TOXICITY OF LEACHATE FROM AUTOMOBILE TIRES TO AQUATIC BIOTA

A laboratory study was conducted to determine if automobile tires imme rsed in fresh water leach chemicals which are toxic to aquatic biota. Three tire types were examined - tires obtained from a floating tire b reakwater; road-worn tires from the same vehicle; and new tires. Whole tires were immersed in 300 L of water (natural groundwater) and subsa mples (40 L) of water were removed at 5, 10, 20 and 40 d for use in ac ute static lethality tests. Overlying water from both new and used tir es was lethal to rainbow trout (Oncorhynchus mykiss) but leachate from used tires was more toxic (96-h LC50s - 11.8 to 19.3 %v/v) than leach ate from new tires (96-h LC50s - 52.1 to 80.4 %v/v). In addition, leac hate remained relatively toxic to rainbow trout over time (8 d for new and 32 d for used) after tires were removed from the aquaria indicati ng that the chemicals responsible for toxicity degrade slowly and are non-volatile. No toxicity to cladocerans (Daphnia magna; 48-h exposure ) or fathead minnows (Pimephales promelas; 96-h exposure to leachate f rom 20 and 40 d only) was observed with these same leachates. Tires fr om a floating tire breakwater which had been installed for several (10 ) years did not release chemicals Which were toxic to any species test ed. In separate experiments, concentrated (10X) leachate from tires im mersed for 25 d in water inhibited bioluminescence in the marine bacte rium, Photobacterium phosphoreum, (Microtox(TM) test), the enzyme, bet a-galactosidase, in mutant Escherichia coli (ToxiChromo(TM) Test) and the enzyme, NADH-coenzyme Q reductase, in the inner membrane of mitoch ondria (beef heart submitochrondria particle test). Several other scre ening tests (e.g., nematode lethality/mutagenicity test; bacterium (Sp irillum volutans) motility inhibition test and the SOS-Chromotest with and without S-9 activation) were not sensitive to tire leachates. Fur ther studies to identify the toxic compounds and to determne the exten t of toxicity under field conditions of dilution are necessary.