Beskæftigelsesudvalget 2018-19 (2. samling)
BEU Alm.del Bilag 28
Offentligt
2069111_0001.png
Health effects of exposure to diesel exhaust in diesel-powered trains
Maria Helena Guerra Andersen
1,2*
, Marie Frederiksen
2
, Anne Thoustrup Saber
2
, Regitze Sølling
Wils
1,2
, Ana Sofia Fonseca
2
, Ismo K. Koponen
2
, Sandra Johannesson
3
, Martin Roursgaard
1
,
Steffen Loft
1
, Peter Møller
1
, Ulla Vogel
2,4
1
Department of Public Health, Section of Environmental Health, University of Copenhagen, Øster
Farimagsgade 5A, DK-1014 Copenhagen K, Denmark
2
The National Research Centre for the Working Environment, Lersø Parkalle 105, DK-2100
Copenhagen Ø, Denmark.
3
Department of Occupational and Environmental Medicine, Sahlgrenska Academy at University
of Gothenburg, Gothenburg, Sweden.
4
DTU Health Tech., Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
*Corresponding author:
[email protected]; [email protected]
Maria Helena Guerra Andersen,
[email protected]; [email protected]
Marie Frederiksen,
[email protected]
Anne Thoustrup Saber,
[email protected]
Regitze Sølling Wils,
[email protected]
Ana Sofia Fonseca,
[email protected]
Ismo K. Koponen,
[email protected]
Sandra Johannesson,
[email protected]
Martin Roursgaard,
[email protected]
Steffen Loft,
[email protected]
Peter Møller,
[email protected]
Ulla Vogel,
[email protected]
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
Abstract
Background:
Short-term controlled exposure to diesel exhaust (DE) in chamber studies have
shown mixed results on lung and systemic effects. There is a paucity of studies on well-
characterized real-life DE exposure in humans. In the present study, 29 healthy volunteers were
exposed to DE while sitting as passengers in diesel-powered trains. Exposure in electric trains was
used as control scenario. Each train scenario consisted of three consecutive days (6 hours/day)
ending with biomarker samplings.
Results:
Combustion-derived air pollutants were considerably higher in the passenger carriages of
diesel trains compared with electric trains. The concentrations of black carbon and ultrafine
particles were 8.5 µg/m
3
and 1.2-1.8x10
5
particles/cm
3
higher, respectively, in diesel as compared
to electric trains. Net increases of NOx and NO
2
concentrations were 317 µg/m
3
and 36.1 µg/m
3
.
Exposure to DE was associated with reduced lung function and increased levels of DNA strand
breaks in peripheral blood mononuclear cells (PBMCs), whereas there were unaltered levels of
oxidatively damaged DNA, soluble cell adhesion molecules, acute phase proteins in blood and
urinary excretion of metabolites of polycyclic aromatic hydrocarbons. Also the microvascular
function was unaltered. An increase in the low frequency of heart rate variability measures was
observed, whereas time-domain measures were unaltered.
Conclusion:
Exposure to DE inside diesel-powered trains for 3 days was associated with reduced
lung function and systemic effects in terms of altered heart rate variability and increased levels of
DNA strand breaks in PBMCs compared with electric trains.
Trial registration: ClinicalTrials.Gov (NCT03104387). Registered on March 23rd 2017,
https://clinicaltrials.gov/ct2/show/NCT03104387?term=Health+Effects+of+Occupational+Exposu
re+to+Combustion+Particles+-
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
+a+Study+on+Volunteers+Performing+as+Train+Conductors+%28BioTrack%29&cntry=DK&cit
y=Copenhagen&rank=1
Keywords
Diesel exhaust, train exposure, lung function, cardiovascular function, DNA damage, comet assay
Background
Diesel exhaust (DE) exposure occurs in both environmental and occupational settings where
engines are used for transportation or heavy-duty equipment for work processes. Exhaust from on-
road vehicles is generally the most important source of DE in the urban environment, but
emissions from diesel trains can also be an important local source of DE. The diesel trains do not
only affect the DE levels in outdoor air, but also inside the trains since the plume may penetrate
the train interior, which is a special problem when the locomotive pulls the train [1, 2].
Accordingly, both the staff and commuters may be exposed to DE on a daily basis. Long-term
exposure to DE is associated with increased risk of lung cancer [3, 4]. In addition, traffic-
generated air pollution is considered to be an important risk factor for cardiovascular diseases [5].
Although ultrafine particles (UFP) from diesel-powered vehicles are considered to be an important
contributor to cardiovascular disease, it is difficult to separate this effect from other sources of
particulate matter (PM) in urban air as diesel vehicles only contribute to 3-15% of the total PM
2.5
mass [6].
Oxidative stress and inflammation are considered important mechanisms of action for particle-
generated cardiovascular diseases and cancer, with the latter also believed to be partially attributed
to polycyclic aromatic hydrocarbons (PAHs) in the DE particle fraction as summarized in a recent
review [7]. The review concludes that exposure to particles affects the vasomotor function,
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
fibrinolysis system and heart rate variability (HRV). Particle exposure may affect the arterial
blood vessels to increase vasoconstriction and reduce vasodilation [8]. The effect of DE has been
investigated in a number of short-term studies (i.e. few hours) where subjects were typically
exposed in a chamber under controlled conditions. This has demonstrated reduced responsiveness
to vasodilator-induced vasodilation [9, 10, 11, 12, 13, 14], whereas HRV measurements have
shown null or mixed results [15, 16, 17, 18]. Lung function measurements have shown essentially
null results [14, 19, 20, 21, 22, 23, 24, 25]. Effects on airways inflammation have consistently
been observed in chamber studies [21, 23, 24, 26, 27] with mixed results for systemic
inflammation [9, 10, 11, 16, 18, 23, 25, 28, 29, 30]. In contrast to vascular, lung function and
inflammation endpoints, only very few controlled DE exposure studies have included endpoints
related to genotoxicity. To the best of our knowledge only one study has assessed DNA strand
breaks and oxidatively damaged DNA in humans after controlled DE exposure in a chamber study
and this showed no effect [31]. The same endpoints, measured by the alkaline comet assay, are
standard genotoxicity tests in particle toxicology and molecular epidemiology on air pollution
exposures [32].
