Pollution Notes

Why Is Pollution A System Problem With Multiple Causes And Stakeholders?

1. Pollution occurs when human activities (production, transport, energy use, agriculture, waste disposal) create outputs that ecosystems cannot absorb without harm.
2. This means pollution is rarely caused by one factor, instead it emerges from a system:
   1. Sources (vehicles, factories, power plants, farms, households)
   2. Pathways (air currents, rivers, groundwater flow, food chains)
   3. Receptors (people, habitats, buildings, crops)
   4. Impacts (health costs, ecosystem damage, economic losses)
   5. Responses (laws, technology, planning, behaviour change)

How Does Air Pollution Concentrate In Cities And Affect Health?

1. Air pollution is one of the most significant environmental risks to health.
2. Air quality is commonly reported using the Air Quality Index (AQI), which converts pollution levels into a single scale to show how harmful the air is to human health, with higher values indicating greater risk.

PM2.5 is a key urban indicator

1. PM2.5 (particulate matter smaller than 2.5 micrometres) is one of the main pollutants used to calculate the AQI.
2. AQI values often rise sharply when PM2.5 concentrations increase, because these particles are small enough to penetrate deep into the lungs and enter the bloodstream.
3. Many cities track air quality using average PM2.5 concentration measured in $\mu g/m^3$.
4. Some countries have very high average PM2.5 levels in urban areas (for example Pakistan, Qatar, Afghanistan, Bangladesh, Egypt), while others are much lower (for example Australia, Brunei, New Zealand, Estonia, Finland, Canada).

Urban green spaces help regulate air quality

1. Urban growth often reduces green space as land is needed for housing and infrastructure.
2. This can worsen air pollution because vegetation can help trap particulates and support cooler, healthier urban microclimates.

How Does Traffic Congestion Increase Emissions And Urban Stress?

1. Congestion has social, economic, and environmental impacts.
2. In fact, the average US commuter wastes 42 hours per year stuck in traffic (and the situation can be similar or worse in many less economically developed contexts).

Why congestion happens in different places

1. In many lower economically developed countries (LEDCs), congestion often rises quickly due to rapid urban growth without adequate forward planning and infrastructure, plus rising incomes increasing vehicle ownership.
2. In many more economically developed countries (MEDCs), congestion is strongly linked to commuting, with people living further from work and often choosing to travel by car.
3. When cars spend longer on the road and idle more, they emit more pollutants.
4. Vehicle exhaust contributes to major greenhouse gases and pollutants such as carbon dioxide, nitrogen oxides, and particulate emissions, which degrade air quality and can contribute to respiratory disease.

How Do Pollution And Inequality Reinforce Each Other In Urban Areas?

1. Pollution is not experienced equally, with urban areas often showing high levels of social and economic inequality, meaning unequal access to housing, jobs, education, and environmental quality.
2. In many MEDCs, inner-city areas can experience high deprivation due to older housing and long term industrial decline.
3. This includes overcrowding, higher death and infant mortality rates, social segregation, and persistent unemployment.
4. These factors can combine in a cycle of deprivation, where disadvantage in one area makes other disadvantages more likely.
5. In many LEDCs, rapid urbanization can lead to slums, shanty towns, and squatter settlements, often linked to rural to urban migration.
6. These communities may face:
   1. Higher exposure to polluted air (near roads, industry, open burning)
   2. Inadequate sanitation and waste collection
   3. Greater vulnerability to floods and contaminated water
   4. Limited access to healthcare

Case study

• Delhi
  • Delhi shows how pollution and inequality overlap in large cities.
  • Rapid urbanization and migration have led to the growth of informal settlements near major roads, construction sites, and industrial zones.
  • Residents in these areas are exposed to extremely high air pollution from traffic, open burning, and nearby industry.
  • Many settlements lack reliable waste collection, sanitation, and drainage, increasing exposure to contaminated water and disease.
  • Limited access to healthcare means pollution-related illnesses such as asthma and respiratory infections are more severe and long-lasting.
  • These conditions reinforce a cycle of deprivation, where poor environmental quality worsens health, reduces employment opportunities, and deepens inequality.

How Does Pollution Link To The Sustainable Development Goals

1. Air pollution links directly to several Sustainable Development Goals (SDGs):
   1. SDG 11 (Sustainable Cities and Communities): city air pollution levels are used as an indicator of urban sustainability.
   2. SDG 7 (Affordable and Clean Energy): access to clean household fuels and technologies is an indicator for sustainable energy.
   3. SDG 3 (Good Health and Well-Being): mortality due to ambient and household air pollution is used as a health indicator.
2. Pollution is therefore as much a development issue as it is an environmental one, affecting health outcomes and living conditions.

How Does Pollution Contribute To Climate Change And Wider Environmental Change?

1. Some pollutants directly harm health (like PM2.5), while others change Earth's climate by enhancing the greenhouse effect.
2. Notable impacts include:
   1. Average global temperature increased by about $0.85^{\circ}C$ between 1880 and 2012
   2. Global mean sea level rose by 19 cm between 1901 and 2010, as oceans warmed and ice melted
   3. Global CO$_2$ emissions increased by almost 50% since 1990, with faster growth between 2000 and 2010 than in previous decades
3. These trends are linked to human activities including industrialisation, deforestation, and pollution, which increase concentrations of greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapor.

How Does Water Pollution From Farming And Irrigation Show Trade-Offs In Resource Use?

Pollution also affects freshwater systems, where rising demand for food and water increases pressure on rivers, lakes, and groundwater.

Intensive agriculture pollutes water

1. To increase yields, intensive agriculture can involve land clearance and heavy water use.
2. This includesL
   1. Deforestation reduces tree cover, increasing soil erosion.
   2. Eroded soil becomes sediment run-off, which enters rivers and lakes, harming water quality.
   3. Inefficient irrigation can cause fields to become waterlogged.
   4. Waterlogging and repeated evaporation can increase salinization (salt build-up), which can make soils infertile.
   5. Sediment and higher salt levels can damage freshwater ecosystems and reduce the usefulness of water for people.

How Can Pollution Be Managed?

Because pollution has multiple causes, solutions usually work best as a package rather than a single fix.

1. Reducing pollution at source
   1. This is often the most effective approach:
      1. Shifting to clean energy for households and industry
      2. Improving vehicle standards and fuel quality
      3. Relocating or regulating high-polluting industry
      4. Reducing waste through reuse and recycling
2. Managing urban congestion
   1. Policies aim to reduce car dependence and idling:
      1. Invest in reliable public transport
      2. Design walkable, cycle-friendly streets
      3. Apply congestion charging or low-emission zones
      4. Improve land-use planning so homes, jobs, and services are closer
3. Protecting and expanding green space
   1. Maintain parks and urban trees
   2. Create green corridors along roads
   3. Protect existing green areas during redevelopment