Correction to: Chronic toxicity of tire and road wear particles to water- and sediment-dwelling organisms.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Chronic toxicity of tire and road wear particles to water- and sediment-dwelling organisms.

Tire and road wear particles (TRWP) consist of a complex mixture of rubber, and pavement released from tires during use on road surfaces. Subsequent transport of the TRWP into freshwater sediments has raised some concern about the potential adverse effects on aquatic organisms. Previous studies have shown some potential for toxicity for tread particles, however, toxicity studies of TRWP collected from a road simulator system revealed no acute toxicity to green algae, daphnids, or fathead minnows at concentrations up to 10,000 mg/kg under conditions representative of receiving water bodies. In this study, the chronic toxicity of TRWP was evaluated in four aquatic species. Test animals were exposed to whole sediment spiked with TRWP at concentrations up to 10,000 mg/kg sediment or elutriates from spiked sediment. Exposure to TRWP spiked sediment caused mild growth inhibition in Chironomus dilutus but had no adverse effect on growth or reproduction in Hyalella azteca. Exposure to TRWP elutriates resulted in slightly diminished survival in larval Pimephales promelas but had no adverse effect on growth or reproduction in Ceriodaphnia dubia. No other endpoints in these species were affected. These results, together with previous studies demonstrating no acute toxicity of TRWP, indicate that under typical exposure conditions TRWP in sediments pose a low risk of toxicity to aquatic organisms.

Manganese superoxide dismutase: effect of the ala16val polymorphism on protein, activity, and mRNA levels in human breast cancer cell lines and stably transfected mouse embryonic fibroblasts.

The manganese superoxide dismutase (MnSOD) ala16val polymorphism has been associated with various diseases including breast cancer. In the present study, we investigated levels of MnSOD protein, enzymatic activity, and mRNA with respect to MnSOD genotype in several human breast carcinoma cell lines and in mouse embryonic fibroblasts (MEF), developed from the MnSOD knockout mouse, stably expressing human MnSOD-ala and MnSOD-val. In human breast cell lines, the MnSOD-ala allele was associated with increased levels of MnSOD protein and MnSOD protein per unit mRNA. In the MEF transformants, MnSOD activity correlated fairly well with MnSOD protein levels. MnSOD mRNA expression was significantly lower in MnSOD-ala versus MnSOD-val lines. MnSOD protein and activity levels were not related to MnSOD genotype in the transformed MEF, although, as observed in the human breast cell lines, the MEF human MnSOD-ala lines produced significantly more human MnSOD protein per unit mRNA than the human MnSOD-val lines. This suggests that there is more efficient production of MnSOD-ala protein compared to MnSOD-val protein. Examination of several indicators of reactive oxygen species levels, including superoxide and hydrogen peroxide, in wild-type MEF and in MEF expressing similar elevated amounts of MnSOD-ala or val activity did not show differences related to the levels of MnSOD protein expression. In conclusion, in both human breast carcinoma cell lines and MEF cell lines stably transfected with human MnSOD, the MnSOD-ala allele was associated with increased production of MnSOD protein per unit mRNA indicating a possible imbalance in MnSOD protein production from the MnSOD-val mRNA.

Physical and chemical characterization of tire-related particles: comparison of particles generated using different methodologies.

The purpose of this study was to characterize the physical and chemical properties of particles generated from the interaction of tires and road surfaces. Morphology, size distribution, and chemical composition were compared between particles generated using different methods, including on-road collection, laboratory generation under simulated driving conditions, and cryogenic breaking of tread rubber. Both on-road collected and laboratory generated particles exhibited the elongated shape typical of tire wear particles, whereas tread particles were more angular. Despite similar morphology for the on-road collected and the laboratory generated particles, the former were smaller on average. It is not clear at this stage if the difference is significant to the physical and chemical behavior of the particles. The chemical composition of the particles differed, with on-road generated particles containing chemical contributions from sources other than tires, such as pavement or particulates generated from other traffic-related sources. Understanding the differences between these particles is essential in apportioning contaminant contributions to the environment between tires, roadways, and other sources, and evaluating the representativeness of toxicity studies using different types of particulate generated.