The present study investigated real-life exposure to DE in diesel-powered trains. The commuter
railway system in the greater Copenhagen area, Denmark, consists of both electric and diesel
trains. Some of the diesel trains are relatively old (from the 1980s) and have rather high emission
rates of PM. In addition, the DE plume from the locomotive penetrates to the interior of the
passenger carriages, giving rise to high particle exposure as demonstrated by net increases of
PM
2.5
(36 µg/m
3
), UFP (2x10
5
particles/cm
3
) and black carbon (8.3 µg/m
3
) compared to the
concentrations in electric trains [33]. The high particle concentration in diesel-powered trains has
caused concerns about possible long-term health effects of train staff and commuters. In order to
investigate the effect of real-life DE exposure, 29 volunteers were recruited to participate in
scenarios involving staying inside the first passenger carriage of regional trains 6 hours/day for 3
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
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consecutive days. Each volunteer was scheduled for two scenarios in diesel trains and one scenario
in an electric train. The study design and the duration of the exposure were overall similar to, and
inspired by a previous study on particle exposure in firefighters, which demonstrated elevated
levels of PAH metabolites in urine, decreased microvascular function and increased levels of
DNA damage in peripheral blood mononuclear cells (PBMCs) in conscripts immediately after a
three day training course in firefighting as compared to two weeks before and two weeks after [34,
35]. The biomarkers included lung function, microvascular function, HRV and systemic levels of
acute phase proteins and cell adhesion molecules, DNA damage in PBMCs and urinary excretion
of PAH metabolites.
Results
Exposure characterization
In total, there were 54 and 29 person scenarios of exposure in diesel and electric trains,
respectively. The exposure assessment showed a clear contrast in exposure levels between diesel
and electric scenarios for concentrations of black carbon, UFP and nitrogen oxides (Table 1). The
average concentrations of UFP were 15 to 24 fold higher in diesel trains, measured with
NanoTracer and DiscMini portable devices, respectively. All the air pollution components were
highly correlated (Figure 1). More details on the exposure assessment and results can be found
elsewhere [33].
Table 1.
Black carbon, ultrafine particles and nitrogen oxides concentrations and contrast between
diesel and electric trains
Exposure
Black carbon (
µg/m )
Ultrafine particles from
DiscMini (#/cm
3
)
a)
Ultrafine particles from
3
Electric (n=29)
1.8 (0.5)
8 100 (2 400)
9 100 (3 500)
Diesel (n=54)
10.3 (2.0)
189 200 (91 900)
133 400 (52 100)
Mean difference (95% CI)
8.5 (7.9; 9.1) ***
181 000 (153 700; 208 400) ***
124 300 (110 000; 138 500) ***
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
2069111_0006.png
NanoTracer (#/cm
3
)
NOx (
µg/m )
NO
2
(
µg/m )
3
3
45 (16)
18 (9)
363 (73)
54 (16)
317 (297; 338) ***
36 (31; 42) ***
The exposure was assigned to study participants (study participants rode the trains in groups of different
sizes. The exposure average levels for each calendar day were assigned to all members of the relevant
group). Exposure levels in both scenarios are presented as mean and standard deviation. PM
2.5
, polycyclic
aromatic hydrocarbons and aldehydes are not assigned to study participants, as the data were not collected
throughout all the study period.
a)
missing values for DiscMini equipment indexed to four study persons for
the exposure scenarios (n=46 diesel and n=25 for electric). *** p<0.001
Figure 1.
Correlation between air pollution components in diesel and electric trains.
The data corresponds to 63 (UFP and black carbon measured with NanoTracer equipment and
Aethalometer, respectively) and 55 (UFP measured with DiscMini equipment) days of exposure. Nitrogen
oxides were measured over 3 days, corresponding to 18 periods.
Association between train scenarios and biomarkers
Table 2 presents the estimated effect of diesel exposure on the assessed biomarkers as compared to
electric trains. The lung function measurements included forced vital capacity (FVC), forced
expiratory volume after 1 second (FEV1) and peak expiratory flow (PEF). FEV1 and PEF showed
a small but significant decrease after exposure to DE. Figure 2 shows the individual results for the
lung function measurements; the mean biomarker level of two measurements is shown.
The microvascular function was measured by reactive hyperemia, using EndoPAT, and reported
as the logarithmically transformed data (Ln.RHI). Neither this, nor nitroglycerin-induced
vasodilation differed between the exposure scenarios, indicating a lack of detectable effect on
endothelial-dependent and endothelial-independent vasomotor responses. As expected the
nitroglycerin-induced vasodilation was larger (2.2) than the reactive hyperemia-mediated
vasodilation (i.e. 1.7, back-transformed from Ln.RHI = 0.57). The only significant change in HRV
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
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measurements was an increase in the low frequency-domain component (LF) (Figure 3), whereas
time-domain components were unaffected.
DE exposure was associated with increased level of DNA strand breaks in PBMCs (Figure 4),
whereas the level of formamidopyrimidine DNA glycosylase (Fpg)- sensitive sites was unaffected
by exposure. Markers of systemic acute phase proteins and soluble adhesion molecules were
unaffected by exposure.
There was no exposure-related effect on urinary excretion of PAH metabolites used as biomarkers
of exposure. The background levels (from electric scenario) of the creatinine adjusted PAHs
showed large variation across individual subjects, from below the limit of quantification to 0.377
μmol/mol
creatinine for 1-hydroxypyrene (1-OHP),
0.012 to 0.278 μmol/mol creatinine for
2-
hydroxyfluorene (2-OHF),
0.117 to 2.55 μmol/mol creatinine for
1-naphthol (1-NAPH) and 0.283
to 10.6
μmol/mol creatinine for
2-naphthol (2-NAPH), respectively.
Table 2.
