; 57:727-733.