reported a TD50 for 6-hydroxyhexanoic acid of ~23 mg/mL for immortalized mammalian fibroblasts. Similarly, Tamayo-Belda et al. showed that PCL degradation products from PCL pellets adversely affected two freshwater cyanobacteria. These studies and our tentative identification of PCL oligomers reinforce the idea that these compounds and other degradation products contributed to the observed toxicity.