Bayko D. Baykov*, Vassil Rangelov*, Kiril Kirov*, Botyo Zaharinov*, Irina Popova*, Hristo Hristev**, Dimo Penkov**
*New Bulgarian University, Science Research Institute of Ecology and
Sustainable Development, 21 Montevideo Str., Sofia1618, Bulgaria
**Agrarian University, 12 Mendeleev Str., Plovdiv 4000, Bulgaria
CHANGES IN THE TECHNO-GENEOUS KLARCK OF CHEMICAL ELEMENTS IN BULGARIA AND THEIR INFLUENCE ON HUMAN HEALTH
Abstract
The
aim of this research is to determine the influence of high techno-geneous
klarck of lead and cadmium in soil, which is the result of mining and ore
treatment, on the quality of secondary (biological) production and to determine
the risk for human health and ecosystems.
Keywords: lead, cadmium, secondary (biological) production, bioaccumulation, xenobiotics
At the end of the
19th century Klarck proved that lithosphere is chemically heterogeneous.
In 1934 Fersman offered a quantity criterion for assessing this heterogeneity -
the klarck unit. According to Dobrvolskii’s data /1984/ in the last
few decades a rising problem, related to human health and ecosystems, is the
increased techno-geneous klarck of many toxic elements in soil. For Bulgaria
the most important toxic chemical elements are lead and cadmium. According to
the Ministry of Environment and Water/MEW/ high content of the two toxic
elements, a risk for human health, is determined in 477 dka agricultural
land/soil/. The characteristics of toxic elements’ movement along the trophic
chain should be considered for risk assessment of their high content in the
ecotopes. In the 20th century Vernadsky discovers
the chemical heterogeneity in the biotic components biosphere too. This means
that there are differences in the quantities of the researched elements not
only in lithosphere, but in living organisms too.
Research till now was carried mainly with a view to determine the degree of
concentration or dispersion of chemical elements in autotrophic organisms in
comparison with their quantity in lithosphere. The ground for such approach is
the fact that 90% of living matter is represented by autotrophic organisms
(Reylly, 1980; Kabata-Pendias and Pendias, 1984; Dobrovolskii, 1984, 1998,
etc.). According to Dobrovolskii (1984), in plants of ground ecosystems
concentration of lead is of order n, which means that the
quantity of this toxic element in autotrophic organisms theoretically is 1 –
9,99 times higher in comparison with its quantity in soil. For cadmium the
value is 0,1 n or this means that dispersion exists in the range
from 0,1 to 0,99 times in comparison with its quantity in soil. For cadmium the
value is 0,1 n or this means that dispersion exists in the range
from 0,1 to 0,99 times in comparison with its quantity in soil. It is important
to research the bioaccumulation of toxic chemical elements along the trophic
chain in order to assess the influence of their increased techno-geneous klarck
on human health and ecosystems. The term bioaccumulation
defines the selective accumulation of toxic substances (chemical elements or
compounds) along the food chain. During the period after the sixties
bioaccumulation of some pesticides and especially of organochlorine compounds
was thoroughly researched. Hebel and Wrigt (1996) summarize the results of this
research: if the quantity of DDT (dichlorodiphenyltrichloroethane) in lake
water is 1 unit, it is 10 000 units in phytoplankton, 1 000 000
units in herbivorous fish and 10 000 000 units in predatory fish.
Research on bioaccumulation of p-dioxin in ground and water ecosystems in South
Vietnam shows that this extremely toxic compound, which concentration in soil
and water ranges from 0,01 to 0,001 ppm, reaches values that cause diseases in
farm animals and they have carcinogenic, mutagenic and neurotoxic effect on
people that consume food obtained from such animals (Petkov and Baykov, 1984).
This phenomenon, for some unknown reason, is mechanically transferred to the
accumulation of toxic chemical elements. In scientific literature it is even
admitted that the degree of bioaccumulation of toxic chemical elements is
comparable with that of xenobiotics.
Our previous
research indicates that food is the main source which is responsible for the
import of these toxic elements in the organisms of humans and animals/99%/,
water/1%/, air/0.03%/.
In the present
research we aim to assess the risk for human health and ecosystems of the
increased techno-geneous klarck of lead and cadmium by analyzing their
bioaccumulation along the trophic chain in the following directions:
1. using the
criterion “Bioconcentration factor” (BCF), proposed by our team (Baykov, 2003),
to analyze the bioaccumulation of lead and cadmium in primary and secondary
production in a grazing ecosystem with antropogenically increased klarck of
lead and cadmium
2. To apply a new criterion – criterion of
safety (CS) for assessing the accumulation of the two toxic elements in tissues
of heterotrophic organisms with a view to their qualities as food resource for
humans.