Outcome levels for electric and diesel scenarios and percent changes in biomarker levels
Biomarker
1-OHP (μmol/mol
creatinine)
Urinary
excretion
2-OHF (μmol/mol
creatinine)
1-NAPH (μmol/mol
creatinine)
2-NAPH (μmol/mol
creatinine)
FVC (L)
Lung function
FEV1 (L)
FEV1/FVC (%)
PEF (L/s)
Ln.RHI
Cardiovascular
function
NIV
pNN50 (%)
RMSSD (ms)
Electric
(mean±SD)
0.049 ± 0.083
0.075 ± 0.067
0.851 ± 0.603
2.084 ± 2.272
4.20 ± 1.24
3.32 ± 0.96
79.1 ± 6.8
7.26 ± 2.13
0.57 ± 0.25
2.26 ± 1.06
0.06 ± 0.08
41.84 ± 30.93
Diesel
(mean±SD)
0.027 ± 0.019
0.070 ± 0.061
0.671 ± 0.560
1.861 ± 1.679
4.18 ± 1.16
3.24 ± 0.96
77.2 ± 9.2
7.15 ± 2.42
0.55 ± 0.28
2.21 ± 0.71
6.54 ± 0.07
36.39 ± 19.02
% Change
(95%CI)
-12.2 (-32.3; 14.0)
0.6 (-17.3; 22.4)
-20.0 (-44.3; 4.3)
-0.4 (-20.7; 25.2)
-2.3 (-4.7; 0.25)
-3.6 (-5.5; -1.6)
-1.8 (-3.8; 0.2)
-5.6 (-10.7; -0.5)
-1.4 (-26.5; 23.7)
-3.7 (-34.6; 27.3)
4.6 (-13.8; 23.0)
-3.5 (-22.1; 19.7)
p-
value
0.331
0.952
0.107
0.975
0.077
0.0003
***
0.073
0.031 *
0.913
0.817
0.626
0.326
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
2069111_0008.png
SDNN (ms)
LF (ms
2
)
HF (ms
2
)
LF/HF
AI normalized to heart
rate of 75 bpm (%)
DP (mm Hg)
SP (mm Hg)
SB (lesions/10
6
bp)
DNA damage
Adhesion
molecules
Acute phase
proteins
Fpg-sensitive sites
(lesions/10
6
bp)
ICAM-1 (ng/mL)
VCAM-1 (ng/mL)
SAA (mg/L)
CRP (mg/L)
48.16 ± 24.29
160.2 ± 59.5
153.6 ± 57.6
1.27 ± 0.83
-8.26 ± 11.79
81.2 ± 11.4
135.1 ± 16.1
0.12 ± 0.13
0.62 ± 0.15
35.04 ± 7.28
134.2 ± 36.2
32.09 ± 41.51
1.83 ± 2.29
44.24 ± 16.76
195.9 ± 78.8
151.8 ± 67.5
1.70 ± 1.37
-6.26 ± 14.68
82.3 ± 10.8
134.4 ± 17.9
0.18 ± 0.13
0.58 ± 0.12
34.34 ± 6.88
129.6 ± 35.8
36.46 ± 47.35
1.90 ± 2.48
-2.1 (-14.9; 12.7)
16.5 (5.9; 27.0)
2.0 (-7.5; 11.5)
18.5 (-5.5; 48.6)
1.6 (-2.2; 5.5)
1.2 (-2.9; 5.2)
-1.0 (-4.9; 2.9)
46.3 (5.0; 100.9)
-5.0 (-11.1; 1.1)
-2.5 (-8.3; 3.7)
-3.2 (-10.5; 4.7)
11.1 (-17.8; 50.2)
-12.3 (-47.5; 46.4)
0.773
0.002 **
0.681
0.141
0.405
0.566
0.630
0.025 *
0.109
0.426
0.416
0.493
0.615
Percent change was estimated by mixed-effects model adjusted for age and sex, comparing diesel with
electric scenarios.
CI, confidence interval; SD, standard deviation; 1-OHP, 1-hydroxypyrene; 2-OHF, 2-hydroxyfluorene; 1-
NAPH, 1-naphthol; 2-NAPH, 2-naphthol; FVC, forced vital capacity; FEV1, forced expiratory volume in
one second; PEF, peak expiratory flow rate; Ln.RHI, reactive hyperemia index with natural logarithmic
transformation (the percent change was back transformed); NIV, nitroglycerin-induced vasodilation;
pNN50, proportion of successive NN intervals differing by more than 50 milliseconds divided by total
number of NN intervals; RMSSD, square root of the mean squared differences of successive NN intervals;
SDNN, standard deviation of all NN intervals; LF, low frequency component (0.04-0.15 Hz); HF, high
frequency component (0.15-0.4 Hz); AI, augmentation index; DP, diastolic blood pressure; SP, systolic
blood pressure; SB, DNA strand breaks; ICAM-1, intercellular cell adhesion molecule-1; VCAM-1,
vascular cell adhesion molecule-1; SAA, serum amyloid A; CRP, C-reactive protein; * p<0.05; **p<0.01.
Figure 2.
Lung function parameters after exposure in electric and diesel trains.
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
The circles in grey represent individual lung function parameters for electric train (one exposure scenario)
or diesel train (mean of two exposure scenarios). The dark line represents the mixed-effects model without
adjustments. Lower levels of FEV1 and PEF were observed at group level (solid symbols) after exposure in
diesel trains (p<0.05).
Figure 3.
Low frequency (LF) component of heart rate variability measured after exposure in
electric and diesel trains.
The circles in grey represent LF measurements in electric train (one exposure scenario) or diesel train
(mean of two exposure scenarios). The dark line represents the mixed-effects model without adjustments.
Higher LF levels were observed at group level (solid symbols) after exposure in diesel trains (p<0.05).
Figure 4.
DNA strand breaks in peripheral blood mononuclear cells after exposure in electric and
diesel trains.
The circles in grey represent DNA strand breaks in electric train (one exposure scenario) or diesel train
(mean of two exposure scenarios). The dark line represents the mixed-effects model without adjustments.
Higher levels of DNA strand breaks were observed at group level (solid symbols) after exposure in diesel
trains (p<0.05).
Association between air pollution components and biomarker levels
In the second step of the analysis, biomarkers that were statistically significant or with borderline
statistical significance (defined as 0.05 > P < 0.10) different for the two exposures scenarios were
subsequently included in tests for association between individual air pollution components and
biomarkers. Table 3 shows the direction of associations between exposure levels (UFP, BC and
nitrogen oxides) and effects on biomarkers that showed statistical or borderline statistical
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
2069111_0010.png
significance in the overall test for effect for diesel versus electric trains. Overall, the
measurements of lung function were inversely associated with levels of particles and nitrogen
oxide levels. Likewise, LF and DNA strand breaks were positively associated with both particles
and nitrogen oxides.
