Threats to human health by great ocean garbage patches

The medical relevance of environmental topics can be blurred by politicised debates and the global scale of the environmental impact of human life. However, a seemingly remote serious health threat is currently floating in our oceans and needs to trigger the attention of the medical community, as its clinical manifestation is only a matter of time. Plastics are one of the most important materials in industrialised countries. Despite huge annual inputs of plastic litter into the oceans (4·8–12·7 million metric tons), the hazards to both the environment and human health are widely neglected.1Jambeck JR Geyer R Wilcox C et al.Marine pollution. Plastic waste inputs from land into the ocean.Science. 2015; 347: 768-771Crossref PubMed Scopus (5535) Google Scholar Marine plastic contamination has spread across the globe. Several garbage patches have formed in the Pacific and Atlantic oceans.2Rochman CM Cook AM Koelmans AA Plastic debris and policy: using current scientific understanding to invoke positive change.Environ Toxicol Chem. 2016; 35: 1617-1626Crossref PubMed Scopus (82) Google Scholar Clockwise ocean currents lead to the retention and convergence of plastic debris. These subtropical gyres prevent plastic debris from moving towards mainland coasts. Plastic pollution substantially threatens marine life.3Mansui J Molcard A Ourmières Y Modelling the transport and accumulation of floating marine debris in the Mediterranean basin.Mar Pollut Bull. 2015; 91: 249-257Crossref PubMed Scopus (143) Google Scholar Numerous chemical monomers are used to produce plastic polymers, which are characterised by high longevity. Partial degradation in seawater leads to generation of macro-waste and micro-waste, which causes physical and biological hazards to marine organisms. Release of ecotoxic chemicals from plastic particles provokes chemical and toxicological threats (figure). Furthermore, plastic litter is frequently mistaken for food by marine life, leading to health complications and death. Plastic ingestion has been observed in numerous animals. Plastic parts were found in the stomachs of turtles, and seabirds die from obstruction of their respiratory or digestive tracts by bottle caps.4Derraik JG The pollution of the marine environment by plastic debris: a review.Mar Pollut Bull. 2002; 44: 842-852Crossref PubMed Scopus (2343) Google Scholar Turtles and seals are trapped by abandoned fishing nets—so-called ghost nets. However, the long persistence of plastic debris is also problematic for other reasons. Combinations of weathering by ultraviolet light, seawater, and mechanical action partly degrade and fragment larger pieces of plastic down to microplastics (<0·5 mm). When they sink, small plastic pieces and microplastics are colonised by certain marine organisms, which affects submarine organisms and entire ecosystems, including non-human and human food chains. Via the intake of microplastics or their chemical compounds, which are set free in various decomposition processes, ocean garbage has become a latent threat to the health of future generations, and already affects human health on a global scale. Human biomonitoring shows that compounds used for plastic production are already ubiquitous in human blood and cells.5Koch HM Calafat AM Human body burdens of chemicals used in plastic manufacture.Philos Trans R Soc Lond B Biol Sci. 2009; 364: 2063-2078Crossref PubMed Scopus (430) Google Scholar Major sources of chemical pollutants are polychlorinated biphenyls, dioxins, perfluorinated carboxylic acids, and perfluoroalkyl acids,6Engler RE The complex interaction between marine debris and toxic chemicals in the ocean.Environ Sci Technol. 2012; 46: 12302-12315Crossref PubMed Scopus (467) Google Scholar which cause hepatotoxicity. Xenobiotic compounds are metabolised in the liver by the phase 1–3 detoxification system. Phase 1 consists of oxidation reactions to increase hydrophilicity of xenobiotics and facilitating extrusion. In phase 2, xenobiotics are coupled to transfer carrier molecules and in phase 3, xenobiotic compounds are transported out of liver cells for excretion out of the organism. Plastic debris-related pollutants induce cytochrome P450 monooxygenase isoenzyme 1A (CYP1A) phase 1 enzyme activity.7Tian S Pan L Zhang H Identification of a CYP3A-like gene and CYPs mRNA expression modulation following exposure to benzo(a)pyrene in the bivalve mollusk Chlamys farreri.Mar Environ Res. 2014; 94: 7-15Crossref PubMed Scopus (28) Google Scholar Polychlorinated biphenyls, polychlorinated dibenzofurans, and polynuclear aromatic hydrocarbons upregulate CYP1A activity in marine organisms. CYP1A is involved in chemical carcinogenesis, and these compounds form DNA adducts as the first step of tumour development.8Michel C Vincent-Hubert F DNA oxidation and DNA repair in gills of zebra mussels exposed to cadmium and benzo(a)pyrene.Ecotoxicology. 