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Oral LD50 (rat), primary skin irritation (rabbit), cutaneous sensitization (guinea pig) and eye irritation (rabbit) studies were conducted on the three tetramethylbenzene isomers: durene , isodurene and prehnitene. The order of oral toxicity was isodurene greater than prehnitene greater durene. Durene was not a skin irritant, while isodurene and prehnitene each produced a mild positive skin response (erythema). None of the tetramethylbenzenes were skin sensitizers or eye irritants. Durene, isodurene and prehnitene are only slightly toxic on an acute toxicologic basis and only pose an acute health hazard when injested in excessive quantities.

Data from a radiotracer study in rabbits and rats to determine the absorption, distribution, and excretion of terephthalic acid (TA) and dimethyl terephthalate (DMT) following oral, intratracheal, dermal and ocular administration indicate the following: (1) a rapid absorption and excretion of 14C-TA and 14C-DMT with no evidence of tissue accumulation in rats following single or repeated oral and intratracheal administration; (2) no evidence of skin irritation in rats after a single or repeated dermal application of 80 mg of 14C-TA or 14C-DMT and no significant skin absorption of 14C-TA; (3) recovery of approximately 11% of a single dose and 13% of five repeated cutaneous doses of 14C-DMT from the urine and feces of rats within 10 days after initial dosing; (4) no significant absorption of 14C-TA when applied to the conjunctival sac of one eye of eight rabbits; (5) excretion of approximately 33% of a single ocular dose (50 mg) of 14C-DMT in the urine and feces of rabbits within 10 days after instillation with no evidence of tissue accumulation or ocular damage. These results suggest that TA and DMT are rapidly absorbed and excreted and that no significant quantities of these compounds accumulate in the tissues following single or repeated oral, intratracheal, dermal, or ocular administration to laboratory animals.