From the Guidelines
The current level of evidence on the harms of microplastics to human health is limited and largely inconclusive, with insufficient epidemiological evidence directly linking microplastic exposure to specific health outcomes in humans. The presence of microplastics in drinking water and its sources has been reported, but the quality of data is often limited due to variability in methodologies used and concentrations reported 1. A critical review of studies reporting concentration data in freshwater and drinking water, which also evaluates the quality of applied sampling methods, microplastic extraction and identification steps, is currently lacking 1.
The implications of microplastics for human health have been reviewed, and although microplastic exposure via ingestion or inhalation could occur, the human health effects are still unknown 1. Some studies suggest that microplastics may accumulate and cause particle toxicity by inducing an immune response, and chemical toxicity could occur due to leaching of plastic-associated chemicals 1. However, establishing clear dose-response relationships and determining safe exposure thresholds remains challenging due to the diverse nature of microplastics and the ethical limitations of conducting controlled human studies.
Key factors to consider in assessing the risks of microplastics to humans include the variability of physical and chemical properties, composition, and concentration of the particles, as well as the level of quality assurance deployed in studies 1. High-quality data are limited, and only a few studies have been deemed reliable enough for exposure assessment. The precautionary principle suggests minimizing exposure where possible, but more research is needed to fully characterize the long-term health implications of chronic microplastic exposure in humans.
Some of the potential health effects of microplastic exposure include:
- Inflammatory responses
- Disruption of the gut microbiome
- Potential endocrine disruption from plastic additives
- The possibility that microplastics may act as carriers for other environmental contaminants However, the current evidence is not sufficient to establish a clear link between microplastic exposure and these health effects. Further research is needed to address the knowledge gaps and to provide a more comprehensive understanding of the potential harms of microplastics to human health.
From the Research
Level of Evidence on Harms of Microplastics
The current state of research on the harms of microplastics to human health is summarized as follows:
- Microplastic contamination is ubiquitous in the environment, and humans are exposed to microplastics through ingestion, inhalation, and dermal contact 2, 3, 4, 5, 6.
- The effects of microplastics on human health are not yet fully understood, but studies suggest that they may cause toxicity through oxidative stress, inflammatory lesions, and increased uptake or translocation 3, 4, 6.
- Microplastics have been found to release their constituent compounds as well as those that are adsorbed onto their surface, which can lead to adverse health effects 3, 4.
- Some studies have demonstrated the potentiality of metabolic disturbances, neurotoxicity, and increased cancer risk in humans due to microplastic exposure 3, 4, 5.
- The size, shape, chemical composition, surface charge, and hydrophobicity of microplastics influence their toxicity 4.
- Maternal transfer of microplastics to the developing fetus has been demonstrated in exposed laboratory animals and through the analysis of human placenta 4.
- There is evidence to support the hypothesis that microplastics and their additives are potential obesogens, contributing to the global increase in overweight and obesity in human populations 4.
- Further research is needed to quantify the effects of microplastics on human health and their pathogenesis, as well as to develop a standardized methodology for determining human exposure to microplastics 2, 3, 5, 6.