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ORIGINAL ARTICLE
Assessment of pollution levels and human health risk of heavy
metals in dust deposited on Yerevan’s tree leaves (Armenia)
N. Maghakyan
1
•G. Tepanosyan
1
•O. Belyaeva
1
•L. Sahakyan
1
•A. Saghatelyan
1
Received: 6 April 2016 / Revised: 23 July 2016 / Accepted: 23 August 2016
ÓScience Press, Institute of Geochemistry, CAS and Springer-Verlag Berlin Heidelberg 2016
Abstract The total concentrations of Cd, As, Pb, Cr, Ni,
Co, Zn, Cu, Ag, Hg, and Mo were determined in the
atmospheric dust of the city of Yerevan by atomic
absorption spectrometry (AAnalyst PE 800). Heavy metal
pollution levels were evaluated by calculating geo-accu-
mulation (I
geo
) and summary pollution (Z
c
) indices.
Potential human health risk was assessed using the United
States Environmental Protection agency’s human health
risk assessment model. The results show that mean con-
tents of all elements tested except Ni and Cr were sub-
stantially higher than local geochemical background
values. According to the I
geo
, Yerevan territory is strongly-
to-extremely polluted by As, Ag, Hg, Mo, and Cd. The Z
c
assessment indicated that very high pollution was detected
in 36 % of samples, high in 32 %, average in 12 %, and
low in 20 %. The health risk assessment revealed a non-
carcinogenic risk (HI[1) for children at 13 samplings sites
and for adults at one sampling site. For children the risk
was due to elevated levels of Mo, Cd, Co, and As, while for
adults, only Mo. Carcinogenic risk ([1:1,000,000) of As
and Cr via ingestion pathway was observed in 25 and 14
samples, respectively. This study, therefore, is the base for
further detailed investigations to organize problematic site
remediation and risk reduction measures.
Keywords Urban dust Heavy metals Pollution levels
Health risk assessment
1 Introduction
Dust, one of the basic atmospheric pollutants, is an
aggregation of naturally occurring and anthropogenic solid
particles. Dust can have a negative impact on human health
(Al Jallad et al. 2013; Zhou et al. 2014; Lu et al. 2015). The
character and degree of basic impacts of dust depend on
particle size, composition, and duration of exposure.
Atmospheric dust is known as a carrier of toxic substances,
especially heavy metals (Duzgoren-Aydin et al. 2006;
Chaudhari et al. 2012). Heavy metals in dust may penetrate
the human organism through inhalation, ingestion, and skin
absorption and induce negative effects such as hematoge-
nesis disorders and problems in the central nervous, cardio-
vascular, and urogenital systems (Li et al. 2013). More-
over, individual heavy metals are known to trigger specific
diseases such as Alzheimer’s and Parkinson’s (Oves et al.
2012).
Pollution by dust and heavy metals is of particular
concern in urban areas because of high population density
and numerous sources of pollution—motor transport,
industrial plants, domestic refuse, corrosion of roadway
surfaces, etc. (Charlesworth and Lees 1999; Sharma et al.
2008; Wei et al. 2010; Cai et al. 2013). Extensive recent
research has sought to estimate pollution levels, identify
sources, and assess potential health risks—both to children
and adults—associated with heavy metals in dust. An
essential element of such studies has been the investigation
of street dust and its heavy metal contents (Lu et al.
2009,2015; Kong et al. 2011; Du et al. 2013; Zhang et al.
2013; Li et al. 2014; Wang et al. 2014). Another way to
study urban atmospheric dust is to use biomonitors such as
higher plants. Although higher plants are not ideal
biomonitors like mosses and lichens, in industrialized and
urban areas that are missing these vegetation types, higher
&N. Maghakyan
nairuhi.maghakyan@cens.am
1
Department of Environmental Geochemistry, Center for
Ecological-Noosphere Studies of the National Academy of
Sciences, Abovian-68, 0025 Yerevan, Republic of Armenia
123
Acta Geochim
DOI 10.1007/s11631-016-0122-6
plants can be used as well. Airborne particles including
dust and heavy metals deposit on the surface of tree leaves
via wet and dry atmospheric precipitation (Mingorance and
Oliva 2006; Pavlı
´k et al. 2011). According to the Toma-
s
ˇevic et al. (2005) study, tree leaf deposits directly reflect
the level of atmospheric pollution by heavy metals.
Yerevan is an old city and, being an industrial center with
dense population and heavy traffic, it has been exposed to
high levels of atmospheric pollution for years (Saghatelyan
and Arevshatyan 2003; Saghatelyan 2004; Sahakyan 2006;
Saghatelyan et al. 2014). During the Soviet period, the
spatial planning of the city was quite ordinary, and there
were more heavily polluted industrial pockets of the city.
