Tire-tread material has a zinc (Zn) content of about 1 wt %. The quantity of tread material lost to road surfaces by abrasion has not been well characterized. Two approaches were used to assess the magnitude of this nonpoint source of Zn in the U.S. for the period 1936−1999. In the first approach, tread-wear rates from the automotive engineering literature were used in conjunction with vehicle distance-driven data from the U.S. Department of Transportation to determine Zn releases. A second approach calculated this source term from the volume of tread lost during lifetime tire wear. These analyses showed that the quantity of Zn released by tire wear in the mid-1990s was of the same magnitude as that released from waste incineration. For 1999, the quantity of Zn released by tire wear in the U.S. is estimated to be 10 000−11 000 metric tons. A specific case study focused on Zn sources and sinks in an urban−suburban watershed (Lake Anne) in the Washington, DC, metropolitan area for a time period of the late ...

Tire-wear particles as a source of zinc to the environment

Occurrence and effects of tire wear particles in the environment--a critical review and an initial risk assessment.

Waste tyres and their accumulation is a global environmental concern; they are not biodegradable, and, globally, an estimated 1.5 billion are generated annually. Waste tyres in landfill and stockpiles are renowned for leaching toxic chemicals into the surrounding environment, acting as breeding grounds for mosquitoes, and fuelling inextinguishable fires. The properties of waste tyre rubber and engineering applications have been previously reported in a range of publications with respect to the environmental, economic, and technical factors. This study compiles and reviews this research with a focus on geotechnical engineering applications, such as earthworks and infrastructure construction. The applications of waste rubber in construction materials includes cementitious concrete, asphalt concrete, and granular materials for earth structures. Crumb rubber, when used as a sand replacement in flowable concrete fill, improved ductility and strength-to-weight ratio. A 40 MPa concrete mix with 0.6% rubber crumb content exhibited optimal strength and air entrainment capabilities, displaying minimal damage after 56 freeze/thaw cycles. Rubber, as a partial replacement for aggregate in road base and sub-base layers, adversely affected the California Bearing Ratio (CBR) of the graded aggregate base course. Rubber-soil mixtures as the interface of foundation and structure yielded a 60–70 % reduction in vertical and horizontal ground accelerations when subjected to earthquake simulation modelling. There is concern regarding the toxicity of waste rubber incorporated products due to leachates of heavy metals and other chemicals common in tyres. Further comprehensive studies in this area are needed. Leachate studies should be conducted under different pH and liquid to solid ratios.

Recycling waste rubber tyres in construction materials and associated environmental considerations: A review

It is estimated that over 80% of respirable particulate matter (PM10) in cities comes from road transport and that tire and brake wear are responsible for the 3–7% emission of it. Data on the indicators of environmental impact of tire debris (TD), originated from the tire abrasion on roads, are extremely scarce, even though TD contains chemicals (zinc and organic compounds) which can be released in the environment. TD particle morphology was analysed with SEM, TEM and FIB instruments. TD eluates and TD organic extracts were tested at dilution series on human cell lines and Xenopus laevis embryos. 50 and 100 g/L TD were used for the eluates obtained after 24 h at pH 3 and the quantity of zinc present was measured with a ICP-AES. Eluates diluted to 1%, 10%, 50% in culture media and undiluted were used on X. laevis embryos in the FETAX test. HepG2 cells were exposed for 24 h to 0.05 – 50 μg/ml of zinc salt while A549 cells were exposed for 24, 48 and 72 h to 10, 50, 60, or 75 μg/ml of TD extract. X. laevis embryos were exposed to 50, 80, 100, or 120 μg/ml TD extract. The solution of undiluted 50 g/L TD produced 80.2% mortality (p < 0.01) in X. laevis embryos and this toxic effect was three times greater than that produced by 100 g/L TD. Zn accumulation in HepG2 cells was evident after 4 h exposure. A549 cells exposed to TD organic extract for 72 h presented a modified morphology, a decrease in cell proliferation and an increase in DNA damage as shown by comet assay. The dose 80 μg/ml of TD extract produced 14.6% mortality in X. laevis embryos and 15.9% mortality at 120 μg/ml. Treatment with 80, 100, or 120 μg/ml TD organic extract increased from 14.8% to 37.8% malformed larvae percentages compared to 5.6% in the control. Since the amount of Zn leached from TD is related to pH, aggregation of particles and elution process, the quantity of TD present in the environment has to be taken into account. Moreover the atmospheric conditions, which may deeply influence the particle properties, have to be considered. The TD organic fraction was toxic for cells and organisms. Thus, because of its chemical components, TD may have a potential environmental impact and has to be further investigated.

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Impact of tire debris on in vitro and in vivo systems

Although chemical measurement techniques and geochemical speciation modelling may detect and predict the different forms of copper in aquatic systems and hence provide some information about the li...

Use and limitations of microbial bioassays for assessing copper bioavailability in the aquatic environment

Cover is important to aquatic habitat and fisheries often try to improve habitats by addition of natural and artificial material to improve cover diversity and complexity. Habitat-improvement programs range from submerging used Christmas trees to more complex programs. Used automobile tires have been employed in the large scale construction of reefs and fish attractors in marine environments and to a lesser extent in freshwater and have been recognized as a durable, inexpensive and long-lasting material benefiting fishery communities. Recent studies by the U.S. Bureau of Reclamation have quantified the importance of tire reefs to enhancing freshwater canal fisheries in the southwestern United States. These studies have demonstrated that fishes and aquatic macroinvertebrates are attracted to these structures, increasing species diversity, densities and biomass where reefs are placed in canals. However, the use of tire reefs in aquatic environments which have relatively small volumes compared to marine or reservoir environments has raised water quality concerns. Effects of tires on water quality have not typically been studied in the past because of the obvious presence of fishes and other aquatic organisms that make use of tire reefs; the implication being that tires are inert and non-toxic. Little information on effects of tiresmore » on water quality is in the literature. Stone demonstrated that tire exposure had no detrimental effects on two species of marine fish while results of Kellough's freshwater tests were inconclusive, but suggested that some factor in tire leachate was toxic to rainbow trout (Oncorhynchus mykiss). Nozaka et al. found no harmful substances leached from tire material soaked in fresh water. Because there are few data on toxicity associated with tires, this became the focus of our study. Toxicity Identification Evaluation (TIE) procedures developed by the EPA were used to evaluate water quality impacted by tires. 17 refs., 4 figs.« less

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Identification of tire leachate toxicants and a risk assessment of water quality effects using tire reefs in canals.

Acute bioassays are well developed and widely used test methods for toxicity assessment of chemicals and effluents. Although these tests are robust and typically provide very definitive results, they can be very time consuming, some requiring 48 to 96 hours to complete. New and revised commercial test methods are being developed, many of these with the goal of increased test rapidity. Some of these tests have as endpoints measurements of enzymatic activity or amount of bioluminescence instead of mortality. Presently, many tests are available that take 24 hours or less to complete. We compared several of these newer commercial tests with the standard 48-hour Ceriodaphnia dubia mortality test. One of our main interests in these tests is as a tool for adding toxicity data to biological field surveys of aquatic systems. The ability to perform tests in a motel room, field office, or other remote location in a short time would make it much easier to make toxicity information part of the field survey package.

S. M. Nelson

Papers

Identification of tire leachate toxicants and a risk assessment of water quality effects using tire reefs in canals.

Evaluation of the sensitivity of rapid toxicity tests relative to daphnid acute lethality tests.