Unable to dispose wasm instance.

Hello,

In my app design i'm compiling WASM once and have to create several instances of WASM on different events.
But i have no idea how to dispose those instances, when i don't need them.
I googled the issue and found that it uses normal garbage collector, so if instance not referenced - it is automatically destroyed.
But this seems doesn't work. The point is my WASM project uses pthreads. And when i instantiate it - i see 8 additional threads (em-pthread) in workers list.
But when i set this.wasmInstance to null - Threads aren't disposed. So i guess instance is not garbage collected.

So how can i properly destroy WASM instances then ?