Outdoor Air Pollution: Causes, Sources, Effects & Solutions

There’s two main types of air pollution – indoor air pollution, and outdoor air pollution.

This guide focuses on outdoor air pollution (also called ‘ambient air pollution’).

We look at what outdoor air pollution is, along with potential causes, sources, examples, effects, and potential ways to prevent, reduce or solve it.


(Note – outdoor air pollution is it’s own atmospheric issue, separate to other issues like greenhouse gases and a changing climate)


Summary – Outdoor Air Pollution

Outdoor air pollution is the release of harmful substances (pollutants) or biological molecules into the outdoor air/atmosphere

Variables in outdoor air pollution can be the levels of an individual pollutant in the air, and the sources they come from

Further to this, these variables differ in each town, city, country and geographic region across the world

Some pollutants are emitted directly (primary pollutants), whilst others form indirectly (secondary pollutants) from primary pollutants interacting or reacting with each other, and other compounds in the atmosphere or environment 

The main human source of outdoor air pollution is the combustion of fossil fuels (coal being one example, as well as natural gas, and oil) – in the generation of electricity, industrial activities, the operation of vehicles/cars, and so on.

Waste management and agriculture are two other potential common sources

In the US for example, it’s estimated that about one third of all air pollution comes from transport and vehicles

However, air pollutants also come from natural sources

Just a few examples are dust storms from open spaces of land without vegetation (which blow up dust), wild fires and forest fires, and volcanic activity

It’s also possible that air pollutants that originate indoors, may find their way into the outdoor air and become and outdoor air pollution issue.

These pollutants come a range of sources such as from burning fuel (wood, kerosene, and other solid ‘dirty’ fuels) in houses for cooking and heating (cookers, heaters, stoves and open fires) 

Air pollution can particularly be heavy around cities and heavily populated areas 

Vehicles and road transport tends to be the main source of outdoor air pollution in cities

Low to middle income communities of people where air pollution is already at unsafe levels, and groups of people living near highways, industrial sites, power plants, and other pollutant emitting sources, may be at higher risks of suffering from outdoor air pollution.

People with existing health conditions, and young children under 5 may also be more heavily affected by air pollution

Some people in some countries may suffer the effects of both indoor and outdoor air pollution

We can measure the levels of outdoor air pollution with an Air Quality Index, amongst other measures.

The level of each individual air pollutant on a given day, in a given area or city, can be measured, along with those levels of air quality that might mean for outdoor activity.

A general health rating for real time air quality levels may also be given.

Some cities, countries and regions in the world are far more polluted and have much worser air quality than others (for various reasons)

India, Pakistan, China, and parts of Africa feature in the top countries and regions in the world for particulate matter (PM) air pollution levels

Parts of the Middle East and South East Asia also rate poorly for general air pollution levels in some areas

One set of data shows that particulate matter is responsible for almost 60% of attributable air pollution deaths, whilst ozone is less than 4%. Indoor air pollution is attributable to almost 40%

About 80% of total outdoor pollution related premature deaths (about 3.8 million a year) are related to heart disease and stroke, with the remainder from respiratory illnesses and cancers

Fine particulate matter (PM2.5) might be the most harmful air pollutant to human health (Some of the cities with the worst PM2.5 pollution levels are in India)

Ground-level ozone is another air pollutant that can cause noticeable health issues for human (according to who.int)

Some organisations highlight air pollution as the greatest environmental risk to human health right now (but a changing climate may be the biggest risk in the future)

Air pollutants have the ability to contribute to premature deaths, and contribute to the development of human health conditions and diseases.

But, they can also cause issues for the general environment, wild life, economy, and other sectors of society too

There’s some question over how strongly premature deaths can be linked or attributed air pollution – because air pollution exacerbates pre-existing cardiorespiratory illnesses and other conditions

So, the question might be how much air pollution really contributes to premature death in these people – is it significant, or not significant? How strong is the attributable link? Why, or why not?

Additionally, what impact does different concentrations of air pollution really have on healthy people without pre-existing health problems?

