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Long-term studies are difficult to do and inherently expensive
because they require monitoring a population over an
extended period of time, and require consideration of multiple
demographics, such as healthy, elderly, and chronically ill
populations.
The duration of exposure is crucial to health outcomes.
Populations can be exposed to re-suspended ash through
routine activities and by efforts to clean-up and remove ash
from communities. On the island of Montserrat, where ash
persists in the environment for years, gardeners were shown
to have the highest exposure to re-suspended ash. Conversely,
the majority of ash from the 2010 eruption of the Merapi
volcano in Indonesia had been removed from towns and cities
within weeks of the cessation of the eruption. For this eruption,
exposure was probably minimal as the eruption took place
during the rainy season, ɕ