Toxicity of particles and chemicals released from surgical face masks to the model aquatic organism Daphnia magna

The use of single-use face masks during the COVID-19 pandemic has resulted in indiscriminate disposal of face masks, some of which end up in the aquatic environment. These masks release microplastics and plastic-associated chemicals when exposed to environmental conditions. However, there is still limited knowledge of their impact on aquatic organisms. We subjected face masks to a simulated weathering process and separated the resulting leachate into three fractions: the first fraction contained a mixture of leached dissolved chemicals and released particles, the second fraction contained dissolved chemicals alone, and the third fraction contained particles alone. These fractions were then used to conduct acute and chronic toxicity tests on Daphnia magna. Complementary spectroscopy techniques were used to confirm that the particles consisted of polypropylene while SEM indicated that the particle sizes were mostly in the nano-range. ICP-MS analysis detected Pb, Zn, Mn, and Cr in the face mask leachates while LC-MS found mono-isobutyl phthalic acid only in the fractions containing particles. Both the acute and chronic tests revealed that the chemicals present in the masks affected the survival of younger daphnids. The particles alone fraction only affected the juveniles during acute exposures. In chronic exposures, the particles did not impact survival, but inhibited growth and reproduction. This study shows that the released microplastics and chemicals may have different and possibly joint toxicity impacts on Daphnia magna, which may also depend on the life stage of the exposed organisms.