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land access rights

Land access rights in England and Wales severely restrict the public from freely accessing local outdoor green spaces for leisure and exercise. Improving these rights is crucial to moving towards a more sustainable outdoors that is fairer to people of different backgrounds, less polluted, and more natural. Recent campaigns which have gained popularity during the pandemic have called for more public and government action on this issue. In this article, we analyse various sources of public data to show that, while public appreciation of the outdoors and local nature has increased since the pandemic, there is a need to give the public wider access to paths and areas of land to sustain this trend. It is hoped that this article will promote awareness of the importance of land access rights in striving towards a more sustainable and fair outdoors for the population of England and Wales and inspire others to follow suit. 

The Benefits of Outdoor Spaces

Access to the outdoors, nature, and green spaces is vital to humans for exercise, mental well-being, creativity, and many other benefits. In the UK, not long ago, coronavirus-induced lockdowns removed the public’s freedom to explore the outdoors, forcing us to make the most of whatever local green space we had on our doorstep. However, two years of these restrictions have changed the UK’s attitudes and we can now expect more interest in exploring these local outdoor spaces for recreation and exercise. As well as the restrictions of the pandemic, increased awareness of sustainability and environmental issues amongst the population has also contributed to this shift. From a sustainability point of view, better access to local natural spaces is desirable, paving the way for a wide variety of social and environmental benefits:

It is unsurprising that access to and within local outdoor spaces highly depends on land access rights. However, in England, (figures are similar in Wales, but rights differ in Scotland and Northern Ireland), current rights dictate that the public have the right to freely access only 8% of land around the country and are excluded from the remaining enclosed private land under the fear of trespass. Such places include high-walled aristocratic country estates (G. Shrubsole, Who owns England?, 2019), golf courses or gardens hidden behind a National Trust membership. Campaigns, such as those of the Ramblers, Wildlife and Countryside Link and Right to Roam, are advocating for the reclamation of land to support nature and for public access, arguing for its environmental and health-related benefits as well as its historical and legal importance.

In this article, we argue that a data-backed approach can support these campaigns to reclaim local outdoor spaces. We present recent data reflecting how the public interact with the outdoors and nature around the country and discuss why this necessitates an improvement in land access rights in the UK.  land access rights

Image by Andrew Wang

Importance of Local Natural Spaces

During the multiple UK coronavirus lockdowns, UK restrictions prohibited travelling “outside your local area” to exercise and walk, and permitted local “public outdoor places” to stay open, including parks, “countryside accessible to the public”, gardens, and “the grounds of a heritage site”. This automatically highlighted the importance of having access to local outdoor spaces, which for most of the public meant nearby public urban parks and paths crossing local countryside, but for a select few, also the grounds of their own estates. 

Data collected during this time showed that the number of people around the country walking for leisure and exercise rose higher than before the pandemic, especially those getting out several times a week, with walking one of the few things one could do out of the house (Figure 1). Local green spaces were crucial in giving the public the opportunity to get outside and improve their mental health. Furthermore, another survey’s data showed that an increasing proportion of the public said that they were spending more time outside than before the pandemic. To encourage people to continue exploring and exercising outdoors and having an interest in nature after the pandemic, we must ensure that more natural spaces are accessible to the public in England and Wales (as explained here).

land access rights

Figure 1: Proportion of adults who walk for leisure averaged across all of England from 2016 to 2021, according to the Active Lives Survey by Sport England. This graph incorporates the recently released 2021 survey data not included on past reports; 2022 survey data is scheduled for release in summer 2023.

To support the idea that these outdoor spaces remain important even after the pandemic has ended, recent data presented in Figure 2 showed that both interest in exercising locally and leisure visits to green spaces has stayed at an elevated level compared to before the pandemic – in particular, local exercise interest remains at a statistically significant higher level than before. This suggests the prolonged importance of local outdoor spaces, supporting the focus on sustainable access to the outdoors long after the pandemic.

land access rights

Figure 2. Left: Google search interest in “walks near me” and “local walks”, according to Google Trends data from 2018 to present, inspired by this article. Each series is normalised according to its own data within the timeframe, so the units are arbitrary and comparison cannot be made between series. An unpaired t-test between pre- and post- pandemic search results suggests a highly statistically significant difference (p≈10-11) for both series (assuming stationarity). Right: proportion of adults who visited green and natural spaces for leisure in the past fortnight from April 2020 to March 2022 in England, according to the People and Nature Survey. This incorporates recently released monthly indicator data not presented on government reports. Data before this period is not available since the data was collected in a different format, and data after this period is unreleased. 

