Table 3.

Median concentrations of PM_2.5, Fe, Cr, and Mn in subway worker personal samples compared to ambient and standard concentrations.

	n	PM2.5(µg/m3)		Fe (µg/m3)		Mn (µg/m3)		Cr (µg/m3)		Fe (as a % of PM2.5 by mass) Median
		Median	5th–95th percentile	Median	5th–95th percentile	Median	5th–95th percentile	Median	5th–95th percentile
OSHA 8h PELa	na	5000b	na	5000c	na	20,000d	na	5000e	na	na
All subway workers	39	27	8–112	7	1–34	75	19–407	27	6–222	27
Track maintenance	6	61	38–439	16	10–156	153	97–1422	49	33–332	28
Track construction	6	53	40–80	16	9–20	121	83–160	57	35–86	25
Refuse train	3	27	27–40	11	8–13	103	76–118	37	25–40	34
Construction flaggers	6	21	17–70	7	5–22	66	52–231	21	13–79	32
Operators and conductors	6	15	7–18	6	3–7	64	36–72	17	10–19	42
Overhaul shop	6	20	8–75	3	0.4–22	62	22–283	25	6–174	12
Station cleaners	6	19	8–27	3	1–6	30	12–58	11	4–27	16
Urban outdoor samplesf	36	13	7–21	0.1	0.04–0.2	2	1–4	0.3	0.1–1	1
Suburban outdoor     samplesg	20	9	5–16	0.07	0.03–0.12	1	1–4	0.3	0.1–1.1	1

na—not applicable.

^aOSHA 8 h permisssible exposure limits are for respirable particulate fraction ~PM₄, and so are not directly comparable to personal samples which are all for the PM_2.5 fraction.

^bFor particulates not otherwise specified.

^cFor Fe as oxide fumes.

^dOSHA TLV-TWA.

^eFor Cr(VI), not total Cr.

^fUrban outdoor samples were collected over a period of 8 weeks outside the residences of high school students who participated in an earlier study (Chillrud et al., 2004). Each of the 36 samples integrates 48 h of monitoring. Participants lived in Manhattan, Brooklyn, Queens, and the Bronx. Results for urban outdoor air samples are given as an example of outdoor air quality in New York City.

^gSuburban outdoor samples were collected over a period of 8 weeks as part of an earlier study (Chillrud et al., 2004). The samples were collected outside the workplace (in Palisades, NY) of the office workers used as a control group in this study. Each of the 20 samples integrates 48 h of monitoring.