There is a potential link between agriculture and air pollution. Agriculture is an emitter of nitrates into the air (from fertilizers) that can contribute to the forming of secondary air pollutants. But, also, there’s some evidence that ozone impacts agricultural productivity by impacting plants and soil

Cleaner energy and electricity sources (like renewables), and cleaner vehicle technology (developing electric battery, hybrid, hydrogen and other alternative fuel vehicle types) could go a long way to helping address outdoor air pollution

Anything which decreases the burning ‘dirty’ energy sources and fossil fuels seems a good starting point

There are other options too though, with trees and vegetation being one option that can absorb toxins and help purify air

There are cities worldwide that have implemented some solutions to outdoor air pollution, and have already experienced a reduction in pollutants.

Some of the cities with the most polluted air in the world have shown in the past that clean air can be achieved relatively quickly with efforts to clean up air quality

Air pollution can vary from day to day, and year to year in different geographic location (particularly if air quality measures are implemented in an area).

Real time air quality indexes can give an idea of the concentration of a particular air contaminant in a particular geographic area, on a particular day.

Weather can play a role in air pollution levels (winds for example can blow pollutants in and out of an area)

Overall, several sources that provide info on air pollution levels over time indicate that air pollution is generally declining globally over the past few decades in many countries.

For example the US has seen a decrease in PM 10 and 2.5 from 1980 to 2017.

However, in some low to middle income and developing cities and countries, it is increasing

Given that the global population is increasing, the % of the global population experiencing premature death attributable in some way to outdoor air pollution appears to be declining (even if total numbers of premature deaths are staying roughly the same or slightly increasing annually)


What Is Outdoor Air Pollution? 

Outdoor air pollution might be broadly classified as:

The release of harmful substances (such as gases), particles (organic and inorganic) and/or biological molecules into the outdoor air


The impact can be on humans and human health, wild life and living organisms, plant life and the environment, and the economy.

Air pollution can also impact aesthetics.


Primary Outdoor Air ‘Pollutants’ (Main Types Of Air Pollutants)

Primary outdoor air pollutants are emitted directly.


The primary outdoor air pollutants are:

Particulate matter (PM10, & also PM2.5) (small suspended particles of varying sizes)

Sulphur dioxide (SO2)

Nitrogen dioxide (NO2)

Ozone (O3)

Carbon monoxide (CO)

And, volatile organic compounds (VOCs)


Secondary Outdoor Air Pollutants

In comparison to primary pollutants, secondary air pollutants form from primary air pollutants reacting, mixing, or interacting in some way with each other, or with other atmospheric compounds.


Examples of secondary pollutants forming are … 

Oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain

Particulates created from gaseous primary pollutants and compounds in photochemical smog

Ground level ozone (O3) formed from NOx and VOCs

Peroxyacetyl nitrate (C2H3NO5) – similarly formed from NOx and VOCs

– wikipedia.org


One other example:

… SO2 and NOx can react in the Earth’s atmosphere to form particulate matter (PM) compounds

– OurWorldInData


Outdoor Air Pollutants vs Greenhouse Gases

There’s a difference between outdoor air pollutants, and (upper atmosphere) greenhouse gases.


Greenhouse gases (upper atmosphere gases) include:

– Carbon dioxide (CO2)

– Methane (CH4)

– Nitrous oxide (N2O)

– Ozone (O3)

– Synthetic gases like CFCs and HFCs


Human Sources & Causes Of Outdoor Air Pollutants

The main humans sources of outdoor air pollutants might be:

… most [outdoor air pollutants] are [by products of] human sources like fuel combustion and industrial (factories, business etc.) activities

– OurWorldInData


In cities specifically, the main source might be:

… in towns and cities, the main source of air pollution is road transport

– blf.org.uk


A fuller list of human sources may include:

Burning of fossil fuels [like coal, oil and natural gas] in electricity generation at power plants, in  transport from burning petrol and diesel (especially private motor vehicle transport), and also in industry, commercial (such as office buildings, especially efficiently designed ones) and households

Industrial processes and solvent use (e.g. chemical and mining industries)


Waste treatment (especially waste incineration)


Indoor Air Pollution Contributing To Outdoor Air Pollution

who.int indicates that indoor air pollution in the form of smoke for example can leak outside and contribute to outdoor air pollution.

