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1. Introduction
After observation of elevated polychlorinated biphenyl (PCB) levels in vegetables grown in the vicinity of an industrial area in Dortmund, Germany, it was finally discovered in May of 2010 that inadequate occupational hygiene in a recycling plant for capacitors and transformers had led to a significant body burden of PCBs in workers and their family members, as well as to the exposure of people working or living in the immediate vicinity of the recycling company [1]. As a consequence, the medical surveillance program HELPcB (Health Effects in High-Level Exposure to PCB) was initiated [2]. It provides bio-monitoring to identify potential health risks related to PCB exposure for the affected group of persons. Unusually high exposure levels of the sum of six indicator congeners (PCBs 28, 52, 101, 138, 153, 180) of up to 236 µg/L plasma were observed in some of the workers [1]. This significantly exceeds the background burden previously reported for German subjects with no known exposure to sources of PCB [3]. Exposure also extended to relatives that have not been in direct contact with the contaminated materials [1].
PCBs belong to the persistent organic pollutants, a group of chemicals causing concern due to their widespread accumulation in the environment and food chain, especially in light of their toxic effects. The toxicological profile for PCBs by the International Agency for Research on Cancer (IARC) lists several severe health effects, including the classification of several congeners as carcinogenic to humans (group 1) [4]. Moreover there are data indicating that PCBs are toxic to the nervous, endocrine, and immune systems [5,6].
So far, immunotoxic effects of PCBs in humans were predominantly investigated with a focus on pre- and early postnatal exposure. An elevated risk for respiratory infections due to PCB exposure was identified in Swedish children [7]. Reduced antibody formation in response to vaccination against diphtheria and tetanus was found in a cohort of children from the Faroe Islands. These children had an elevated risk for PCB exposure based on uptake from the consumption of pilot whale blubber [8]. A study in Dutch infants did not confirm a relationship between PCB exposure and antibody production or the incidence of respiratory infections [9]. Instead, it found a positive relationship between current PCB body burden...