Research is
carried out in two ecotopes: ecotope1- the klarck of lead and cadmium is
techo-geneously increased from mining and ore treatment and ecotope2 – the
klarck of lead and cadmium is normal for Bulgaria. For assessing the risk for
human health and ecosystems of the increasing concentration of the two toxic
elements along the trophic chain, experiments were carried out with equal
groups of kids (Capra hircus) bred in the two ecotopes with different klarck of
lead and cadmium from their birth till their 70th day (1st
technological phase). A typical for the region plant community is formed for
studying the chemical heterogeneity at the first trophic level (the
autotrophs): 30 % graminaceous
plants, where the following species prevail - Andoropogon ischaemum, Poa
bulbosa, Festuka ovina; 5% legumes of the species Genista tincoria, Onibrychis
arenaria, Sanguisorba minor; 55% grass plants, including the species Euphorbia
cyparisias, Tecrium chamaedris, Thymus Montana, Filagi germanica, Sclerantus
annus, Verbascum thapsiformae, Eringuim campestre, Sempervivum patens; 5%
shrubs - Juniperus communis , Rubus idaeus, Caprinus orientalis; and 5% trees -
Pinus silvestris. Samples have been
periodically taken from the plant community as each sample includes graminaceous
plants, legumes and grass plants. The
kids have been studied for: biomass, forage consumption, health condition, and
slaughter indexes. Soil from the surface soil layer, pasture grass and hay,
muscular tissues, liver and kidneys have been studied for content of lead and
cadmium applying the method of Jorchrem/1993/ using AAS Perkin-Elmer 4100 type.
The chemical
heterogeneity of soil has been determined using the klarck /К/ unit which is defined as a correlation between the quantity of the
examined chemical element in 1 kg dry soil and the average quantity of the element in Bulgarian soils. For autotrophic organisms the chemical
heterogeneity has been determined using the criterion - Bioconcentration factor
(BCF), which (unlike other researchers think) according to our previous
research /Baykov, 2003/ should be calculated as a correlation between the
quantity of the chemical element in 1 kg dry plant biomass / not ashes as some
researchers recommend/ and the quantity of the chemical element in 1 kg dry soil.
At the first heterotrophic level we applied differentiated approach. BCF is
determined at two levels: BCF1 = quantity of the chemical
element (in mg) in 1 kg dry biomass from the secondary production / quantity
(in mg) in 1 kg soil; BCF2 = quantity of the chemical element (in
mg) in 1 kg dry biomass from the secondary production / quantity (in mg) in 1
kg forage.
Using a new criterion - criterion
of safety (CS), we assessed the accumulation of the two toxic elements in the
tissues of heterotrophic organisms,
considering their qualities as a human food resource.
Results and discussion:
Chemical heterogeneity data
is presented in table 1 for the two ecotopes and for the two trophic levels. When
determining the degree of concentration at the autotrophic level the klarck is
calculated as a correlation between the content of the chemical element in one
unit dry sample biomass and the content of the same element in 1 kg dry soil.
We take soil as a bio-structural body which is different from lithosphere.
Experiments are
carried out in two ecotopes: a region anthropogenically contaminated with lead
and cadmium (First ecotope) and a region without any anthropogenic changes of
the chemical content of the surface soil layer (Second ecotope). Studying 24
soil samples from the 0 – 20 cm horizon, we have determined that the
average quantity of lead in the First ecotope is 118 mg/kg and of cadmium 3,44
mg/kg; in the Second ecotope the quantity is respectively 25,3 mg/kg and 0,42
mg/kg. The average quantity of lead in Bulgarian soils is 25 mg/kg and of
cadmium – 0,07 mg/kg (according to data in 2002). The concentration klarck of
lead in the First ecotope is 4,27, and in the Second ecotope it is 1,01 (equal
to the average value in Bulgaria). Corresponding values of K for cadmium are 49,14 and 6,0.
Analysis of
literature shows that the content of cadmium in many regions in Bulgaria is
high but that’s not a result of anthropogenic pressure and techno-geneous
changes in the distribution of chemical elements. Research on soil forming
rocks gives ground to affirm that the increased klarck of cadmium in the second
ecotope has a natural origin.
Data in Table 1
shows that there is dispersion of cadmium and lead at the autotrophic level.
