Table 4

Environmental concentrations of PM10 (containing approximately 10% crystalline silica) in μg/m3 as estimated from DUSTTRAK measurements made between June 1997 and September 1998

Little volcanic ashHigh volcanic ash, dry
WetDryWind not from southSoutherly wind
The ranges of measured 15 minute (approximate) means at each location are shown in brackets. High ash days are those in which indoor surfaces are covered with a visible layer of dust.
Plymouth35150 (70–180)>1000 (1000–2000)Not measured
Cork Hill30 (19–35)60 (35–75)1000 (1000–3500)Not measured
Salem20 (15–30)30 (25–130)200 (55–500)800 (100–1000)
North20 (15–25)30 (20–60)50 (45–80)500