Towards A Public-Informed Approach to Land Access Rights

The data above has shown that green and natural spaces in the local area are important to people seeking to go outdoors for leisure and have an interest in nature. However, the public is legally barred from setting foot on the vast majority of the outdoors around the country – 92% – because of poor land access rights dictating the few places granted access to the public and defining the rest as trespass. In this section, we consider a direction for a possible solution.

In line with the data-backed approach of this article, we compare where there is land granted public access by law with where the public are actually walking and moving. The hypothesis is that there may be private paths or areas of land which show public activity, whether out of convenience, unawareness, or simple desire to explore local green spaces. Surely land access rights should evolve to reflect and protect by law the places where people want to walk? Suggestions from these findings could then strengthen existing campaigns to reclaim private areas for the public, such as that of the Ramblers.

For our approach, we take the English and Welsh network of publicly accessible paths, called public rights of way (PRoW), as a proxy for land access. As a simple illustrative analysis using openly available data, we compare the rights of way network with a large dataset of public GPS traces recorded around the country by members of the public. Example results for Bedfordshire are shown in Figure 3.

It must be mentioned that there are many other interesting data-oriented avenues of highlighting regional need for access to outdoors spaces. For example, in hyper-urban settings such as Greater London, a tool was built to suggest areas for green space creation based on current green space access and demand, pollution and land availability.

 Figure 3. Interactive map showing GPS activity recorded by the public (such as walking, running and cycling) in Bedford and Central Bedfordshire up to 2013, taken from a dump of GPX file data from OpenStreetMap in 2013. Black represents activity data that coincides with public rights of way, that is, where the activity was legal. Red/magenta represents activity data that does not, that is, where the activity counted as trespass. Deeper red indicates higher activity levels. Read more and get started with analysing other areas by following the instructions in the code: github.com/Andrewwango/prow-ml

We see that, while most activity coincides with where it is legal (and often signposted), there are paths of interest that are not public, which therefore can be fenced or blocked without notice. For such a path, this information could be used to support a campaign to change their status, especially if the path has already been identified as, for example, a former historic right of way (cf. the Ramblers). Of course, our identified paths will inevitably be a subset of all possibilities since trespass that is recorded is a subset of the total desire to trespass.


Nature should be accessible for all, and survey data presented in this article has shown us that the public’s interest in nature and accessing the outdoors for exercise and recreation locally is now higher than before the pandemic. This is important in moving towards a more sustainable approach towards the outdoors. 

The limited public land access rights in England and Wales mean that for the majority population, access to much of the outdoors and countryside is illegal, behind closed doors or subject to a fee. By looking at data showing public activity on footpaths, we can identify possible paths to protect with the status of being free for the public to access. 

There is much more work to be done in providing fairer access to the outdoors in England and Wales. For readers from other countries, I would love to hear about attitudes towards how land access rights shape the sustainability of the outdoors – please get in touch!

Featured image by Andrew Wang

Note: all statements about availability of released data is true as of date of publication.

You might also like: Indigenous Community Wins Recognition of its Land Rights in Panama

Nineteen of the twenty hottest years on record have occurred since 2001, not including 2020 which is on track to top the list. Now, research has found that Saudi Arabia might face deadly heat by 2070. 

Earth.Org takes a closer look.

This case study is based on the paper “Future of the human niche”, published in PNAS by Xu, Chi et al. (2020). 

As a species, we have historically avoided living outside of mean annual temperatures (MATs) between ∼8°C to 20°C. MATs above 29°C, found only in parts of the Sahara and Saudi Arabia, mean deadly levels of summer heat. The hottest inhabited place on Earth today is the city of Mecca in Saudi Arabia, whose MAT stands at 30.5°C, and stays above a 34°C average between May and September. Even in such conditions, an average 2 million Muslim pilgrims go each year, densely packing the streets in temperatures that can reach 54°C.

A decisive factor in whether temperatures go beyond human tolerance is humidity. When high enough and combined with extreme heat, it can inhibit the body’s ability to cool itself off through sweating. With the exception of its western coast, the Kingdom of Saudi Arabia has an arid desert climate with extreme heat during the day, replaced with low temperatures at night and very little rainfall. Lower humidity makes the heat more bearable to a degree, but even healthy, fit individuals need to avoid extended exposure to peak summer heat. 