2015; 24: 2009-2016Crossref PubMed Scopus (12) Google Scholar An important phase 3 protein is the ATP-binding cassette (ABC) transporter P-glycoprotein, which is involved in hepatic excretion. P-glycoprotein acts as an ATP-consuming efflux transporter that extrudes a large array of diverse chemicals out of cells.9Efferth T The human ATP-binding cassette transporter genes: from the bench to the bedside.Curr Mol Med. 2001; 1: 45-65Crossref PubMed Scopus (133) Google Scholar P-glycoproteins are present in mammals (eg, human beings, pigs, and cattle), other vertebrates (eg, fish and reptiles), and invertebrates (eg, worms, molluscs, and insects).10Efferth T Volm M Multiple resistance to carcinogens and xenobiotics: P-glycoproteins as universal detoxifiers.Arch Toxicol. 2017; 91: 2515-2538Crossref PubMed Scopus (62) Google Scholar Many aquatic organisms live in water that is highly polluted with anthropogenic or natural toxins. ABC-transporters enable many aquatic organisms to tolerate toxins and survive even in highly polluted water. This phenomenon is termed multi-xenobiotic resistance. Inhibition of multi-xenobiotic resistance has important implications for environmental risk assessment. If P-glycoprotein-mediated efflux processes are blocked by environmental poisons, marine organisms will die.11Smital T Kurelec B The chemosensitizers of multixenobiotic resistance mechanism in aquatic invertebrates: a new class of pollutants.Mutat Res. 1998; 399: 43-53Crossref PubMed Scopus (86) Google Scholar These observations imply that toxic substances released from plastic litter in ocean garbage patches will inhibit the ABC-transporter-mediated detoxification capabilities of aquatic organisms, with fatal consequences for their survival in polluted water. Furthermore, plastic constituents cause other detrimental effects. Di(2-ethylhexyl)phthalate is a standard plasticiser in polyvinylchloride, which induces teratogenicity, male infertility, carcinogenesis, and immunotoxicity.12Sogbanmu TO Nagy E Phillips DH Arlt VM Otitoloju AA Bury NR Lagos lagoon sediment organic extracts and polycyclic aromatic hydrocarbons induce embryotoxic, teratogenic and genotoxic effects in Danio rerio (zebrafish) embryos.Environ Sci Pollut Res Int. 2016; 23: 14 489-14 501Crossref Scopus (41) Google Scholar Bisphenol A (BPA; 2,2-bis(4-hyddroxyphenyl)propane) is a widely used monomer in the production of epoxy resins and polycarbonate plastics.13Kang JH Kondo F Katayama Y Human exposure to bisphenol A.Toxicology. 2006; 226: 79-89Crossref PubMed Scopus (655) Google Scholar With a global production of 3 billion tons annually, BPA is one of the most highly produced chemicals by volume. BPA is an endocrine disrupter that exerts oestrogenic and genotoxic effects in aquatic organisms and human beings.13Kang JH Kondo F Katayama Y Human exposure to bisphenol A.Toxicology. 2006; 226: 79-89Crossref PubMed Scopus (655) Google Scholar BPA binds oestrogen receptors and disturbs reproductive behaviour,14Bonefeld-Jørgensen EC Long M Hofmeister MV Vinggaard AM Endocrine-disrupting potential of bisphenol A, bisphenol A dimethacrylate, 4-n-nonylphenol, and 4-n-octylphenol in vitro: new data and a brief review.Environ Health Perspect. 2007; 115: 69-76Crossref PubMed Scopus (401) Google Scholar and inhibits fertility of male aquatic organisms. This chemical has officially been declared as an endocrine disrupting chemical by the US Environmental Protection Agency. Bioaccumulation of toxic compounds represents a threat to the food chain, because aquatic organisms that have ingested these compounds serve as human food.5Koch HM Calafat AM Human body burdens of chemicals used in plastic manufacture.Philos Trans R Soc Lond B Biol Sci. 2009; 364: 2063-2078Crossref PubMed Scopus (430) Google Scholar Driven by responsibility for human health, the global medical community needs to address the danger posed by great ocean garbage patches and demand urgent implementation of strategies to tackle this global threat. WHO and the World Medical Association could—or should—take a leading role. Potential strategies include, but are not restricted to voluntary abstinence from plastic products; legal regulations to reduce plastic use (eg, banning or higher taxation of plastic parts); recycling of plastic wares or burning of plastic waste (with appropriate filter systems); development of biodegradable plastics (eg, hydrolysable polyhydroxyalkanoates) or petroleum-derived plastics (aliphatic polyesters and polycarbonates) that can be degraded by microorganisms;15Tokiwa Y Calabia BP Ugwu CU Aiba S Biodegradability of plastics.Int J Mol Sci. 2009; 10: 3722-3742Crossref PubMed Scopus (910) Google Scholar removal of great ocean garbage patches as an international task; medically meaningful definition and implementation of critical and maximum permissible values of chemical compounds and xenobiotics in human beings; and development of safe, efficient, and affordable toolkits for biomonitoring of food chains and people, to identify the transition from a latent to an acute threat to human health. Until now, marine plastic pollution has been considered a remote environmental problem. However, a latent threat to marine life has become an acute threat to human health. Biochemical pathways of degraded and decomposed materials and xenobiotics released by great ocean garbage patches are clear enough to alert us and stimulate us to work on prevention of an otherwise immense health problem. We declare no competing interests.