It’s worth noting that some regions in the world with both poor indoor and outdoor pollution levels may suffer from both issues.


Natural Sources & Causes Of Outdoor Air Pollutants

Natural sources may include:

Volcanic eruption

Dust blown from one location to another in the air

Sea salt spray

Emissions of volatile organic compounds from plants, or biogenic emissions from vegetation (pollen and mould spores)

Smoke from bushfires


[In India, forest fires and dust storms are natural sources of air pollutants, whilst the topography in and around some regions and cities serves to trap air pollution over these areas]


Each Air Pollutant Can Have A Different Source/Cause

Each air pollutant:

– is made up of different chemicals

– can come from different activities and sources in different geographic areas

– and can have a different impact

They can also vary in concentration levels on any given day, in any given place.


Particulate Matter (PM10, & PM2.5) As An Air Pollutant

What PM Is, & What’s It Made Of?

Particulate matter … is extremely small solid particles and liquid droplets suspended in air.

The Health.NSW.Gov.Au resource outlines what chemicals and material particulate matter is made of 


Where It Comes From (Sources)

Particle pollution mainly comes from motor vehicles, wood burning heaters and industry (Health.NSW.Gov.Au)

Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles. Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires (EPA.gov)

The friction of brakes and tyres on the road also creates particulate matter (blf.org.uk)


Pollution Trends

[There’s been a decrease of both PM 2.5 and PM 10 when considering the] national average in the US from 1980 to 2017 (EPA.gov) 

[Comparatively] Particle pollution is a major air quality issue in Australia (Environment.gov.au)



Studies have linked exposure to particle pollution to a number of health problems [and vulnerable groups may involve] the very young and the elderly. Particle pollution is the major cause of reduced visibility (Environment.gov.au)


Ozone As An Air Pollutant

Also called ‘Tropospheric, or ground level ozone]


Where It Comes From (Sources)

… created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). It is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight (Epa.gov)


Pollution Trends

[It has decreased based on the] national average in the US from 1980 to 2017 (EPA.gov)



Ground level ozone can [affect the airways and breathing]. People with asthma and children, older adults, and people who are active outdoors, especially outdoor workers are most at risk (EPA.gov)


Nitrogen Dioxide As An Air Pollutant

Where It Comes From (Sources)

Comes from the burning of fossil fuels like coal, oil and gas [and] Most of the nitrogen dioxide in cities comes from motor vehicle exhaust (about 80%) 

[A small amount comes] from electrical storms via electrical discharge, and plants, soil and water [and] Other sources of nitrogen dioxide are petrol and metal refining, electricity generation from coal-fired power stations, other manufacturing industries and food processing.

Unflued gas heaters and cookers are the major sources of nitrogen dioxide in Australian homes 

– Environment.gov.au


Pollution Trends

[Has decreased when considering the] US national average … from 1980 to 2017 (EPA.gov)

In Australia, since the early 1990s [nitrogen dioxide has been at levels thought to] be acceptable for humans (Environment.gov.au)



[Can affect the respiratory system and the lungs]. People with asthma, and in particular children and older people are most at risk (Environment.gov.au)


Carbon Monoxide As An Air Pollutant

Where It Comes From (Sources)

[comes from the] combustion of [carbon containing] fuel such as natural gas, coal or wood [and] Vehicular exhaust contributes to the majority of carbon monoxide [roughly 50% in some years] (Wikipedia/Union Of Concerned Scientists, and NAP.edu)


Pollution Trends

[There’s been a decrease in the] carbon monoxide national average in the US from 1980 to 2017 (EPA.gov)

In most Australian towns and cities [levels are mostly below levels considered hazardous for human health, and only] some capital cities, have the potential to have harmful levels of carbon monoxide (Environment.gov.au)



Increased levels of carbon monoxide [can lead to reduced oxygen in the body], [but small increases in carbon monoxide only have minor effects]