Table 3.
Association between exposure levels and biomarkers estimated by mixed-effects model
adjusted for age and sex
Exposure
levels
UFP
(NanoTracer)
UFP
(DiscMini)
BC
NO
x
NO
2
FVC
FEV1
FEV1/FVC
PEF
LF
DNA SB
-




-
-












-
Exposure levels are averages of 3 days.
UFP, ultrafine particles; BC, black carbon; FVC, forced vital capacity; FEV1, forced expiratory volume in
one second; PEF, peak expiratory flow rate; LF, low frequency component; DNA SB, DNA strand breaks.
,
,

,

p
≤0.08;
<0.05; <0.01; <0.001, respectively
Table 4 presents the association between each of the 3 days exposure levels from direct-reading
instruments and effects assessed on biomarkers sampled on day 3, at the end of the exposure
scenario, estimated for the biomarkers that showed statistically or borderline statistical
significance in the overall test for effect for diesel versus electric trains. There were no consistent
trends between exposure (UFP and BC) and outcomes.
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
2069111_0011.png
Table 4.
Estimates for associations between daily averages of exposure levels and biomarkers
(91% CI)
Exposure markers
FVC (L)
FEV1 (L)
FEV1/FVC
PEF (L/s)
LF (ms
2
)
DNA SB
(lesions/10
6
bp)
a)
4.1E-06
(1.3E-06;
6.9E-06)
4.9E-06
(2.8E-06;
7.0E-06)
3.9E-06
(0.7E-06;
6.9E-06)
3.9E-06
(1.6E-06;
6.1E-06)
2.7E-06
(1.0E-06;
4.4E-06)
2.6E-06
(0.6E-06;
4.7E-06)
4.3E-02 (-
1.2E-02;
9.8E-02)
6.6E-02
(2.0E-02;
11.2E-02)
6.6E-02
(2.3E-02;
10.9E-02)
UFP (NanoTracer) (#/cm
3
)
-0.7E-06 (-
Day 1
1.4E-06; -
0.04E-06)
-0.6E-06 (-
Day 2
1.1E-06; -
0.02E-06
-0.7E-06 (-
Day 3, sampling
1.4E-06;
day
0.05E-06)
3
UFP (DiscMini) (#/cm )
-0.6E-06 (-
Day 1
1.2E-06;
0.01E-06)
-0.4E-06 (-
Day 2
0.8E-06;
0.06E-06)
-0.5E-06 (-
Day 3, sampling
1.0E-06;
day
0.02E-06)
3
BC (µg/m )
-1.5E-02 (-
2.8E-02; -
Day 1
0.3E-02)
-1.2E-02 (-
Day 2
2.2E-02; -
0.1E-02)
-0.8E-02 (-
Day 3, sampling
1.8E-02;
day
0.2E-02)
-0.7E-06 (-
1.2E-06; -
0.2E-06)
-0.6E-06 (-
0.9E-06; -
0.2E-06)
-0.8E-06 (-
1.3E-06; -
0.3E-06)
-5.2E-07 (-
9.2E-07;
1.2E-07)
-3.2E-07 (-
5.5E-07; -
0.9E-07)
-5.2E-07 (-
8.6E-07; -
1.8E-07)
-1.4E-02 (-
2.2E-02; -
0.5E-02)
-1.3E-02 (-
1.9E-02; -
0.5E-02)
-1.1E-02 (-
1.8E-02; -
0.4E-02)
-0.6E-05 (-
1.7E-05;
0.5E-05)
-0.8E-05 (-
1.7E-05;
0.04E-05)
-1.0E-05 (-
2.2E-05;
0.1E-05)
-0.5E-05 (-
1.5E-05;
0.5E-05)
-0.4E-05 (-
0.9E-05;
0.2E-05)
-0.8E-05 (-
1.6E-05;
0.06E-05)
-1.2E-01 (-
3.3E-01;
0.9E-01)
-1.6E-01 (-
3.3E-01;
0.1E-01)
-1.8E-01 (-
3.4E-01; -
0.2E-01)
-2.2E-06 (-
4.3E-06; -
0.08E-06)
-1.1E-06 (-
2.7E-06;
0.6E-06)
-3.1E-06 (-
5.2E-06; -
0.9E-06)
-1.9E-06 (-
3.7E-06; -
0.1E-06)
-1.2E-06 (-
2.6E-06;
0.1E-06)
-2.3E-06 (-
3.8E-06; -
0.8E-06)
-5.4E-02 (-
9.1E-02; -
1.7E-02)
-3.1E-02 (-
6.3E-02;
0.2E-02)
-3.0E-02 (-
6.0E-02;
0.06E-02)
2.2E-04
(0.5E-04;
3.9E-04)
1.3E-04
(0.03E-04;
2.6E-04))
2.8E-04
(1.2E-04;
4.3E-04)
1.7E-04
(0.3E-04;
2.9E-04)
1.4E-04
(0.5E-04;
2.3E-04)
1.5E-04
(0.4E-04;
2.5E-04)
4.5 (1.8; 7.2)
3.1 (0.7; 5.6)
3.4 (1.3; 5.5)
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
Estimated by mixed-effects model adjusted for age and sex. The values in the table are the beta-estimates
of the linear associations (linear mixed model for each day and pollutant).
UFP, ultrafine particles; BC, black carbon; FVC, forced vital capacity; FEV1, forced expiratory volume in
one second; PEF, peak expiratory flow rate; LF, low frequency component; DNA SB, DNA strand breaks.
The exposure data were collected during 3 days and biomarkers data assessed from sampling in the 3
rd
day
of exposure. Day 1 corresponds to the first day in the trains, two days before sampling; day 2 corresponds
to the second day in the trains, one day before sampling; and day 3 to the third day in the trains and the
sampling day.
a)
SB was transformed with cubic root.