Dispersion of the two studied elements is determined at the first heterotrophic
level as well. Dispersion was calculated using BCF1, regarding the
chemical elements’ quantity in the ecotope. For determining the chemical
heterogeneity regarding the preceding trophic level we propose a second criterion
as well / BCF2 /, which is calculated by dividing the quantity of
the studied chemical element in 1 kg dry biomass to the quantity of the same
element in 1 kg pasture grass or concentrated forage. In table 1 data for BCF2
is presented taking into account the herbaceous (grass) community in each ecotope. BCF2 for cadmium in
both groups is around 1 in kidneys, BCF2 for lead is 1.49 in the
second group of animals. In all of the other cases a dispersion of cadmium and
lead exists, determined according to the BCF2 criterion.
BCF1
is a fundamental criterion for bioecological monitoring. Analysis of the
obtained results shows that for both autotrophic organisms and primary
bioconsumers BCF is lower in the groups bred in an ecotope with high klarck of
cadmium and lead in soil.
Analyzing the
bioaccumulation of lead and cadmium in the organisms of kids, bred in ecotopes
with different klarck of the two chemical elements, we register differences in
their bioaccumulation compared to that of xenobiotics. Xenobiotics are
characterized by progressive increase of their concentration at each trophic
level. Using the criterion BCF1, it is seen that in the examined
organs and tissues of kids a considerable dispersion of both toxic
elements exists compared to their quantity in soil. It is determined that in
the group of animals bred in ecotope I (with anthropogenically increased klarck of lead) the degree of concentration
is considerably lower in comparison with that of animals bred in an environment
with normal quantity of lead in soil (ecotope II). This characteristic is
expressed well when analyzing the bioaccumulation of cadmium. BCF1
in kids’ liver from ecotope I is 0,14 and for kids bred in ecotope II - 0,40. In kidneys the corresponding values are 0,15 and 0,71, and in muscular tissue 0,03 and 0,14. We put the
accent on the analysis of BCF1 because we take that a trophic chain
forms in a biocenosis and it is a biological macro system of elements connected
by trophic bonds.
Nevertheless we
calculate BCF2 as an additional index – this is the correlation
between the quantity of the studied element in the studied sample (liver,
kidneys and muscular tissue) and its quantity in pasture grass. We point out
the conditional character of the obtained results as we are aware that the
animals have consumed grain forages which have chemical content in accordance
with the requirements of Decree No 5 for both groups of animals. That’s
why we exclude the imported quantities of lead and cadmium by grain forages and
we put the accent on the research of the classic grazing trophic chain. We have
not noticed any regularity for the BCF2 criterion of lead, but for
cadmium the determined fact, that the degree of bioaccumulation of the toxic
element (calculated by BCF2) is considerably lower in kidneys and in
muscular tissue of kids bred in ecotope with anthropogenically increased
klarck, is repeated once again. We explain this characteristic with the
difference between the klarck of the two toxic elements, for cadmium it is
considerably higher in comparison with the klarck of lead (49,14 against 4,27).
The chemical
concept about the “behavior” of nature contaminants, formulated by Tinsley /1982/, is often applied to explain the characteristics of movement of toxic
elements and compounds. According to this concept 50 %
of the biomass taken with food transforms in specific for the organism tissues
and due to the lack of mechanisms, which eliminate contaminants, their
concentration in the organism will be two times higher in comparison with their
concentration in food. At the next trophic level, in case this tendency
preserves, accumulation will be 4 times higher, etc. This concept is can be
applied to xenobiotics and especially to pesticides.
Our research
gives us ground to claim that differences regarding the movement of xenobiotics
and toxic chemical elements along the food chain exist. For xenobiotics
extremely high bioaccumulation values are determined (DDT concentration is 10
million times higher in the tissues of predatory fish than in water). Toxic
elements are part of natural environment for both autotrophic and heterotrophic
organisms. High degree of concentration at each trophic level is not determined
for toxic elements as for xenobiotics. The reason for this is the effect known
as substrate induction, which is determined for other factors as well. Research shows that the increase of the
quantity of tryptophan in the ration causes substrate inducement of some
enzymes, amongst which is tryptophan pyrolyzate. That is the reason why the degree of
bioconversion of the amino acid considerably decreases /Baykov, 1976/. Substrate inducement changes the metabolism and processes of catabolism
are activated. These changes give us ground to claim that high doses of lead
and cadmium are regular stressor for the organism /increased energy
consumption, decreased resistance of the organism, leading to high
mortality/. This stress influence leads to the activation
of mechanisms that significantly decrease the accumulation of lead and cadmium
in the examined tissues. As it is seen in our previous research/Baykov, 1995; Baykov et al., 1996/, a range exists where the
increase of lead and cadmium in the ration does not cause an increase of the
quantity of the two toxic elements in secondary production(used for food by
people) above the concentrations dangerous for people’s health.
