Climate change general

LOs: Overview of how climate change affects human health • Changes to vector-borne disease • Effects of extreme events on human health • Changes to water-borne disease

What are syndemics? (3)

• Closely interrelated complex of health and social crises (interplay between biological and contextual factors) - substance abuse/violence/AIDs

• Clustering of two or more health conditions

  • Biological interactions among the health conditions that lead to an increased health burden in the affected population

• Adverse contextual factors - e.g., poverty, violence, limited access to care – facilitate the clustering of some health conditions and worsen their pathogenesis and treatment efficacy

  • Social inequalities drive disease interaction

What is global syndemic?

• Obesity, undernutrition, climate change, vulnerability

• Affects business models, food systems, civil society involvement, national and international governance

Warmest year on record

2024

List effects of climate change on human health

• Respiratory disease: air pollution, pollen and other allergens

• Food shortages, malnutrition and undernutrition (eg from flood wiping out crops)

• Mental illness

• Vector borne disease

• Water borne illness

• Extreme events

• Temperature related morbidity and mortality

• Ecoanxiety (anxious abt state of environment)

Climate change vulnerabilities

• Vulnerability factors

• Exposure pathways

• Health system capacity and resilience

Vulnerabilites differ based off geography

Vector-borne diseases

• Rats, fleas, mosquitoes and ticks

• Carry pathogen from one host to the next bringing disease with them

• Heat and moisture provide ideal breeding conditions and improve survival

• Faster replication time of some pathogens

• Global warming means wider distribution

What are endemic diseases?

• Examples of long-established diseases

Diseases that are consistently present within a specific geographic area or population. They occur at a stable, predictable rate over time, unlike epidemics or pandemics which involve sudden spikes in cases

List examples of vector-borne diseases and vectors

• Zika virus

• Malaria

• Ticks

• Bats

• Zoonotic diseases

Zika virus

• Which weather does it flourish in and 3 reasons why

• Hot weather:

  • Heat makes mosquitoes hungrier

  • Warm air incubates virus faster

  • Territory expands to new areas

• First detected in Africa (1940s), then spread to NE Brazil

Zika virus

• Symptoms (8)

• First identified when and how many infections now in 2016 Americas

• How will its prevalence increase?

• Congenital effects and foetus effects

• 1947 in rhesus monkey in Zika forest, Uganda

• 4 million in Americas 2016

• Will increase with climate change

Zika virus

• Congenital and foetal effects

  • Transmission (3)

  • Maternal clinical symptoms (4)

  • Possible clinical consequences (4)

  • Mechanisms of fetal infection (4)

  • Mechanisms of microcephaly and CNS abnormalities (2)

• Highest risk of birth defects is from Zika virus during 1st and 2nd trimester

• Can be asymptomatic (4.2%)

  • Birth defect rate similar with/without symptoms – lab confirmed infection

How is climate change expected to affect malaria patterns globally? (4)

• Climate change is increasing global climate suitability for malaria transmission, especially in new regions

• Due to rising temperatures and changing precipitation patterns, which expand the habitable range of Anopheles mosquitoes (malaria vectors).

• → Global net increase in the population at risk, particularly from the 2050s onward.

• Areas currently unaffected (e.g., parts of Europe, Asia, and the Americas) may begin to see malaria emergence due to vector spread into warmer regions.

• Climate change creates new ecological niches for vector-borne diseases

How are zoonotic diseases transmitted?

Zoonotic diseases are transmitted from animals to humans via direct or indirect contact, through several routes:

• (Vector-borne transmission: via insects like mosquitoes or ticks.

• Air-borne / water-borne: inhalation or ingestion of contaminated particles.

• Direct contact: touching or handling infected animals.

• Indirect contact: exposure to environments contaminated with animal waste (e.g. bird droppings).

• Food-borne transmission: consuming infected animal products.

• Intermediate hosts: animals like camels, civet cats, or pangolins may carry viruses that jump to humans.

• Viral mutation: enables the virus to adapt and spread between humans, as seen in SARS-CoV and SARS-CoV-2.)

