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doi: 10.1111/j.1471-0307.2012.00846.x
ORIGINAL
RESEARCH
Heavy metal concentrations in raw milk collected from
different regions of Samsun, Turkey
HASAN TEMIZ* and ARZU SOYLU
Department of Food Engineering, Engineering Faculty, University of Ondokuz Mayis, TR-55139 Samsun, Turkey
In this study, 144 raw milk samples were analysed for heavy metal contamination derived from emissions
from industrial operations in Tekkekoy, Samsun, Turkey. Cu, Fe, Zn, Cr, Ni, Cd, As and Pb levels in samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The average amounts
of copper, chromium, iron, zinc, nickel, cadmium, arsenic and lead were determined as 1.130, 0.441,
12.920, 0.032, 0.483, 0.006, 0.003 and 0.004 mg ⁄ kg, respectively. It was determined that the summer
period has the highest levels for copper, lead and cadmium. The highest contents of arsenic and copper
were found at the two industrial regions that were close to Black Sea, described as ‘1st’ and ‘2nd’
region. Whereas the 3rd and 4th regions that were far from an industrial zone and also from the Black
Sea, nickel, lead and chromium had the highest levels.
Keywords Heavy metals, ICP- MS, Milk, Milk contaminants.
INTRODUCTION
*Author for
correspondence. E-mail:
[email protected]
2012 Society of
Dairy Technology
Rapid urbanisation and industrial development
have caused environmental pollution all over the
world. As a result, many dangerous elements or
compounds, such as dioxins, pesticides, metals and
metalloids, accumulate along the food chain. Their
concentrations in the environment grow with the
increase in urban, agricultural and industrial emissions (Rubio et al. 1998; Zheng et al. 2007).
Heavy metals are invaluable and unavoidable
components of our environment (Vidovic et al.
2005). They are in varying quantities throughout
the geosphere and are being cycled continuously
through different components of the ecosphere.
The amounts of different heavy metals in ambient
atmospheres have been increasing with advances
of human civilisation and are likely to increase further with increasing exploitation of geological
resources, such as mining and fossil fuel development. An additional concern with the metals is
their concentration in domestic and industrial waste
products, because the elements are indestructible
(Sharma et al. 1982). Heavy metals may enter to
the human body through inhalation of dust, consumption of contaminated drinking water, direct
ingestion of soil and consumption of food plants
grown in metal-contaminated soil (Chary et al.
2008).
Vol 65 International Journal of Dairy Technology
Milk and most of the dairy products, which
are important parts of human’s diet, are likely to
be exposed to heavy metal contamination from
ingestion of feed during the lactation period
(Simsek et al. 2000). Some heavy metals having
toxic effects on human and animal health can
accumulate in these products (Dahiya et al.
2005). The toxicity induced by excessive levels
of these elements, such as chromium (Cr), lead
(Pb) and mercury (Hg), is well known (Anastasio
et al. 2006). Heavy metal residues in milk are of
particular concern because milk is largely consumed by infants and children. The toxic metal
content of milk and dairy products depend on
several factors, in particular environmental conditions, the manufacturing process and the possible
contamination during several steps of the manufacturing processes.
Tekkekoy region is located at eastern part of
Samsun Province of Turkey (Figure 1) and has different pollution parameters (high volume of traffic,
industrial plants, small-medium towns, intensive
agricultural activities). The Gelemen Farm that
serves as a source of food for the city is located in
Tekkekoy.
In this region, there are some researches about
heavy metal concentration at soil and vegetables
samples, but there is no data about milk and dairy
products. The aim of this work was to determine
1
Vol 65
Table 1 Monthly wind situation, Samsuna
Study Area
Figure 1 Map of Samsun.
Months
Wind
speeds (m ⁄ s)
Prevailing
direction
Maximum
speed (m ⁄ s)
Strongest
direction
January
February
March
April
May
June
July
August
September
October
November
December
Yearly
2.3
2.2
2.1
1.4
1.2
1.9
2.3
2.0
1.8
1.4
2.2
2.0
1.9
SSE
SSE
SSE
NNE
NNW
NNW
WNW
NNE
SW
SW
WSW
WSW
NNW
15.1
16.5
19.7
10.7
8.5
10.7
11.1
12.5
12.2
15.6
18.2
14.7
19.7
SSE
S
S
SW
WNW
WNW
WNW
N
NW
NNW
SSW
SW
S
a
the concentration of some heavy metals in milk, collected from
several farms in the Tekkekoy region.