After the collapse of the Soviet Union, during social and
economic transformations in the 1990s and now, during
recovery of industry, the spatial distribution of industrial
units throughout Yerevan reflects a more mosaic character,
i.e. irregularly spread across the city. This complicated the
process of identification of pollution sources for exact con-
taminants. Although geochemical investigations have been
conducted for many decades, it should be stressed that
assessment of dust and heavy metal-induced health risks to
Yerevan’s residents has never been done before. The goal of
this research was to assess levels of heavy metals pollution
in urban dust using tree leaves as dust accumulators and
assessing health risks to different groups of the population
(children and adults).
2 Materials and methods
2.1 Study site
Yerevan (latitude 40°1004000N, longitude 44°3004500E),
Armenia’s capital, covers an area of 223 km
2
with a pop-
ulation of just over one million people. The relief is rather
diverse and is represented by plains, plateaus, foothills, and
the River Hrazdan canyon. The city is situated at a height
of 850–1420 m a.s.l. The climate is typically dry conti-
nental; the amount of annual precipitation is 250–400 mm.
Mean air temperature varies from 22 to 26 °C in summer
and -4to-6°C in winter. Persistent snow cover occurs in
January and February, but not regularly. Northeastern
winds dominate the city year-round, but the air cycle is
substantially complicated because of the topography (in-
termountain trough) and specificity of site development.
Thermal inversions occur during winter. Dry steppe and
semi-desert natural landscapes are common.
The main industrial branch is processing. The city con-
tains metallurgical plants, manufacturing enterprises (pro-
duction of concrete, wood- and metalware, food, medicines,
paper, etc.), and stone- and woodworking workshops. In the
area of Yerevan and its outskirts there are active sandpits
and quarries of basalt, tuff, and clay. Presently, the city area
is under intense construction; in most cases, construction
sites are not properly isolated.
2.2 Sampling and analysis
Sampling density in local-scale projects does not follow
any exact rules, as it mainly depends on the objectives of
the project and available funds (Demetriades et al. 2015).
In the case of multifunctional cities having mosaic distri-
bution of pollution sources such as Yerevan, this issue
becomes more complicated; collection and analysis costs
can restrict sampling scale and sample size.
In this study, sampling sites were based on the geo-
morphological features and the peculiarities of the spatial
distribution of urban green areas which cover 5.6 %
(12.5 km
2
) of the territory of Yerevan. The number of
samples was determined taking into account available
funds and the long-term air monitoring points of the Center
for Ecological-Noosphere Studies (CENS) NAS RA in
order to ensure continuity of research.
In the summer 2011, 25 tree-leaf samples were collected
from the city. Samples were collected from the most wide-
spread tree species having relatively good dust absorption
properties (Kretinin and Selyanina 2006): white elm (Ulmus
laevis), Chinese elm (Ulmus parvifolia), Persian walnut
(Juglans regia), oriental plane tree (Platanus orientalis),
common lilac (Syringa vulgaris), white poplar (Populous
alba), and white mulberry tree (Morus alba) (Fig. 1).
Leaves were sampled at a height of 1.5–2 m above the
ground from at least three trees of the same species per sam-
pling site then placed in paper bags and transported to the
Central Analytical Laboratory CENS accredited by ISO-IEC
17025.
After the sampled leaves had been dried at room tem-
perature, they were washed with de-ionized water (MilliQ).
The generated liquid underwent filtration using a weighed
ash free filter (retention limit 2–3 lm).
Dry residue was dissolved in nitric acid (1:1), then the
acid was evaporated and MilliQ water was added to the
residual solution until 20 ml was achieved.
In the filtrated matter the contents of eleven elements—
Cd, As, Pb, Cr, Ni, Co, Zn, Cu, Ag, Hg, and Mo—were
determined by AAnalyst 800 AAS PE, USA.
Concentrations below detection levels of the employed
analytical method were given a value half of the detection
limit as proposed by Reimann et al. (2008).
2.3 Assessment of pollution with heavy metals
in dust
Based on the concentrations of heavy metals in Yerevan’s
atmospheric dust, single-element and multi-element
Acta Geochim
123
pollution level assessments were done. Particularly, the
degree of each heavy metal contaminant in the dust was
characterized by geoaccumulation index (I
geo
) (Muller
1969; Lu et al. 2009; Johnson et al. 2011):
Igeo ¼log2
Ci
1:5Bi
ð1Þ
where C
i
is the concentration of element i in dust, while B
i
is the local geochemical background concentration from
Tepanosyan et al. (2016) of the ith element in Yerevan’s
soil. The following classification is given for the I
geo
:
unpolluted (I
geo
B0), unpolluted to moderately polluted
(0 \I
geo
B1), moderately polluted (1 \I
geo
B2), mod-
erately to strongly polluted (2 \I
geo
B3), strongly pol-
luted (3 \I
geo
B4), strongly to extremely polluted
(4 \I
geo
B5), and extremely polluted (5 \I
geo
) (Muller
1969; Lu et al. 2009; Johnson et al. 2011).
