Air pollution is the worst single environmental health problem in the world, here's a guide of six simple measures that city administrations can take to reduce the burden starting today.

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Air pollution is much worse than many of us realise. This year the World Health Organisation (WHO) named air pollution as the world’s largest single environmental health risk. Yet many of us remain unconcerned. Media images of smog-filled industrial cities such as Guangzhou in China or Ahwaz in Iran perversely reassure those living in cities free from visible air pollution that they are not exposed to noxious levels of emissions. 

Just because you cannot see it does not mean it’s not there. A recent WHO investigation into air quality in cities across the globe found that “half of the urban population being monitored is exposed to air pollution that is at least 2.5 times higher than the levels WHO recommends.” This means that there is a high probability of city-dwellers living in neighbourhoods breaching air pollution legal limits or recommendations, and yet air quality repeatedly fails to make lists of people’s major environmental concerns. In the UK, where the days of the smog filled industrial cities have been consigned to history, air pollution is twice as deadly as road accidents, and yet people remain more concerned about traffic safety.

The major air pollution problems in cities come from particulate matter and gas. Particulate matter, or PM, floats through the air as a fraction of the size of human hair, and can be caused by vehicle exhausts, burning carbon such as wood, or smelting metals. Gases affecting air quality and human health such as nitrogen dioxide are also the result of oil, gas and coal being burned at high temperatures, like in car engines. When absorbed through breathing these air pollutants are known to cause respiratory problems, heart attacks, and strokes, but have also been linked to autismschizophrenia, and dementia. The combination of these air pollution issues adds up to staggering health and economic costs.

BUT - it’s not all bleak. The good news is that this is not inevitable, and cities can actively reduce the toll of air pollution with simple solutions. There is not one solution, instead there are a network of solutions that should be pursued simultaneously. Here are a combination six things that all city administrations should be actively working on to improve air quality:

1. Reduce Traffic By Promoting Walking & Cycling

Image from irishcycle.com

Image from irishcycle.com

Making the city more accessible for cyclists and pedestrians is the most effective way of incentivising walking and cycling and discouraging car use. 

Fear of roads safety is a big problem, people’s perception of roads as dangerous is the main reason for them not cycling. A recent UK poll found that more than 60% of people who don’t already cycle regularly said they would if they felt safer, and another British survey found that news of bike crashes reduced bicycle trips by around a fifth. 

To reverse this, strong political will is needed to create the proper cycle infrastructure to ensure cycle safety. As Urban Times recently reported, a study looking at eight new segregated bike lanes across five US cities reported a 171% increase in bike traffic as well as a drop in the number of accidents. It’s no coincidence that the country with the highest number of cyclists per capita in the world, the Netherlands, is also the safest place to cycle. But, as the film below explains it was not always this way, it took a protracted campaign in the 1970s to develop the political will to change the country’s cycling culture.

Increasing the walkability of cities is also key to reducing car use. A series of simple but effective measures can all contribute to making the city more walkable. These include creating pedestrianised areas, increasing and enhancing crossings, introducing marked maps, improving pavements’ quality and size, and encouraging mixed-use developments that shorten travel distances for access to amenities. 

Legible street maps with walking times in London

Legible street maps with walking times in London

Of course walking and cycling not only reduce air pollution, but can contribute to what Charles Montgomery believes is a happier city (read an Urban Times interview with him here). And active transport lessens the burden of health problems such as diabetes, and can boost neighbourhood economies. The planner Jeff Speck suggests that 85% of money spent on driving leaves the local economy, and the UK Charity Sustrans says that annually £2 billion could be saved if parents ditched their cars and instead walked or cycled to school.

2. Eliminate Polluting Vehicles With Limited Access Zones

The concentration of polluting vehicles all in one place rapidly deteriorates air quality, and it is these concentrations of emissions that is truly problematic for health. Limited Access Zones in cities have been successful tools in reducing both congestion and pollution. 

Piazza Maggiore, Bologna

Piazza Maggiore, Bologna

In London, UK Department for Transport figures show that the congestion charge, a measure that charges vehicles entering the centre of the city, has diminished traffic since its introduction. And yet the campaigning group Clean Air In London’s analysis found that in 2010 the city had the highest NO2 of any capital city in Europe. This mismatch in results may be because the congestion charge’s has only exclude lower income drivers and unnecessary journeys rather than deter the trips made by taxis and delivery lorries who depend on the centre of the city for business. The concentrations of these diesel-powered vehicles in the city is truly problematic for environmental health given diesel engines have been officially recognised as carcinogens since 2012.

