Plastics are not the only contaminants that are accumulating in our marine environment. Human-derived micro debris materials and human bacterial pathogens, including paint, milk supplement powders, talc, and kerosene, also contaminate oysters and other important fishery species. This is according to a new study from the University of California – Irvine.
Pollution in aquatic environments
The authors wrote that seafood is one of the top imported products that is linked to foodborne outbreaks. The FDA considers it when two or more people get the same illness from the same contaminated food or drink. Given the significance of seafood exchanged as a protein source, it is imperative to maintain the safety of seafood worldwide. This is why the researchers use next-generation technology DNA sequencing to comprehensively study the contaminants in Myanmar oysters.
In collaboration with the University of Queensland, Cornell University, the Environmental Defense Fund, and local researchers in Myanmar, the researchers obtained their samples from the Tanintharyi region. The area is densely populated but still rural, covering nine coral reefs off the country’s Mergui Archipelago. It is also about 40 miles from Myeik city, which has an estimated population of over 250,000.
Over 5,000 potential human pathogens detected
After applying DNA sequencing from oysters and seawater obtained from the Tanintharyi region, they found 5,459 potential human pathogens that belong to 87 species of bacteria. Their study, which appeared in Science Daily, details that more than 50% of the pathogens detected are detrimental to human health.
Raechel A.Littman from the University of California, Irvine's Department of Ecology and Evolutionary Biology and team also examined the individual micro debris particles detected in the oysters using infrared spectroscopy. Of the 1,225 micro debris tested, they found 78 different contaminant materials.
About 48% of the microparticles they tested were also microplastics but many other particles originated from various human-derived materials that are part of cosmetics, paints, and fuels. UCI’s assistant professor of ecology and evolutionary biology Joleah Lam said that they were particularly surprised to find thee different brands of baby formula in their DNA sequencing result and the said milk powder comprise 14% of the micro debris contaminants.
Why the detection of milk supplement particles is of particular interest
Littman and the team went on to say that the prominence of milk supplement they found in oysters and other fishery species suggest a direct fecal-oral link between potential food products and human waste. This also has a possible transmission of contaminants or disease through seafood consumption. The finding of milk supplement is of particular interest to the team because Myanmar has recently undergone major economic and political changes, including the opening to new corporations that sell or market milk substitutes.
The two types of contaminants (microparticles and pathogens) found further reflect the runoff from animal and human sources and the presence of sewage too. The authors believe that the implications for other coastal regions are also important because global coastal marine environments are being increasingly subjected to reduced water quality due to urbanization. The author cautions that more than half of seafood exports now originate in developing countries. It is important to keep in mind that our seafood may come from places that may be contaminated. Thus, improvements in coastal water quality and adequate testing worldwide are recommended.
The study was supported by the Atkinson Center for a Sustainable Future and the Environmental Defense Fund Innovation for Impact Award.
Coastal urbanization can also increase the contamination of important fishery species worldwide and not just oysters. In another study that appeared in the Proceedings of the National Academy of Sciences of the United States of America, authors from Trent University in Canada also shared that oyster reproduction, offspring performance, and energy update are affected by exposure to polystyrene microplastics.
Marine scientist J. Evan Ward, who was not involved in both studies, was also featured by environmental writer Chris Woodside. When Evan checked on oysters that he and his colleagues at the University of Connecticut cultivate, they found the presence of microplastics.
Oysters as water filterers
According to the marine scientist, oysters are master water filterers. A single oyster can filter up to 1.3 gallons of water per hour and the can process tiny pieces of waste plastic. Some of these plastics can end up in their bodies. From waterways and oceans, microplastics have a way to enter the water supplies, guts of marine animals, shellfish, fish, food, and even humans. When plastic particles accumulate in the human body, such as around joint replacements and lymph nodes, they can carry the harmful chemicals and cause immune system problems. The particles can lodge in the lungs, for instance, and cause breathing disorders.
The plastics pieces that lodge in the intestinal tracts and tissues of the oysters, scallops, mussels, and clams also have a way to enter the human body since these animals are often eaten in whole. What’s more alarming is that the microplastics continue to get smaller and smaller and they don’t biodegrade.
Since oysters in Tanintharyi, Myanmar is a part of the local’s diet and they typically consume it whole and raw, it increases their risk of foodborne illness. Common symptoms of foodborne diseases are stomach cramps, vomiting, diarrhea, and nausea but symptoms may vary among different types of foodborne diseases. Some foodborne illnesses can be severe and some can be life-threatening. The groups that are more likely to develop foodborne illnesses are older adults, young children, pregnant women, and people with weakened immune systems due to medical conditions, such as kidney disease, diabetes, HIV/AIDS, organ transplants, or from receiving radiation treatment or chemotherapy, states CDC.
Consumption of fish and oysters
According to scientific online publication, Our World in Data, countries that have the highest fish and seafood consumption per capita in 2017 were Iceland (90.71 kg per year), Maldives (90.41 kg), Malaysia (57.62 kg), South Korea (54.97 kg), Myanmar (47.32 kg), and Spain (42.47).
Meanwhile, FAO mentioned that Belgium and the Netherlands are the two countries that consume more oysters and mussels (mollusks), followed by Germany and the UK.
So far, little is known about the extent of health risk for the contaminants that the UCI team detected. What is highlighted, though, is the benefit of using new technologies to target local monitoring and infrastructure interventions on the impacts of wastewater contamination.