Injuries from extreme events (4)

• Fires, floods, rising sea levels

• Bushfires - (increased frequency, intensity, duration of bushfires in the world, costs the US $1.7)

  • Affects food chain

• Fires – risk of being burned or of smoke inhalation

  • Air quality affected: (eg smoke ploumbs) particulates entering body → respiratory tract, CV system → CVDs, respiratory diseases

  • (Air quality affected even in areas not affected by bushfire)

• Flooding – drowning and changes terrain introducing hazards

Effects of bushfire on aquatic wildlife and food chain (6)

• Direct asphyxiation of fish – gills clogged with ash

• Bacteria grow in water – deoxygenation of water and kills fish

• Changes pH of the water

• Disrupts breeding habitats

• Prevent/promote phytoplankton growth (base of aquatic food chains, effects fish ecosystem)

• Tainted drinking water supplies:
  Contamination of freshwater reservoirs reduces safe water for agriculture and livestock, compounding food production issues, reducing food availability for us

What can air pollution come from?

• Components of air pollution (3)

• Man-made examples

• Natural examples

• Components of air pollution: Gases (e.g. CO₂, NOx, SO₂) chemicals, particulate matter

  • PM₂.₅: combustion particles, metals, organic compounds

  • PM₁₀: dust, pollen, mould

• Man-made: indoor environment (eg cleaning products), cooking, factories, vehicle emissions, construction + demolition

• Natural: volcanoes, bushfires, pollens, spores, dust storms

• (7 million premature deaths each year due to the bad quality of the air we breathe (WHO))

Short (5) and long-term effects (3) of air pollution on health

Biological effects of air pollution (7)

How Does Climate Change Affect Water and Health?

• Changes in water temperature
  → Especially in oceans; alters ability of organisms to grow, survive, and thrive
  → Affects species distributions and ecosystems

• Droughts, floods, and fires
  → Impact water availability and quality
  → Increase water stress and contaminate sources

• Changes in debris in water
  → More pollutants and sediments enter aquatic systems

• Changes in microbial content
  → Warmer waters foster bacterial growth
  → ↑ risk of water-borne illnesses (e.g. cholera, giardia)

• Changes in nutrient levels
  → Can disrupt aquatic ecosystems
  → Leads to algal blooms and eutrophication

What is eutrophication?

Eutrophication is the excessive enrichment of water with nutrients, especially nitrogen (N) and phosphorus (P), usually from:

• Agricultural runoff (fertilizers, manure)

• Wastewater discharge

• Industrial pollutants

➡ These nutrients act like a "fertilizer" for algae and aquatic plants, leading to rapid growth.

What are algal blooms?

Algal blooms are the sudden overgrowth of algae, especially phytoplankton, triggered by eutrophication.

• Some blooms are harmless, but harmful algal blooms (HABs) can:

  • Produce toxins (affecting humans, fish, and animals)

  • Block sunlight

  • Use up oxygen when algae die and decompose

Consequences:

• Hypoxia (low oxygen) → fish kills and biodiversity loss

• Contaminated water → unsafe for drinking or recreation

• Economic damage → fisheries, tourism, water treatment costs

What are the causes and risks of water-borne illnesses?

• Caused by heated or contaminated water

• Supports growth of bacteria, viruses, and protozoa

• Algal blooms (driven by excess nutrients + climate change) release toxins

• Risks with drinking, swimming, and washing

• Contamination affects plants and animals associated with water

• Reduces water safety for agriculture and livestock

What are the health impacts of cyanotoxins from harmful algal blooms in humans and pets?

In humans (via ingestion, contact, or inhalation):

• Brain: Headache, incoherent speech, drowsiness, loss of coordination

• Respiratory: Dry cough, pneumonia, sore throat, shortness of breath

• Digestive: Nausea, vomiting, diarrhoea, cramps

• Skin/contact: Rashes, tingling, blistering, fever

• Organs: Kidney & liver damage

• Nervous system: Tingling, numbness

In pets: Vomiting, fatigue, respiratory distress, convulsions, liver failure, paralysis → death

Note: Not all algal blooms are toxic. Toxicity depends on bloom type and environmental conditions.