Potential Environmental Impacts of Tyre Leachate
Leaching
The biggest problem with discarding old tires is that they contain chemicals and heavy metals that leach into the environment as the tires break down. Some of these chemicals, according to the California Integrated Waste Management Board, are carcinogenic and mutagenic (cause cancer and gene mutations).
Leaching affects the soil around the old tire, which at first may not seem like a big problem. But if the tire is eventually moved, the soil will still have the toxins. Another major concern is groundwater. If toxins get into any water in the soil, the water can transport them to other locations, potentially harm to any animals that come in contact with the poisoned water.
Laboratory Research
Summary of reviewed laboratory research on tyre leachate
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Summary of reviewed field trials on tyre leachate
In field trials tyre leachate is generated by water percolating through the tyre sample (whole tyre, shred or chip). There are limitations when comparing the results of the reviewed field trials as different makes of tyres were used and different compounds were measured; however the following general observations can be made about the nature of tyre leachate generated in the field:
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levels of manganese and iron are likely to be elevated in groundwater, especially when steel is exposed
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levels of aluminium, zinc and organic compounds may be elevated in groundwater; however the majority of studies reported negligible levels
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level of cadmium and lead may be elevated in soil; however no studies reviewed reported elevated levels in groundwater
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levels of other substances measured are likely to be below United States Drinking Water Standards
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level of leachate compounds in groundwater are likely to decrease down gradient of the tyre site.
General Observations
The potential environmental impacts of tyre leachate are contamination of soil, surface water and groundwater on the site and surrounding area. Based on the reviewed literature and previous MWH experience in site contamination, factors that may affect the rate of leaching and/or the concentration of tyre leachate compounds in soil, surface water and groundwater include:
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tyre size: leaching from whole tyres is likely to be slower than leaching from tyre chips or shreds - this is because of the differences in the surface area to volume ratio
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amount of exposed steel: if steel is exposed, say in tyre chips, there is likely to be faster leaching of manganese and iron than from whole tyres where the steel is not exposed
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chemical environment: leaching of metals is likely to be more rapid under acidic conditions while leaching of organic compounds is likely to be more rapid under basic conditions
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permeability of soil: leaching is likely to be faster when soils are permeable
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distance to groundwater table: the greater the vertical distance to the groundwater table, the less likely the contamination of groundwater
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distance from tyre storage site: the further the downstream distance from the tyre storage site, the lower the contaminant concentration in the soil and groundwater
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contact time with water: the longer the tyres are in contact with water, the greater the risk of groundwater contamination
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vertical water flow through soil: the greater the water flow through the soil (eg, from rainfall), the greater the dilution of contaminants
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horizontal groundwater flow: the greater the groundwater flow, the greater the spread of the contaminant plume
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leached compounds at site: levels of manganese and iron are likely to be elevated in groundwater when steel is exposed. Levels of aluminium, zinc and organic compounds may be elevated in groundwater. Levels of zinc, cadmium and lead may be elevated in soil.
Pests
The hollow middle of a tire will easily fill up with rainwater if the tire is just left out in the open. If the tire is left undisturbed, the water will sit in the tire and become a breeding ground for pests such as mosquitoes. The mosquitoes then go about spreading diseases to humans and animals.
Combustibility
Some disposal sites have tried to get rid of old tires by burning them up—either by open or controlled combustion. These process not only release harmful chemicals into the air, but they are also extremely dangerous.
Tires become a great fuel source if they are heated. Consequently there have been numerous unwanted combustions at the sites that burn them. These combustion sites pose a health and safety risk not only to the environment, but to the workers as well.
Even if tires aren’t being sent to tire burning disposal facilities, they still pose a fire threat. Fires that are fueled by tire material are harder to control and extinguish than regular fires. If tires are discarded rather than recycled, they could combust, release their carcinogens into the air, and start a destructive fire.
Responsibility
Recycling tires can help harmful chemicals stay out of the earth, water, and air. It can prevent tires from becoming disease-carrying-pest breeding grounds, and can keep them from starting raging fires. When you are ready to get rid of your old tires, make sure they get recycled.
If you get your tires replaced, ask the mechanic what they plan on doing with the old tires. If they are not going to recycle them, take them home and drive them to a recycling facility yourself.
Credit: Ministry of Environment, EPA, Ecogreen, AGS Research team.