The outbreak of the COVID-19 has caused an enormous worldwide demand for face masks to mitigate airborne transmission of SARS-CoV-2. (1?3) It is estimated that ?200 million disposable plastic face masks are manufactured per day in June 2020 in China, which is the main supplier. (2) Meanwhile, more than 1 billion face masks are consumed globally each month in 2020. (1) As a result, about 1.4 billion face masks were casually discharged into the environment in March 2023 in China. (4) This improper disposal of face masks has led to their presence in aquatic environments (rivers and estuaries), ultimately contaminating the ocean ecosystem. (5?7) The discarded face masks have attracted public attention as a new pollution source of the marine environment. (8) However, there is a lack of data on the complete evaluation of the face mask pollution and their impact in marine wildlife. (1,2)

Face masks are typically manufactured using synthetic thermoplastic carbon polymers such as polypropylene (PP), polyethylene (PE), and polylactic acid (PLA). (2,6,9) Various organic additives, including plasticizers, flame retardants, dyes, etc., are supplemented in the polymers to enhance the properties of face masks. (10,11) These additives have been reported to be present in face masks. (10?12) For instance, up to 4.8 ?g/g di-n-butyl phthalate in face masks with 98.2% detection frequency (11) and 0.02 to 27.7 ?g/mask of organophosphate esters have been reported. (12) In addition, elevated levels of lithium (49.7 mg/g) and aluminum (6.2 mg/g) are found in face masks. (13) Nonetheless, the chemicals added in the face masks are far from fully understood due to the complexity of these additives.

The additives in the face masks can be leached out once they are in the ocean, posing a potential hazard to marine organisms. (2,6) Previous studies have demonstrated that plastic additives can cause various adverse effects on the development, nerve, and endocrine system in aquatic animals. (14?17) In addition, mask fragments can downregulate the transcription of target genes related to reproduction in zebrafish, (13) cause histopathological alterations of the liver, gills, and intestine of zebrafish, and disrupt their aggressive behavior. (18) However, research on the toxicity of face masks, particularly their additives, to marine organisms is extremely scarce.

In this study, one of the main objectives was to qualify and quantify the organic additives and metals in 13 face masks (biodegradable and nondegradable masks). The additives in face masks might be numerous and complex, necessitating the use of multiple biomarkers from different biological organizations to assess their toxicity. In addition, marine medaka (Oryzias melastigma) has been used as a marine fish model for the evaluation of the toxicity of pollutants. (19,20) Therefore, the potential toxicities of face masks (i.e., developmental toxicity, locomotor behavior, and estrogenic activity) using O. melastigma embryos and larvae were evaluated. The findings of this study will enable a better understanding of the risk face masks pose to marine ecosystem...

Figure 2. Levels of organic additives (A) and metals (B) in face masks (FM). TeP: tris(2-ethylhexyl) phosphate; DiBP: diisobutyl phthalate; OM: octyl 4-methoxycinnamate; DEP: diethyl phthalate; TEP: triethyl phosphate; TPP: triphenyl phosphate; DHP: dihexyl phthalate; TbP: tris(2-butoxyethyl) phosphate; BBP: benzyl butyl phthalate; EDP: 2-ethylhexyl diphenyl phosphate.