Accumulation of microplastics (MP). it is ubiquitous in the natural environment and has attracted considerable attention from researchers. These are extremely minute plastic particles (<5mm) entering the environment from both primary and secondary sources. Microplastic debris is a pervasive and long-lived pollutant that is highly resistant to environmental degradation and readily adheres to hydrophobic persistent organic pollutants.
According to the most recent global microplastics estimate, there are between 51 trillion microplastic particles drifting on the ocean surface. A human being consumes at least 50,000 microplastic particles per year due to contamination of the food chain, drinking water and air. The widespread increase of MPs in the natural environment and in the food chain is a result of the continued and rapid expansion of synthetic plastic production, mismanagement and improper fragmentation of plastic waste. Regarding the contamination of air, soil, water with microplastics, the ecological and health risks associated with exposure to microplastics are of great concern.
Prevalence of MPs in human foods
The prevalence of MPs has been found in food, beverages (bottled water, beer, honey, salt, etc.) and air samples, and exposure to MPs through ingestion or inhalation can have an adverse effect on human health. The presence of microplastics in human edible marine species and seafood (such as fish and shellfish) raises concerns about the potential health impacts of microplastics. MPs are also associated with morbidity and mortality in various marine and aquatic organisms. The deleterious effects on human health of microplastics can be due to the toxicity of the associated chemicals or the toxicity of the particles.
The main toxic chemical additives found in microplastics that are of great concern to human health include bisphenol A (BPA), phthalates, triclosan, brominated flame retardants (BFRs), bisphenone and organotins.
The biggest associated health risk is with the chemical BPA, which is used to harden plastic and then later seeps into food. BPA has been detected in concentrations ranging from 5 to 284 g/kg of microplastics, and shellfish eaters are estimated to consume up to 11,000 microplastic particles per year, according to studies. BPA can contaminate food and drinks and cause impaired liver function, insulin resistance, fetal development in pregnant women, reproductive system and brain function.
Some visible effects of microplastics on human health
Microplastics in human blood: In 2022, Prof. Dick Vethaak, ecotoxicologist, Vrije Universiteit Amsterdam, The Netherlands, examined blood samples from 22 healthy adult donors and discovered plastic particles in 17 of them. A third of the samples contained polystyrene, which is used to package food and other products, while half of the samples contained PET plastic, commonly used in beverage containers. A quarter of the blood samples contained polyethylene; the material used to make plastic bags.
Accumulation of microplastics in the human placenta: In 2021, a study analyzed the presence of microplastics in pregnant women using Raman microspectroscopy in Italy and found MPs in all portions of the placenta, including maternal, amniochorial and fetal membranes.
Effect of Microplastics on Gut Health: PD compromises the gut microbiome, leading to an imbalance of gut bacteria essential to the human body called gut dysbiosis. The other adverse human health effects of microplastics include the onset of obesity, cancer, DNA damage, oxidative stress, neurotoxicity, cardiovascular disease, and numerous reproductive and developmental outcomes. In addition to this, laboratory tests have shown that microplastics cause damage to human cells, including allergic reactions, cell death, cell damage and the induction of inflammatory and immune responses. In vitro studies have demonstrated that translocation of microplastics from the gastrointestinal cavity to the lymphatic and circulatory systems results in systemic exposure and accumulation in tissues such as the brain, kidney and liver. MPs can cross the epithelial barrier of the lungs and intestines, gastrointestinal tract and placenta with special absorption profiles.
From the deepest parts of the ocean to our lungs, microplastics seem to have infiltrated every aspect of our existence. MPs are difficult to remove from the environment, as they are often too small to detect or catch in moving water and can remain active contaminants for up to 450 years. The effects on human health of MPs are challenging and difficult to understand and the risk posed is quite difficult to assess and remains controversial. Therefore, scientific and public discourse has increasingly focused on the human health implications of exposure to microplastics. There is an immediate need for researchers to develop a new standardized methodology for analyzing and determining the potential health risk of plastics at the micro- and nano-scale.
Many countries have implemented or are planning to establish regulations to minimize MPs in the environment. Recently, a Global Treaty on Plastics at the United Nations Environment Assembly (UNEA-5) in Nairobi to end plastic pollution and create a legally binding international agreement by 2024, the first most significant international environmental laws in world history. In May 2023, more than 160 countries, including India, joined together to join the treaty and eliminate plastic pollution for the protection of the ocean, human health and climate. The key to solving the plastics crisis and driving transformative change requires exceptional collaboration and collective action by forming regional partnerships, crafting effective strategies, and engaging the community at the grassroots level.
(The author is Professor, Department of Community Medicine and School of Public Health, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh)
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