Where is the evidence that human exposure to microplastics is safe?

An Overview of the Sorption Studies of Contaminants on Poly(Ethylene Terephthalate) Microplastics in the Marine Environment

Marine pollution is one of the biggest environmental problems, mainly due to single-use or disposable plastic waste fragmenting into microplastics (MPs) and nanoplastics (NPs) and entering oceans from the coasts together with human-made MPs. A rapidly growing worry concerning environmental and human safety has stimulated research interest in the potential risks induced by the chemicals associated with MPs/NPs. In this framework, the present review analyzes the recent advances in adsorption and desorption studies of different contaminants species, both organic and metallic, on MPs made of Poly(Ethylene terephthalate). The choice of PET is motivated by its great diffusion among plastic items and, unfortunately, also in marine plastic pollution. Due to the ubiquitous presence of PET MPS/NPs, the interest in its role as a vector of contaminants has abruptly increased in the last three years, as demonstrated by the very high number of recent papers on sorption studies in different environments. The present review relies on a chemical engineering approach aimed at providing a deeper overview of both the sorption mechanisms of organic and metal contaminants to PET MPs/NPs and the most used adsorption kinetic models to predict the mass transfer process from the liquid phase to the solid adsorbent.

Uncertainty about the risks associated with microplastics among lay and topic-experienced respondents

Microplastics are contaminants of emerging concern but there is currently a lack of evidence on actual risks relating to them, despite claims in media and scientific articles. Research on people’s perceptions on microplastics is in its infancy. Here we present part of a larger survey about people’s perceptions of issues with microplastics. Our analysis of 1681 responses across the globe to an online questionnaire demonstrates a certain level of uncertainty, not only in lay people but also respondents who study/work on the topic of plastics and microplastics as a pollutant. This uncertainty ranges from level of concern about microplastics as an environmental issue to existing evidence for effects. Further, there is some discrepancy between risk perception and state of the research. Some of this may be driven by scientific work with some serious limitations in reporting and methods. This highlights the need for fact-checking of circulating information about microplastics, but also for addressing the discordance between ecotoxicological risk and how risk is framed within the scientific community.

Microplastics and metal burdens in freshwater Tilapia (Oreochromis niloticus) of a metropolitan reservoir in Central Mexico: Potential threats for human health

In the present study, microplastics (MPs) and metal concentrations were studied in the widely consumed tilapia (Oreochromis niloticus) fishes (n = 15) collected from a metropolitan reservoir of the Atoyac River basin, Mexico. Nearly 139 fibers were extracted from the gastrointestinal tracts and assessed using optical microscopy to evaluate their physical characteristics. The colour distribution of the fibers was mainly black (40%), blue (19%), red and white (14%). SEM images represented the surface morphology, while the elemental composition of the fibers was studied using EDX spectra. Polymer characterization using μFTIR aided in confirming the fibers as plastics (polyamide, polyester, and synthetic cellulose) and non-plastics (natural cellulose). Henceforth, ∼33% of the fibers, provisionally thought to be plastics, were natural fibers. The total metal concentrations were higher in the liver (259.24 mg kg^-1) than the muscle (122.56 mg kg^-1) due to diverse metabolic functions in the hepatic tissues. Human health risk assessment in terms of Hazard Index (HI) presented Pb and Zn values above unity in both adults and children, prompting regulatory measures. Statistical tests between MPs and fish biometry did not present any substantial correlations. The present study also affirmed that the presence of MPs and metals in fishes of a highly contaminated region is not only governed by their bioavailabilities, but also on the physiological characteristics of the individual organism.

Impact of Microplastics and Nanoplastics on Human Health

Plastics have enormous impacts to every aspect of daily life including technology, medicine and treatments, and domestic appliances. Most of the used plastics are thrown away by consumers after a single use, which has become a huge environmental problem as they will end up in landfill, oceans and other waterways. These plastics are discarded in vast numbers each day, and the breaking down of the plastics from micro- to nano-sizes has led to worries about how toxic these plastics are to the environment and humans. While, there are several earlier studies reported the effects of micro- and nano-plastics have on the environment, there is scant research into their impact on the human body at subcellular or molecular levels. In particular, the potential of how nano-plastics move through the gut, lungs and skin epithelia in causing systemic exposure has not been examined thoroughly. This review explores thoroughly on how nanoplastics are created, how they behave/breakdown within the environment, levels of toxicity and pollution of these nanoplastics, and the possible health impacts on humans, as well as suggestions for additional research. This paper aims to inspire future studies into core elements of micro- and nano-plastics, the biological reactions caused by their specific and unusual qualities.

