The toxicological impact of the sunscreen active ingredient octinoxate on the photosynthesis activity of Chlorella sp.

Abstract

Products designed to filter ultraviolet (UV) light are responsible for growing levels of anthropogenic environmental contamination. Octinoxate (ONT) is among the most common UV filtering active ingredients in cosmetics and sunscreens. The present study was designed to evaluate the toxicological effects of ONT on the photosynthetic activity of the Chlorella species of marine microalgae. These analyses identified ONT as a potent photo-toxicant, the effects of which were more pronounced upon light exposure relative to in the dark. Short-term ONT exposure had no effect on photosynthetic electron transport capacity in the dark but did significantly reduce the ribulose-1,5-bisphosphate carboxylase/oxygenase activity in Chlorella cells, suggesting that this compound can directly suppress the photosynthetic Calvin cycle. When cells were subsequently exposed to light, the disruption of this cycle resulted in an excess of excitation energy, in turn driving the excessive generation of reactive oxygen species (ROS). ROS-mediated disruption of cellular metabolism further aggravated this ONT-induced microalgal damage. As such, under natural light conditions, these microalgae cells are exposed to increased oxidative stress that impairs their growth and causes pigment bleaching. Restricting the utilization of ONT-containing sunscreens thus has the potential to better preserve the integrity of aquatic and terrestrial ecosystems.