Lecture 11: Emerging contaminants and pollutants

What is Anthropocene Syndrome?

“a complex of environmental degradation, biological annihilation in the form of species losses, non-communicable disease epidemics, climate chanhe and increasing incivility in public and professional discourse”

“a set of signs and symptoms that are intertwined with politics, economics, policies (or lack thereof), and social values

AKA: Triple Planetary Crisis

Contaminants vs pollutants

Contaminant: any physical, chemical, biological or radiological substance present in the env at levels that are not naturally occuring - do not necessarily cause harm

Pollutant: contaminants that cause, or are likely to cause, adverse biological, chemical or physical effects to organisms or ecosystems

Transition of contaminant to pollutant is determined by evidence of harm

What are plastics? What are their uses?

• group of materials produced from natural or synthetically created resources

• raw materials used to produce plastics are mostly found in nature e.g. cellulose, coal, natural gas, salt and crude oil

How is plastic made?

Plastic is made by refining crude oil or natural gas into monomers, which are chemically bonded into polymers through polymerization.

Why is plastic an environmental issue?

They are persistent and can last millions of years: around 52.1 million tonnes enters the environment each year

• plastic has strong chemical bonds (long chains of C-C or C-H bonds

• resistance to biological attack

• hydrophobicity - plastics repel water which reduces chemical weathering processes

• physical durability - resist mechanical damage, abrasion and temp changes

Why can’t plastic be recycled easily?

Not all plastics are equally recyclable

What is the reality of plastic recycling?

• virgin plastic is often cheaper, reducing demand for recycled plastic

• wealthy nations export plastic overseas where it is poorly disposed of

• without strong legislation, recycling ramains voluntary or economically unattractive for many industries

• mixed/dirty plastics are costly to clean and recycle, meaning much collected material is incinerated or landfilled

What are Microplastics?

<5mm

• come mostly from land-based sources (80-90%) like urban runoff, wastewater and industrial activities

• coean based (10-20%) fishing activities mostly

Primary: microbeads in cosmetics

Secondary: breakdown of larger plastics

• they are found everywhere - in all environments

Research of microplastics

• Womens health: microplastics found in human ovary follicular fluid

• Bioaccumulation of microplastics in decedent human brains

• Leaf absorbtion contributes to accumulation of microplastics in plants

• One piece of chewing gum could expose you to 250,000 microplastics

Transport of microplastics: rivers

Rivers:

• contamination of riverbeds significantly reduced by catchment-wide flooding

• there are multiple urban contamination hotspots with a max microplastic concentration of ~517,000 particlesm-²

• the concentration of microplastics in river bed sediments of the Mersey catchment is higher than in any other environment

• the post-flooding microplastic dataset reveals a striking pattern of microplastic evacuation from study catchments

Transport of microplastics: oceans

• seafloor microplastic hotspots are controlled by deep-sea circulation

Hadal trenches:

• major depositories for plastic pollution

• microplastics found in the deepest parts of the ocean

• cascading processes that transport microplastics from land to sea are at play

• tropic transfer, biological interaction and physical processes play key roles

Are microplastics contaminants or polutants?

• in the ocean plastic debris kills marine animals

• marine plastic has impacted ~267 species worldwide uncluding 86% of turtle species, 44% seabird species and 43% of all marine mammals

• fatalities are due to: ingestion, starvation, suffocation, infection, drowning and entanglement

• studies assess presence of microplastics in organisms

• “Oyster reproduction is affected by exposure to polystyrene microplastics” - this study provides evidence that microPS cause feeding modifications and reproductive distruptions in oysters

they are POLLUTANTS

Microbial degredation of plastics

Microbial degradation uses specific microbes and enzymes (like depolymerases, hydrolases and peroxidases) to break down plastics

• Microbes can decompose biodegradable plastics (PHA, polyesters) even in extreme environments like the deep sea floor (757-5552m)

• New microbial communities and pathways have been identified in plastic contaminated soils

• Genomic studies reveal novel enzymes and microbes for bioplastic production and degradation

• The bacterium Ideonella sakaiensis can degrade PET plastic by using it as an energy source, producing two enzymes that break it down into environmentally friendly monomers (terephthalic acid and ethylene glycol)

Mussles as Plastic Filters

• they naturally filter microplastics from water

• pilot projects suggest mussel beds can trap and concentrate plastics for easier removal

• prof Lindeque from plymouth marine laboratory has been experimenting with nature-based solutions using mussels - “5kg mussles can remove microplastics by a quarter of a million pieces per hour”

What is the most effective approach to addressing the plastic pollution crisis?

A multi-pronged strategy is essential, combining:

• Waste reduction (less production and use of single-use plastics)

• Improved recycling (mechanical & chemical recovery)

• Active collection (e.g., river booms, beach cleanups)

• Emerging innovations like biodegradable plastics and microbial degradation (e.g., PETase), though promising, are not yet scalable.
  → Combination of reduction, recycling, and recovery is the most realistic and effective solution.

What are PFAS?

‘Forever Chemicals’

• Synthetic compounds found in firefighting foams, stain resistant fabrics, non-stick cookware, food packaging

• Characterised by extremely strong carbon-fluorine (C-F) bonds

• Highly mobile, leaching into groundwater and surface waters

• resistant to chemical, biological and thermal breakdown

Per - and polyfluoroalkyl substances in the environment (study)

• PFAS persist on geologic time scales and can bioaccumulate to toxic levels

• remediation is possible but expensive and is complicated by dispersion in soil, water and air

Environmental behaviour of PFAS

• longer chain PFAS (more C atoms) bioaccumulate more strongly

• marine environments show higher bioaccumulation than freshwater or brackish systems

• both PFCA and PFSA accumuklate, but patterns differ slightly by chemical type and ecosystem

PFAS evidence of harm

• bioaccumulates in human and animal bloodstreans

• linked to cancers (kidney, testicular), immune suppression, thyroid disease (EPA, 2022)

• Detected in drinking water, wildlife (even remote arctic)

• health advisories now recmmend near-zero exposure levels

• urgent regulatory and public health responses underway

POLLUTANTS

How is the issue of PFAS being addressed?

1. Capture technologies: Activated carbon, ion exchange resins

2. Destruction methods: High-temperature incineration, plasma treatment (expensive)

3. Nature-based solutions (early stage): Wetland attenuation, sorption into organic-rich soils

4. Prevention focus: Reducing use and emissions of PFAS at source

Name some other emerging contaminants

• pharmaceuticals and personal care products

• endrocrine disrupting chemicals

• industrial additives and plasticisers

• pesticides and herbicides

• flame retardants

• nanomaterials

Why are plastics and PFAS so critical

They contribute to the Triple Planetary Crisis: Climate, Nature, Pollution

The solutions directly align with SDGs:

• 6 - Clean water

• 12 - Responsible consumption and production

• 14 - Life below water

• 15 - Life on land

Lecture key takeaways

Paper: Pharmaceutical pollution of the worlds rivers

Global study of 1,052 sites in 104 countries found widespread contamination of rivers with 61 active pharmaceutical ingredients (APIs) - particularly in low to middle income countries which lach proper waste infrastructure.

• Common APIs: Carbamazepine, metformin and caffeine

• Hotspots: Sub-Saharan Africa, South Asia, South America

• 25.7% of sites have API levels above safe limits for aquatic life or antimicrobial resistance concerns

Pharmaceutical pollution is a global threat to ecosystems, human health, and SDG progress