*,**,***, p<0.05; <0.01; <0.001, respectively
Discussion
This study shows that DE exposure in carriages of diesel-powered trains, for 6 hours per day for
three consecutive days, was sufficient to cause a reduction of lung function and systemic effects in
terms of altered heart rate variability and increased levels of DNA strand breaks in PBMCs in
healthy volunteers.
The reduction in lung function after DE exposure although small was remarkably consistent
between the subjects. Nevertheless, the study participants could not be blinded for the exposure,
which could potentially influence their effort in the spirometry performance. This is an
unavoidable study limitation. We minimized this potential bias through the study design, which
included a repetition of the diesel scenario, and 21-day wash out periods. It was not possible to
separate the acute and late effects of DE exposure in the present study where exposure was
repeated for three consecutive days before measurement of biomarkers. Similar associations
between lung function measures and NO
X
gases and particles were found, indicating that effects of
specific DE constituents cannot be differentiated in the current study. A study showed that DE
exposure (300 µg/m
3
for 2 h) had no immediate effect on the lung function, whereas there was a
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
stronger decline in ozone-mediated (300 ppb) FEV1 in the DE exposed group as compared to
filtered air the day after the exposure [20]. Other studies on short-term exposure to DE have not
demonstrated effects on FEV1 in humans [14, 19, 20, 21, 22, 23, 24, 25], whereas one study
showed reduced PEF starting at 75 min after the exposure [25]. PEF is reduced as a result of
obstruction in the airways, which is seen in asthma patients. In addition to a reduced PEF in our
study, there were reduced FEV1 and FVC and a near-normal FEV1/FVC ratio. Reduction of both
FEV1 and FVC, and unaltered FEV1/FVC ratio is typically observed in restrictive lung diseases,
including fibrosis. However, the current exposure is too short for inducing fibrosis and it is more
likely that the DE exposure affected the lung compliance towards decreased ability to expand.
This effect could be reversible, although recurrent exposures may have a long-term effect on the
lung function.
In the present study, there was unaltered vasomotor function and no effect on systemic levels of
acute phase proteins (CRP and SAA). Low-grade systemic inflammation is an integrated part of
the suggested mechanism of action of particle-generated toxicity in secondary tissues or cells [7].
It can be speculated that the exposure levels in the current study may not be sufficiently high to
induce an acute phase response. There was no effect of DE exposure on vasomotor function in the
current study. Other short-term controlled exposures to DE have yielded conflicting results in
vasomotor function; blunted vasodilator-induced forearm blood flow in certain studies [9, 10, 11]
and skin microvascular dysfunction [13]. Studies using flow-mediated vasodilation or reactive
hyperemia by EndoPAT have shown unaltered vasomotor function [18, 36, 37]. Interestingly,
certain studies have also reported increased vasoconstriction in DE exposed humans [18, 37, 38].
The available results may indicate a decreased sensitivity of vasodilator-induced foramen blood
flow, although it should also be noted that the diesel fuels and engine types differ between studies.
Our previous studies have indicated that exposure to PM from combustion processes were
associated with microvascular dysfunction in elderly subjects [39, 40, 41, 42, 43], whereas no
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
effects have been observed in young subjects [44, 45]. The wide age span in the present study
might have diluted the effect on vasodilation due to inclusion of young subjects who may not be
as susceptible to DE-induced vasomotor dysfunction. However, it should also be noted that a
meta-analysis from controlled exposures in animal models indicates that DE (or DEP) exposure
produces less effect on vasomotor responses as compared to outdoor air pollution particles and
nanoparticles [46]. In contrast to the unaltered vasomotor function, we observed effects in the
frequency-domain of HRV (16.5% increase in LF and a statistically non-significant 18.5%
increase in LF/HF ratio) that suggests a minor increase in sympathetic to vagal activity [47]. This
is consistent with our previous finding of increased LFn after 5
–h
exposure to street air in elderly
slightly overweight subjects [43]. In contrast, a study with controlled DE exposure at 206 µg/m
3
for 2 h showed a transient alteration in frequency domain outcomes in terms of increased HF and
decreased LF/HF ratio at 3 h post exposure [17]). Two other studies have found unaltered HRV in
subjects after short-term controlled DE exposure [15, 16].
We observed increased levels of DNA strand breaks after exposure to DE, whereas there were
unaltered levels of DNA oxidation lesions in the same PBMCs. In a previous study on controlled
DE exposure (276 µg/m
3
for 3 h) we observed no effect on these endpoints immediately after
exposure [31]. However, a controlled exposure study on traffic-generated air pollution showed a
positive association between personal particle number concentration of especially size modes 23
and 57 nm, with high deposition fractions, and levels of Fpg-sensitive sites in PBMCs [48].
Personal exposure to UFP, obtained by bicycling in streets with heavy traffic, was positively
associated with levels of Fpg-sensitive sites in PBMCs, whereas there was no effect on levels of
DNA strand breaks [49]. On the other hand, elderly and overweight subjects had unaltered levels
of DNA strand breaks and Fpg-sensitive sites after exposure to urban street air in a controlled
exposure study, whereas the total number of DNA lesions was positively associated with the
particle number concentration [50]. Studies on high-dose exposure in animals have demonstrated
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mixed results for the association between pulmonary exposure to DEP and DNA strand breaks in
lung tissue with certain studies showing increased levels of DNA damage [51, 52, 53] and no
effect [54, 55, 56]. The literature on oxidatively damaged guanine lesions is partly flawed by
studies that have used non-optimal techniques for measurements of 8-oxodG due to unspecific
detection or spurious oxidation of DNA during the processing of samples [57]. Two studies on
OGG1- or Fpg-sensitive sites, measured by the comet assay have shown unaltered levels of
oxidatively damaged DNA in lung tissue at 24 h after i.t. instillation [55, 56]. A study on repeated
inhalation (20 mg/m
3
for 1.5 h on 4 consecutive days) showed unaltered levels of Fpg-sensitive
sites and 8-oxodG in lung tissue of wild-type mice [54]. Interestingly, a previous study had shown
that a single inhalation exposure to 80 mg/m
3
of DEP increased the levels of 8-oxodG in mice,
whereas the same total administered dose on four consecutive days increased the expression of
OGG1 accompanied by unaltered levels of 8-oxodG [58]. This indicated that a high bolus
exposure may saturate the DNA repair system, whereas the oxidative damage to DNA can be
efficiently removed when DEP is administered in multiple lower doses.