For an integral description of heavy metal pollution, the
summary pollution level was assessed and a contamination
index (Z
c
) was calculated (Perelman and Kasimov 2000;
Johnson and Demetriades 2011) according to formulas (2)
and (3).
Kc¼Ci
Cf
ð2Þ
Zc¼X
n
i¼1
Kcn1ðÞ ð3Þ
where K
c
is a concentration coefficient, C
i
is the content of
ith metal in dust, C
f
is local background content of the ith
element in soil from Tepanosyan et al. (2016), and nis the
number of elements in the same sample with K
c
[1. The
summary pollution level was classified as low (Z
c
\16),
moderately hazardous (16 \Z
c
\32), high/hazardous
(32 \Z
c
\128), or very high/extremely hazardous
(Z
c
[128) (Perelman and Kasimov 2000).
Finally, to obtain qualitative and quantitative charac-
teristicics of heavy metals in soil, decreasing geochemical
series were created.
2.4 Risk assessment
Taking into account toxic and carcinogenic effects of
heavy metals, calculations of both non-carcinogenic and
carcinogenic risks were done. Two pathways of exposure
of humans to dust heavy metals—direct ingestion of dust
particles and dermal absorption of dust heavy metals (Lu
et al. 2009; RAIS 2014)—were considered for non-car-
cinogenic risk assessment. Risk from inhalation was not
assessed as undifferentiated dust was investigated.
Health risks to children and adults posed by heavy
metals in dust were calculated in a manner consistent with
a health risk model developed by the US Environmental
Protection Agency (US EPA 1989,2002; RAIS 2013).
Fig. 1 Position of Yerevan in Armenia’s area, sampling points and sampled tree species
Acta Geochim
123
2.5 Non-carcinogenic risk
Non-carcinogenic risk was calculated with respect to all the
detected heavy metals: Hg, Pb, Mo, Cd, Zn, Cu, Ni, Ag,
Co, Cr, and As.
Per metal chronic daily intake (CDI) per pathway of
exposure was calculated by formulas (4) and (5) (US EPA
US 1989,2002; RAIS 2013).
CDIing
mg
kg day
¼CIngR EF ED 106
AT BW ð4Þ
CDIdermal
mg
kg day
¼CEF ED SA AF ABSd 106
AT BW
ð5Þ
Non-carcinogenic hazard quotient per element via each
pathway was calculated by formulas (6) and (7):
HQing ¼CDIing
RfDing
ð6Þ
HQdermal ¼CDIdermal
RfDdermal
ð7Þ
Description and values of factors used in formulas (4–7)
are given in Tables 1and 6.
RfD values (Table 1), which underpinned the assess-
ment of non-carcinogenic risk, were taken from the risk
assessment information system (RAIS 2013). There exists
no Oral RfD value for Pb, so this research used the value
from the WHO guidelines for drinking water quality (WHO
1998).
RAIS lacks dermal RfD values, so instead, with respect
to all the elements, oral chronic RfD
ing
values multiplied
by respective gastrointestinal absorption factors (US EPA
2002,2004; RAIS 2013) were used.
The sum of all HQ values represents a Hazard Index
HI =RHQ
i
. In addition, a single-element HI including
ingestion and dermal absorption pathways was calculated
to reveal priority of elements, while multi-element HI of all
studied elements via two pathways was evaluated to
describe total human health risk. HI\1 indicates the
absence of harmful effect on the health, whereas HI[1
denotes a possibility of adverse health effects.
2.6 Carcinogenic risk
Carcinogenic risk is defined as occurrence probability for
any type of cancer during the whole lifetime in case of
exposure to a carcinogenic element. The allowable risk
limits are defined as 10
-6
–10
-4
(Lu et al. 2009). Particu-
larly, in the case of a single element, allowable carcinogenic
risk limit is 10
-6
, while for multi-element carcinogenic risk
the allowable limit is\10
-4
(TCEQ Regulatory Guidance).
According to the International Agency for Research on
Cancer, Cr, Cd, As, Ni, and Co are considered to have a
carcinogenic effect (Cao et al. 2014). Taking into consid-
eration the existence of slope factors, the carcinogenic risks
of Cr and As through ingestion were assessed.
