How Plastic Pollution May Influence Antimicrobial Resistance

Plastic pollution, antimicrobial resistance (AMR) and climate change are some of the greatest global challenges currently facing society and yet, research and mitigation efforts are often not joined up.

Vast quantities of plastics are produced and used each year, with an estimated 376 million metric tonnes of plastic produced globally in 2020, with almost a quarter of the world’s plastic waste being mismanaged or littered.

Owing to its durability, plastics will remain in the environment for centuries, posing a multitude of threats to humans, animals and global ecosystems.

AMR is one of the greatest threats to modern medicine. In 2019, there were an estimated 4.95 million deaths worldwide associated with bacterial AMR, with drug-resistant infections predicted to become the world’s primary cause of death by 2050, if left unchecked.

Historically, AMR has largely been considered a clinical, human health issue. However, the environment is now recognized as playing an important role in the emergence and spread of AMR microbes, and previous research has shown that plastic litter is likely contributing to this.

Now with the addition of climate change, for which there is a growing evidence base linking climate change and the emergence and evolution of AMR, it is crucial that research efforts gain a better understanding of the interplay between these issues.

Emily Stevenson, lead author and PhD researcher with the University of Exeter and Plymouth Marine Laboratory, said:

“By highlighting the interactions between plastics at different lifecycle stages and AMR under the umbrella of a changing climate, research and mitigation efforts may be more appropriately targeted, and solutions can be developed to address these issues in parallel, such as reformed governance, interconnected policy or joint monitoring frameworks”.

The comprehensive study explored the various touch-points between plastics at different lifecycle stages and AMR:

The various touch-points between plastics at different lifecycle stages and AMR are summarised below (for the full description of the touch-points please visit the full article):

Raw Material Extraction & Transport

• Fossil fuels (crude oil, natural gas, coal) are the base for oil-based plastics.
• Biocides used in pipelines may co-select for AMR, especially when spilled or leaked.
• Oil spills increase AMR in environmental bacteria and wildlife (e.g., dolphins).
• Heavy metals and aromatic compounds in oil may drive AMR development.

Production & Manufacturing

• Plastic additives (e.g., biocides, heavy metals, bisphenols, phthalates) are not chemically bound and can leach into the environment.
• These additives can:
  • Promote horizontal gene transfer of AMR genes.
  • Enrich infection-causing genes in marine environments.
  • Increase co- or cross-resistance to antibiotics.
• Exhaust particles from chemical processing (e.g., diesel, petrol) can enhance AMR gene transfer.
• PVC leachate and recycled plastics have been shown to enrich AMR genes.

Use Phase

• Human exposure to leached chemicals (e.g., from food packaging) may promote AMR in the gut microbiome or respiratory tract.
• Hot food increases leaching of heavy metals from plastics.
• Antimony, a flame retardant, can exceed safe levels in recycled bottles and is linked to AMR.

Collection & Waste Handling

• Waste workers face infection risks and potential exposure to AMR microbes.
• Mixed waste streams, especially with medical waste, can spread AMR genes.
• Personal protective equipment (PPE) and monitoring are essential to reduce exposure.

Disposal & Recycling

• Landfills are AMR hotspots due to:
  • Leachates containing antibiotics, heavy metals, and personal care products.
  • Spread of contaminants during heavy rainfall.
• Recycling can concentrate hazardous chemicals in secondary plastics.
• Washing agents and biocides used in recycling may persist and support AMR co-selection.

Prof. Pennie Lindeque, co-author on the paper and Head of Group for Marine Ecology and Society at Plymouth Marine Laboratory, added:

“AMR may also be an inadvertent driver of plastic production, use, and pollution. For example, the demand for single-use plastics to ensure sterility in clinics could increase plastic waste. Furthermore, microbial pandemics, like COVID-19, have increased single-use plastic PPE, with vast quantities of waste resulting from discarded masks and gloves”.

This study has highlighted several theoretical links between plastics and AMR that lack first-hand investigation, and identifies the following outstanding research questions in particular:

• Do biocides used to de-contaminate pipes in raw material (crude oil) extraction co-select for AMR?
• Is there an AMR selection risk posed by crude oil spills?
• What is the AMR selective potential of common plastic additives?
• Could the leaching of heavy metals from food-related plastic packaging present an exposure risk of the human gut microbiome to co-selecting compounds?
• What is the role of landfill sites as a source of AMR bacteria and ARGs?

Using these questions, studies should be conducted to validate the proposed mechanisms. Data from these studies may then be used to inform interdisciplinary efforts to develop sustainable plastic alternatives and large-scale monitoring programs.