Plastics, pathogens and baby formula: What's in your shellfish?
The first landmark study using next-generation technology to comprehensively examine contaminants in oysters in Myanmar reveals alarming findings: the widespread presence of human bacterial pathogens and human-derived microdebris materials, including plastics, kerosene, paint, talc and milk supplement powders.
The study led by scientists from the University of California, Irvine, in collaboration with Environmental Defense Fund, Cornell University, the University of Queensland and Dr. Jeroen van de Water from the Centre Scientifique de Monaco -- was conducted in the eastern Andaman Sea through partnerships with local researchers in Myanmar.
The area covered by the study spanned nine coral reefs off Myanmar's Mergui Archipelago, situated roughly 40 miles from Myeik, a city with a population of over 250,000 people. The study examined contaminants in seawater and in oysters using next-generation DNA sequencing to reveal 5,459 potential human pathogens belonging to 87 species of bacteria. More than half of these pathogens are considered detrimental to human health. In addition, infrared spectroscopy was used to examine individual microdebris particles found in the oysters. Of the 1,225 individual microdebris particles examined, 78 different types of contaminant materials were found. While 48 percent of the microparticles were microplastics - a finding representative across numerous ocean ecosystems - many other particles were not plastic and originated from a variety of human-derived materials that are constituents of fuels, paints and cosmetics, as well as three different brands of milk powder formula, which comprised 14 percent of the microdebris contaminants.
Many plastic particles can carry toxins, like dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs) and bisphenol A (BPA), that subsequently enter the ocean and marine food webs, and can eventually be transferred to people through food. Therefore, the uptake of microplastics in the marine environment could have far-reaching consequences for human consumption of seafood and can be an emerging risk to public health globally.
Both types of contaminants - pathogens and microparticles - reflect the pervasive presence of sewage and runoff from human and animal sources. Coastal marine environments worldwide are being increasingly subjected to reduced water quality from urbanization, which could be leading to the contamination of important fishery species on a global scale. Implications for human health are also significant as oysters are part of the local diet and typically consumed raw and whole. The contaminants found in this study indicate that even the Mergui Archipelago in largely rural Myanmar has significant and widespread pollution from runoff of agricultural and human waste that can affect downstream food sources over a wide area far from urban centers.
The study concludes that coastal urbanization and lack of sewage treatment increases contamination in seafood and can cause potential health risks to humans, even large distances from pollution sources; and highlights the importance of adequate wastewater and stormwater management.
- Littman, R. A., E. A. Fiorenza, A. S. Wenger, K. L. E. Berry, J. A. J. M. van de Water, L. Nguyen, S. T. Aung, D. M. Parker, D. N. Rader, C. D. Harvell & J. B. Lamb, 2020. Coastal urbanization influences human pathogens and microdebris contamination in seafood. Science of The Total Environment 736:139081.