An article by a reputable science and environment journalist in the current issue of Environmental Health Perspectives, a journal of the US National Institute of Environmental Health Sciences, summarizes what is known and not known about the public health effects of eating seafood from oceans that are contaminated with plastic residues. GallonDaily’s summary: we do not know much about this complex topic, we need to conduct much more research, but in the meantime we should recognize that seafood is probably not the major pathway for human exposure to microplastics and their possibly associated toxic chemical burden. Among the findings:
- Studies have demonstrated plastics’ tendency to take up persistent, bioaccumulative, and toxic substances, which are present in trace quantities in almost all water bodies.
- The constituents of plastics, as well as the chemicals and metals they have taken up, can travel into the bodies of marine organisms upon consumption where they may concentrate and climb the food chain, ultimately into humans.
- While current research cannot quantify the amount, plastic in the ocean does appear to contribute to persistent, bioaccumulative, and toxic substances in the human diet.
- There is a lack of controlled experimental work completed on the topic and it’s very difficult to disentangle direct human pollutant exposures and bioaccumulation via plastic versus food and environmental sources.
- Due to their hydrophobic nature, persistent organic chemicals—including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), dioxins, and DDT—have been shown to preferentially sorb to [be taken up by] plastics when they encounter them in the ocean.
- Once plastics have been consumed, laboratory tests show that chemical additives and adsorbed pollutants and metals on their surface can leach out and transfer into the guts and tissues of marine organisms. However this process has not been proven to occur in the natural environment.
- A 2014 study showed an association between concentrations of certain PBDEs in fish and levels of plastic debris accumulation in the South Atlantic Ocean. However, no such association was seen for concentrations of BPA, alkylphenols, alkylphenol ethoxylates, or PCBs in fish.
- Government, academic, and independent sources interviewed for the article almost unanimously expressed a mix of skepticism and concern toward the thought of ocean plastics posing a human health risk.
- Human exposure to microplastics and plastic additives is more likely to stem from intact goods prior to disposal than from seafood. Clothing fibres make up a large proportion of the microplastic found worldwide and even drinking water and foods such as honey can be contaminated with microplastics.
- The end goal need not be to abandon the use of plastic. The benefits of plastics can be realized without the need for emission to the ocean.
- New laws could require handling plastics more responsibly at the end of their useful life through recycling, proper disposal, and extended producer responsibility.
- Rolf Halden, director of the Center for Environmental Security at the Biodesign Institute at Arizona State University, advocates for another solution: manufacturing more sustainable plastics from the start. “We need to design the next generation of plastics to make them more biodegradable so that they don’t have a long half-life, they don’t accumulate in the oceans, and they don’t have the opportunity to collect chemicals long-term,” he says. “There’s just no way we can shield people from all exposures that could occur. Let’s design safer chemicals and make the whole problem moot.”
The complete eight page article, with 53 references, can be found at http://ehp.niehs.nih.gov/123-A34/