Source: Anonymous 2006 (N, north; S, south; SW, south-west; SSE,
south-south-east; NNE, north-north-east; NNW, north-north-west;
WSW, west-south-west; WNW, west-north-west; NW, north-west;
SSW, south-south-west).
MATERIALS AND METHODS
Site characteristics
The study area is located in northern Turkey, at the coast of
Black Sea, 4121¢ N latitude and 3615¢ E longitude and surrounded by Carsamba Plain in the east and the south-east.
There are small-scale industrial operations and small settlements located in the centre of Samsun Province.
2.km
Climate
The minimum temperature was measured in January as 2 C,
and the maximum temperature was measured in August as
29.9 C. The mean temperature is 14.5 C. The mean annual
rainfall is 714.7 mm. Even though changes in wind-direction
occur every month, the prevailing wind is from the north and
west, as shown in Table 1 (Anonymous 2006).
Sampling
Milk sampling was carried out at 24 different locations along
the south–east of Samsun. The location map of the Tekkekoy
with 24 sampling sites is shown in Figure 2. The sampling area
started from the seaside and going up to 30 km north. Sampling
areas have been selected in relation to the distance from the
Black Sea because the industrial zones were located through
the seaside. These areas were characterised by different elevations and ecological features. Therefore, the region was divided
into four different spots according to their distance: 1st region
up to 2 km from seaside, 2nd region between 2 and 5 km, 3rd
region between 5 and 15 km and 4th region between 15 and
30 km. The 1st and 2nd regions were close to industrial area
and have a low altitude. The 3rd and 4th regions were far from
the industrial area according to the other regions and have a
high altitude. Between the first and second regions, there is a
2
5.km
15.km
30.km
Figure 2 Map of Tekkekoy.
highway having a high traffic volume. The heavy metal emissions of some domestic large industrial corporations located at
study area are shown in Table 2.
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Table 2 Heavy metal emissions of the industrial branches of
Tekkekoy region, Samsuna
Metals
Petro
chemistry
Choler-alkali
production
Fertilizer
industry
Iron–steel
industry
Power
plant
Cd
Cr
Cu
Hg
Pb
Ni
Sn
Zn
+
+
)
+
+
)
+
+
+
+
)
+
+
)
+
+
+
+
+
+
+
+
)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
a
Source: Kahvecioglu et al. (2009).
Sampling was carried out with three replications in two periods: summer (May, July and September of 2010) and winter
(November of 2009, January and March of 2010). All the samples were collected according to procedures excluding metallic
containers, mechanical milkers, etc. to minimise possible external contaminations. For each sampling location, 10 milk samples were collected from different farms and they were mixed
to obtain laboratory sample. So, in all sampling period, 240
milk samples were collected, and totally 1640 milk samples
were collected to reach homogenous sample that represents
each area. Milk samples were collected from the cattle grazing in pasture land between 6:00 to 10:00 a.m. in clean polyethylene bottles. Each milk sample was stored at )18 C until
analysis.
Sample preparation
Test portions were dried in an oven at 95 C and then ashed at
450 C under a gradual increase (<50 C ⁄ h). 5 mL 6 M HCl
(1 + 1) was added to ashed samples, and then the solution was
evaporated to dryness. The residue was dissolved in 0.1 M
HNO3, and the analyses were performed using ICP-MS (Jorhem 2000).
Inductively coupled plasma mass spectrometry (ICP-MS)
measurements
Inductively coupled plasma mass spectrometry analyses were
performed in the Environmental Geochemistry laboratory at the
Mersin University Geological Engineering Department, Mersin,
Turkey. Concentrations of eight elements (Cu, Fe, Zn, Cr, Ni,
Cd, As and Pb) in the solution extracts were determined in triplicate by Agilent 7500ce ICP-MS (Tokyo, Japan) equipped
with a collusion ⁄ reaction cell in the form of octopole reaction
system (ORS). The argon gas utilised was of spectral purity
(99.998%). The external standard calibration method was
applied to all determinations, using Li, Sc, Ge, Y, In, Tb and Bi
internal standard mix (in 2% HNO3 matrix). NIST single-element reference standards are used to construct five-point calibration curves. At regular intervals during analysis, calibration
2012 Society of Dairy Technology
standards were analysed as samples to monitor instrument drift.
Furthermore, extractant and ultra pure water blanks were frequently analysed alongside samples to check for contamination.
