A Seven Months Prospective Study of the Respiratory Effects of Exposure to Ash from Popocatepetl Volcano, Mexico

This paper describes the 7 month follow-up of 35 non-smoker farmers exposed to suspended particles of volcanic ash of Popocatepetl volcano in central Mexico during a series of small explosive eruptions which occurred the last week of 1994 and the first week of 1995 as well as several smaller eruptions until April 1995. There was concern about the effect that the ash might have on the airways. Spirometric parameters and respiratory symptoms were recorded at the baseline and 7 months after the exposure. Analysis of spirometric data showed a significant low forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1) that occurred during the major exposure period. This finding was possibly acute exposure-related because 7 months later, FVC and FEV1 increased to the normal predicted values. Self-reported respiratory and ocular symptoms showed a similar pattern. These findings are consistent with the hypothesis that short exposure to volcanic ash is associated with reversible inflammation of the airways. The reversibility was explained by the small total ash volume as well as by the non-fibrogenic nature of the Popocatepetl ash, because the content of free silica was less than 3.5%.