TABLE 2.

The predicted percentage and estimated number of workers exposed to silica at least twice the NIOSH REL in 2014 by five-digit NAICS code^a

NAICS title	NAICS code	Number of inspections with silica samples after data editing	Estimated workers exposedb	Percentage exposedc	90% CIc
Residential building construction	236110	14	32 100d	5.36d	1.40–9.31
Poured concrete foundation and structure contractors	238110	39	9000	4.88	2.42–7.35
Commercial and institutional building construction	236220	37	7000	1.41	0.70–2.12
Testing laboratories	541380	9	6600	5.08	0.53–9.62
Masonry contractors	238140	157	6200	5.00	3.61–6.40
Tile and terrazzo contractors	238340	19	3100	6.48	0.08–12.9
Painting and wall covering contractors	238320	31	2800	1.61	0.77–2.45
All other specialty trade contractors	238990	54	2800	1.31	0.71–1.90
Highway, street, and bridge construction	237310	97	2700	1.04	0.67–1.40
All other nonmetallic mineral product manufacturing	327990	268	2100	3.56	2.85–4.27
Other heavy and civil engineering construction	237990	22	1200	1.42	0.58–2.25
Ready-mix concrete manufacturing	327320	41	1200	1.69	0.62–2.76
Brick, stone, and related construction material merchant wholesalers	423320	18	1200	4.04	0.45–7.63
Ferrous metal foundries	331510	490	1000	1.52	1.27–1.78
Clay building materials and refractories manufacturing	327120	121	500	2.17	1.54–2.81
Other concrete product manufacturing	327390	127	500	0.93	0.54–1.31
Coating, engraving, heat treating, and allied activities	332810	78	400	0.28	0.16–0.40
Pottery, ceramics, and plumbing fixture manufacturing	327110	71	300	2.19	1.41–2.97
Glass and glass product manufacturing	327210	56	200	0.23	0.12–0.35
Plate work and fabricated structural product manufacturing	332310	60	200	0.11	0.07–0.16
Pump and compressor manufacturing	333910	15	200	0.27	0.05–0.48
Asphalt paving, roofing, and saturated materials manufacturing	324120	24	100	0.45	0.03–0.87
Concrete pipe, brick, and block manufacturing	327330	59	100	0.59	0.23–0.96
Iron and steel mills and ferroalloy manufacturing	331110	35	100	0.07	0.02–0.12
Nonferrous metal foundries	331520	208	100	0.24	0.15–0.32
Agriculture implement manufacturing	333110	11	100	0.10	0.01–0.18
Mining and oil and gas field machinery manufacturing	333130	14	100	0.15	0.03–0.26
Ship and boat building	336610	18	100	0.05	0.02–0.08
			82 000

Abbreviations: CI, confidence interval; NAICS, North American Industry Classification System; NIOSH, National Institute for Occupational Safety and Health; REL, recommended exposure limit.

^aThis does not account for respirator use.

^bRounded to the nearest 100 workers.

^cRounded to the nearest 100th percent.

^dNote that fluctuations in parameter estimates resulted in a higher estimate, contrary to expectations, in Table 2 than in Table 1 for the percentage exposed for residential building construction (NAICS 236110). For example, the negative slope estimate which represents a decrease in exposure over time was smaller in absolute value for the modeling results used for the estimates in Table 2.