Table 12

Approximate mean personal exposure concentrations (μg/m3) of respirable dust and cristobalite (assuming a mean cristobalite content of 15% in airborne dust) during the course of the current eruption (April 1996 to August 1999)

Respirable dustCristobalite
Cork Hill*Salem†NorthCork HillSalemNorth
The US (ACGIH) limit for workplace exposure to cristobalite adjusted for 24 hour exposure over 365 days/year is equivalent to 10 μg/m3.
*Assumes evacuation to Salem in June 1997 and then to north of island in August 1997.
†Asumes evacuated to north of island between August 1997 and October 1998.
Sedentary adults100604015105
Active adults1409060202010
Adults with dusty occupations390260180604030