Polychlorinated biphenyls (PCBs) are a class of industrial chemicals that were mass-produced globally and in several Europe countries (Germany, France, Italy, Czech Republic) from the late 1920s to 1985, even after their ban in the end of 1970s (Cerná et al., 2012; Grimm et al., 2015; Komprda et al., 2019).

PCBs are lipophilic, organic compounds from the persistent organic pollutants (POPs) group with the high potential for bioaccumulation and long-distance transfer (WHO Europe, 2003; Alharbi et al., 2018). Due to their environmental and biological persistence, low levels of PCBs are still found in wildlife and humans (Ashraf, M., 2017; Gyllenhammar et al., 2021). Pollutants tend to reach raised concentrations in organisms from higher trophic levels, including humans, due to biomagnification through aquatic and terrestrial food chains (Stancheva et al., 2017; Metcalfe et al., 2022). More than 90% of the total daily human exposure to PCBs is made up of intake from fat-rich food of animal origin (Massart et al., 2008; Sun et al., 2022).

PCBs have low acute toxicity but may pose a health risk in case of chronic human exposure (ATSDR, 2000; ATSDR, 2011). Experimental data indicate that exposure to low levels of PCBs may be associated with chronic non-lethal effects such as endocrine disruption, immune dysfunction, neurological disorders, liver injury, diabetes, cardiovascular problems and carcinogenicity (World Health Organization, 2009; Fernández-Cruz et al., 2017; Guo et al., 2019).

Human biomonitoring is a suitable tool for assessing human exposure to PCBs (Zietz et al., 2008). Biomonitoring data directly reflect the total body burden taking into account all routes of exposure, as well as the interindividual variability in exposure levels, metabolism and excretion rates (WHO, 2015). Biomonitoring involves measurements of biomarkers in biological fluids, such as blood, urine, saliva, breast milk and sweat. Human breast milk analysis is a non-invasive method for assessing the actual exposure of the mothers and has an advantage over any other type of human sample due to its high lipid content (Angerer et al., 2007). However, the determination of PCBs in breast milk has its limitations. Samples can be obtained only during lactation and only from lactating women, which excludes other groups of the population. (Brajenović et al., 2018)

The six indicator PCBs (IUPAC № 28, 52, 101, 138, 153 and 180) have been selected by the European Food Safety Authority (EFSA) as the major congeners which are present in various food matrices in high concentrations (EFSA, 2005). Low chlorinated congeners, such as PCB 28, 52 and 101 can metabolize by the human body faster than highly chlorinated PCBs due their half-life of almost 5 years (El-Shahawi et al., 2010; Helou et al., 2019). Highly chlorinated PCB congeners, containing more than five chlorine atoms (PCB 138, 153, 170, 180), tend to bioaccumulate in adipose tissue, human serum lipids and breast milk (Grimm et al., 2015) and can persist for 10–47 years (ATSDR, 2000).

Since 1987, the World Health organization (WHO) and the United Nations Environment Programme (UNEP) have conducted seven global surveys of POPs in human milk (van den Berg et al., 2017). Bulgaria was included in the 3rd Round of WHO coordinated Exposure Study on the POP levels in breast milk. In the third survey (2000–2003) pooled milk samples from three groups of Bulgarian mothers were analyzed for PCBs and organochlorine pesticides. The levels of indicator PCBs measured in milk samples from Bulgaria (2003), reported by van den Berg et al. (2017), were among the lowest in the European countries. There are limited data on PCB levels in breast milk of mothers from Bulgaria in the last twenty years.

The aim of the study was to examine the accumulation profile of polychlorinated biphenyls in breast milk of women, living in two regions in north-eastern Bulgaria, and to assess its relation to individual characteristics.