The lifetime (LT =70) average daily dose was calcu-
lated for the ingestion pathway by formula (8) (US EPA
1989,2002; RAIS 2013):
LADDing ¼CEF 106
AT LT
EDchild IngRchild
BWchild
þEDadult EDchild
ðÞIngRadult
BWadult
ð8Þ
Carcinogenic risk from ingestion for each element was
assessed by formula (9) (RAIS 2013), while multi-element
Table 1 Description and values of factors used in the risk assessment equations
Factors (measurement unit) Description Value Source
Adults Children
IngR (mg/day) Ingestion rate 100 200 (US EPA 2002)
EF (day/year) Exposure frequency 90* 90* –*
ED (year) Exposure duration 30 6 (US EPA 2002)
BW (kg) Average body weight 70 15 (US EPA 1989)
SA (cm
2
) Skin area 5700 2800 (US EPA 2002)
AF (mg/cm
2
) Skin adherence factor 0.07 0.2 (US EPA 2002)
AT Average time In the case of non-carcinogenic exposure AT =365 9ED (US EPA 2002)
ABS
d
Dermal absorption (ABS =0.03 for As, ABS =0,001 for the rest of elements. (RAIS 2013)
RFD
ing
(mg/kg-day), Chronic reference dose Chemical specific (RAIS 2013)
SF(mg/kg-day)
-1
Cancer slop factor Chemical specific (RAIS 2013)
*Values used for this particular research
Acta Geochim
123
carcinogenic risk (RI) was calculated by summing single
element carcinogenic risk values.
Oral Risk ¼LAADing SF ð9Þ
Description and values of the coeffients are given in
Tables 1and 7, while carcinogenic risk level classification
is given in Table 2(Rapant et al. 2010).
3 Results and discussion
3.1 Contents of heavy metals in atmospheric dust
Ni, Co, Ag, Cr, Pb, Mo, Cd, Zn, and Cu were detected in all
samples, whereas As in two samples and Hg in six samples
had concentrations below the detection limit. A value of
half of the detection limit was given in these cases as
proposed by Reimann et al. (2008).
Descriptive statistical parameters and local geochemical
background values of heavy metals are given in Table 3.
As demonstrated in Table 3, asymmetry and excess
values of all the elements differ from 0 which proves
deviation from normal distribution.
The standard error (k) of the mean of studied heavy
metals at the level of 5 % (p \0.05) reflects the repre-
sentativeness of the 25 samples’ studied. Mean standard
errors (Table 3) of heavy metals in dust deposits of Yere-
van territory’s tree leaves show that studied heavy metals
categorized into the following three groups: (1) Ni, Cr, Zn,
and Co (k\20 %); (2) Ag, Hg, Cu, and Pb
(20 % \k\50 %); and (3) As, Mo, and Cd (k[50 %).
The highest standard mean errors were observed for As,
Mo, and Cd: 24.38 (155.2 %), 1914.43 (188.7 %) and
60.51 (124.3 %), respectively. After removing some
extreme values of these elements which were thought to be
the results of discharges from point pollution sources, the
standard mean error values became As 39.2 %, Mo 40.2 %,
and Cd 44.1 %. According to Revich et al. (1982), allow-
able standard mean error to be considered background sites
(or natural) is kB30 %. For this study k\50 % can be
considered sufficient, but further detailed investigations
should be carried out to reveal sources and spatial distri-
bution peculiarities of As, Mo, and Cd.
Meanwhile, Ni, Co, and Zn may be regarded as having
an approximately normal distribution according to the rule
of ±3 (Beus et al. 1976). Also, typical of Ni, Co, and Zn
are relatively low values of the coefficient of variation
(CV): 26, 47 and 40, respectively. Relatively low CV was
determined for Cr, Ag, Hg, Pb, and Cu. However, their
distribution significantly deviated from normal distribution,
which might be due to the presence of outliers and extreme
values of manmade contents. CV values of As, Mo, and Cd
were 396, 481, and 317, respectively. This is attributed to
extremely high manmade contents of heavy metals detec-
ted in some dust samples.
Mean contents of almost all elements except Cr and Ni
exceeded background contents (Tables 3,4). As seen from
the arranged geochemical series (Table 4), mean contents
of Mo, Cd, Hg, and Ag are manifold excessive versus the
background: by 579.8, 155.9, 33.5, and 26.8 times,
respectively. At their highest contents Mo, Cd, As, and Hg
showed the highest excesses versus the background: by
13,974.86, 2510.9, 453.5 and 139.4 times, respectively.
