OECD Test Guideline 432, known as the In Vitro 3T3 Neutral Red Uptake (NRU) Phototoxicity Test, is designed to identify the phototoxic potential of chemicals that become toxic only when exposed to light.
This in vitro assay uses mouse fibroblast cells (3T3 cells) to assess whether a chemical causes toxicity under exposure to a light source, simulating solar radiation.