Map of traffic control, Rome

Map of traffic control, Rome

Some cities have had more success in reducing air pollution through the introduction of limited access zones based on vehicle emissions. Bologna, Italy, is an example of a city that – like London – originally sought vehicle reduction measures to reduce traffic in the historical centre, but then successfully shifted the emphasis of its access zone to environmental concerns. Access criteria became the vehicle’s emission class, and not only was absolute traffic reduced by 23% or 31% (depending on the time of the day), but PM10 emissions were reduced by 47%, and the city’s comprehensive approach to pollution won it the European Mobility Week Award in 2011.

Low emission zone sign, Berlin

Low emission zone sign, Berlin

Other cities like Berlin and Stockholm have also introduced wide-ranging low emissions zones to great effect. Stockholm’s measures have achieved considerable falls in nitrogen dioxide and PM, and Berlin’s ban of all diesel vehicles and petrol vehicles without a closed loop catalytic converter has been equally successful.

3. Establish A Construction Industry That Respects Air Quality 

Construction worker in Xinjiang, Uighur Autonomous Region, China (Stringer/Reuters)

Construction worker in Xinjiang, Uighur Autonomous Region, China (Stringer/Reuters)

A clean construction industry is a key aspect of improving air quality in cities, both in the energy efficiency of new buildings as well as the process of construction itself. As construction and demolition activities can cause serious air quality issues, releasing site dust, wood dust, grit, and sand, all cities should ensure that no new developments breach limits of air quality. And this needs to be accompanied by focusing on the construction of energy efficient buildings. 

Examples of cities taking bold moves can be traced to the 1990s when Manila in the Philippines banned the construction of new incinerators and Freiburg in Germany became one of the first cities to adopt a resolution only permitting low energy buildings in new development schemes. Freiburg’s Vauban district, a new neighbourhood that resulted from this legislation, is entirely composed of buildings meeting minimum low energy consumption standards. Grey-water is recaptured after cleaning, and heat is generated by a woodchip-powered combined heat and power generator connected to a district heating grid. All the houses have their organic waste treated with an anaerobic digester that generates biogas, which is in turn used for cooking, a truly circular process.

Vauban, Freiburg

Vauban, Freiburg

In London, campaign pressure saw the Air Quality Neutral provision integrated into the Mayor’s London Plan for all new major developments. As the plan states ”benchmarks have been produced for buildings’ operation and transport across London based on the latest technology … Where schemes do not meet the ‘air quality neutral’ benchmarks, after mitigation measures have been implemented on-site, the developer will be required to off-set emissions off-site.” These off-setting measures include green planting, retro-fitting abatement technology for vehicles, and upgrading or abatement work to combustion plants.

4. Stop Building Roads

Image from Communicare Pensando

Image from Communicare Pensando

Road building has been historically employed by cities to fight congestion and add capacity. As with many other historical phenomena, road building with this purpose continues to repeat itself today. Last month London’s Mayor Boris Johnson unveiled a plan for a new network of motorway tunnels under London, saying “It’s about freeing up capacity on the city surface, improving air quality, and reclaiming space for public parks, pedestrians and cyclists.”

At first glance this seems like a great idea, but study after study suggest that increasing road capacity only worsens air quality. As Todd Litman asserts in the conclusion of his study, Generated Traffic and Induced Travel, “Increasing road capacity allows more vehicle travel to occur.  In the short term this consists primarily of generated traffic … Over the long run an increasing portion consists of induced vehicle travel, resulting in a total increase in regional vehicle miles travel.”  This outlooks is shared by Gilles Duranton and Matthew Turner who suggest that ”where the extension of most major roads is met with a proportional increase in traffic.” Of course, increased circulation and more vehicle miles travelled means more emissions and air quality deterioration, precisely the opposite of what many city administrations may hope to achieve with road building schemes.

Unfinished freeways, Cape Town. Photo: Sandiso Phaliso/WCN

Unfinished freeways, Cape Town. Photo: Sandiso Phaliso/WCN

The evidence of road building worsening congestion is compounded by a 2012 Arizona transport report entitled Land Use and Traffic Congestion that found roads in denser and mixed-use communities tend to be less congested. This discovery inverts our perception of suburbs and garden cities as peaceful low-traffic places, warning against administrations green-lighting low-compact developments on the city periphery.

