The results showed that there were significant differences between
the exposure levels to total respirable dust (p = 0.025 < 0.05). The
workers using DustBubble exposed to low level of respirable dust,
which meant the use of DustBubble could reduce the respirable
concentrations by 63% (GM: from 0.27 mg/m3 to 0.10 mg/m3; estimated
reduction = (1 0.09/0.29) 100% = 63%).
For respirable quartz dust, the estimated reduction of respirable
quartz by DustBubble is 43% ((1 0.04/0.07) 100%). However, the
results of statistical comparison indicated that there were no significant
differences between the exposure levels to total respirable
quartz dust (p = 0.144 > 0.05), which suggested that the use of Dust-
Bubble could not significantly reduce the quartz exposure level of
workers when drilling concrete. Moreover, both the GM of quartz
concentration values of two groups (0.07 mg/m3 and 0.04 mg/m3
respectively) were over or close to the exposure limit