Effect of water vapor on the by-products and decomposition rate of ppb-level toluene by photocatalytic oxidation

► Water vapor has significant influence on the PCO by-products generation of toluene. ► Maximum decomposition efficiency does not always lead to minimum by-products. ► By-products make the typical L-H model unfeasible in real application. ► Health related index (HRI) was used to evaluate the health risk of by-products. ► Health risk assessment shall be included to evaluate the PCO performance.