3. Results and Discussion

Air samples were taken in three Nordic capitals, one town in Iceland and at one background monitoring station in Norway in winter and summer 2022. Field blank samples were included for all sample types (i.e. filter types and PUFs). The levels of CPs in the field blanks depended on the size of the filters, and when converting to concentrations also on the total amount of air volume sampled for the representative filter. CP levels were higher in field blanks compared to lab blanks suggesting some degree of contamination during sampling and/or transport. However, most of the exposed samples had concentrations above the field blanks. Exceptions were LCCPs from Helsinki for which 71% of the samples were below the field blanks, and SCCPs from Oslo in summer and winter for which 100% and 60% of the samples were below the field blanks.

Of the three CP groups, LCCPs were most frequently detected (97%) followed by MCCPs (80%) and SCCPs (67%). The reason for lower detection frequency of MCCPs and SCCPs is partly due to higher LODs than for LCCPs. MCCPs were measured at the highest concentrations in a majority of the urban samples (88%) with detectable concentrations. The concentrations of LCCPs were higher than both MCCPs and SCCPs in four samples while lower than both MCCPs and SCCPs in 67% of the samples. The individually highest concentrations were measured for MCCPs in Helsinki and LCCPs at the urban site in Reykjavik. The lowest concentrations and lowest detection frequency were found for SCCPs and LCCPs at the urban site in Oslo and LCCPs at the sub-urban site in Reykjavik and the urban site in Helsinki.

The concentrations of LCCPs and MCCPs were significantly lower at Reykjanesbær than at Reykjavik, both in winter and summer. For SCCPs no difference was found between the two sites in Iceland. The results for Oslo and Helsinki indicate higher concentrations of SCCPs and MCCPs in wintertime than in summertime but no difference was observed in Reykjavik (Table 4). In contrast, higher concentrations were observed in summer than in winter at the background site in southern Norway.

Comparison of the urban concentrations with background air concentrations from Birkenes shows no difference for SCCPs. For MCCPs, higher concentrations were observed in Helsinki than at Birkenes while the other urban sites were similar to Birkenes.

Overall, the measured concentrations of all CP groups at all sites in this study are significantly lower than the concentrations measured at the urban site in Reykjavik in 2019 (Table 3). The reason for lower concentrations at the urban site in this study is unknown as identical sampling methods were used in both studies and the same blank treatment was applied for all samples. The concentrations of SCCPs and MCCPs at the background site (Birkenes) are similar to those previously measured at Birkenes for the Joint Nordic Screening Group in 2019 (Schlabach et al. 2022) and those from the Norwegian Monitoring Programme “Atmospheric Contaminants” (Bohlin-Nizzetto et al. 2022). This shows consistency in the analytical method.

Table 3: Average concentration of chlorinated paraffins in urban air from the three Nordic capitals (Reykjavik, Helsinki and Oslo), Reykjanesbær, the background site, and field blank samples. Presented are also the concentrations measured in Reykjavik in 2019.

*Schlabach et al. (2022).

Table 4: Seasonal concentrations (pg/m³) of chlorinated paraffins in air samples from the urban and the background site presented as average and range for each season.

*More than 66% of the samples below the field blanks.

Brandsma et al (2019) showed that end-of-life car tires contain high concentrations of CPs with dominance of MCCPs. One goal of this study was therefore to see whether mechanical car tire wearing release CPs to air. Active air samples were collected indoors at a research facility in Sweden (VTI) during mechanical wearing of car tires and while no wearing was performed. Unfortunately, the concentrations of all CPs in the field blank samples for this sampling campaign were elevated and at the same level as or even higher than the exposed samples. No conclusion can therefore be drawn from this side-activity.