It should be noted that collation of statistical charac-
teristics of Ni, Co, and Zn with results obtained during
comparison of mean of these elements versus local back-
ground values suggests that Ni may have a natural origin,
while Co and Zn come from both natural and anthro-
pogenic sources. The known source for heavy metals,
especially Mo, in the Yerevan area is Mo concentrate
smelting and processing in plants located in the south of
Yerevan, where all studied elements with the exception of
Ni exceeded local background values. In addition, for Cd,
vehicle tire wear is supposed to be one of the main sources
of pollution. For Hg, sources include combustion of diesel,
jet fuel, medical waste disposal facilities, dental offices,
and some consumer products. Arsenic may have come
from metal smelting, glass, textiles, and paper production.
At the lowest contents Hg, Ag, Pb, Zn, and Cu are also
excessive versus the background (Tables 3,4).
3.2 Heavy metal pollution assessment
3.2.1 Geoaccumulation index
The calculated results of I
geo
of heavy metals in dust are
presented in Table 5. The mean values of I
geo
decrease in
the order of Cd[Mo[Ag[Hg[Pb[Cu[Zn[Co[As[
Ni[Cr. The I
geo
ranges from -1.56 to 0.07 with a mean
value of -0.70 for Ni (unpolluted); -7.96 to 2.1 with a
mean value of 0.68 for Co (moderately polluted); -4.88 to
8.24 with a mean value of 0.56 for As (unpolluted to
moderately polluted); 2.06 to 6.35 with a mean value of
Table 2 Carcinogenic risk level classification (Rapant et al. 2010)
Risk level Calculated cases of cancer
occurrence
Cancer risk
I\10
-6
Very low
II 10
-6
–10
-5
Low
III 10
-5
–10
-4
Medium
IV 10
-4
–10
-3
High
V[10
-3
Very high
Acta Geochim
123
3.59 for Ag (strongly polluted); 0.23 to 6.54 with a mean
value of 3.46 for Hg (strongly polluted); -2.21 to 0.49 with
a mean value of -1,09 for Cr (moderately polluted); 0.75
to 3.91 with a mean value of 1.96 for Pb (moderately
polluted); -0.77 to 13.18 with a mean value of 3.65 for Mo
(strongly polluted); -2.4 to 10.7 with a mean value of 4.82
for Cd (strongly to extremely polluted); 0.13 to 2.12 with a
mean value of 1.15 for Zn (moderately polluted); and 0.005
to 3.66 with a mean value of 1.83 for Cu (moderately
polluted).
Table 3 Mean contents of heavy metals, descriptive statistical parameters, and background values
Value Ni Co As Ag Hg Cr Pb Mo Cd Zn Cu
Mean
a
29.09 62.26 15.71 6.68 0.57 54.23 32.43 1014.68 48.66 281.93 294.65
Std. error (p \0.05), k2.91 11.50 24.38 2.93 0.23 10.05 8.10 1914.43 60.51 44.36 90.47
Median
a
28.65 70.66 2.05 3.40 0.43 48.03 30.15 24.89 12.84 288.73 261.05
SD 7.44 29.34 62.19 7.49 0.59 25.64 20.67 4883.76 154.36 113.17 230.80
Skewness 0.27 -1.14 4.93 2.30 1.43 2.45 2.30 5.00 4.87 0.56 0.83
Std. error of skewness 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46 0.46
Kurtosis 0.19 0.43 24.52 4.96 2.18 7.63 7.08 25.00 24.07 -0.53 -0.60
Std. error of kurtosis 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90
Minimum
a
15.48 0.09 0.04 1.56 0.03 23.11 12.10 1.54 0.09 129.01 60.24
Maximum
a
47.77 100.90 312.94 30.63 2.37 149.81 108.47 24456.00 783.43 511.45 757.70
CV, % 26 47 396 112 102 47 64 481 317 40 78
Background
b
30.4 15.65 0.69 0.25 0.017 71.1 4.8 1.75 0.312 78.38 40.03
a
values are described in mg/kg: n =25
b
Tepanosyan et al. (2016)
