Table 3.

Exposure levels (mg m^–3) of TD, RD, and RCS by company.

Companies	N	TDa		RDb		RCSc
		GMd (GSDe)	Range	GM (GSD)	Range	GM (GSD)	Range
A	30	–		0.082 (1.542)	0.052 ~  0.240	0.001 (1.988)	0.001 ~  0.007
B	30	–		0.033 (2.155)	0.004 ~  0.115	0.003 (2.457)	0.001 ~  0.015
C	5	0.042 (2.196)	0.014 ~  0.106	0.016 (1.757)	0.007 ~  0.027	0.002 (2.137)	0.001 ~  0.004
D	2	7.385 (2.337)	4.052, 13.460	0.350 (1.649)	0.246, 0.499	0.019 (1.507)	0.014, 0.024
E	12	0.162 (1.727)	0.058 ~  0.389	0.048 (1.578)	0.022 ~  0.104	0.003 (1.235)	0.002 ~  0.004
F	9	0.588 (1.454)	0.345 ~  0.978	0.065 (1.392)	0.040 ~  0.097	0.007 (1.462)	0.004 ~  0.013
G	2	1.040 (1.122)	1.128, 0.958	0.126 (1.332)	0.103, 0.154	0.003 (1.417)	0.002, 0.004
Total	90	0.278 (4.168)	0.014 ~  13.460	0.053 (2.205)	0.004 ~  0.499	0.0026 (2.383)	0.001 ~  0.024
Background levelf		–	–	0.028 (1.545)	–	0.0007	–

^aTotal dust.

^bRespirable dust.

^cRespirable crystalline silica.

^dGeometric mean.

^eGeometric standard deviation.

^fThe background RCS and RD concentrations are the values obtained by the authors of this study through another research project in 2018²⁴.