Hotspots are concentrated along the Southern Red Sea coast, where temperatures are as bad as it gets, so global warming won’t mean higher temperatures, but rather longer periods of intolerable heat. Some places stay cool, like the government officials’ summer favorite, Riyadh (MAT 28°C), though most cannot afford this luxury. Climate change is set to level the playing field by covering over half of Saudi Arabia in potentially deadly heat by 2070. Saudi Arabia summers 2070

The Saudis haven’t “grown used to” these conditions and simply managed, but rather have developed the necessary infrastructure to counter the problem. Most people can move between home and work without ever leaving an air-conditioned space, though ironically, emissions for such extensive AC networks are adding to the problem. The government is considering more efficient systems that could significantly reduce environmental impacts, though whether this will stop temperature rise is doubtful.

There is still a relatively large proportion of Saudi Arabians living in rural areas, where heat mitigation comes through intelligent building and street design, or traditionally vetted nomadic strategies. These people represent a more vulnerable segment because AC may not be accessible to all of them, and extreme heat is likely to destroy agricultural livelihoods.  

Saudi Arabia summer heat vulnerable population

Proportion of Saudi Arabians exposed to MATs above 29°C, with the portion of those highly vulnerable due to decreased access to heat mitigation. Population numbers based on UN predictions for population growth by 2070.

Of course, it is likely that the Saudi government will implement AC for all of its inhabitants by 2070, thus fixing the problem. But picture a world in which you spend 5-6 months entirely indoors because your country has become Mars on Earth. It is also reasonable to imagine that the agriculture and fishing industries will take a severe hit, if not disappear entirely. This would leave the Kingdom dependent on external aid, while it continues to warm our atmosphere with its indispensable AC networks. Things will get hairy quite fast if we reach this point, so let’s make it our responsibility to learn, educate those around us and act where we can while there is still time. 

This article was written by Owen Mulhern. 

You might also like: Too Hot to Live: Climate Change in Thailand

longer summers earth index

Why This Metric?

A February 2021 study, published in the Journal of Geophysical Research Letters, reported that seasons in the Northern Hemisphere are now changing lengths, all except summer becoming shorter. 

They found that over a 60 year period, from 1952 to 2011, winters, springs and autumns shortened together by an average 17 days, which summer assimilated for itself. Modelling revealed that it could become another 12 days longer by mid-century, and 4 to 6 months long by 2100. 

Exploring the Metric

Our natural world is built around biological clocks. The body’s rhythm changes between night and day, and many animals, insects and plants depend on seasonal cues. Longer summers have the potential to throw these systems out of whack. 

The effect on wildlife has already been observed: pollinators emerge out of sync with plant blooms they rely on for reproduction, threatening both parties. An exceptionally warm “false spring” in March 2012 lured vegetation out of dormancy before temperatures dropped again in April, killing many crops. 

But it isn’t only early onsets and length, summers are also getting hotter. There’s a high probability that future generations will face up to 6 times more extreme heat events than ours, and up to 3 billion people could face temperatures beyond human tolerance by 2070. Some scientists have even warned that disease-carrying mosquitoes could expand their range both polewards and elevation-wise thanks to warmer nights. Along with this, scientists expect more droughts and floods, and an acceleration to sea level rise. 

Where the Numbers Come From

The authors of the paper, Changing Lengths of the Four Seasons by Global Warming, looked through daily climate data from 1952 to 2011 and defined the start of summer as the onset of temperatures in the hottest 25% during that period. Conversely, winter was defined as the onset of the 25% coldest. 

Future Outlook

Governments should take stock of this information and prepare accordingly. Potential mosquito range increases have been modelled, and preventive measures need to be taught and promoted among the newly vulnerable populations. 

Agriculture is also an area to keep an eye on. Freakish extremes happen and can be dealt with, but baseline changes could mean rethinking what crops are best suited to new weather patterns, and how infrastructure can be adapted. 

As for summers becoming lethally hot, our actions now will determine the onset. Significant cuts in greenhouse gas emissions will buy time to adapt to or even avoid catastrophic levels of global warming. 

This article was written by Owen Mulhern.



