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Imported oysters, the slurped seafood of choice for fancy people and old sea dogs, may often be riddled with a cocktail of contaminants, according to a new study.
Ecologists at the University of California, Irvine (UCI) found that oysters in Myanmar contain a broad range of contaminants, including infectious pathogens, plastics, kerosene, paint, and milk supplement powders. On a particularly grim note, the presence of some of these pollutants suggests that human poop and raw sewage is making its way back into the food chain.
Reported in the journal Science of the Total Environment, the new research shows how increasing coastal urbanization could be having an undesired effect on seafood in some parts of the world and could, in turn, have some nasty consequences for human health.
While this research purely focuses on oysters from the Southeast Asian nation of Myanmar, the researchers argue their findings have implications for people globally since around half of the exported seafood worldwide comes from developing countries.
“It’s important to keep in mind that much of our seafood is imported from overseas, from places that may be contaminated, emphasizing the importance of both adequate testing and improvements to coastal water quality worldwide,” lead author Raechel Littman, a postdoctoral scholar in ecology and evolutionary biology at UCI, said in a statement.
“This study is important in its global implications. There is strong evidence of transferability of the findings from Myanmar to other seafood sources around the world,” added Douglas Rader, study author and chief scientist for the Environmental Defense Fund's Oceans program.
The study looked at oysters found in nine coral reefs located roughly 64 kilometers (40 miles) from the small coastal city of Myeik in Myanmar. Within the samples, they found 87 species of bacteria, over half of which are considered a threat to human health. They also discovered the presence of at least 78 different types of contaminant materials.
“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,” said senior author Joleah Lamb, assistant professor of ecology & evolutionary biology at UCI. “We were particularly surprised to find three different brands of milk powder formula, which comprised 14 percent of the microdebris contaminants.”
Scientists are still undecided about how microplastics might affect human health. Although a number of studies have suggested they could lead to potential issues for human health, the World Health Organization (WHO) said in 2019 that “there is no evidence to indicate human health concern” from microplastics in drinking water. However, plastic particles are known to harbor known toxins in the form of persistent organic pollutants, or "forever chemicals," such as dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), and bisphenol A (BPA).
The presence of other non-plastic contaminants is also of concern. For example, finding milk powder formula in oysters suggests that human poop and raw sewage is finding its way back into the food web.
"These findings highlight both the risks of coastal urbanization and the importance of adequate wastewater and stormwater management. It also shows clearly the need for better science related to the potential impacts of these contaminants, and the need for better testing programs so that seafood consumers can rely on its wholesomeness," concluded Rader.
