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Toxicokinetic data from the literature is available for 3 -methylpyridine and its analogues, which form a category comprised of: pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine. The basis of the category is structural similarity (based on the pyridine unsaturated ring structure) and similar physical properties, environmental fate and ecotoxicity, and mammalian toxicity. Similar toxicological properties derive from similar physical-chemical properties and common pathways of metabolism and elimination among all members of the category. This category is accepted by the U.S. Environmental Protection Agency (EPA). Pyridine and its methyl derivatives are absorbed during inhalation, oral and dermal exposures. They are distributed into the body water compartment as evidenced by the finding of the highest levels in the kidney and being eliminated primarily in the urine. Pyridine and its derivatives are metabolised by CYP enzymes in the liver, with primary metabolites being pyridine-N-oxide, 2-pyridone, 4-pyridone, 3-hydroxypyridine, and N-methyl pyridinium ion.3-Picoline is also metabolized by cytochrome P-450 enzymes to 3 methylpyridine N-oxide in mice, rats hamsters, guinea pigs and rabbits, indicating the utilisation of similar or identical metabolic pathways as pyridine.These substances have a low risk of bioaccumulating in body fat or milk.