(Micro)Plastics Are Toxic Pollutants

Abstract

Plastics, including microplastics, have generally been regarded as harmful to organisms because of their physical characteristics. There has recently been a call to understand and regard them as persistent, bioaccumulative, and toxic. This review elaborates on the reasons that microplastics in particular should be considered as "toxic pollutants". This view is supported by research demonstrating that they contain toxic chemicals within their structure and also adsorb additional chemicals, including polychlorinated biphenyls (PCBs), pesticides, metals, and polycyclic aromatic hydrocarbons (PAHs), from the environment. Furthermore, these chemicals can be released into tissues of animals that consume microplastics and can be responsible for the harmful effects observed on biological processes such as development, physiology, gene expression, and behavior. Leachates, weathering, and biofilm play important roles in the interactions between microplastics and biota. Global policy efforts by the United Nations Environmental Assembly via the international legally binding treaty to address global plastic pollution should consider the designation of harmful plastics (e.g., microplastics) with associated hazardous chemicals as toxic pollutants.

Keywords: bioaccumulation; biofilm; leaching; microplastics; plastics; sorption; toxicity.

Figure 1

Diversity of microplastic particles (MPs) with bioavailability as a function of their physical–chemical properties, influencing exposure to zooplankton. Based on the review by Botterell et al. (2019) [1].

Figure 2

Illustration showing persistent organic pollutant sorption and accumulation over time, using flame-retardant compounds (polybrominated diphenyl ethers (PBDEs)) as example, via microplastic ingestion in fish. Adapted from Wardrop et al., 2016 [57]. = microplastics (MPs); = chemical contaminant or pollutant; and = microplastic with sorbed pollutant.