Microplastics in Water and Potential Impacts on Human Health

Plastic materials were first produced in the early 1900s, with those very first pieces probably still existing somewhere in our environment. One century later, millions of tonnes of plastic waste enter our oceans and freshwater ecosystems every year. Undeniably, plastics have benefited substantially our way of life; yet, they pose a threat to humans and wildlife on a global scale, impacting not only present but also future generations. We currently face unprecedented levels of plastic debris in our food, water, and environment, much of it present as microplastics (< 5 mm). They are produced either intentionally at this size (primary) or generated by breakdown of larger plastic particles (secondary). Microplastics may accumulate in the food web, leach toxic compounds, and even concentrate and transport other chemicals, microorganisms, and pathogens. Humans are constantly exposed to microplastics through airborne particulate matter, drinking water, consumer products, and the food chain, for example. Detailed information on the bioaccumulation and translocation of microplastics to different human tissues is limited, but data suggest that microplastics, in particular those at lower micron and sub-micron sizes, can cross important barriers in the lungs, gut, and the blood-brain barrier. Thus, it is not surprising that microplastics have been found in human faeces and tissues, including the brain and the placenta. Despite the urgent need to assess this topic, the effects of microplastics on our bodies remain largely unknown. Microplastics can potentially cause physical, chemical, and microbiological toxicity, leading to oxidative stress, cellular damage, inflammatory and immune responses, neurotoxic and even metabolic changes. Their wide range of sizes, shapes, polymer types, and complex surfaces (chemical, protein, and eco-corona) indicate that microplastics comprise a complex class of emerging contaminants with a broad range of toxicity profiles. Considered one of the final sinks for plastic waste, water bodies receive significant amounts of microplastics every year, likely endangering water quality and human health. The challenges for a comprehensive risk assessment are numerous, but more than ever, research on microplastics (and nanoplastics) is critical to accurately characterize the potential hazard of small plastic particles to human health.

This Research Topic aims to create a virtual environment to discuss the challenges and impacts of microplastics as potential disruptors of water quality and human health. Articles will address major questions or topics in the field of small plastic particles (micron and sub-micron sized) and human health, including (i) the toxicity profile of microplastics in response to particle characteristics such as size, shape, composition, concentration, and corona, (ii) characterization of routes of exposures to waterborne microplastics, (iii) absorption, bioaccumulation, and translocation of microplastics in human tissues and organs, (iv) mechanisms of toxicity and characterization of Adverse Outcome Pathways, (v) plastics as vectors of pathogens and environmental pollutants, (vi) toxicity of real-world “environmental” plastics, and (vii) effects of aging or weathering on microplastics toxicity. Ultimately, by bringing together key researchers from across the globe to discuss this theme, this Research Topic also seeks to provide and compile scientific evidence for risk assessment, policy-making, and mitigation projects. The following topics are welcome:

- Toxicity of nano /sub-micron and microplastics (in vitro and in vivo).
- Toxicity of new and engineered plastic materials.
- Alternative animal, non-animal, and in-vivo models to investigate the health impacts of microplastics in humans.
- Characterization and toxicity of plastic additives, leachates, co-contaminants, bacteria, and other pathogens associated with microplastics of human concern.
- Human exposure to microplastics through aquatic food chains.
- Drinking water and exposure to microplastics.
- Treatment techniques to remove microplastics from water.
- Long-term or chronic exposure to plastics, epidemiological studies.
- Biomonitoring studies of micro and nanoplastics, as well as particles containing additives and including size classes that are small enough to translocate, in human tissues.
- Effects of weathering and aging on the toxicity of waterborne microplastics.
- Effects of microplastics on gut microbiome.

This Research Topic will accept submissions from Original Research Articles, Systematic Reviews, Mini Reviews, Methods, Perspective and Opinion pieces. Research Article and Methods can use in vivo approaches with established or alternative animal models, as well as in vitro and in silico studies. Studies describing mechanisms of toxicity or adverse outcome pathways are highly recommended, as well as studies filling the gaps on the roles of particle characteristics, bioaccumulation, and translocation between tissues and organs. Submission of studies on nanoplastics are also highly encouraged.

Photo Credits: Photo by Daniel Cespedes, Oregon State Productions