Table 1.

Concentrations of RCS and RD in personal samples.

Job/task	Sampling duration	n a	TWA Respirable silica conc.b (µg/m3)		TWA Respirable dust conc. (µg/m3)		Time (hours) needed to exceed the new PEL of 50 µg/m3	Percent of samples with 8-h. TWA RCS2 conc .>PEL
			GM (GSD)	Range	GM (GSD)	Range
Chipping workers	54–318	31	527 (2.1)	101–1554	4,750 (2.1)	471–19,525	0.25–3.93	80%
Crushing machine tendersc	120–378	8	93.3 (2.2)	21–220	737.6 (2.3)	138–1423	1.82–19.05	50%
Laborers in demolition	222–295	3	17.0 (2.6)	8–51	231.0 (1.6)	138–356	7.8–50	0%
Operating engineersd	267–380	9	6.2 (2.4)	Nde–29	68.4 (4.1)	3–311	Nd–64.5	0%

^a n = Number of samples collected.

^bTWA concentrations for the duration of sampling.

^cIncludes the crushing tender at site B.

^dOperating engineers in both demolition and crushing sites.

^eNd = Non-detectable levels (n = 4, 44% of operating engineers’ samples).