Table 4 Geochemical series arranged according to highest, mean, and lowest contents
Contents Geochemical series
Highest Mo
(13974.9)
[Cd
(2510.9)
[As
(453.5)
–Hg
(139.4)
–Ag
(122.5)
[Pb
(22.6)
–Cu
(18.4)
[Zn
(6.5)
–
Co
(6.5)
–Cr
(2.1)
–Ni
(1.6)
Mean Mo
(557.7)
–Cd
(151.6)
[Hg
(42.9)
–Ni
(28.9)
–Ag
(26.8)
–As
(23.8)
[Cu
(7.5)
–Pb
(6.7)
–Co
(4.0)
–Zn
(3.6)
Lowest Ag
(6.3)
–Pb
(2.5)
–Hg
(1.8)
–Zn
(1.7)
–Cu
(1.5)
Table 5 Values of I
geo
and single-element pollution levels
I
geo
Elements
Ni Co As Ag Hg Cr Pb Mo Cd Zn Cu
Max 0.07 2.10 8.24 6.35 6.54 0.49 3.91 13.19 10.71 2.12 3.66
Min -1.56 -7.96 -4.89 2.06 0.23 -2.21 0.75 -0.77 -2.41 0.13 0.005
Mean -0.70 0.68 0.56 3.59 3.46 -1.09 1.96 3.65 4.82 1.15 1.83
SD 0.38 2.46 2.91 1.18 2.09 0.55 0.77 2.44 2.15 0.59 1.22
Samples (%)
I
geo
B0 96.0 16.0 24.0 0.0 0.0 96.0 0.0 4.0 4.0 0.0 0.0
0\I
geo
B1 4.0 0.0 28.0 0.0 24.0 4.0 12.0 4.0 0.0 44.0 32.0
1\I
geo
B2 0.0 76.0 28.0 0.0 0.0 0.0 36.0 8.0 0.0 48.0 16.0
2\I
geo
B3 0.0 8.0 8.0 32.0 12.0 0.0 44.0 20.0 0.0 8.0 32.0
3\I
geo
B4 0.0 0.0 4.0 36.0 12.0 0.0 8.0 36.0 16.0 0.0 20.0
4\I
geo
B5 0.0 0.0 4.0 16.0 28.0 0.0 0.0 12.0 40.0 0.0 0.0
5[I
geo
0.0 0.0 4.0 16.0 24.0 0.0 0.0 16.0 40.0 0.0 0.0
Acta Geochim
123
The concentrations of Ni, Co, As, Cr, Mo, and Cd reg-
ister at the unpolluted level (I
geo
B0) in 96 %, 16 %,
24 %, 96 %, 4 %, and 4 % of all samples, respectively.
The unpolluted to moderately polluted (0 \I
geo
B1) level
was determined in 4, 28 %, 24 %, 4 %, 12 %, 4 %, 44 %,
and 32 % of all samples for Ni, As, Hg, Cr, Pb, Mo, Zn,
and Cu, respectively. The moderately polluted (1 \I
geo
B2) level included 76 %, 28 %, 36 %, 8 %, 48 %, and
16 % of all samples for Co, As, Pb, Mo, Zn, and Cu,
respectively. The moderately-to-strongly polluted
(2 \I
geo
B3) level was observed in 8 %, 8 %, 32 %,
12 %, 44 %, 20 %, 8 %, and 32 % of all samples for Co,
As, Ag, Hg, Pb, Mo, Zn, and Cu respectively. The strongly
polluted (3 \I
geo
B4) level was detected in 4 %, 36 %,
12 %, 8 %, 36 %, 16 %, and 20 % of all samples for As,
Ag, Hg, Pb, Mo, Cd, and Cu, respectively. The concen-
trations of As, Ag, Hg, Mo, and Cd belong to the strongly-
to-extremely polluted (4 \I
geo
B5) level in 4%, 16%,
28%, 12%, and 40 % of all samples, and to the extremely
polluted (I
geo
[5) level in 4 %, 16 %, 24 %, 16 %, and
40 % of all samples, respectively. Only for Ni, Co, Cr, and
Zn were concentrations belonging to the strongly polluted
to extremely polluted levels not observed.
3.2.2 Summary pollution level
The summary pollution levels (Z
c
) are given in Fig. 2. The
contamination index value varied from 21 to 14,172,
averaging 805.5 (extremely hazardous level). According to
the contamination index, 36 % of samples exhibited a very
high level of pollution, i.e. extremely hazardous; 32 % a
high level of pollution, i.e. hazardous degree; 12 % a mean
level, i.e. moderately hazardous degree; and 20 % a low
level of pollution. Very high and high levels of pollution
were detected in the southern (industrial) and central
(densily populated and exposed to heavy traffic load) dis-
tricts of Yerevan.
As seen from Fig. 2, a relatively large share in the
contamination index of almost all the samples belongs to
Mo, Cd, Hg, and Ag. In addition, Cd approximating 93 %
and 83 % of the contamination index falls on sampling
points N8 and N15 located in the north and west of the city.
