World Health Organization (WHO) report assesses human exposure to micro- and nanoplastics via inhalation and diet as well as potential health implications; finds available data of limited use for risk assessment
On August 30, 2022, the World Health Organization (WHO) published a report summarizing the scientific knowledge on human exposure to micro- and nanoplastics (MNPs) and potential associated health risks. As a follow-up to the WHO report on microplastics in drinking water published in 2019 (FPF reported), the organization assembled an international group of experts to review the available data published up to December 2021 to work on this new report.
Topics discussed in the article include (i) human exposure to plastic particles present in food, beverages, drinking water, and air; (ii) impacts on human health considering exposure, toxicity, and occurrence data; (iii) option to reduce exposure; and (iv) knowledge gaps and research recommendations.
Concerning foods and beverages, the article summarizes in which consumables microplastics have been detected including fish (FPF reported), seafood (FPF reported), salt (FPF reported), sugar, honey (FPF reported), milk, and drinking water (FPF reported and here), and also provides the numbers and characteristics of particles detected by the reviewed studies. Outcomes of MNP ingestion are assumed to be similar to other well-studied insoluble particles, including the generation of reactive oxygen species and induction of an inflammatory response. Most of the reviewed studies suggested MNP contamination in foodstuff originates from environmental contamination (e.g., fish taking up microplastics), is deposited onto the food from the air, or stems from manufacturing or processing. Only recently has food packaging also been discussed as a relevant exposure source (FPF reported and here). The authors recommend conducting more research on MNP sources and characteristics to develop effective measures to reduce exposure. In particular, “more research on the role of plastic packaging should be conducted for quantitative assessment.” To estimate dietary exposure levels standardized analytical methods would need to be developed that are also suitable to detect particles < 10 µm.
Generally, the authors recommend developing standard methods to generate more robust data since they found that “the available data are of only very limited use for assessing the risk of MNP to humans” which was to a great part due to the heterogeneity of the methods applied in scientific studies. Another identified limitation is that exposure studies rarely look at particles < 10 µm while effect studies focus on exactly this size leading to a mismatch. Therefore, the authors express the need to better study exposure to particles < 10 µm.
Although the report concluded that “the limited data provide little evidence that MNPs have adverse effects in humans… measures should be taken to mitigate exposure” since stakeholders would agree that plastics should not be present in the environment. To this aim, the use of plastics should be reduced, waste management improved, as well as the release of MNPs from plastic products prevented.