Results from the
research of the quantity of lead and cadmium in muscular tissues, liver and
kidneys of kids, bred in two regions – with normal and anthropogenically
increased klarck of the studied toxic elements per 1 kilogram fresh biomass and
per 1 kilogram dry weight- are presented in Table 1. Data concerning the
quantity of these elements per kilogram fresh biomass is necessary because the
normative documents - Decree No 12 / 2002 of the Ministry of Health in Bulgaria which is based on EU - regulation 466/ 2001 - are written for fresh biomass. Research shows
that high techno-geneous klarck of the two toxic elements reflects on the
quality of the obtained secondary production. The MRL of lead for liver and
kidneys is 0,5 mg/kg. The determined quantity is 0,28 mg/kg
fresh mass for liver from the second group of kids which gives us ground to say
it is safe for human health whilst the same index for the first group of
animals is 1,59 mg/kg which is 3,18 times higher than the MRL.
The concentration values of lead in kidneys from the first group are very high
as well – 2,2 times higher than the
MRL, whilst for the second group the quantity of the toxic element is around
the MRL value. Evaluating the quantity of lead, the highest
values are in muscular tissue according to the safety regulations of the EU.
The MRL is 0,1 mg/kg and the determined quantity is 0,83 mg/kg for the first group of kids which exceeds 8,3
times the MRL. In the second group of animals, inexplicably why,
the quantity is 2,8 times higher than the MRL as well. Preceding
regulations ought to be taken into consideration when analyzing the results
(for example Decree No 5 / 1983, etc. - where the
MRL of lead in muscular tissues is 0,5 mg/kg).
The quantities of
cadmium in liver of kids from the first and the second groups are under the MRL
(MRL = 0,5 mg/kg). The quantities of the toxic element
in kidneys of kids from the first and the second groups are significantly
lower as well –0,10 mg/kg for the
first group and 0,06 mg/kg for the second group (MRL=1,0
mg/kg). The MRL of cadmium in muscles is 0,05 mg/kg. The
values are 0,03 mg/kg for the first group and 0,02 mg/kg for the
second group, i.e. under MRL.
In order to ease the
interpretation of data we propose a new criterion - criterion of
safety (CS). It is determined by dividing the quantity of the toxic element (in
mg) in one kilogram fresh secondary production to the regulated MRL quantity for
one kilogram fresh secondary production regarding the cited documents. We got
the following results: CS of lead in liver is 1.58 for the first group and 0.28
for the second group. When CS is more than 1 there is a risk for human health
and when CS is less than 1 the product meets the hygienic (sanitary)
requirements.
When analyzing
these results according to the CS it is necessary to take into consideration
the fact that this criterion has been developed for the preservation of human
health, without taking into account the characteristics of movement of toxic
chemical elements in natural ecosystems. The characteristics regarding the MRL
of lead in muscular tissues and liver give us ground to recommend revision of
some regulations and to underline that CS is a sanitary, but not an ecological
criterion. The ecological assessment should include the healthy status of
animals as well. Deviations of the normal indexes - animals’ temperature,
pulse, respiration, and condition of the mucous membranes - haven’t been
recorded during clinical examinations. We have not discovered any indications
of acute or chronic intoxication as well.
This research
gives us ground to make the following conclusions:
1. Differences exist
between the movement of xenobiotics and toxic chemical elements along the
trophic chain where primary consumers are farm animals. Because of the absence
of evolutionary formed mechanisms xenobiotics intensively accumulate along the
trophic chain. Considering toxic elements we observe decrease in the degree of
accumulation proportional to their increase in primary production.
2. At the increase
of lead and cadmium quantity in primary production mechanisms are activated for
the decrease of the degree of bioaccumulation in the organisms of farm animals.
Such mechanisms are known about other nutritive factors as well and are
characterized as substrate induction. These mechanisms help the preservation of
plant and animal community’s health.
3. In spite of the
decrease of BCF, high doses of lead and cadmium in the ecotope have a
stress impact expressed in high-energy expenditure per one unit secondary
production and in reduced resistance of the organism.
