Human biomonitoring of polychlorinated biphenyls (PCBs) in plasma of former underground miners in Germany – A case-control study

Abstract

Polychlorinated biphenyls (PCBs) are very persistent organic pollutants of severe environmental concern due to their toxic properties. Former underground miners might have been exposed to this substance group due to the widespread use of PCBs in hydraulic oils from the late 1960s to the mid 1980s. We have conducted a blinded case-control study in order to evaluate the possibility of retrospective exposure assessment of PCBs using human biomonitoring in former underground miners decades after the last possible exposure. We have identified n = 34 male former underground miners and n = 136 age-matched male control persons from the database of patients of our occupational outpatient clinic aged between 47.9 and 83.7 years at the time of sampling (June 2006-June 2016). These archived plasma samples have been blinded and analysed for 21 different PCB-congeners using a validated and quality controlled procedure using GC/MS (LOQ: 0.01 μg/L). Highly significant differences between cases and age-matched controls were only found for the PCB-congeners PCB 74 and PCB 114. The median (95th percentile) levels of PCB 74 in cases and controls were 0.126 μg/L plasma (0.899 μg/L plasma) vs. 0.058 μg/L plasma (0.368 μg/L plasma) and the 95th percentile levels for PCB 114 were 0.039 μg/L plasma vs. 0.017 μg/L plasma. Linear regression models revealed that this difference in plasma levels was unequivocally attributed to the underground mining activity. Thus, retrospective exposure assessment for underground miners by use of human biomonitoring seems feasible and further studies with a particular focus on this special group of workers should be performed.

Assessment of a potential PCB exposure among (former) underground miners by hydraulic fluids

“…The detectable influence of age on internal PCB 74 burden of underground miners is attributed to the relatively long half-life of PCB 74. The same age dependency was noted in by Schettgen et al (2018). However, in this case-control study, a regression analysis indicated that the influence of age on biomonitoring results for PCB 74 and PCB 114 was much lower than the effect of being a former underground miner (cases) or not (controls).…”

“…Pearson's Chi-square for at least one congener above reference was 0.13 (p=0.937) and for PCB 74 it was 0.011 (p= 0.994). The differences between individual coal mines in % of participants with a minimum of one congener above the individual reference value and with mining specific (Schettgen et al 2018) PCB 74 above the individual reference also did not show significant differences between mines (see Supplement Figure 1). Due to the small numbers of participants from individual coal mines the Fisher's exact test was applied and showed a value of 46.8 (p=0.41) and 51.6 (p=0.19), respectively, for PCB 74.…”

“…For workers exposed to PCBs in the field of capacitors and transformers, a significant increase of these congeners could be demonstrated even after 28 years. Schettgen et al (2018) identified PCB 74 (and PCB 114) as a suitable marker to detect a long past occupational exposure to PCB for former underground coal mining workers in a blinded case-control study. Neither reference values for the PCBs 66, 74, and 99 nor a characterization of their health effects was available.…”

“…These values indicate, if exceeded, an additional exposure to lower chlorinated PCBs. Based on own previous findings (Schettgen et al 2018) and the work of Seegal et al (2010) it was decided to also determine the lower chlorinated congeners PCBs 74, 66, and 99. For workers exposed to PCBs in the field of capacitors and transformers, a significant increase of these congeners could be demonstrated even after 28 years.…”

“…After such a long time since the potential exposure ended, the authors could not anticipate to detect the classical markers of occupational exposure, such as PCB 28, 52, or 101, in the blood of (former) miners. In view of the results of the work of Seegal and colleagues (2011) their own previous work (Schettgen et al 2018), the authors decided decided to include PCB 66, 74, and 99 in the analysis in addition to the usual indicator congeners and representatives of dioxin-like congeners.…”