Environmental impacts on health from continuous volcanic activity at Yasur (Tanna) and Ambrym, Vanuatu.

Continuous low-level basaltic volcanic activity, from Yasur Volcano in Tanna, and Marum and Benbow vents on Ambrym, occurred for as long as records have been kept in Vanuatu. The potential chronic health implications for the inhabitants of these two areas were investigated in a preliminary environmental sampling program. The focus was particularly on fluoride and other volcanic gas-derived chemical contamination in areas surrounding the volcanic centres. Little immediate contamination of the environment was evident for areas affected by volcanic ash and gas on Tanna, with water fluoride concentrations being elevated (to 0.42 mg x l(-1)) only within a lake adjacent to the active volcanic cone. Selected re-sampling in April 2001 following the long active phase of Yasur, revealed higher F levels in surface waters (to 1.05 mg x l(-1)). Analysis of cow rib bone and teeth indicated a possible long-term accumulation of F in grazing animals, which probably consume F-bearing volcanic ash and gas hydrates on the surface of plant leaves. No human impacts (including stress and respiratory problems) were noted, probably due to the constant and familiar low-level activity, plus the coarse nature of most ash ejecta. Ambrym appears to be a more F-concentrated system than Tanna, with volcanic ash containing 281 total and 36.7-43.6 soluble mg F x kg(-1) (cf. 178 total and 7.3-9.1 soluble mg F x kg(-1) on Tanna), and water levels reaching up to 2.8 mg F x l(-1) in rainwater tanks. The drinking water F levels on Ambrym are higher than WHO recommended levels, despite the being sampled during a substantial lull in eruptive activity, and signal potential for chronic dental and skeletal fluorosis.