If you eat lindane, it would take a teaspoon to kill. But on the skin would have to be multiple teaspoons poured on you. Breathing, not sure, but probably same higher-type amounts.

"Acute toxicity: Lindane is a moderately toxic compound via oral exposure, with a reported oral LD50 of 88 to 190 mg/kg in rats [2]. Other reported oral LD50 values are 59 to 562 mg/kg in mice, 100 to 127 mg/kg in guinea pigs, and 200 mg/kg in rabbits [2,9]. It is moderately toxic via the dermal route as well, with reported dermal LD50 values of 500 to 1000 mg/kg in rats, 300 mg/kg in mice, 400 mg/kg in guinea pigs, and 300 mg/kg in rabbits [2,9]." EXTOXNET PIP - LINDANE