One study performed in 2000 raised safety concerns about octyl methoxycinnamate by demonstrating toxicity to mouse cells at concentrations lower than typical levels in sunscreens. However, another study concluded that octyl methoxycinnamate and other sun screening agents do not penetrate the outer skin in sufficient concentration to cause any significant toxicity to the underlying human
keratinocytes. Estrogenic and neurological effects were noted in laboratory animals at concentrations close to those experienced by sunscreen users and were also shown
in vitro. Octyl methoxycinnamate has been shown to be light sensitive with a decrease in UV absorption efficiency upon light exposure. This degradation causes formation of the Z-octyl-p-methoxycinnamate from the E-octyl-p-methoxycinnamate. In contrast, the OMC does not show degradation when kept in darkness for extended periods of time. A study carried out in 2017 by the Research Centre for Toxic Compounds in the Environment at Masaryk University, Czech Republic, indicates that octyl methoxycinnamate (EHMC) may damage human cell DNA. When exposed to sun rays, the spatial arrangement of its molecules changes and isomerisation takes place. While until now only unchanged EHMC has been researched, Massaryk University researchers focused on its isomers and found out that it has a significant genotoxic effect under lab conditions. It means that it may potentially damage human DNA and cause genome mutations which may lead to serious health risks. In swimming pools with hypochlorite in aqueous solution, octyl methoxycinnamate has been shown to produce chlorine-substituted intermediates. The chlorination intermediates of octyl methoxycinnamate demonstrated weak mutagenic effects on the Salmonella typhimurium TA 100 strain. The reactions depended on the pH, compound structures, and chlorine dose. ==Ecological damage==