With discarded plastics making up more than 80% of the trash that accumulates in some locations, (1) microplastics (MPs) have become ubiquitous in the environment. Generally defined as synthetic polymers less than 5 mm in diameter, (2) MPs have been found in fish, shellfish, crustaceans, mollusks, and even mammals. (3) In a systematic review and meta-analysis recently reported in Environmental Health Perspectives, investigators estimated the level of MP contamination in seafood and, consequently, how much people may ingest each year. (3)
It is not clear whether MP consumption harms human health, although particles may carry potential hazardous plastic constituents, microorganisms, and adsorbed chemicals. (3) "In order to assess whether the uptake of microplastics via food can indeed pose a risk to our health, first we need to quantify this exposure, and, second, determine whether this exposure is high enough to have a detrimental effect," says lead study author Evangelos Danopoulos, a doctoral student at Hull York Medical School in England. "Systematic reviews and meta-analyses can play a key function in the risk assessment process."
The systematic review included 50 primary peer-reviewed papers--all field studies that sampled mollusks, crustaceans, fish, and echinoderms for MP contamination--and 19 studies were used in the meta-analysis. The authors developed a novel risk of bias (RoB) quality assessment tool to evaluate all aspects of experimental design, execution, and reporting for each paper. Among other inclusion criteria, studies must have sampled commercially relevant seafood species and used one of four validated procedures to assess the chemical composition of MPs.
The studies measured contamination in terms of MP particles per gram of organism wet weight or per individual organism. Over half the reviewed studies sampled mollusks, reporting a range of 0-10.5 MPs/g. Mollusks collected in Asia tended to be the most contaminated. In addition, mollusks collected directly from fishing waters...