Annals of Behavioural Science

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.

"Vasil Levski" secondary school, the town of Krumovgrad (control) – with code 3.

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 biological material has been studied in clinical laboratory of University Hospital "Alexandrovska" EAD-Sofia.

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.

Table 1: Average values and standard deviations of PbK inμg/l for the period 1991-2013.

Data processing of biological monitoring in 1991 shows that average values of RbK are not statistically significant different (P corresponding values were 0.43 and 0.108). Found mediumgroup results are within the cited literature then (below 200 μg/l).

Statistically significant differences in average values of lead in schools (P<0.0001), monitored in 2002 are found by the Kruskal-Wallis test. A difference between the averages in schools 1 and 2 (P=0.02 and P<0.0001) is found by test the Mann-Whitney. The same applies to schools 1 and 3 (P<0.0001 and P<0.0001), as well as for 2 and 3 (P<0.0001 and P<0.0001).

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 School 3 (P<0.05), i.e., three schools differ significantly in terms of the indicator Lead. According to the Center for Disease Control (CDC) in the United States (ATSDR, 1997), children with levels of lead in blood [3]:

• From 100 to 200 μg/l - are subject to periodic examinations

• Above 200 μg/l - needed further medical tests

• Above 400 μg/l - undergo medical treatment.

The results on the percentage split for the period 1991-2002 year show that values of lead in the blood in 71% of surveyed children in Kardzhali are below 100 μg/l, 24% from 100 to 200 μg/l and 5% 200 μg/l (Table 2).

Table 2: Percentage distribution according to the individual results in children of PbKKardzhali for the period 1991-2013

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 1991-2002 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.

- 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 [6-8].

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.

The confirmation of the link control group-children from environmentally endangered area is established absence of PbK in the studied blood samples in children from the town of Krumovgrad.

References

1. DarlingtonG (2009)Quality of environment and health risks in the area of the town of KardzhaliandSt. KlimentOhridski University, Sofia.
2. Regulation No. 7(1999)To evaluate and manage air quality (Gg. 45/1999, in force from 01.01.2000).
3. Center of Disease Control and Prevention (CDC) (2002) Blood Lead Laboratory Reference System,
4. National Center of Environmental Health.
5. WHO (2008) Health behavior in school aged children, International Report.
6. WHO (2015) Billion people at risk of hearing loss – Press release,2015
7. Whitehead D (2003) Evaluating health promotion a model of nursing practice. Journal of Advanced Nursing 41: 490-498.  
8. Staykova J (2014) Health status of studentsof Kardzhaliregion.P:13-14.