Objectives: Data on high frequency of hepatitis A virus (HAV) antibodies for wastewater treatment staff is contradictory. Literature lacks data on the seroprevalence of antibodies to HAV (anti-HAV) among workers in wastewater treatment plants (WWTPs) in Bulgaria. The aim of this study is to establish a specific humoral immune response to hepatitis A virusanti-HAV total antibodies among staff in WWTPs. Material and Methods: A complex study of health and working conditions included 110 subjects working in 3 WWTPs in Bulgaria (74% of all workers in the 3 studied WWTPs and 20% of all employees in Bulgaria registered in 2014 under the wastewater collection, discharge and treatment code of economic activity). Workers had been differentiated in 3 groups on the basis of their occupational work: operators, support staff and other workers exposed to biological agents. Venous blood from all 110 subjects was tested once for carriers of HAV antibodies. Results: Anti-HAV total antibodies were found for 52.7% of workers in WWTPs. There is a positive association between activity performed in WWTPs (operators, maintenance personnel and others exposed) and a positive one for the presence of anti-HAV (Chi 2 = 6.882, df = 2, p = 0.032). Odds ratio (OR) for hepatitis A increases 2.9 times in the group of operators vs. others exposed to biological agents in WWTPs (OR = 2.914, 95% confidence interval (CI): 1.149-7.393, Fisher's p = 0.039). Odds ratio for hepatitis A increases 4.3 times in the group of support staff from WWTPs vs. others exposed to biological agents in WWTP (OR = 4.295, 95% CI: 1.075-17.167, Fisher's p = 0.049). Conclusions: Higher frequency of anti-HAV antibodies among operators and maintenance personnel at WWTPs has been established as compared to other workers exposed to biological agents in WWTPs. There is a positive association between increasing age of the workers and the presence of anti-HAV. Int J Occup Med Environ Health 2018;31(3):307 -315

Noise pollution is one of the four major pollutions in the world. In order to implement adequate strategies for noise control, assessment of traffic-generated noise is essential in city planning and management. The aim of this study was to determine whether space syntax could improve the predictive power of noise simulation. This paper reports a record linkage study which combined a documentary method with space syntax analysis. It analyses data about traffic flow as well as field-measured and computer-simulated traffic noise in two Bulgarian agglomerations. Our findings suggest that space syntax might have a potential in predicting traffic noise exposure by improving models for noise simulations using specialised software or actual traffic counts. The scientific attention might need to be directed towards space syntax in order to study its further application in current models and algorithms for noise prediction.

Background: The compensatory mechanisms of social security include expenses for sick leave. The aim of the study is to determine the economic cost due to sick leave among workers in wastewater treatment plants (WWTPs), comparing with the same economic indicators of the National Social Security Institute (NSSI) in Bulgaria. Material and Methods: The sick leave of 111 workers at 3 WWTPs was studied in the period 2012-2014 on the grounds of registered absences from work due to temporary incapacity for work. The economic indicators of the NSSI, the gross salary at WWTPs, payable social security contributions and compensatory payments for sick leave have been used for economic cost calculation for temporary incapacity of the workers. Results: The frequency of cases and the frequency of lost days due to temporary incapacity were increased in the observed period at WWTPs and in Bulgaria, and it is significantly higher for the employed at WWTPs. The percentage share of workers equivalent to 1.66% at WWTPs have not worked for an entire year as a result of temporary incapacity in 2012, 2.76% -in 2013, and 4.61% -in 2014. The economic burden due to sick leave at WWTPs was raised from EUR 4913.02 in 2012 to EUR 16 895.80 for 2014 for employers and the NSSI. Conclusions: The frequency of cases and the frequency of lost days due to temporary incapacity were increased in the observed period at WWTPs and in Bulgaria, and it is significantly higher for the employed at WWTPs. The economic burden was equally distributed between employers and the NSSI. Med Pr 2018;69(2):129-141

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