Final answer:
Coca chewing leads to few instances of toxicity because the cocaine is absorbed slowly through the cheek linings, allowing little cocaine to reach the brain rapidly, and the quantity of cocaine in coca leaves is low.
Step-by-step explanation:
The reason coca chewing produces few instances of toxicity is because little cocaine is distributed to the brain since absorption from the digestive system is slow. When coca leaves are chewed, the cocaine is absorbed through the cheek linings, bypassing absorption in the digestive tract.
This mode of absorption results in a slower release of cocaine into the system compared to snorting or smoking, where cocaine reaches the brain rapidly. Furthermore, the quantity of cocaine in coca leaves is relatively small, and when chewed, it releases its content slowly, reducing the likelihood of toxicity seen with higher, more concentrated doses, such as those from processed cocaine products.