The contrast between exposure levels in passenger carriages of diesel driven trains and electric
trains in the present study is clear, as indicated by the net average difference of 8.5 µg/m
3
in BC
(6-fold), 1.2 x 10
5
–
1.8 x 10
5
particles/cm
3
(15
–
24 fold) and 36 µg/m
3
NO
2
(3-fold) during the 6
h exposure periods. In addition, the average difference in PM
2.5
concentration between diesel and
electric trains was 36 µg/m
3
[33]. Previous studies on controlled DE exposure have used PM
concentrations up to 300 µg/m
3
for 1-3 h in chambers [19, 20, 21, 23, 25]. The time-integrated
exposure in the present study (216 µg*h/m
3
per day or 648 µg*h/m
3
per 3-day exposure period) is
similar to previous studies (300
–
900 µg*h/m
3
). We have previously reported a contrast in the
levels of particulate PAHs, but not for gaseous PAHs in the present train exposure scenarios,
although the limited number of samples available did not allow a statistical analysis [33]. We
observed unaltered urinary excretion of PAH metabolites; however, it is unclear if the current
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exposure contrast was large enough not to be masked by dietary exposure, despite the precautions
made. Moreover, the sampling time (morning of the third day) may have not been optimal to
detect urinary PAH metabolites. In a controlled wood smoke exposure study, urinary excretion of
nine hydroxylated PAHs reached maximal concentrations within 2.3 - 19.3 hours and returned to
background levels 24h after exposure [59]. 1-OHP has been used in epidemiological studies,
showing positive association with air pollution exposure, although confounding from smoking,
occupational PAH exposure and environmental tobacco smoke cannot be ruled out [60]. In
contrast, stricter control of other PAH exposures from diet and exclusion of smokers in controlled
trials ameliorate confounding.
Conclusions
The present study showed a consistent reduction in lung function and increased levels of DNA
strand breaks after exposure to DE inside passenger carriages of diesel-powered trains, whereas
the exposure did not affect the level of oxidatively damaged DNA in PBMCs. The only effect on
cardiovascular endpoints was an increased LF in the frequency-domain HRV, suggesting an
increase in sympathetic to vagal activity. In agreement with other studies on DE exposure, PAH
metabolites were not increased in urine. This may be due to lack of contrast in exposure and lack
of sensitivity from the biomarker to detect minor increases in PAH exposure from the background
levels of PAH exposure from e.g. diet. Overall, the 3-day exposure to DE in diesel-powered trains
was associated with lung and systemic effects.
Methods
Study participants
The participants were recruited by registering the study on a human trial web platform
(forsoegsperson.dk) and through flyers handed out in the area of Copenhagen, Denmark. We
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2069111_0017.png
enrolled 33 self-reported healthy, non-asthmatic, without prescribed medication, non-smoking
(defined as cessation of smoking at least one year before enrolment) and non-pregnant participants
living in the Copenhagen region. One subject was excluded after further medical examination and
three dropped out before completion. Table 5 presents the general characteristics of the study
participants. The age ranged from 21 to 71 years. Fifteen participants had a body mass index
(BMI) between 18.6 and 24.8 Kg/m
2
, ten between 25.2 and 28.1 Kg/m
2
and four between 30.8 and
39.0 Kg/m
2
.
Table 5.
Characteristics of the study participants at the control measurements (mean (±SD))
Characteristics
Age (years)
Height (cm)
Weight (kg)
BMI (kg/m
2
)
FVC (%)
FEV1 (%)
FEV1/FVC (%)
PEF (%)
Females (n=15)
34.7 (±14.7)
166.6 (±4.7)
71.5 (±17.5)
25.6 (±5.3)
92.7 (±15.6)
89.4 (±16.6)
96.3 (±7.6)
87.3 (±20.4)
Males (n=14)
43.4 (±17.6)
181.4 (±10.1)
81.4 (±16.5)
24.7 (±3.8)
91.2 (±21.5)
89.4 (±19.2)
98.0 (±6.5)
85.4 (±18.2)
Total (n=29)
38.9 (±16.5)
173.7 (±10.7)
76.3 (±17.4)
25.2 (±4.6)
92.0 (±18.2)
89.4 (±17.5)
97.1 (±7.0)
86.4 (±19.1)
SD, standard deviation; BMI, body mass index; FVC, forced vital capacity; FEV1, forced expiratory
volume in one second; PEF, peak expiratory flow rate. The lung function parameters are presented as the
percentage of the predicted value from the general population in the NHANES III survey.
Study design
The study participants travelled 6-hours per day during three consecutive days (always on
Tuesday, Wednesday and Thursday) inside diesel or electric trains running in the Zealand region,
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
exposure scenarios that have been previously described [33]. The study design was a crossover,
repeated measures, where participants served as their own control with a randomized order of
exposure inside diesel or electric trains. The diesel scenario exposure was repeated twice, to
account for the observed exposure levels and daily variations (four participants only participated
in one diesel train exposure). All exposure scenarios were separated by 2-week periods. The
participants were instructed to wear a mask (3M Aura
TM
9320+, USA) on the way from home to
the train station and back home on the exposure days, to prevent other ambient air PM exposure in
their transportation activity. At the end of the third day in each scenario, the participants walked
for 15 minutes from the station to the university facility where the biological samples were
collected. They did not use the mask on this walking trip, with the instruments collecting data on
exposure. They were also told to avoid consumption of smoked food on the exposure days, and
were offered a packed lunch consisting of a sandwich (of humus, tuna or chicken with salad and
sauce), fruit, water and a muesli bar every day on the trains. In the morning of the third day in
each exposure scenario, the participants gave a urine spot sample, and in the end of the day, we
sampled blood and measured lung and cardiovascular function. The participants filled four
questionnaires, one for housing characteristics and lifestyle and one for each sampling day about
food, activity and medication intake. The volunteers were travelling in groups of 3 to 6 subjects
and the entire study was completed within a 7-month period, from May to end of November 2017,
with intermission during July.