Fig. 2 Levels of the
contamination index and shares
of individual elements in it (%)
Acta Geochim
123
Table 6 Non-carcinogenic health risk of heavy metals in dust
Element Group HQ
ing
HQ
derm
HI =PHQi RFDing (mg/kg day
-1
)
min max mean min max mean min max mean
Hg Child 6.16E-04 4.87E-02 1.17E-02 1.73E-06 1.36E-04 3.26E-05 6.18E-04 4.88E-02 1.17E-02 1.60E-04
Adult 6.60E-05 5.22E-03 1.25E-03 2.64E-07 2.08E-05 4.98E-06 6.63E-05 5.24E-03 1.25E-03
Pb Child 1.14E-02 1.02E-01 3.06E-02 2.12E-04 1.90E-03 5.71E-04 1.16E-02 1.04E-01 3.12E-02 3.50E -03
Adult 1.22E-03 1.09E-02 3.28E-03 3.24E-04 2.90E-03 8.72E-04 1.54E-03 1.38E-02 4.15E-03
Mo Child 1.01E-03 1.61E?01 6.67E-01 2.84E-06 4.50E-02 1.87E-03 1.02E-03 1.61E?01 6.69E-01 5.00E-03
Adult 1.08E-04 1.72E?00 7.15E-02 4.33E-07 6.87E-03 2.85E-04 1.09E-04 1.73E?00 7.18E-02
Cd Child 2.89E-04 2.58E?00 1.60E-01 3.24E-05 2.88E-01 1.79E-02 3.22E-04 2.86E?00 1.78E-01 1.00E-03
Adult 3.10E-05 2.76E-01 1.71E-02 4.95E-06 4.40E-02 2.74E-03 3.59E-05 3.20E-01 1.99E-02
Zn Child 1.41E-03 5.60E-03 3.09E-03 3.96E-06 1.57E-05 8.65E-06 1.42E-03 5.62E-03 3.10E-03 3.00E-01
Adult 1.51E-04 6.01E-04 3.31E-04 6.04E-07 2.40E-06 1.32E-06 1.52E-04 6.03E-04 3.32E-04
Cu Child 4.95E-03 6.23E-02 2.42E-02 1.39E-05 1.74E-04 6.78E-05 4.97E-03 6.25E-02 -4.00E-02
Adult 5.30E-04 6.67E-03 2.59E-03 2.12E-06 2.66E-05 1.04E-05 5.33E-04 6.70E-03 2.61E-03
Ni Child 2.54E-03 7.85E-03 4.78E-03 1.78E-04 5.50E-04 3.35E-04 2.72E-03 8.40E-03 5.12E-03 2.00E -02
Adult 2.73E-04 8.41E-04 5.12E-04 2.72E-05 8.39E-05 5.11E-05 3.00E-04 9.25E-04 5.63E-04
Ag Child 1.03E-03 2.01E-02 4.39E-03 7.18E-05 1.41E-03 3.07E-04 1.10E-03 2.16E-02 4.70E-03 5.00E-03
Adult 1.10E-04 2.16E-03 4.70E-04 1.10E-05 2.15E-04 4.69E-05 1.21E-04 2.37E-03 5.17E-04
Co Child 1.03E-03 1.11E?00 6.82E-01 2.88E-06 3.10E-03 1.91E-03 1.03E-03 1.11E?00 6.84E-01 3.00E-04
Adult 1.10E-04 1.18E-01 7.31E-02 4.40E-07 4.73E-04 2.92E-04 1.11E-04 1.19E-01 7.34E-02
Cr Child 2.53E-02 1.64E-01 5.94E-02 2.84E-03 1.84E-02 6.66E-03 2.82E-02 1.83E-01 6.61E-02 3.00E -03
Adult 2.71E-03 1.76E-02 6.37E-03 4.33E-04 2.81E-03 1.02E-03 3.15E-03 2.04E-02 7.38E-03
As Child 3.84E-04 3.43E ?00 1.72E-01 3.22E-05 2.88E-01 1.45E-02 4.16E-04 3.72E?00 1.87E-01 3.00E -04
Adult 4.11E-05 3.67E-01 1.84E-02 4.92E-06 4.40E-02 2.21E-03 4.60E-05 4.11E-01 2.07E-02
In italics [1 values are given
Acta Geochim
123
Rather a large share of Mo (98 % of the contamination
index) falls on a sampling point in the south of the city near
the Mo concentrate smelting and processing plants.
3.3 Non-carcinogenic risk assessment
Results of assessment of non-carcinogenic risk of heavy
metals in leaf dust are given in Table 6. Both to children
and adults, the major route of exposure from multi-ele-
mental risk is ingestion followed by skin absorption. For
children, major (HQ[1) risk is determined for Mo, Cd, Co,
and As; in adults, for Mo only. In the case of children, the
single-elemental HI for Mo varies from 0.001 to 16.1; for
Cd, 0.0003 to 2.86; for Co, 0.001 to 1.11; and for As,
0.0004 to 3.72, with means of 0.67, 0.18, 0.68, and 0.19,
respectively. Moreover, for children, single-elemental HI
was greater than 1 in one sample in the cases of Mo, Cd,
and As, and in three samples in the case of Co. Single-
elemental HI for adults for Mo varies from 0.0001 to 1.73,
with a mean of 0.072, and HI greater than 1 was detected in
one sample.
