Authored by Carina Harkin*
Abstract
Plastic is ubiquitous with recent studies having highlighted that plastic is in bottled and tap water and food products including honey, sugar and beer. 3-10 tonnes are estimated to fall on Paris per year. Plastic has recently been shown to be a vector for heavy metal contamination and to cross the blood–brain barrier (BBB). Global concern regarding the health implications is mounting, with the World Health Organisation (WHO) having conducted a risk assessment review of plastics. Whilst knowledge gaps exist, we remain to eat, drink and inhale plastic without knowing what harm it is potentially causing. This paper discusses the scale of global microplastic contamination, the sources and routes of microplastic contamination including inhaling and ingesting plastics, and the potential health implications of plastic bioaccumulation. Research into biotransformation is new and evolving. This paper looks at how plastic is bio transformed and the potential pharmacognostical approaches that have the potential to maximize plastic biotransformation. This paper discusses what is known about how plastic is bio transformed by Phase I cytochrome P450 enzyme group modification and Phase II glutathione, sulphation, glucuronidation and glycine conjugation pathways, and the importance of supporting endogenous antioxidants to assist plastic biotransformation. The paper specifically discusses what is known about how ingested plastics including phthalates and bisphenol A (BPA), and inhaled plastics, including dioxins and furans are bio transformed by these processes and what herbal medicine and nutritional supplementation may maximise plastic biotransformation and address plastic bioaccumulation.
Keywords: Plastic bioaccumulation; Plastic biotransformation; Microplastic; Nano plastic; Microplastics in drinking-water; Microplastic exposure and impacts on human health; Complementary and alternative medicine (CAM); Herbal medicine; Nutritional Supplements; Pharmacognosy
Keywords: Acetyl-Coa: Acetyl Coenzyme A; ALS: Amyotrophic Lateral Sclerosis; ADHD: Attention Deficit Hyperactivity Disorder; BPA: Bisphenol A; BBB: Blood-Brain Barrier; CDG: Caclium D-Glucarate; CAT: Catalase; CDC: Centers For Disease Control And Prevention; CD: Cluster Of Differentiation; CAM: Complementary And Alternative Medicine; Cuzn-SOD: Copper-Zinc SOD; CYP450: Cytochrome P450; DDT: Dichlorodiphenyltrichloroethane; DINP: Diisononyl Phthalate; DIDP: Diisodecyl Phthalate; EDCS: Endocrine Disrupting Chemicals; FSAI: Food Safety Authority Of Ireland; GSH: Glutathione; GPX: Glutathione Peroxidase; GR: Glutathione Reductase; GST: Glutathione S-Transferase; GST Family: Glutathione S-Transferases; GMIT: Galway-Mayo Institute Of Technology; GNRH: Gonadotropin-Releasing Hormone; HSE: Health Service Executive; HPA: Hypothalamic-Pituitary Axis; LGBTQI: Lesbian, Gay, Bisexual, Transgender, Queer Or Questioning And Intersex; BZIP: Leucine Zipper; Mn-SOD: Manganese SOD; MFO: Mixed-Function Oxidase Enzyme; NAC: N-Acetylcysteine; NHANES: National Health And Nutrition Examination Survey; NATS: N-Terminal Acetyltransferases; NDDS: Neurodevelopmental Disorders; NDGS: Neurodegenerative Diseases; NRF2: Nuclear Factor-Erythroid-2-Related Factor 2; PCOS: Polycystic Ovary Syndrome; POPS: Persistent Organic Pollutants; PTS: Persistent Toxic Substances; PAHS: Polycyclic Aromatic Hydrocarbons; PCBS: Polychlorinated Biphenyls; PETE: Polyethylene Terephthalate; SAM-E: S-Adenosyl-L-Methionine; SFN: Sulforaphane; SOD: Superoxide Dismutase; TCR: T-Cell Receptor; TCDD: Tetrachlorodibenzo-P-Dioxin; TEQ: Toxic Equivalent; T2D: Type 2 Diabetes; US: United States; UDP: Uridine Diphosphate; UDPGA: Uridine Diphsphate Glucuronic Acid; UGT: UDP-Glucuronosyltransferase; WHO: World Health Organisation
Background
Plastic is a crude oil product a non-renewable energy source [1]
The largest global consumer of oil is the United States (US) military, consuming 100 million barrels of oil per year [2]. Despite overwhelming evidence of carbon-fuelled climate change and billions in subsidies for alternative technologies, global oil consumption will reach 100 million barrels per day, more than twice what it was 50 years ago, with no sign of abating [3]. The US alone uses 330 million barrels of oil per year in plastics production alone, [4] three times the US military use.
