| Letter: A | |
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| Abrasion | The cause of tyre tread (see entry) wear. Determined by the phenomena of friction between the tread itself and the ground. Heavily influenced by temperature and abnormal tyre inflation pressures. |
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| Aromatic hydrocarbons (CO2) | Organic compounds whose structures are characterized by the presence of at least benzene ring. |
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| Atmospheric emission | Any solid, liquid or gaseous substance introduced to the atmosphere from an industrial plant or any other source that may produce atmospheric pollution. |
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