Retinoids have a significant role in many vital biological processes such as regulation of skin function and neuronal development. There are over 2,500 retinoid related compounds used in cosmetic products and as anti-acne therapeutic agents. There is increasing concern about the presence of retinoids and synthetic chemicals with retinoid like properties entering the environment. Retinoid activity has been detected in wastewater effluent, pulp mill effluents, and from unknown/diffuse sources, suggesting that a variety of chemicals exist in nature (natural and/or man-made) that mimic the activity of natural endogenous retinoids. Despite this, there is little information on what these chemicals might be, or where they come from and identifying these chemicals (and developing reliable tests) is now on the OECD agenda. This project will develop bioassay directed methods to determine the identity of these chemicals and investigate if retinoid-like chemicals are prevalent in the environment and if they pose an ecotoxicological risk.