Blanks were prepared by completion of the full analytical procedure without samples. The analytical accuracy was checked
from replicate measurement of several samples and by measuring certified reference materials. The relative error is <±5% for
all analysed elements (Guler and Alparslan 2009).
Statistical analysis
The data obtained from three replicates were analysed by ANOVA using the SPSS statistical package program, and the differences between the means were compared using the Duncan’s
multiple range test at the significance level of 0.05.
RESULTS AND DISCUSSIONS
Copper
Copper contents of the raw milk samples from different regions
are shown in Table 3. According to analysis of variance, the
differences between both region and period were statistically
significant (P < 0.05). The copper values obtained in this study
ranged between 0.618 and 1.889 mg ⁄ kg. The highest copper
value was obtained from samples collected from 2nd region at
the summer period. The copper value detected from summer
period was higher than those of winter period. Herbicide used
in agriculture might increase the amount of copper in the milk.
So, the copper amount of milk could be increased by both
industrial emissions and herbicides at the summer season. The
results for the copper concentrations of milk were higher than
that reported by Simsek et al. (2000) and by Licata et al.
(2004) but lower than that reported by Temurci and Guner
(2006).
The World Health Organization (FAO ⁄ WHO, 1982) and
Food and Nutrition Board (2001) have reported some critical
levels for metals that are shown at Table 4 as provisional maximum tolerable daily intake (PMTDI) level, provisional tolerable weekly intake level (PTWI), dietary reference intakes (DRI)
and an upper level (UL). While the copper values obtained in
this study compared with PMTDI, DRI and UL values, it seems
that the results are between the published values, but milk is
not the only source of this metal. So, it can be concluded that
consuming large amounts of milk obtained from the region
may cause toxic effects in humans.
Iron
The iron concentrations observed in this study varied between
0.12 and 0.64 mg ⁄ kg (Table 3). No statistical difference
(P > 0.05) was detected between both region and periods. The
iron results of this study were lower than the values reported by
Simsek et al. (2000) and by Temurci and Guner (2006). While
the copper results obtained in this study are compared with
PMTDI, DRI (FAO/WHO, 1983) and UL values (Table 4), it
seems that the results are lower than the established values. The
3
±
±
±
±
±
±
±
±
0.47
0.92
0.04
12.58
0.00
0.01
0.64
0.03
0.62
0.59c
0.03bc
2.96
0.00b
0.00ab
0.55b
0.11a
±
±
±
±
±
±
±
±
0.32
0.63
0.03
12.25
0.00
0.01
0.49
0.07
0.55
1.17
0.05
11.59
0.00
0.01
1.13
0.02
0.44
1.25
0.03
13.80
0.00
0.00
0.44
0.02
±
±
±
±
±
±
±
±
5–15 km
2–5 km
15–30 km
Copper (mg ⁄ kg)
DRI
UL
PMTDI
Nickel (mg ⁄ kg)
UL
Lead (mg ⁄ kg)
PTWI
Zinc (mg ⁄ kg)
DRI
PMTDI
± 1.00
± 0.66abc
± 0.03c
± 1.70
± 0.00
±.0.00bc
± 0.45b
± 0.02b
1.53
0.42c
0.02abc
4.56
0.00b
0.00ab
0.29b
0.01b
±
±
±
±
±
±
±
±
0–2 km
0.60
0.62
0.04
12.70
0.00
0.01
0.35
0.01
±
±
±
±
±
±
±
±
Letters indicate difference among period (P < 0.05).
Letters indicate difference among region (P < 0.05).
*
All values are mean ± SD of triplicate.
abc
AB
Average
0.40
1.36
0.05
13.26
0.00
0.01
0.33
0.03
0.46
1.02abc
0.04abc
2.53
0.00ab
0.00bc
0.10b
0.07ab
±
±
±
±
±
±
±
±
0.26
1.22
0.04
14.91
0.00
0.01
0.33
0.05
15–30 km
0.3–1
0.025
8–11
1
Iron (mg ⁄ kg)
DRI
8–18
UL
40–45
PMTDI
0.8
Chromium (mg ⁄ kg)
DRI
0.015–0–030
Cadmium (mg ⁄ kg)
PTWI
0.007
Arsenic (mg ⁄ kg)
PTWI
0.015
average iron concentration of milk was reported as 1.4 mg ⁄ kg
by Metin (2010). The average iron concentration of samples in
this study was found to be lower than that reported by Metin
(2010). According to results, the milk obtained from research
area supplies 3.17% of daily iron requirement of an individual.
