Microplastic and additive release into seawater from face masks and cigarette butts: A laboratory experiment and risk estimation

Plastic waste in the environment gradually degrades into microplastics, while organic additives within these plastics, can leach out over time during plastic aging. Each year, approximately 5.4 trillion cigarettes are produced, leading to the disposal of 4.5 trillion of cigarette butts worldwide. Similarly, with mask production potentially reaching 34.5 billion units annually, as observed in 2022 during the pandemic, and 10-20% of plastic waste being inadequately managed globally—whether left uncollected, improperly disposed of, or released into natural environments—it’s estimated that between 0.69 and 1.04 billion masks may end up in marine ecosystems each year. Yet, the environmental impact of these plastics, especially in marine ecosystems covering over 70% of the Earth’s surface, is still poorly understood.

In this study cigarette butts and face masks, were incubated in natural seawater under laboratory-controlled conditions for 80 days. The generation of microplastics and the leaching of toxic organic additives, such as phthalates (PAEs) and organophosphate esters (OPEs), from these plastic items into the dissolved phase were closely monitored. Changes were tracked using LDIR for microplastics and GC/MS for additives, with bacterial conditions (biotic and abiotic) varied throughout the experiment. Our results showed that polypropylene (98.5%) was the primary polymer released from face masks, while modified cellulose acetate (91.5%) was predominant in cigarette butts. We found that that a single cigarette butt releases approximately 590 ± 310 microplastic particles (n = 6) per litter, while a single face mask contributes around 1 500 ± 1 000 particles into seawater (n = 6). Additionally, our findings revealed that these microplastic debris types (cigarette butts and masks) were composed of around 20% fibers and 80% fragments.

Our results also indicated that both cigarette butts and face masks released significant amounts of PAEs followed by OPEs into the surrounding seawater during the first month. Di-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DnBP) were the primary PAEs leached from face masks, accounting for 31% and 21%, respectively, of the total PAEs released. In cigarette butts, diethyl phthalate (DEP) was the dominant PAE at 57%, followed by di-isobutyl phthalate (DiBP) at 11%. In both materials, 2-ethylhexyl diphenyl phosphate (EHDP) was the main OPE detected, contributing 19% and 18%, respectively. Finally, our results demonstrated that bacterial exposure had minimal impact on the average concentrations of additives released.