People with heart problems are … [are] at greater risk of heart attack [and] Children and unborn babies are particularly at risk 

– Environment.gov.au


Sulphur Dioxide As An Air Pollutant

Where It Comes From (Sources)

[mainly] industrial activity that processes materials that contain sulfur, e.g. the generation of electricity from coal, oil or gas that contains sulfur. Some mineral ores also contain sulfur, and sulfur dioxide is released when they are processed (Environment.gov.au)

Sulphur dioxide can also be produced by volcanoes [but 99% comes from human sources] (Wikipedia.org)


Pollution Trends

In the US, sulfur dioxide emissions have been decreasing … (Statista.com)

Air quality regarding sulfur dioxide in improving in the US (EPA.gov)

In Australia … the highest concentrations of sulfur dioxide in the air are found around petrol refineries, chemical manufacturing industries, mineral ore processing plants and power stations … But, sulfur dioxide levels in air are not generally a problem in Australia (Environment.gov.au)



[Can impact breathing]. People most at risk [of developing problems] are those with asthma or breathing conditions (Environment.gov.au)


Volatile Organic Compounds As Air Pollutants

What They Are

VOCs comprise volatile hydrocarbons and other organic molecules released into the atmosphere (APIS.ac.uk)

SOE.environment.gov.au list some common VOCs


Where They Come From (Sources)

In the UK it is estimated that less than 5% of … VOCs … are emitted from vegetation. The rest comes from transport, including distribution and extraction losses (50%), solvent use (30%) and other industrial processes (15%). Road transport alone accounts for 30% of VOC emissions (APIS.ac.uk)

Pesticides that are sprayed on to fields and used to fumigate soil can give off chemicals called volatile organic compounds, which can react with other chemicals and form a pollutant called tropospheric ozone. Pesticide use accounts for about 6 percent of total tropospheric ozone levels (wikipedia.org)


Pollution Trends

… concentrations of many VOCs are consistently higher indoors (up to 10 times higher) than outdoors ( SOE.environment.gov.au)



Different VOCs have different health effects, and range from those that are highly toxic to those with no known health effect … (SOE.environment.gov.au)


Impact Of Outdoor Air Pollution On Humans & Human Health

There’s two main effects outdoor air pollution can have on human health:

– Attributable deaths 

– Contribution to health conditions and diseases like respiration conditions, cancers, lung disease, cardiovascular disease, and so on


Air Pollution As The Greatest Environmental Risk To Human Health

The World Health Organisation (WHO) highlights air pollution as the greatest environmental risk to human health [note that this is based on current risk, and that longer-term environmental threats such as climate change may exceed this in the future] 

– OurWorldInData/WHO


Crop Productivity

Ozone also [has the ability to impact] crop productivity (who.int)


What Is The Most Harmful Outdoor Air Pollutant For Humans & Human Health?

Fine particulate matter and ozone might be two of the most detrimental air pollutants.

But, particulate matter and indoor air pollution are by the major concerns.


… fine particulate matter (PM2.5) [is] the most health-harmful air pollutant [and, a major reason is that it can cause premature death in humans exposed to it via respiratory illnesses and cancers] 

Ground-level ozone … is another health risk, raising rates of asthma and chronic respiratory illness as well as other sorts of breathing problems and reduced lung function

– who.int


The three key sources of air pollution deaths are from the indoor burning of solid fuels (indoor air/household pollution), exposure to ambient outdoor ozone (O3), and ambient outdoor particulate matter (PM) pollution.

In 2015, deaths from these 3 pollutants were as follows (as total %’s):

Particulate Matter – 57.54%

Indoor Air Pollution/Solid Fuels – 38.72%

Ozone – 3.45%

– OurWorldInData


Number Of Human Deaths Outdoor Air Pollution Contributes To Per Year

Worldwide, ambient air pollution contributes to 7.6% of all deaths in 2016 

– who.int


Some 3.8 million premature deaths annually are attributed to outdoor (ambient) air pollution.