4. When analyzing
high techno-geneous klarck of Pb and Cd data and the analysis according to the
CS it is determined that regardless of the evolutionary formed mechanisms for
protection of ecosystem’s health, there is a risk for human health.
References:
1. Baykov, В., 1976. Changes of content of tryptophan in sitting hens’ organisms
under influence of environmental temperature – moisture regime.
Veterinary-Medical Sciences. vol XIII, N3, 25-31 .
2. Baykov, В., 2003. Application of new criteria for estimation of chemical
heterogeneity at stock-raising animals – phytophagans for the purpose of bio
ecological monitoring improvement. Jubilee collection of UF, S, 52-54.
3. Baykov, B.,
1994. Toxicol. Environ. Chem. 42, 227-233.
4. Baykov, B., et
al., 1994, An objective method for assessment of the movement of chemical elements
in anthropogenic ecosystems /domestic animal farms /. Toxicol. Environ. Chem.
49, 119-121.
5. Baykov, B. D.,
Stoyanov M. P., Gugova M. L., 1996. Lead and cadmium bioaccumulation in male
chickens. Toxicol. Environ. Chem, 54, 155 – 159.
6. Dobrovolskii,
V. V., 1984. Problems of geochemistry in physical geography, M.
“Prosveshtenie".
7. Dobrovolskiy,
V. V., 1998. Fundamentals of biochemistry. M. “Vischaia shcola",
8. Hebel, B.,
Wrigt, R., 1996. Environmental Science,
5/e. Prentice Hall, NY.
9. Jorchem, L.,
1993. Determination of Metals in Foodstuffs by AAS. J of AOAC International 76 /4/, 798-813.
10.
Kabata-Pendias. A. & H. Pendias, 1984. Trace element in Soil and Plants.
CPC Press Inc. Florida, 28.
11. Petkov, G.,
Baykov, В., 1984. Ecological
consequence of chemical war. Journal of BAS , 1, 5-10.
12. Reylly, C.,
1980. Metal contamination of Food. Applied Science Publ., London.
13. Tinsley, I.,
1982. Chemical concept in pollutant behaviour. A.Wiley – Inter science
publication, NY, 90 - 203.
Table1 : Chemical
heterogeneity in an anthropogenic ecosystem for production of meat with
different Clarke of lead and cadmium in the ecotope
|
|
|
Lead |
Cadmium |
||
|
I group |
II group |
I group |
II group |
||
|
|
Soil of pasture
|
118 ± 9,0 |
25,3 ± 1,2 |
3,44 ± 0,3 |
0,42 ± 0,1 |
|
1. |
Average contents for
Bulgaria |
25 |
25 |
0,07 |
0,07 |
|
|
К |
4,27 |
1,01 |
49,14 |
6,0 |
|
|
Hay |
6,63 ± 0,21 |
2,0 ±
0,05 |
0,72 ±
0,02 |
0,30 ±
0,08 |
|
Fb |
0,06 |
0,08 |
0,21 |
0,71 |
|
|
|
Phytophags |
|
|
|
|
|
Kids |
|
|
|
|
|
|
|
Liver |
5,42 ±
0,42 |
0,98 ±
0,24 |
0,49 ±
0,11 |
0,17 ±
0,08 |
|
3.1. |
Fb1 |
0,05 |
0,04 |
0,14 |
0,40 |
|
|
Fb2 |
0,81 |
0,49 |
0,68 |
0,57 |
|
|
|
1,59 ± 0,10 a |
0,28 ± 0,06 a |
0,14 ± 0,06 a |
0,05 ± 0,01 a |
|
|
Kidney |
5,61 ±
0,63 |
2,98 ±
0,25 |
0,51 ± 0,08 |
0,30 ±
0,09 |
|
3.2. |
Fb1 |
0,05 |
0,12 |
0,15 |
0,71 |
|
|
Fb2 |
0,85 |
1,49 |
0,71 |
1,00 |
|
|
|
1,10 ± 0,11 a |
0,58 ± 0,07 a |
0,10 ± 0,02 a |
0,06 ± 0,01 a |
|
|
Muscles |
3,00 ±
0,32 |
1,03 ±
0,18 |
0,09 ±
0,02 |
0,06 ±
0,01 |
|
3.3. |
Fb1 |
0,03 |
0,04 |
0,03 |
0,14 |
|
|
Fb2 |
0,53 |
0,51 |
0,125 |
0,20 |
|
|
|
0,83 ± 0,11 a |
0,28 ± 0,11 a |
0,03 ± 0,02 a |
0,02 ± 0,01 a |
a fresh tissue (mg/kg)