This document specifies a procedure to evaluate acute phototoxicity of nanoparticles (NPs), suspended in cell culture media, by measuring the relative reduction in cellular viability under near ultraviolet (UVA) exposure (315 nm to 400 nm).

The measurement is intended to assess the potential for acute phototoxicity of NPs by comparing NP photoactivity in vitro to a positive control chlorpromazine. It is not designed to predict other joint effects of nanomaterials and light, such as genotoxicity, photo-allergy or photo-mutagenicity. The method is also applicable to NP aggregates and agglomerates.