New Link in the Food Chain? Marine Plastic Pollution and Seafood Safety

In recent years plastic pollution in the ocean has become a significant environmental concern for governments, scientists, nongovernmental organizations, and members of the public worldwide. A December 2014 study derived from six years of research by the 5 Gyres Institute estimated that 5.25 trillion plastic particles weighing some 269,000 tons are floating on the surface of the sea.1 At the same time, plastics in consumer products have become subject to increasing scrutiny regarding their potential effects on human health. Bisphenol A (BPA),2 a component of polycarbonate plastics and suspected endocrine disruptor, is one of the most widely known chemicals of interest. But BPA is only one of many monomers, plasticizers, flame retardants, antimicrobials, and other chemicals used in plastics manufacturing3 that are able to migrate into the environment. Investigators are researching whether consumption of plastic debris by marine organisms translates into toxic exposures for people who eat seafood. At the junction of these two lines of inquiry is an emerging third field that is in many ways even more complex and less well understood: investigating human exposures to and potential health effects of plastics that have entered the marine food chain. Studies have demonstrated plastics’ tendency to sorb (take up) persistent, bioaccumulative, and toxic substances, which are present in trace quantities in almost all water bodies.4 The constituents of plastics, as well as the chemicals and metals they sorb, can travel into the bodies of marine organisms upon consumption,5,6,7,8,9 where they may concentrate and climb the food chain, ultimately into humans. This topic has attracted interest and funding from the U.S. Environmental Protection Agency (EPA), the National Oceanic and Atmospheric Administration (NOAA), and the National Academy of Sciences (NAS), as well as researchers, nonprofit groups, and institutions around the world. At this point “there are more questions than answers,” says Richard Thompson, a professor of marine science and engineering at England’s Plymouth University. Thompson coined the term “microplastics” in 200410 and later undertook a three-year study of these particles in the marine environment for the UK’s Department of Environment, Food, and Rural Affairs.11,12,13 “From a human perspective,” he says, “at the moment I think there’s cause for concern rather than cause for alarm.” Viewpoints on the human health risks of marine debris are nearly as complex as the underlying science, as was evident at an inaugural EPA and NAS symposium on the topic held in Washington, DC, in April 2014. In addition to myriad small details, the researchers in attendance considered an overarching question: Within the context of limited oceanographic research funding, the variety of other problems affecting ocean health (including overfishing and acidification), and the extent of humans’ daily and direct exposures to potentially harmful chemicals from consumer plastics and other sources—how concerned should we be about marine plastics as far as human health goes? Researchers don’t yet have an answer, even if they believe they’re asking the right question. As EPA chemist Richard Engler concluded in a 2012 review, “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.”14