This rate is consistent with the rate given by Metin (2010).
± 0.87
± 1.17ab
± 0.004a
± 5.16
± 0.00ab
± 0.00bc
± 0.17b
± 0.01b
0.64
1.42
0.07
13.48
0.00
0.00
0.31
0.02
5–15 km
0.95
1.43a
0.05ab
5.40
0.00b
0.00c
0.23b
0.03ab
±
±
±
±
±
±
±
±
0.62
1.89
0.06
11.96
0.00
0.00
0.33
0.05
2–5 km
0.25
0.79bc
0.01abc
4.12
0.01a
0.00ab
0.01b
0.02b
±
±
±
±
±
±
±
±
0–2 km
0.12
0.89
0.05
12.70
0.01
0.01
0.34
0.02
Iron
Copper
Lead
Zinc
Arsenic
Cadmium
Nickel
Chromium
Summer period
Table 3 Mean values of heavy metal concentrations measured in regions and periods (mg ⁄ kg)*
4
0.7–0.9
3–10
0.05–0.5
DRI, Dietary reference intakes; UL, upper level; PMTDI, provisional
maximum tolerable daily intake, PTWI, provisional tolerable weekly
intake level.
0.72
1.16A
0.04A
4.49
0.00
0.00B
0.16B
0.04
Winter period
Table 4 Some critical levels of observed metals, published by
WHO ⁄ FAO and Food and Nutrition Board
0.77
1.04bc
0.07abc
2.25
0.00ab
0.01a
1.84a
0.02b
Average
1.02
0.76B
0.04B
3.10
0.00
0.01A
1.04A
0.06
Vol 65
Zinc
The average zinc values of the raw milk samples were between
11.597 and 14.907 mg ⁄ kg (Table 3). According to the statistical analysis, the differences between the regions and periods
were not statistically significant (P > 0.05). The results
obtained in this study were higher than those reported by Simsek et al. (2000) and by Licata et al. (2004) and lower than
those reported by Baranowska et al. (2005). The study carried
out by Vidovic et al. (2005) shows that 58% decrease in the
rate of zinc in the atmospheric deposits caused 17% decrease in
the rate of zinc in milk. Compared to the zinc results obtained
in this study with established levels at Table 4, it might be
speculated that the milk itself could provide the requirement
zinc of an individual. The amount of zinc in milk was reported
as 3.5 mg ⁄ kg by Metin (2010). The results obtained from
research area were four times higher than that reported by
Metin. In this case, zinc amount of milk was determined over
the toxic limits.
Chromium
The chromium values obtained in this study varied between
0.013 and 0.075 mg ⁄ kg (Table 3). The differences among the
regions were statistically significant (P < 0.05), and the highest
chromium value was detected in 4th region during winter period. Compared to the previous results, the chromium results of
this research were lower than the values detected for some
region of Ankara, Turkey, by Temurci and Guner (2006) and
for two regions of southern Italy by Anastasio et al. (2006).
2012 Society of Dairy Technology
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But higher values were detected in raw milk which was collected from different regions of Calabria, by Licata et al.
(2004) and Southern Italy by Caggiano et al. (2005). Chromium is used in the leather industry, in inks and in processing
of steel. The sampling sites in the Tekkekoy region, there are
some of those types of industries. The results obtained in the
study were higher than DRI value given at Table 4. Metin
(2010) reported the amount of chromium in milk as
0.015 mg ⁄ kg and that were lower than those of study area.
Nickel
Nickel contents of the raw milk samples from different regions
are shown in Table 3. According to analysis of variance, the
differences among both region and period were statistically significant (P < 0.05). The nickel values obtained in this study
were ranged between 0.312 and 1.127 mg ⁄ kg. Figure 3 presents mean values of nickel associated with regions and period
interactions. As shown in Figure 3, the highest nickel value
was detected at 3rd region during winter period. Temurci and
Guner (2006) studied on heavy metal contents of milk and
cheese in Ankara, Turkey. In this research, the nickel contents
of milk were determined as 2.754 mg ⁄ kg, which were higher
than that observation.
According to the Table 4, the amount of nickel at this
research was higher from UL values at some regions. However,
the Turkish Codex (Anonymous 2002) had published the maximum amount of nickel obtained from milk as 0.1–0.2 mg ⁄ kg.
