Plastics

what are plastics and why are they a problem?

  • plastics are synthetic materials made from polymers plus other additives

  • they are mostly made up of fossil fuels

  • they are produced in huge quantities and are the biggest contributor to marine trash

    • about 475 mega tonnes (2022)

  • they do no biodegrade, instead they just breakdown into more tiny pieces called micro and nano plastics.

microplastics and nano plastics (MNPs)

  • microplastics are smaller than 5 mm

  • nano plastics are smaller than 1 µm (not visible under microscopes)

  • where do they come from?

    • breakdown of larger plastic materials

    • food packaging that release plastic when heated

    • microbeads (nurdles)

    • fibres from textiles through washing

    • baby bottles, during preparation of formula

  • where are they found

    • in oceans, rivers, the deep sea, arctic, antarctic

    • can be found in marine mammals

      • turtles confuse floating plastic with jellyfish and consume them, causing their digestive tract to become obstructed

    • traces of micro/nanoplastics have been found in human bodies, even the placenta during pregnancy

    • in food: seafood, drinking water, fruits, vegetables, etc.

impacts of plastics across the plastic lifecycle

figure 2 from the Lancet article

  • the key stages that plastics go through are as follows:

    • fossil fuel extraction

    • plastic production

    • product manufacture

    • consumer use

    • recycling / waste

    • environmental leakage to land/ocean

  • each stage introduces:

    • plastic chemical → human exposure

    • micro and nano plastics → environmental and biological contamination

    • toxic air, water, and soil pollution

    • greenhouse gasses → climate impacts

  • this is important because marine plastics originate from teh entire lifecycle, not only from “litter”

  • microbial pathogen proliferations:

    • when plastics breakdown into macro and nano plastics, they provide an ideal surface for bacteria, viruses, and fungi to attach. these organisms then colonise and form a biofilm, creating a plastisphere. This biofilm promotes microbial growth and the spread of antibiotic resistant genes. These plastics are then transported over long distances in the water, increasing the indirect exposure risks to humans and animals

marine ecosystem impacts 

physical harm

  • nature article

    • when zooplankton are exposed to microplastics, they have reduced growth and reproduction rates

    • the fibres in microplastics are the most harmful as they remain in the gut of the zooplankton longer, weighing and slowing them down, interfering with their feeding and swimming ability

    • turtle hatchlings have been found with plastic pieces within their gastrointestinal tract

  • lancet article

    • MNPs are harmful to mangroves, seagrasses, and salt marshes, as it reduces photosynthesis, nutrient uptake, and the ecosystem stability in the coastal regions.

      • the MNPs block the pathways in which these plants can take up oxygen and other nutrients

    • MNPs also disrupt nutrient cycling, destabilise food webs, and reduce biodiversity

chemical exposure

  • plastics leach harmful chemicals like PFAS, and flame retardants. These are endocrine disruptors

  • these chemicals are ingested by animals and get accumulated up the food chains.

  • humans are then exposed to high concentrations of these chemicals as we consume animals higher up in the food chain

ecosystem level impacts

  • soil contamination → harming the microbiome, affecting important ecosystem functions

  • reduced plant photosynthesis

  • disruption of carbon sequestration

  • habitat alteration

  • spread of pathogens in marine debris

  • microplastics as a vector for antibiotic resistant bacteria (plastisphere)

human health impacts

  • exposure pathways

    • inhalation (airborne chemicals that are released during plastic production and burning)

    • ingestions (through seafood, water, food packaging)

  • health effects of plastic-associated chemical

    • developmental disorders

    • hormonal disruption

    • cancer

    • cardiovascular disease

    • immune dysfunction

    • metabolic disorders

    • reduced fertility

    • neurological impairment

  • health effects of micro/nanoplastics

    • in mice: gut inflammation, low sperm count (reduced fertility), leading to lower offsrpings, liver uptake

    • particles can cross blood-brain barrier and palcenta

    • MNPs found in human blood, placenta, heart, liver, lungs

    • potential links to lung diseases, strokes, heart attacks

plastic waste in marine environments

  • 10 to 12 mega tonnes of plastic enter the ocean each year

  • accumulation of plastic in aquatic systems so far is 139 mega tonnes

  • open burning of plastic wastes → toxic emissions, including microplastics

  • vectors for diseases

    • mosquito breeding

    • spread of antibiotic resistant bacteria

why this problem is getting worse

  • plastic production rising rapidly

  • recycling is quantitatively less than the rate of plastic being produced

  • plastics persist in the environment from decades to centuries

  • nanoplastics are too small to detect or remove

  • even without ne production, MNPs will continue to increase

what policies are needed?

  • reduce production, remove toxic chemicals, ban single use plastics

  • global plastics treaty - aims for lifecycle wide regulation

  • monitoring environmental + human exposure