About 80% of those deaths are due to heart disease and stroke, while another 20% are from respiratory illnesses and cancers related to exposure to fine particulate matter (PM2.5)

– who.int


The World Health Organization estimate that 3 million people die from ambient outdoor pollution every year

– ourworldindata.org


Outdoor Air Pollution vs Indoor Air Pollution: Comparing Contribution To Premature Human Deaths

According to ourworldindata.org:

‘It’s estimated [air pollution contributes to] seven million premature deaths every year (4.3 million from ambient outdoor pollution, and 2.6 from households)


According to who.int:

Exposure to outdoor air pollution results in 4.2 million deaths every year

Exposure to smoke from dirty cookstoves and fuels in households indoors results in 3.8 million deaths every year 


Challenges In Reporting Deaths Attributable To Outdoor Air Pollution

It is important to emphasize the challenges in reporting on deaths attributable to air pollution …


A ‘death’ from air pollution is defined as someone who dies prematurely (could be in the range of months or years) than would be expected in the absence of air pollution] 

In many cases, air pollution exacerbates pre-existing cardiorespiratory illnesses—individuals suffering from asthma, for example, are particularly vulnerable.

– OurWorldInData, and StateOfGlobalAir.org


Environmental Impact Of Outdoor Air Pollution

[In addition to human health] Outdoor air pollution can [also] damage ecosystems, food crops and the built environment 

– OurWorldInData/WHO


Air pollutants like nitrogen dioxide, and sulfur dioxide also mix with other pollutants and compounds, and water, to contribute to acid rain, and this contributes to the acidification of natural water sources and soils.


Economic Impact Of Outdoor Air Pollution 

Air pollution [as a whole] costs the world economy $5 trillion per year as a result of productivity losses and degraded quality of life (wikipedia.org)


The Relationship Between Air Pollution And Agriculture/Food Production

There is a relationship between food production and air pollution – they both have the ability to contribute to and impact each other. 


Agricultural air pollution comes mainly in the form of ammonia (NH3), which enters the air as a gas from heavily fertilized fields and livestock waste.

It blows in over cities, reacts with emissions of oxides of nitrogen (NOx) and sulphur (SO2)  from traffic and industry, and leads to the formation of … secondary particles

– airclim.org


Agriculture is the single largest contributor of ammonia pollution as well as emitting other nitrogen compounds … This affects soil quality and thus the very capacity of the soil to sustain plant and animal productivity

… there is increasing evidence that food production is also threatened by air pollution. Ozone precursor emissions (nitrogen oxides and volatile organic compounds) are of particular concern for global food security as these compounds react to form ground-level ozone. This, in turn, penetrates into the plant structure and impairs its ability to develop

– unece.org


In India in 2014, it was reported that air pollution by black carbon and ground level ozone had reduced crop yields in the most affected areas by almost half in 2011 when compared to 1980 levels

– wikipedia.org


How Many Cities Worldwide Have Polluted Outdoor Air?

[from a survey with a sample size of] 4300+ cities worldwide, only 20% of the urban population surveyed live in areas that comply with WHO air quality guideline levels for PM2.5.

Average particulate air pollution levels in many developing cities can be 4-15 times higher than WHO air quality guideline levels, putting many at risk of long-term health problems

– who.int


Which People Might Be Most At Risk From Outdoor Air Pollution?

Some of the people that might be most affected might be:

People living in areas close to air pollutant emitting sources

People in developing cities

People in low to middle income areas

People with pre existing health conditions (particularly respiratory conditions)


Possibly the elderly


[ … neighbourhoods, cities and people might be at more risk if they are] sited near environmental hazards, such as highways, power plants, and industrial complexes

– who.int


Lower income and developing areas, as well as children might be most at risk:

The problem is even more acute in the developing world … Children under age 5 in lower-income countries are more than 60 times as likely to die from exposure to air pollution as children in high-income countries

– wikipedia.org


Countries, Cities & Regions With The Most Outdoor Air Pollution

Regions with the highest particulate matter pollution include cities in India, Pakistan, China, and parts of Africa feature in the top regions

11 of the 12 cities with the worst PM2.5 pollution are in India

China, and parts of the Middle East, Africa & South East Asia also have cities with poor outdoor air pollution levels


You can read more about countries, cities and regions where outdoor and indoor air pollution might be the worst in this guide.