So, the values for nickel concentrations in milk samples
observed in this research were higher than those reported in
Turkish Codex and threaten human health.
Figure 4 Interactions of period and region for cadmium.
concentration observed in the study, and the lowest concentration was determined in samples of 2nd region, collected in summer period (Figure 4). The values were lower than those
reported by Rubio et al. (1998), Anastasio et al. (2006), Caggiano et al. (2005) and Temurci and Guner (2006), but higher
than those reported by Licata et al. (2004) and Baranowska
et al. (2005). The cadmium results of this research are closely
related to the values reported by Vidovic et al. (2005). There
are no data on Turkish Codex about the cadmium levels of
milk, but for the other foodstuff, the cadmium levels ranged
from 0.005 to 1.0 mg ⁄ kg (Anonymous 2008). The results of
the study were less than PTWI values (FAO/WHO, 2006)
(Table 4). So, cadmium levels could not lead to any health risk
at the researched area according to results of this study.
Cadmium
The concentrations of cadmium in analysed samples are
reported in Table 3. The cadmium values were changed
between 0.001 and 0.013 mg ⁄ kg. According to analysis of variance, the differences among regions and periods were found to
be significant (P < 0.05). Besides, a significant region–period
interaction was detected (P < 0.05). The samples collected in
3rd region during winter period produced the highest cadmium
Arsenic
Arsenic contents of the raw milk samples from different regions
are shown in Table 3. The arsenic values varied between 0.001
and 0.007 mg ⁄ kg. No statistical significance was detected
between periods, but the difference in the content of arsenic in
milks, sampled from different regions, was found to be significant (P < 0.05). Our results of arsenic concentrations were in
accordance with those of Simsek et al. (2000), while Licata
et al. (2004) reported higher values. According to PTWI value
(FAO/WHO, 1989) (Table 4), the amount of arsenic in milk
samples of the present study had no health concern.
Figure 3 Interactions of period and region for nickel.
Lead
The lead concentrations observed in this study were 0.028–
0.068 mg ⁄ kg (Table 3). As shown in Table 3, lead levels in
two sets of samples, obtained from 2nd and 3rd regions, were
higher than the levels of other regions. It is clear that the lead
level was variable in Turkey, especially in these areas. While
the highest lead concentration was detected in the samples from
3rd region during summer period, the lowest lead concentration
was detected in samples from 2nd region during winter period.
The differences among the regions were statistically significant
(P < 0.05), and the highest lead concentration was detected at
samples collected during summer period. The lead contents of
milk from regions were higher than the limits of Turkish
Codex, 0.02 mg ⁄ kg (Anonymous 2008). The lead results of
2012 Society of Dairy Technology
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this research were closely related to the values reported by
Simsek et al. (2000) and lower than those reported for the milk
samples collected from in two regions of southern of Italy by
Anastasio et al. (2006), different regions of India by Singh
et al. (1997) and different regions of Poland by Baranowska
et al. (2005), but were higher than those reported for milk samples collected from different regions of Iran by Tajkarimi et al.
(2008), different regions of Calabria, Italy, by Licata et al.
(2004) and the industrial area of Huludao city, China, by Zheng
et al. (2007). One of the possible reasons for the increase in
lead concentrations of milk among countries may be the wide
use of leaded gasoline during recent decades.
The PTWI value (FAO/WHO, 2000) of lead was reported as
0.025 mg ⁄ kg (Table 4). For a person of an average of 60-kg
body weight, this would mean 0.214 mg lead ⁄ day. The amount
of lead in milk samples obtained from the research was higher
than those reported in both the Turkish Codex and FAO ⁄ WHO
lead residue level. It is recommended that local and national
authorities should make farmers aware of appropriate practices
for preventing heavy metal contaminations of farmlands.
CONCLUSION
The results of this study show that the raw milk samples collected in summer period were highest for copper, lead and cadmium, also higher than those of the winter period. The results
indicated that raw milk samples obtained from those regions
may not be safe for consumers in terms of copper, lead, zinc,
nickel and chromium metals. The environmental pollution at
study area was attributed to adjacent heavy industry.
Further studies are necessary to evaluate the content of heavy
metals on a greater number of milk samples from various dairy
in Tekkekoy and to confirm the absence of possible toxicological risks in this region.
ACKNOWLEDGEMENTS
This research was supported with PYO.MUH. 1904.09.007 Project
Number by the University of 19 Mayis, Samsun, Turkey.
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