The scale of microplastic contamination is staggering
An estimated 8 million tons of plastic enters our oceans each year. Microplastics are omnipresent in marine waters, from deep ocean sediments to polar icecaps [5].
Microplastics contain and absorb toxic chemicals
Microplastics are a vector for heavy metal contamination from the marine environment [6,7]. Microplastics attract harmful pathogenic bacteria in sewage and contain and absorb toxic chemicals. More than 50 persistent organic pollutants (POPs), specifically polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) are found in the five most common types of plastic [8]. POPs are also called persistent toxic substances (PTS) [9].
Plastic in Tap Water Globally
Billions of people are drinking water contaminated by plastic particles with 83% of samples found to be polluted. The US had highest contamination rate, at 94%, with plastic fibres found in tap water at Congress buildings, ironically the US EPA headquarters and Trump Tower in New York. Lebanon and India had next highest rates. European nations including UK, Germany and France had lowest contamination rate at 72%. The average number of fibres found in each 500ml sample ranged from 4.8 in the US to 1.9 in Europe [10,11]. An Irish study (June 2017) found microplastic contamination in a handful of tap water and well samples “We don’t know what the health impact is and we should follow the precautionary principle so we can find out what the real risks are,” said Dr Anne Marie Mahon at the Galway-Mayo Institute of Technology (GMIT) [12]
Plastic in Bottled Water Globally
The Orb study (Orb Media U.S-based non-profit journalism organisation) tested 259 bottles from 19 locations in 9 countries across 11 different brands were found to contain on average 325 plastic pieces for every liter of water. Scientists used Nile red dye to fluoresce plastic particles in the water, developed by Dr Andrew Mayes, University of East Anglia scientist. Nestlé Pure Life was worst offender; concentrations as high as 10,000 plastic pieces per liter. Of 259 bottles tested, only 17 were plastic free [13]. The contamination is said to be partially coming from packaging and/ or bottling process [14]. The most common plastic fragment was polypropylene plastic used to make bottle caps. Polypropylene is number 5 in triangle and considered safe. The study was not published in a journal, nor has been peer reviewed. A second unrelated Story of Stuff Study examined 19 bottled water brands in the US, also found plastic microfibers were widespread. Plastic fibers in bottled water brands are twice as high as those found in tap water [15]. See (Appendix) for brands Orb Media and Story of Stuff tested.
Plastic Water Bottles
Plastic water bottles are made from polyethylene terephthalate (PETE recycling code 1). This symbol is normally also found in soft drinks. PETE does not contain BPA/Phthalates, but studies find the endocrine disrupting chemical (EDC) antimony, a toxic phthalate ‘plasticiser’ used to make plastics flexible, leaches from PET bottles placed in heat for prolonged periods (16). Reusable plastic drinking water bottles are or more generally now, were made from polycarbonate (recycling code 7). Polycarbonate is made of BPA [17]. Investigations show in some cases, BPA-free PETE containers might leach of estrogen like chemicals [18].
Sources of Environmental Microplastic
Washing acrylic, polyester and nylon
Plastic derived, acrylic, polyester and nylon persist in the environment. Synthetic clothing that ends up in landfill soaks through the land, into the water table and into our drinking water. Alternatively, it ends up in our sea and evaporates into our clouds and back into our drinking water. One truck load of used clothes goes to landfill every second. One truckload of plastic enters the sea every second. By 2050 scientists estimate there will be more plastic in the sea than fish [19]. Acrylics are by far the worst offender. When acrylics are washed in washing machines, the average load of household washing shed 750,000 microplastics per wash, 5 times more than polyester-cotton. When drying synthetics, we are venting microplastic straight into the atmosphere [20, 21].
Burning plastics
Burring plastics releases endocrine disrupting cancer causing dioxins and furans the most toxic chemicals known to humankind [22].
Human sludge
A 2017 study for the Environmental Protection Agency (EPA) co-written by Dr Anne Marie Mahon from the Marine from the Freshwater Research Centre, Galway-Mayo Institute of Technology (GMIT) identified sludge spreading and the washing of plastic by the recycling industry as significant sources of environmental microplastics. It estimated that at least a billion microplastic particles are spread on Irish farmland each year (not all farms acquire and spread sludge) [23].
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