No mortality was observed for embryos exposed to ~60 mg/mL (4 pellets/mL) of consumer-grade TPU. Conversely, ~60% of embryos perished within 24 h of continuous exposure to the same concentration of consumer-grade PCL (Figure ). No changes in mortality for the consumergrade TPU-treated embryos were observed for the remainder of the exposure experiment (through 72 hpf). Given the significant acute toxicity caused by the consumer-grade PCL and the lack of acute toxicity caused by the consumer-grade TPU, we focused our investigation on the consumer-grade PCL. No further experiments were conducted with the consumer-grade TPU.