Mean single-elemental HI values of studied metals are
represented by the following decreasing series for both
children and adults:
Co [Mo [As [Cd [Cr [Pb [Cu [Hg [
Ni [Ag [Zn
Multi-elemental HI varies from 0.27 to 17.51 for chil-
dren and 0.03 to 1.86 for adults with means of 1.89 and 0.2,
respectively. Moreover, a probable heavy metal–induced
non-carcinogenic risk to children and adults is posed by
thirteen and one dust samples, respectively (Fig. 3).
3.4 Carcinogenic risk assessment
To assess carcinogenic risk of Cr and As, appropriate SF
values were taken from RAIS (2013). However, RAIS
Fig. 3 Multi-elemental risk to
children and adults according to
sampling point
Table 7 Summary of carcinogenic risk via ingestion and inhalation
exposure of dust, based on min., max., and mean concentrations
Element Value Oral risk SF(mg/kg-day)
-1
Cr min 4.42E-06 5.00E-01
max 2.86E-05
mean 1.04E-05
As min 2.01E-08 1.50E?00
max 1.80E-04
mean 9.01E-06
RI
ing
min 4.44E-06
max 1.89E-04
mean 1.94E-05
In italics[10
-6
values are given for single-element carcinogenic risk,
[10
-4
for multi-element carcinogenic risk values
Acta Geochim
123
contains no values for ingestion pathway for the rest of the
detected elements.
The results of the carcinogenic risk calculation are given
in Table 7.
It is evident (Table 7) that minimum carcinogenic risk
values of Cr via ingestion pathway belong to the low risk
level, while mean and maximum carcinogenic risk values
of Cr belong to the medium risk level. In the case of As,
carcinogenic risk was detected only for mean (low risk
level) and max (high risk level) values. From all 25 sam-
ples, a low level ([10
-6
and \10
-5
) of Cr and As car-
cinogenic risk was detected in seventeen and twelve
samples, respectively; and a medium level ([10
-5
and
\10
-4
) in eight and one samples, respectively. A high
level ([10
-4
and\10
-3
) of carcinogenic risk was observed
only in the case of As in one sampling site. Multi-element
carcinogenic risk ([10
-4
) via ingestion pathway has been
observed only by the maximum RI
ing
value.
4 Conclusions
The concentrations, pollution levels, and health risks of
heavy metals (Cd, As, Pb, Cr, Ni, Co, Zn, Cu, Ag, Hg, and
Mo) in tree leaf dust deposits from Yerevan territory were
studied. The obtained results show that mean contents of
all studied elements, except Cr and Ni, exceed background
values. A geochemical series of mean contents of heavy
metals is represented as Mo
(579.8)
–Cd
(155.9)
[Hg
(33.5)
–
Ag
(26.8)
–As
(22.8)
[Cu
(7.4)
–Pb
(6.7)
–Co
(4.0)
–Zn
(3.6)
. Statistical
descriptions of the contents indicate that high contents of
As, Mo, and Cd detected in Yerevan are due to man-made
sources, while Ni has a natural origin, and Co and Zn
originate from both natural and anthropogenic sources.
This fact was also complemented by low levels of I
geo
for
these elements. Summary pollution levels based on the
contamination index show that 36 % of all samples
exhibited a very high level of pollution; 32 %, high; 12 %,
mean; and 20 %, low.
The results of risk analysis suggest that both in children
and adults the major pathway of risk is ingestion of dust
particles. Children, as compared with adults, are at a higher
risk, and such a level of air pollution with heavy metals can
trigger serious health problems. A probable cause of non-
carcinogenic risk to children was found to be Mo, Cd, Co,
and As; to adults, Mo only. From very low to high levels of
carcinogenic risk were observed for single-element and
medium levels for multi-element ingestion of Yerevan
dust.
It should be stressed that there are some limitations in
the used risk assessment model: (1) all employed coeffi-
cients are set for US citizens, (2) lack of respective coef-
ficients for individual pathways of some elements, (3) dust
particle size and rate of penetration are not taken into
account, (4) seasonal variations are not taken into account,
and (5) calculations are based on total concentrations of
heavy metals. Despite this, application of the described risk
model helped us get a better vision of probable health risks
to Yerevan’s residents.
Acknowledgments This research was implemented in the frames of
a theme ‘‘Studying geochemical stream of elements in atmospheric air
of Yerevan’’ (No 13-1E220, 2011) under agreement-based (thematic)
financial support of the State Committee of Science to the Ministry of
Education and Sciences RA.
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