Sr. Woskie et al., THE REAL-TIME DUST EXPOSURES OF SODIUM-BORATE WORKERS - EXAMINATION OF EXPOSURE VARIABILITY, American Industrial Hygiene Association journal, 55(3), 1994, pp. 207-217
As part of an epidemiologic study of acute respiratory irritation, an
assessment of the short term (TWA-0.25 hr) and daily (TWA-6 hr) dust a
nd boron exposures of workers in a sodium borate production facility w
as undertaken. A real-time continuous aerosol monitor was used in an a
ctive mode with an in-line filter to collect a TWA-6 gravimetric sampl
e with a datalogger to store the continuous aerosol measurements. Over
430 person-days of personal exposure measurements were made, resultin
g in more than 10 000 15-minute average (TWA-0.25) dust concentration
measurements. The arithmetic mean total dust concentrations for the 13
job groups exposed to sodium borate dust ranged from 0.29 to 18.95 mg
/m3. The geometric standard deviation of the TWA-6 total dust exposure
s within the sodium borate exposed job groups had a median of 2.78. Th
e geometric standard deviation of the TWA-0.25 total dust exposures ha
d a median of 3.97. In most jobs the ''within-day'' variability accoun
ted for over 50% of the total variability in exposure levels. In jobs
with constant exposure to sodium borate, the second most important sou
rce of exposure variability was attributable to ''between worker'' dif
ferences. Where there was only intermittent exposure, the second most
important source of exposure variability was ''within-worker'' variabi
lity. The implications of these findings for control strategies are di
scussed. Based on boron measurements, a substantial portion of a total
dust air sample is nonborate material such as cigarette smoke, vehicl
e exhaust, ambient dust, or hydration mass. Thus, even in an environme
nt where sodium borate is being packaged, total dust measurements are
an overestimate of the actual borate exposure level.