Tire related additive chemicals were present in road run-off from Nordic countries as well as in associated compartments/sites such as snow dumping sites, stormwater recipients and soils/sediments. They were further detected in blue mussel samples collected in the wild, indicating that a transfer into biota is taking place. Target chemicals were present in 98% of samples and only one target chemical (CPPD) was not detected in any sample. This suggests a ubiquitous contamination by tire related additive chemicals, though at varying degrees depending on the sample type and location. For example, concentrations in marine sediments near the snow dumping sites in Tromsø (Norway 08-13) were relatively low, while sediments collected at a snow treatment facility in Oslo (Norway 05 & 07) exhibited concentrations 30–40 times higher. This is probably due to heavier traffic in Oslo and/or because the water mixing in marine waters can lead to a rapid dilution of chemicals, thus limiting their accumulation in sediments.
TPPD, an antioxidant, was the most abundant compound in all sample matrices. Literature on the occurrence of TPPD is almost nonexistent, but a laboratory exposure study has shown that ingestion of rubber particles by lumpfish can lead to a transfer of TPPD into the fishes’ blood (Hägg et al., 2023). The high concentrations of TPPD detected in this study and the lack of comparable scientific literature indicate that more data is urgently needed.
The crosslinking agent HMMM is highly water soluble, explaining its presence in sometimes very high amounts in water samples, but its near absence in sediment and biota samples.
While road run-off water samples from the Faroe Islands and Iceland exhibited highest tire chemical concentrations, clear differences between the two countries could be seen concerning the relative abundance of individual chemicals: in samples from the Faroe Islands TPPD is highly predominant, while in samples from Iceland HMMM is very abundant. Different tire brands with different formulations could be used more commonly in certain countries than in others, but a detailed analysis of the tire market in Nordic countries would be needed to draw any conclusions. In general, variations in chemical concentrations between sampling sites can for example depend on the sample type, the amount of precipitation and UV irradiation before/during sampling or the frequency with which the roads are being cleaned and tire wear particles are hence being removed from the roads. The sampling timepoint can also be relevant when comparing tire additive concentrations in environmental samples: due to a lack of rain in many locations during spring 2023, the sampling campaign spanned from March until July (October for opportunistic atmospheric deposition samples), i.e., a period where transitions from winter tires, including studded tires, to all-year tires or summer tires are taking place.
The antioxidant and antiozonant 6PPD and its transformation product 6PPD-Q have recently been reported in three different fish species (Ji et al., 2022). However, this report is, to our knowledge, the first report on the occurrence of other tire related additives such as TPPD and CPPD-Q in wildlife. No data on toxicological effects of these compounds is known to us.