According to OurWorldInData are:

… majority of pollution-related deaths are in Asia – South, Southeast and East Asia alone accounted for nearly 3 million in 2016.

You can read more about air pollution related deaths by type, country and more here (ourworldindata.org)


The most polluted city in a 2016 report, Zabol in Iran, has had its pollution level cut fourfold in the latest version of the database, and now appears to be cleaner than Australia’s capital Canberra

Based on the amount of particulate matter under 2.5 micrograms found in every cubic metre of air, Indian regions and cities are the most polluted in the world in 2018, followed by China.

Some places in Saudi Arabia are also highly polluted

– WeForum.org


Egypt, Mauritania, Libya, Niger, Cameroon and Pakistan also show high mean annual averages of migrograms per cubic meter of PM 2.5 air pollution in 2015 

Some of the least polluted countries in the world in terms of mean annual averages of migrograms per cubic meter of PM 2.5 air pollution in 2015 are Kirbati, Samoa, Brunei, Solomon Islands, Sweden, Finland, Australia, Canada, United States, New Zealand, Norway, Spain, and Iceland. 

– OurWorldInData


Impact Of Weather On Air Pollution Levels

It’s important to note that there is an additional key factor at play, which has some impact on pollution concentrations over time and space: the weather.

Local weather conditions, and seasonal and weather patterns have an important influence on the year-round fluctuations in exposure levels reported in each place

– OurWorldInData


How To Measure Outdoor Air Pollution (Air Quality Index), & What Level Of Air Quality Is Safe?

The air quality in a particular geographic location gives an indication of how safe the air is to breathe in that area.

An Air Quality Index is a common measure of air quality in several countries.

The AQI usually monitors and reports on the levels of individual air pollutants in the air, and provides up to date health ratings of air pollutant levels. 

There are large online global sites that keep track of the Air Quality Index (such as WAQI, Airnow and AQICN), and individual governments in countries and cities also have their own tracking programs.

The NSW Government in Australia for example has their own air monitoring networks where they measure particles (PM10, PM2.5), sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2) and visibility. 

The major pollutants that are measured in the air in the US are ozone, particulate matter (PM2.5 and PM10), carbon monoxide, and sulfur dioxide.

Other countries may use other air quality/air pollutant indexes to measure air quality, such as the Air Quality Health Index (Canada), the Air Pollution Index (Malaysia), and the Pollutant Standards Index (Singapore) + others.

Some of these other countries measure nitrogen dioxide as well.

Air Quality sites usually list key indicators such as main air pollutants of concern, what to do in the event of certain levels of air pollution, and more.

Read more about air pollution and air quality in this guide.


How To Reduce Outdoor Air Pollution (Potential Solutions)

There are cities worldwide that have implemented solutions to air pollution, and have already seen a reduction in air pollutants.

Cities in Spain, Portugal, Canada, Colombia and South Korea are some of the locations that have seen some sizable reductions.

Some of the solutions that have enabled these cities to achieve these reductions involve:

Adding plantlife, tree cover and greenery

Reducing the use of personal vehicles (especially those that use fossil fuel like petrol and diesel)

Substituting some fossil fuel vehicles with electric vehicles

Introducing better public transit systems

Encouraging the use of bikes and car sharing

Retrofitting buildings with more energy efficient designs and equipment

Introducing programs to encourage the saving of energy


Other potential solutions may include:

Using clean energy for electricity generation, households, business and industrial activity, and so on

Reducing emissions from the agricultural sector

Reducing emissions from the waste management sector

Reducing the total number of vehicles used in cities, or the per capita number of vehicles

Increasing the fuel efficiency of vehicles, and reducing emission rates

Using air pollution control devices in industry and transport – particulate control (precipitators, baghouses, scrubbers, collectors), scrubbers, NOx control, VOC abatement, Acid gas control, mercury control, dioxin control and so on


Where it is hard to reduce emissions significantly from or in any one activity, process or geographic locations, people may look to move to areas where the air is cleaner and better quality for breathing in.

