By Dr Ma Zheng Feei, Dr Ibrahim Yusof Shuaib & Dr Lee Yeong Yeh
Microplastics, broadly defined < 5 mm, are plastic particles of different shape, size and polymer composition. Recently, there has been extensive media coverage on microplastic pollution including news release from the World Health Organization on the potential environmental health threat from microplastics. Single-use plastics and inappropriate plastic waste management are the primary reasons for pollution. There are several studies that have investigated the fate and abundance of microplastics, especially in the marine environment. Polyester, polycarbonate, polypropylene (PP), polyamide, polyvinyl alcohol, polyvinyl chloride (PVC) and polyethylene (PE) are the common polymers in microplastics found in the environment.
Since 1950s, the world plastic production has increased exponentially with current production exceeding 348 million tonnes but only about 9% of plastics are recycled worldwide. Production of plastics is forecasted to continue to grow ~3% annually, with Asia being the largest producer. Inappropriate plastic waste management is a threat for Malaysia, one of the 10 countries in the world with the biggest threat. Of the 0.9 million tons of plastic waste, almost half (0.4 million tons) were inappropriately released into the Malaysian waters. The most common plastic pollutants found in the Malaysian shore include plastic grocery bags, cigarette buds and plastic bottles.
Are We Eating Microplastics and/or Microplastic-Containing Foods?
According to recent studies, microplastics are widespread in our drinking water, but also found in some food products, especially seafood and salt. A study by the University of Newcastle reported that an average adult could consume about 5 g of plastic (approximate equivalent to a credit card) weekly from a variety of commonly eaten foods and beverages. In addition, there is increasing evidence supporting that microplastics could be ingested by animals and humans via food chains. In Malaysia, microplastics are detected in some commercial fish species, which may pose potential health concerns to consumers. Aquatic and seafood products are important protein sources and dietary component of many Malaysians with reports of per capita consumption of fish of 58 kg per person.
There are three kinds of potential health hazards associated with microplastic ingestion, and these are chemical, physical particles and microbial pathogens. Firstly, plastics can leach estrogenic-like chemicals (e.g. bisphenol-A or BPA) when exposed to a certain temperature and/or sunlight (ultraviolet radiation). These estrogenic chemicals mimic the actions of naturally occurring estrogens, which subsequently disrupt the endocrine activity with resulting metabolic disorders including obesity and diabetes. In addition, microplastics can absorb and bind harmful additives and monomers including organic pollutants that are present together with microplastics in the environment. In mammals, these chemicals found in plastics are associated with increased risk of obesity, some forms of cancers e.g. breast cancer, low sperm count in males and early puberty in females. We can postulate that similar adverse consequences are mostly likely found in humans because endocrine system is highly conserved across all vertebrate classes. However, confirmatory studies are greatly needed.
Secondly, as a physical particle, after ingestion, some microplastics may pass through the gastrointestinal (GI) tract and are excreted through defecation. However, microplastics may potentially accumulate and cause mechanical or physiological disruption to the GI tract and elsewhere. Microplastics may be translocated through blood or lymph to the cardiovascular and respiratory systems causing adverse health consequences. For instance, accumulation of microplastics in the circulatory system has been shown to block blood flow and subsequently cause severe damage to the cardiac tissue and its activity. In addition, a study has found that inhalable microplastics may also reach the lung alveoli, causing inflammation of the respiratory tract and cardiovascular diseases.
Thirdly, microplastics has been shown to induce gut microbiota dysbiosis in fishes, and dysbiosis can interfere with the immune system and trigger life-threatening diseases including infection and death. However, the adverse health consequences of short- and long-term microplastic ingestions in humans are not well studied. It is important to be aware that the adverse consequences from microplastic ingestion may depend on the type of microplastics and exposure (i.e. dosedependent).
**The second part of this article looks at the strategies or limitations highlighted in the Malaysia’s Roadmap to Zero Single-Use Plastics 2018–2030. Read full article here
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Reference: Ma ZF, Ibrahim YS, Lee YY. Microplastic pollution and health and relevance to the Malaysia’s Roadmap to Zero Single-Use Plastics 2018–2030. Malays J Med Sci. 2020;27(3):1–6. https://doi.org/10.21315/mjms2020.27.3.1