Effects of volcanic ash on ocular symptoms:

Objective

To study the effects of volcanic ash on the ocular symptoms of schoolchildren ages 6 to 15 residing near Mt. Sakurajima, an active volcano.

Design

Retrospective, cross-sectional study.

Participants

A total of 10 380 children ages 6 to 15, 1175 in a high-exposure area and 9205 in a low-exposure area, were studied.

Methods

High- and low-exposure areas for volcanic ash were selected. All subjects in both areas were examined annually each September in the decade from 1994 to 2003.

Main outcome measures

The frequency of positive ocular symptoms in years with and without active volcanic eruptions was compared. The association of ocular symptoms with volcanic ash dispersal was assessed with the Mantel–Haenszel test or chi-square test.

Results

Subjects in the high-exposure area showed ocular symptoms more often than those in the low-exposure area (P<0.0001). Years of active volcanic eruptions (volcanic ash of 5000 g/m²/year or more) were closely related to years with a high frequency of ocular symptoms in subjects in the high-exposure area (P<0.05) but related conversely in subjects in the low-exposure area (P<0.01). Major ocular symptoms were redness, discharge, foreign body sensation, and itching, all treated effectively with eyedrops.

Conclusions

Ocular symptoms in subjects were strongly influenced by volcanic eruptions in the Mt. Sakurajima area, but direct influence was limited to those living in areas very near the volcano (i.e., 4 km from the volcano's crater).