For lower income and poorer neighborhoods and groups of people, this is obviously a major issue they may not be able to address themselves, and they will need some type of external (government assistance, private project funding, or something else) to help them with a viable solution to air pollution problems that could be a threat to their health if they stay where they are.


Solutions Specifically To Reduce Air Pollution From Transport

Some specific solutions for transport pollution might involve:

Focus on cities and heavily populated areas, or areas dense with people as places where the biggest improvement in pollution reduction could take place (as this is where a lot of transport pollution happens)

Focus on the main polluting sources of transport – which tend to be road transport such as cars and trucks. But, in addition to road, look at reductions air, water, rail, and so on

Consider the impact of freight/shipping transport pollution, and not just personal transport [when looking at greenhouse gas emissions, freight transport can make up as much as 41% of emissions in some countries – so, it’s likely air pollution numbers could be similar]

Consider cutting down consumption of fossil fuels and consumption related to car usage as the main strategy, compared to simply trying to convert to electric transport and alternative fuel transport. Reducing the total number of vehicles, reducing distance travelled, and reducing the amount of fuel being used per year will all likely lower emissions more significantly than switching to alternate fuel sources

One way the above could be achieved is with more focus on walking, riding and other human powered forms of transport

Focus on pollution rates per passenger mile travelled as another key statistic – different modes and models of transport have different rates to be aware of (fuel and passenger efficiency of transport is important in this regard)

Consider how hybrid, electric vehicles, hydrogen vehicles and other alternative fuel vehicles can be used most effectively, and how they can become more feasible to use long term

Consider how effective redesigns and new features like regenerative braking and fuel efficiency can be

Encourage better city planning – re-designing inner city and urban area for less congestion, less built up traffic, more efficient driving without as much stopping, starting, braking and acceleration

Consider how urban and CBD areas can be more friendly to walking, biking and public transport

Focus on the operation/use stage of transport, as this is where a significant portion of pollution occurs. But, also look for opportunities to reduce pollution at the other stages such as mining and sourcing of materials, fabrication and manufacture, disposal and recycling etc. for opportunities for pollution reduction

Maintain and improve vehicle emission and air quality standards, policies, regulations and legislation 

Look outside of the transport sector for more effective ways to reduce pollution – for example, is it better or more cost effective to focus on reducing pollution from stationary power plants that run on fossil fuels than cars and vehicles? Some scientists and researchers think so

Inform and educate the public on how they can personally reduce pollution and emissions buy using cars less, driving less, maintaining their vehicles, buying ‘greener’ cars and knowing what to look for etc. And, have some way for governments or third party organisations to relay to the public progress of transport pollution over time


Other options and solutions might include …

Pollution control/capture technology on power plants, on vehicles (cars and trucks)

Regulations and policies to support air pollution control

Cleaner energy and fuel – for power plants and vehicles

More efficient energy and fuel (that gets similar output for less energy used)

Improved design on vehicles that helps with efficient burning of fuel (engine, tires, aerodynamics, etc), as well as keeping cars maintained

Modes of transport such as public transport that might help lower per passenger air pollution footprints


Vehicle emission standards have helped cut pollution from cars and trucks by about 90 percent since 1998, with further improvements coming from the Tier 3 standards.

– ucsusa.org


General Air Pollution Trends

As a % of the overall global population, death rates attributable to air pollution look to have decreased over the last few decades.

However, it does also look like in some low to middle income countries, air pollution levels have become worse in the last few years as well. 


Death rates from air pollution—across countries of all income levels [have declined over the] last few decades … [usually] by more than 50 percent.

Globally, it’s estimated that outdoor air pollution resulted in 4.2 million deaths in 2016; this represents an increase from 3.4 million in 1990 [however, it should be considered that the global population has increased in that time]

– ourworldindata.org


[in some] low to middle income cities … air pollution has become worse over the past several years

– who.int


OurWorldInData also shows levels of the different levels of different air pollutants over the years.

