Table 1 Studies investigating the health effects of exposure to underground railway air pollution in vivo

Klepczynska Nystrom [15]

2010 (October 2006–March 2007)

Stockholm, Sweden

PM₁₀ = 242 ± 40; PM_2.5 = 77 ± 10;

PM_0.1 PNC = 8283 ± 1716/cm³

PM₁₀: Fe = 58.6 ± 21.0%; Ba = 1.0 ± 0.4%; Cu = 0.8 ± 0.4%; Mn = 0.5 ± 0.2%

2 h, afternoon rush hour

20 healthy non-smoking volunteers (13 M 7F), mean age 27 y (range 18–46)

No change in lung function or airway cellular parameters, increased plasma fibrinogen, increased blood Treg count.

Bigert [20]

2011 (November 2004–March 2005)

Stockholm, Sweden

PM_10–1 DataRAM and PM_2.5 ticket office = 13 ± 3, 10 ± 3; train drivers = 33 ± 12, 19 ± 3; platform workers = 182 ± 57, 63 ± 12

Not stated

~ 8 h working day

81 non-smoking workers (55 M 26F), mean age 38 y (range 25–50)

No changes in F_ENO or lung function over working day.

Klepczynska Nystrom [21]

2012 (mid November-early April, year not stated)

Stockholm, Sweden

PM₁₀ = 232 ± 51; PM_2.5 = 71 ± 13;

PM_0.1 PNC = 8960 ± 660/cm³

PM₁₀: Fe = 49.3 ± 7.3%; Ba0.7 ± 0.1%; Cu = ND; Mn = 0.4 ± 0.1

2 h, afternoon rush hour

16 mild asthmatic non-smoking volunteers (5 M 11F), mean age 26 y (range 18–52)

Increased activated T cells in BALF, no effect on blood T cell counts or coagulation markers.

Bigert [27]

2008 (November 2004–March 2005)

Stockholm, Sweden

PM_10–1 DataRAM and PM2.5 ticket sellers = 13 ± 3, 10 ± 3; train drivers = 33 ± 12, 19 ± 3; platform cleaners = 256 ± 97, 79 ± 17; platform ticket collectors = 108 ± 26, 50 ± 8

Not stated

48 h (over 2 working days)

79 non-smoking workers (54 M, 25F), mean age 38 y (range 25–50)

Increased PAI-1 in ticket sellers, increased fibrinogen in train drivers. More exposed platform workers had higher baseline PAI-1 and hsCRP, but no effect over exposure period. No obvious PM effect.

Lundstrom [28]

2011 (mid November-early April, year not stated)

Stockholm, Sweden

Not stated – see [15, 21]

Not stated – see [15, 21]

2 h, afternoon rush hour

18 healthy, 15 mild intermittent asthmatic non-smoking volunteers (17 M, 16F), mean age 26 y (range 18–52)

9/64 oxylipins assayed in BALF increased in healthy vs. asthmatic, volunteers, principally 15-lipoxygenase-generated derivatives of linoleic and α-linolenic acids.

Liu [30]

2015

Taipei, Taiwan

PM₁₀, PM_2.5 underground = 32 ± 12, 22 ± 7; bus = 40 ± 16, 32 ± 12; car = 34 ± 13, 29 ± 11; walking = 50 ± 21, 42 ± 18

Not stated

1 h morning commute

120 healthy volunteers (58 M, 62F), mean age 21 y (range 19–24)

Underground commute showed lowest PM_2.5 exposure and lowest effect on heart rate variability vs. bus, car, or walk.

Bigert [33]

2007 (data from 1976 to 1996)

Stockholm, Sweden

Not stated

Not stated

Chronic workplace exposure

131,496 M (250 underground drivers), 22,311 myocardial infarction cases (54 underground drivers)

No increased risk of myocardial infarction in underground drivers (RR = 0.92 [95% CI 0.68–1.25] vs. manual workers, 1.06 [95% CI 0.78–1.43] vs. other employed males).

Gustavsson [34]

2008 (subjects followed from 1970 to 1989)

Stockholm, Sweden

Not stated

Not stated

Chronic workplace exposure

319,979 M (348 underground drivers), 4731 lung cancer cases (9 underground drivers)

No increased risk of lung cancer in underground drivers (standardised incidence ratio 0.82 [95% CI 0.38–1.56]).

Grass [35]

2010 (November 2004–February 2005)

New York City, USA

PM_2.5 exposure median across all subway roles = 27 (5th–95th %ile = 8–112)

PM_2.5: median Fe = 27%

Chronic workplace exposure

39 M underground drivers (median age 48 y, IQR 38–53), 11 M bus drivers (45 y, 41–48), 25 M office workers (44 (37–51))

Across a wide range of chemical and biomarker assays in blood and urine, only urinary 8-isoprostate was associated with (cumulative) underground exposure.

Mehrdad [36]

2015 (September–October 2012)

Tehran, Iran

Not stated

Not stated

Chronic workplace exposure

81 M healthy underground workers, mean age 32 ± 7 y

Increased urinary 8-OHdG in underground tunnel workers vs. underground non-tunnel workers.