Despite the LC50 for consumer-grade PCL being well above the concentration of plastic found in natural waters (~10s ng/L to ~100s mg/L; <100 particles/L), the plastic's acute toxicity raises concern. Mortality of zebrafish embryos from exposure to relatively large pieces of plastic compared to the size of an embryo is rare. For instance, toxicity studies using zebrafish embryos are often conducted in polystyrene well plates because of the material's apparent inertness.