5. Retrofit Polluting Vehicles 

catalytic converter

catalytic converter

Nowadays many new vehicle models are being developed to run on cleaner fuels or as hybrids, but a significant proportion of global cities’ traffic runs on old polluting engines that are much more damaging to air quality than their modern counterparts. One solution to this issue could be to introduce incentives to retrofit these vehicles with filters and/or new engines to reduce their environmental health burden. 

The first major problem is diesel powered vehicles, especially older ones, which pollute more than newer engines, are less efficient, and cost more to operate. The US-based Diesel Clean-Up Campaign say that these vehicles “create a cancer risk that is seven times greater than the combined risk of all 181 other air toxics tracked by the Environmental Protect Agency.” Their campaign is centred on introducing retrofits to these vehicles, either in either through exhaust filters or engine replacement. 

It may seem like a costly job with an estimated 11 million old diesel vehicles still on America’s roads that could be around for several more decades, but the Diesel Clean-Up Campaign suggest that ”every dollar spent on reducing PM pollution from diesel engines, $12 would be avoided in monetised health damages.” In many places retrofitting actually helps boost the local economy. The result of Oregon’s Clean Diesel Initiative - which provides funds to local businesses as grants, low-interest loans or matched dollars to initiate retrofits or diesel engine replacements – has seen many businesses reduce their operational costs with significant fuel savings while eliminating large volumes of PM and nitrogen oxides from their environmental impact.

Diesel cleanup campaign

Diesel cleanup campaign

Old polluting vehicles are not limited to diesel. Many of the three-wheeler auto-rickshaws that feature heavily in the traffic of Asian cities run on two-stroke engines that according to the Scientific American ”cough up roughly 13 times more lung-damaging particulates than other engine types.” Despite the environmental toll of these vehicles and the introduction of newer cleaner models, getting rid of the old models is problematic because two-stroke engines are more straightforward mechanically, making them more popular as they’re cheaper to operate and repair.

Despite this polluting status quo, the World Resources Institute sees the rickshaw as crucial in the drive towards sustainable transport. Focusing their report on India, they recognise the importance of the tuk tuk in providing an alternative to private motor vehicle journeys while ensuring that all parts become accessible to public transport stations. So with the right vehicle upgrades to clean emissions, dramatic air quality improvements can occur. This is already happening, most notably in San Fernando, a city in the Philippines, where two-stroke tuk tuk drivers are offered cheap loans and free healthcare in exchange for upgrading to less polluting four-stroke machines

6. Green The City 

Maintaining and increasing green spaces in the city cannot be a solution in isolation for air pollution reduction, but planting can enhance air quality and help urban areas become resource efficient.

One of the most important things that vegetation in the city does is counteract the urban heat island effect. Concrete and tarmac absorb radiation and emit heat to increase the demand for cooling energy, accelerate the formation of smog, worsen heatwaves, and contribute to climate change. Plants on the other hand absorb radiation and emit vapour, and have cooling effect that can mitigate this urban heat island and decrease neighbourhoods’ demand for energy. So using plants to mitigate the heat island effect can reduce air pollution

Green wall Paris, photo – dinneratmidnight

Green wall Paris, photo – dinneratmidnight

Plants can also help absorb some emissions including PM and nitrogen oxides. Research from Lancaster University suggests that birch trees are particularly good at absorbing PM, “and the efficacy of roadside trees for mitigation of PM health hazard might be seriously underestimated.” And other research suggests that green walls as well as plants like ivy and algae, could be used to reduce street level concentrations of noxious emissions.

Chicago has been a pioneer on this front introducing measures that have seen it establish 5,469,463 square feet of green roof coverage in less than a decade. The city’s Green Roofs Initiative offers planning incentives in return for green roofs integrated into proposed schemes. These include a density bonus, allowing for an increase number of units allowed on a piece of property if 50% or 2,000 square feet (whichever is greater) of a roof is covered with vegetation. 

Other vegetation in cities that can reduce air pollution is urban agriculture. Farming in cities reduces the distance that food has to travel from source to plate eliminating many of the air pollution costs of long distance food transportation. Often urban farming is inhibited by old zoning laws, but some cities are actively changing rules to enhance this sustainable food source. Seattle, for example, changed its rules to facilitate the keeping of livestock and bees, established over eighty neighbourhood pea patches, and has community gardens that contribute large quantities of food to local food banks.

Urban farming

Urban farming

These are just a few suggestions, share your recommendations for city administrations in the comments below …