Health Risk Assessment of Children in the Environmental Pollution Region of Kardzhali for the Period 1991-2013

For more than 55 years is the environmental pollution region of Kardzhali in Bulgaria has been due to intense emissions from mining-processing, smelter plant and processing of nonmetallic minerals. The main source of pollution in those years is smelter plant (Lead and Zinc Complex), but from 2011 to 2012 respectively, lead and zinc production was gradually stopped. One of the mechanisms to assess the health risk among the population is to conduct biological monitoring, to make biological materials to determine the concentration of heavy metals in them. The most vulnerable group is children. The aim of this study is to benchmark the results of the biological monitoring of children aged between 9 to 14 years in the city of Kardzhali for the 1991-2013 periods. Biological monitoring includes determination of lead in the blood of 356 children from two schools in the city of Kardzhali (located near and far away from OCK-AD) and one in Krumovgrad (for control). In accordance with the methodology in Bulgaria (included children), drawing of USA methodology received results in the following: According to the individual results for the period 1991-2002, when smelter plant has worked, in 71% of the children in Kardzhali values of lead in the blood are below 100 μg/l, in 24% between 100 and 200 μg/l and in 5% over 200 μg/l. In 2013, when the company ceased operation in 92% of surveyed children the levels of lead in the blood is below 100 μg/l, in 7% from 100 to 200 μg/l and in 1% above 200 μg/l. The results indicate a link between air pollution with lead aerosols and the level of lead in the blood of children: In the intensive work of the plant during 1991-2002 years in 29% of children amounts of lead in the blood is above 100 μg/l. In 2013 (when closed proceedings) only 8% of children are with lead content in the blood of more than 100 μg/l. The blood of the children in the control group demonstrated no lead content at 100% of children.

One of the mechanisms to assess the health risk among the population is to conduct biological monitoring, to make biological materials to determine the concentration of heavy metals in them. The most vulnerable group is children.
The aim of this study is to benchmark the results of the biological monitoring of children aged between 9 to 14 years in the city of Kardzhali for the 1991-2013 periods. Biological monitoring includes determination of lead in the blood of 356 children from two schools in the city of Kardzhali (located near and far away from OCK-AD) and one in Krumovgrad (for control).
In accordance with the methodology in Bulgaria (included children), drawing of USA methodology received results in the following: According to the individual results for the period 1991-2002, when smelter plant has worked, in 71% of the children in Kardzhali values of lead in the blood are below 100 μg/l, in 24% between 100 and 200 μg/l and in 5% over 200 μg/l.
In 2013, when the company ceased operation in 92% of surveyed children the levels of lead in the blood is below 100 μg/l, in 7% from 100 to 200 μg/l and in 1% above 200 μg/l.
The results indicate a link between air pollution with lead aerosols and the level of lead in the blood of children: In the intensive work of the plant during 1991-2002 years in 29% of children amounts of lead in the blood is above 100 μg/l.
In 2013 (when closed proceedings) only 8% of children are with lead content in the blood of more than 100 μg/l.
The blood of the children in the control group demonstrated no lead content at 100% of children.

Methods
Within the scope of the study during the period 1991-2013 included 356 children aged from 9 to 14 years old from two schools in the town of Kardzhali (located on near and distant off OCK) and one in the town of krumovgrad.
According to data of the Executive Agency for the environment, the area of the town of Krumovgrad is rated as an area in which the levels of pollutants are below the lower assessment threshold [1,2]. The share of industry in the economy of the municipality of Krumovgrad is too limited. In the area there is no significant organized emission source of harmful substances, which is designated as a control for the purposes of the study.
For ease of benchmarking data schools are labeled as follows: School "St. Kliment Ohridski", Kardzhali, which is situated near the sources of contamination -with code 1.
"St. St. Cyril and Methodius, Kardzhali, which is remote from sources of pollution -with code 2.
Every child is a venous blood sample taken to detect the presence of lead using a closed vacuum-system (S-Monovette ® for trace metal analysis) for one-time use, containing aditiv-LH (Lithium heparin).
The concentration of lead in the blood is measured by Atomic absobrcionna spectrometry with graphic atomizator.
For a comparison of the average values of the variables used the criterion of the Mann-Wh Whitney and Kruskal-Wallis test.

Results
Summary statistical characteristics of the indicator of the research lead for the period 1991-2013, traced in the dynamics in the three educational institutions are shown in Table 1.  According to the individual results of the study in 2002, when Lead and Zinc Complex (LZC) worked, the average level of lead in blood of children from Kardzhali was 92.7 ± 44.7 μg/l, (median 82 μg/l), with registered individual values from 30 to 259 μg/l. The mean PbK concentration of children from Krumovgrad was 57.9 ± 15.1 μg/l, (median 58 μg/l) and results ranging from 30 to 93 μg/l. The level of lead in blood of children from Kardzhali is statistically significantly higher than that of the children from Krumovgrad (P<0.0001).
In 2013, when the activity of the enterprise is discontinued, the average level of lead in blood of children from Kardzhali was 67.1 ± 25.3 μg/l, (median 63 μg/l), with registered individual values from 31 to 211 μg/l. The mean PbK concentration of children from Krumovgrad was 48.0 ± 11.0 μg/l, (median 46 μg/l) and results ranging from 31 to 78 μg/l.
The test of Kruskal-Wallis reveals that the educational institutions differ statistically significant (P<0.0001). In order to be found exactly between which schools there are significant differences, an appropriate post-hoc test is used. Which shows difference between School 1 and School 2 (P<0.05), between School 1 and School 3 (P<0.05) and between School 2 and  Table 2).
In 2013 at 92% of the studied children, the levels of lead in the blood are below 100 μg/l, 7% from 100 to 200 μg/l and 1% over 200 μg/l. The results indicate a link between environmental pollution by lead aerosols and the level of lead in blood of children: -In the intensive work of the plant in the period [1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002] year in 29% of children the values of lead in the blood are above 100 μg/l. -In 2013 (in closed proceedings) only 8% of children have lead content in blood above 100 μg/l.

Annals of Behavioural Science
-The blood of the children in the control group did not prove lead content at 100% of children.

Conclusion
The research on the content of lead in the blood of children from both villages does not prove the increased intake of metal in the body. Children of Kardzhali with values of PbK under 200 µg/l represent 99.0 percent sample, which is above the recommended 98.0% of the WHO [4,5].
According to the requirements of the CDC-United States, at 7.0% of surveyed children from Kardzhali regular testing for lead content in the blood. About 1.0% of children, with values of over 200 g PbK µ/l, there is a risk to health from the increased intake of metal in the body and requiring further medical research [6][7][8].
Analysis of the results obtained clearly finds correlation between environmental pollution by aerosols of lead and heavy metal levels in the blood while the exposure of the surveyed children.
Data show lower values of PbK in children from the town of Kardzhali in both different remote from polluter schools in 2013 compared with the same in 1991.