Exposure assessment
The study participants carried instruments to monitor UFP (DiscMini and NanoTracer), BC
(MicroAeth AE51) and nitrogen oxides (passive samplers Ogawa) as described previously [33].
Daily averages of UFP and BC were determined (without being synchronized and including the
data collected when the study participants walked from the station to the university facility where
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the biological sampling was performed) and averages over the 3 days of each exposure scenario
were allocated to each study participant. For nitrogen oxides the accumulated averages exposure
were used and also allocated to each study participant. Two measurement days with DiscMini
were excluded due to battery failure. A more comprehensive description of exposure data has been
published [33], although with a different treatment, as here all the collected data was included in
the daily averages, without synchronization start and end times and without eliminating days with
delays in the trains.
Lung function
Lung function was assessed with the EasyOne
TM
Sprirometer 2001 (ndd, Medical technologies,
Zurich, Switzerland), in diagnostic mode, measuring FVC, FEV1 and PEF. All measurements
were performed after careful instructions and with the participants standing. At least three
acceptable manoeuvres were performed to obtain reproducible tracings. The measurements were
performed 30-60 minutes after ending the exposure scenario. Two spirometer results were
eliminated due to deficient test quality.
Urine and blood sampling and analysis
First morning urine samples were delivered by the participants in 120 mL flasks, aliquoted and
stored at -20°C. Peripheral venous blood samples were collected at the Department of Public
Health laboratory facilities in Vacutainer cell preparation tubes (CPT
TM
, Becton Dickinson A/S,
Brøndby, Denmark) for isolation of PBMCs and ethylenediaminetetraacetic acid (EDTA)-coated
tubes for plasma preparation. The samples were stored at -80°C in preserving medium, as
previously described [34]. It was not possible to collect (and further analyse) 3 samples of blood.
Analysis of biomarkers of exposure in urine
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Levels of 1-OHP, 2-OHF, 1-NAPH and 2-NAPH in urine were measured after solid phase
extraction (SPE) using liquid chromatography with tandem mass spectrometry (LC-MS-MS). In
brief, 1ml of urine was mixed with a buffer solution and deconjugated (β-glucoronidase,
37°C, 18-
20h), after which deuterium-labeled internal standards were added. The samples were loaded onto
pre-washed 500mg C18 SPE-columns (Bond Elut, Agilent Technologies) and subsequently
washed using 6ml methanol:water (1:3) and 6ml water. The SPE-columns were dried overnight at
55°C and eluted with 3 ml methanol. The extract were evaporated to dryness under a gentle stream
of nitrogen and reconstituted in 300 µL methanol. The extracts were analyzed on an Agilent LC-
MS-MS (series 6460) using a Phenomenex C18, 100Å, 100x2 mm column with a gradient of
water and methanol. 1-OHP and 2-OHF were quantified using d
9
-1-OHP while d
8
-2-NAPH was
used for 1-NAPH and 2-NAPH. The limit of quantification was set to 10 times the signal-to-noise
ratio.
All urine concentrations were standardized for diuresis with the concentration of creatinine as
previously described [61].
Analysis of biomarkers of effect in blood
The concentrations of SAA and CRP in plasma were determined by the enzyme-linked
immunosorbant assay kits from Invitrogen (CA, USA) and IBL International GMBH (Hamburg,
Germany), as previously described [62]. Plasma levels of soluble ICAM-1 and VCAM-1 were
measured with BD cytometric bead array system, using Accuri CFlow Plus software (BD
Bioscience) as described previously [63]. DNA damage was assessed by levels of DNA strand
breaks and Fpg-sensitive sites using the comet assay as described elsewhere [64]. The number of
Fpg-sensitive sites was obtained as the difference in scores of parallel slides incubated with and
without Fpg (gift from Professor Andrew Collins, University of Oslo, Norway). These scores were
transformed to lesions per 10
6
base pairs (bp) by means of a calibration curve based on induction
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of DNA strand breaks by ionizing radiation (0-2.5 Gy), which has a known yield. We used an
investigator-specific conversion factor of 0.0162 lesions/10
6
bp per score in 0-100 range, based on
the assumption that an average molecular weight of a DNA bp is 650 Dalton and one Gy yields
0.29 breaks per 10
9
Dalton DNA [65]. Assay control (i.e. cryopreserved samples of THP-1 cells
exposed to 5 mM KBrO
3
for 1 hour at 37°C as recommended elsewhere [66]. The assay controls
were 1.29 ± 0.12 and 0.14 ±0.05 for Fpg-sensitive sites and DNA strand breaks, respectively
(mean ± SD, n = 10).
Cardiovascular function
RHI, HRV and augmentation index were measured non-invasively using the portable
EndoPAT2000 (Itamar Medical Ltd., Israel), as previously described [35]. The cardiovascular
function was the last measurement performed on the study participants (1-2 hours after end of
exposure). Blood pressure was measured with a single measurement using an automatic upper arm
blood pressure monitor (Microlife Colson BP 3BXO-A, Widnau, Switzerland), before the
peripheral arterial tonometry (PAT) measurement and in the contralateral arm (control arm),
where the blood sample was also taken. Pneumatic sensors were placed on the index fingers to
measure pulse volume changes in three test phases: a baseline recording (6-minutes), a brachial
arterial occlusion of one of the arms (5-minutes), and a post-occlusion recording of the induced
reactive hyperemia response (5-minutes), with reference to the finger probe on the control arm.
Additionally, we also measured the vasodilation induced in the control arm after sublingual
administration of 0.25 mg of nitroglycerin. The nitroglycerin-induced vasodilation was calculated
as the ratio of one-minute average amplitudes of the PAT signal after and before administration,
chosen from the 5 minutes signal at baseline after reactive hyperemia effect and the peak reached
during the 15 minutes after nitroglycerin treatment. The nitroglycerin was administrated only to 10
participants in both exposure scenarios because of limited medical supervision or a possible
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history of migraine precluded the administration of nitroglycerin. The EndoPAT software
determines the HRV based on 5 minutes from the baseline recording, including time domain
(SDNN, pNN50 and RMSSD), high (HF) and low frequency (LF) components as well as the ratio
LF/HF. It is also from the baseline recording that the augmentation index is determined. All the
measurements were done with the participants resting seated, in a quiet room. HRV and LnRHI
measurements had 6 missing values.