You can see that there was a huge increase up until 1970/1980 for most regions, followed by a steady decline (ourworldindata.org)

Although some pollutants have decreased since 1980, there has been small increases or flatlines in progress in the years before 2017.

Particulate matter 10 levels are one example of this – with minimal progress being made since 2004.




1. Hannah Ritchie and Max Roser (2018) – “Air Pollution”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/air-pollution’ [Online Resource]

2. http://www.health.nsw.gov.au/environment/air/Pages/outdoor-air-pollution.aspx

3. https://www.blf.org.uk/support-for-you/air-pollution/where-does-it-come-from

4. https://www.environment.nsw.gov.au/topics/air/monitoring-air-quality

5. http://www.environment.gov.au/protection/publications/factsheet-sulfur-dioxide-so2

6. http://www.environment.gov.au/protection/publications/factsheet-nitrogen-dioxide-no2

7. https://en.wikipedia.org/wiki/Air_pollution

8. https://archive.epa.gov/ozonedesignations/web/html/faq.html#whatisozone

9. https://www.climatechangeinaustralia.gov.au/en/climate-campus/climate-system/greenhouse-gases/

10. http://www.health.nsw.gov.au/environment/air/Pages/particulate-matter.aspx

11. https://www.epa.gov/pm-pollution/particulate-matter-pm-basics#PM

12. https://www.nap.edu/read/10378/chapter/3

13. http://www.apis.ac.uk/overview/pollutants/overview_VOCs.htm

14. https://www.statista.com/statistics/501303/volume-of-sulfur-dioxide-emissions-us/

15. https://www.epa.gov/air-trends/sulfur-dioxide-trends

16. https://www.epa.gov/air-trends/nitrogen-dioxide-trends

17. https://www.statista.com/statistics/501284/volume-of-nitrogen-oxides-emissions-us/

18. https://www.epa.gov/air-trends/ozone-trends

19. https://www.epa.gov/air-trends/carbon-monoxide-trends

20. https://www.epa.gov/air-trends/particulate-matter-pm25-trends

21. https://www.epa.gov/air-trends/particulate-matter-pm10-trends

22. https://www.dec.ny.gov/chemical/66472.html

23. https://www.epa.gov/ozone-pollution/health-effects-ozone-pollution

24. http://www.environment.gov.au/protection/publications/factsheet-carbon-monoxide-co

25. https://soe.environment.gov.au/theme/ambient-air-quality/topic/2016/volatile-organic-compounds

26. https://www.weforum.org/agenda/2018/05/these-are-the-worlds-most-polluted-cities

27. https://www.who.int/sustainable-development/cities/health-risks/air-pollution/en/

28. https://www.eea.europa.eu/themes/air/air-pollution-sources

29. https://www.bettermeetsreality.com/how-to-reduce-solve-air-pollution-with-examples-of-cities-that-have-already-done-it/

30. https://www.bettermeetsreality.com/countries-cities-with-the-worst-ambient-outdoor-air-pollution-household-indoor-air-pollution/

31. https://www.who.int/airpollution/en/

32. https://www.bettermeetsreality.com/what-level-of-air-quality-pollution-is-safe-for-us-to-breathe-live-in/

33. https://www.unece.org/environmental-policy/conventions/envlrtapwelcome/cross-sectoral-linkages/air-pollution-and-food-production.html

34. http://www.airclim.org/acidnews/agriculture-major-cause-air-pollution

35. https://www.bettermeetsreality.com/impact-of-transport-vehicles-on-the-environment/

36. https://en.wikipedia.org/wiki/Environmental_impact_of_pesticides#Air

37. http://www.pollutionissues.com/Ve-Z/Vehicular-Pollution.html

38. https://en.wikipedia.org/wiki/Environmental_impact_of_transport

39. https://www.ucsusa.org/clean-vehicles/vehicles-air-pollution-and-human-health#.XGIFv-IzbR0

40. https://www.epa.vic.gov.au/your-environment/air/vehicle-emissions-and-air-quality

41. https://sciencing.com/effects-car-pollutants-environment-23581.html

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