Microplastic Contamination of Seafood Intended for Human Consumption: A Systematic Review and Meta-Analysis

BACKGROUND

Microplastics (MPs) have contaminated all compartments of the marine environment including biota such as seafood; ingestion from such sources is one of the two major uptake routes identified for human exposure.

OBJECTIVES

The objectives were to conduct a systematic review and meta-analysis of the levels of MP contamination in seafood and to subsequently estimate the annual human uptake.

METHODS

MEDLINE, EMBASE, and Web of Science were searched from launch (1947, 1974, and 1900, respectively) up to October 2020 for all studies reporting MP content in seafood species. Mean, standard deviations, and ranges of MPs found were collated. Studies were appraised systematically using a bespoke risk of bias (RoB) assessment tool.

RESULTS

Fifty studies were included in the systematic review and 19 in the meta-analysis. Evidence was available on four phyla: mollusks, crustaceans, fish, and echinodermata. The majority of studies identified MP contamination in seafood and reported MP content < 1  MP / g , with 26% of studies rated as having a high RoB, mainly due to analysis or reporting weaknesses. Mollusks collected off the coasts of Asia were the most heavily contaminated, coinciding with reported trends of MP contamination in the sea. According to the statistical summary, MP content was 0 - 10.5  MPs / g in mollusks, 0.1 - 8.6  MPs / g in crustaceans, 0 - 2.9  MPs / g in fish, and 1  MP / g in echinodermata. Maximum annual human MP uptake was estimated to be close to 55,000 MP particles. Statistical, sample, and methodological heterogeneity was high.

DISCUSSION

This is the first systematic review, to our knowledge, to assess and quantify MP contamination of seafood and human uptake from its consumption, suggesting that action must be considered in order to reduce human exposure via such consumption. Further high-quality research using standardized methods is needed to cement the scientific evidence on MP contamination and human exposures. https://doi.org/10.1289/EHP7171.

Micro- and nanoplastics - current state of knowledge with the focus on oral uptake and toxicity

The production and use of plastics has constantly increased over the last 30 years. Over one third of the plastics is used in disposables, which are discarded within three years of their production. Despite efforts towards recycling, a substantial volume of debris has accumulated in the environment and is slowly degraded to micro- and nanoplastics by weathering and aging. It has recently been discovered that these small particles can enter the food chain, as for example demonstrated by the detection of microplastic particles in honey, beer, salt, sea food and recently in mineral water. Human exposure has further been documented by the detection of plastic microparticles in human feces. Potential toxic consequences of oral exposure to small plastic particles are discussed. Due to lacking data concerning exposure, biodistribution and related effects, the risk assessment of micro- and nanoplastics is still not possible. This review focuses on the oral uptake of plastic and polymer micro- and nanoparticles. Oral exposure, particle fate, changes of particle properties during ingestion and gastrointestinal digestion, and uptake and transport at the intestinal epithelium are reviewed in detail. Moreover, the interaction with intestinal and liver cells and possibly resulting toxicity are highlighted.

Quantitative Analysis of Selected Plastics in High-Commercial-Value Australian Seafood by Pyrolysis Gas Chromatography Mass Spectrometry

Microplastic contamination of the marine environment is widespread, but the extent to which the marine food web is contaminated is not yet known. The aims of this study were to go beyond visual identification techniques and develop and apply a simple seafood sample cleanup, extraction, and quantitative analysis method using pyrolysis gas chromatography mass spectrometry to improve the detection of plastic contamination. This method allows the identification and quantification of polystyrene, polyethylene, polyvinyl chloride, polypropylene, and poly(methyl methacrylate) in the edible portion of five different seafood organisms: oysters, prawns, squid, crabs, and sardines. Polyvinyl chloride was detected in all samples and polyethylene at the highest total concentration of between 0.04 and 2.4 mg g^-1 of tissue. Sardines contained the highest total plastic mass concentration (0.3 mg g^-1 tissue) and squid the lowest (0.04 mg g^-1 tissue). Our findings show that the total concentration of plastics is highly variable among species and that microplastic concentration differs between organisms of the same species. The sources of microplastic exposure, such as packaging and handling with consequent transference and adherence to the tissues, are discussed. This method is a major development in the standardization of plastic quantification techniques used in seafood.