Statistics
The results were analysed in a hierarchical approach: first, the effect of diesel exposure as
compared to electric trains on all the assessed biomarkers was assessed, and secondly, for
biomarkers with statistical significance or border line significance, the associations between air
pollution components and biomarkers were assessed. We analysed our results in R statistical
environment by linear mixed-effects model using the package
lme4
[67]. As fixed effects we used
factorial variables of exposure (diesel/electric) and sex and continuous variable of age. The
analyses were adjusted for sex and age because we had missing data. As random effects we used
by-participant intercepts. P-values were obtained with the function
glht
from
multcomp
package
[68]. We tested the interaction of the order of exposure scenario (electric or diesel) for the relevant
biomarkers (with significance or border line significance in the first analysis) and there were no
significant interactions. The percent changes were determined by dividing the estimate change
with the intercept value and multiplying with 100, except for RHI, augmentation index, SDNN,
RMSSD, LF/HF, FVC, ICAM-1, VCAM-1, 2-OHF, 2-NAPH, SAA and CRP that were natural
logarithmically transformed and DNA strand breaks and 1-OHP that were transformed with cubic
root, and therefor percent changes were obtained from (EXP
estimate
-1)*100 and
(((((estimate+intercept)
3
-intercept
3
)+intercept)/intercept)-1)*100, respectively. The residuals were
checked for normality with Shapiro-Wilk test, kurtosis and graphically with histogram and Q-Q
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plot. Augmentation index, SDNN, RMSSD, LF/HF, FVC, ICAM-1, VCAM-1, 2-OHF, 2-NAPH,
SAA, and CRP, showed better distributions after natural logarithmic transformation and DNA
strand breaks and 1-OHP after cubic root transformation. Associations that were statistically
significant in mixed effects models have been depicted in graphs with the mean of the two
measurements for each study participant in the DE scenario. The corresponding univariate
analyses of the data in the graphs are mixed effects models without control for age and sex
(similar to paired sample t-test).
List of abbreviations
BC, black carbon
BMI, body mass index
bp, base pairs
CRP, C-reactive protein
DE, diesel exhaust
DEP, diesel exhaust particles
FEV1, forced expiratory volume in one second
FVC, forced vital capacity
Fpg, Formamidopyrimidine DNA glycosylase
HF, high frequency component (0.15-0.4 Hz)
HRV, heart rate variability
LF, low frequency component (0.04-0.15 Hz)
PAH, polycyclic aromatic hydrocarbons
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PAT, peripheral arterial tonometry
PBMCs, peripheral blood mononuclear cells
PEF, peak expiratory flow
PM, particulate matter
pNN50, proportion of successive NN intervals differing by more than 50 milliseconds divided by
total number of NN intervals
RHI, reactive hyperemia index
RMSSD, root mean square of the successive differences
SAA, serum amyloid A
SDNN, standard deviation of all NN intervals
UFP, ultrafine particles
Declarations
Ethics approval and consent to participate
The Danish Committee on Health Research Ethics of the Capital Region approved the study (H-
16033227). All study participants were given both oral and written information and provided
written consent before enrolment.
Consent for publication
Not applicable.
Availability of data and materials
The datasets analysed during the current study are available from the correspondent author on
reasonable request.
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
Competing interests
The authors declare that they have no competing interests.
Funding
The research leading to these results has received funding from Danish Centre for Nanosafety II.
Author’s contribution
MHGA, PM, SL, ATS and UV designed the study. MHGA and PM were responsible for ethical
submission and recruitment of participants. MHGA was responsible for study coordination, and
acquisition of data on vasculature effects and DNA damage. PM was responsible for the
acquisition of data on lung function. SL and RW were responsible for medical supervision and
assisted the acquisition of data on independent endothelium vasodilatation. ATS and MR
supervised the acquisition of data on inflammatory markers and cell adhesion molecules,
respectively. MF was responsible for the acquisition of data on urinary excretion of PAHs
metabolites. MHGA, ASF, IKK and SJ were responsible for exposure characterization. MHGA
and PM analysed the data. MHGA, PM, RW and SL interpreted the health related data. MHGA
drafted the manuscript, which was critically revised by PM, SL, ATS and UV. All authors have
read, corrected and approved the manuscript.
Acknowledgments
The technical assistance from Annie Jensen, Yuki Tokunaga, Lisbeth Carlsen, Halema Sadia and
Ulla Tegner is gratefully acknowledged. A special thanks goes to Danish State Railways for all the
logistical support. We are also grateful to the study participants for the considerable time and
willingness put into this study.
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2069111_0026.png
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Figure 1.
Correlation between air pollution components in diesel and electric trains.
The data corresponds to 63 (UFP and black carbon measured with NanoTracer equipment and
Aethalometer, respectively) and 55 (UFP measured with DiscMini equipment) days of exposure. Nitrogen
oxides were measured over 3 days, corresponding to 18 periods.
Figure 2.
Lung function parameters after exposure in electric and diesel trains.
The circles in grey represent individual lung function parameters for electric train (one exposure scenario)
or diesel train (mean of two exposure scenarios). The dark line represents the mixed-effects model without
 BEU, Alm.del - 2018-19 (2. samling) - Bilag 28: Orientering om resultater vedr. dieseludsættelse i tog, fra beskæftigelsesministeren
adjustments. Lower levels of FEV1 and PEF were observed on group level (solid symbols) after exposure
in diesel trains (p<0.05).
Figure 3.
Low frequency (LF) component of heart rate variability measured after exposure in
electric and diesel trains.
The circles in grey represent LF measurements in electric train (one exposure scenario) or diesel train
(mean of two exposure scenarios). The dark line represents the mixed-effects model without adjustments.
Higher LF levels were observed on group level (solid symbols) after exposure in diesel trains (p<0.05).
Figure 4.
DNA strand breaks in peripheral blood mononuclear cells after exposure in electric and
diesel trains.
The circles in grey represent DNA strand breaks in electric train (one exposure scenario) or diesel train
(mean of two exposure scenarios). The dark line represents the mixed-effects model without adjustments.
Higher levels of DNA strand breaks were observed on group level (solid symbols) after exposure in diesel
trains (p<0.05).