Since Adam and Eve bit the apple, we’ve been burdened with the need for clothing whenever we walk outside. More than a necessity, it’s become a means of expression, a statement, and the vehicle of many trends. However, overconsumption has led to the rise of fast fashion, a wasteful and polluting system that our environment bears the cost of, while its emissions accelerate climate change.

Earth.Org takes a closer look.

In the past 20 years, clothing production has approximately doubled due to higher demand from a growing middle class around the world. Meanwhile, garment usage lifetime has decreased on the consumer side. This embodies the “fast fashion” phenomenon: more options, quicker trend turnaround, lower prices, and unpriced damage to the environment. 

clothing utilisation clothing sales fast fashion

Most shocking in the graph above is the decrease in clothing utilisation: 36% globally. China saw a whopping 70% decrease over the same time period, and 60% of German and Chinese citizens admit to owning more clothes than they need. The picture varies from location to location, with Europeans usually spending more on fewer items each year, while Americans or Chinese buy far more pieces per person. 

clothing bought per person fasst fashion price per item of clothing, pieces of clothing per capita

Fast Fashion and the Environment

The industry is representative of consumerism, creating need and producing excessively. Moreover, our clothing production, distribution and disposal system is horrendously wasteful and polluting. According to McKinsey, the textile industry (60% of which goes into clothing) pumped 2.1 billion metric tons of greenhouse gases into the atmosphere in 2018, accounting for 4% of global emissions that year. For context, that is much as the economies of France, Germany and the United Kingdom combined.

The fashion industry itself consumes an estimated 93 billion cubic metres of water each year, much of which ends up contaminated by toxic chemicals. According to the UN Environment Programme, 20% of global wastewater comes from textile dyeing. Because the bulk of these operations are in countries with less regulation, the wastewater often finds its way to the ocean where it can wreak havoc.

textile dyeing toxic pollution waste water wastewater greenpeace

Industrial wastewater containing hazardous chemicals discharged into the Cihaur River, a tributary of the Citarum River. Source: Greenpeace.

In this age of fast fashion, we discard around 92 million tons of clothes-related waste each year. In other words, a garbage truck full of clothes is either incinerated or sent to the landfill every second, enough to fill one and a half Empire State Buildings every day

Before they’re even thrown out, our synthetic garments produce serious amounts of pollution by shedding microfilaments in the wash or drying machine. Around 50% of our clothing is made from plastic, and they produce half a million tons of microplastics that make their way into the ocean every year. 

Ironically, these absorb the toxic chemicals we let leak, then work their way up the food chain back to us. 

The current system is simply unsustainable due to its high volume, yet linear nature. Massive amounts of resources are extracted, processed, used only briefly, then thrown out.

clothing material flow

Less than 1% of the material used to make clothes is recycled into new clothing, meaning over USD 100 billion worth of material is lost each year. We are missing out on opportunities to reuse, recycle and even profit from a more circular system. 


Fast Fashion’s Societal Impacts

Beyond fast fashion ‘s effect on the environment are the deplorable conditions people work in to satisfy the ever-soaring demand. 

According to non-profit Remake, 75 million people are making our clothes this very day, 80% of which are young women between 18 and 24. 

The Bangladeshi female garment workers make about USD 96 per month according to The Fashion Law. That’s 3.5 times less than is needed to live a “decent life with basic facilities”, based on the Bangladeshi government’s wage board statistics. 

Worse yet, forced child labor is very real, and ongoing in Argentina, Bangladesh, Brazil, China, India, Indonesia, Philippines, Turkey, Vietnam and other countries. 

You can find out where and how your favorite brands make their products anytime. It could be worth it. 


Fast Fashion and Climate Change

As mentioned before, it emitted 2.1 billion metric tons of CO2 equivalent (CO2e) greenhouse gases in 2018, which is highly incompatible with the 1.5°C pathway targeted by the Paris Agreement. If no action is taken, its yearly emissions are expected to surpass 2.74 billion tons by 2030, but if mitigation continues at its current pace, emissions will stay where they are. According to McKinsey’s “Fashion on Climate” report, a 50% reduction is necessary to meet the 1.5°C pathway.

McKinsey Fast Fashion climate change

Source: Fashion on Climate, McKinsey (2020).

The report explains that such a reduction is in fact feasible, but first, let’s break down the industry’s emission sources. 

fast fashion greenhouse gas emission cuts

Source: Fashion on Climate, McKinsey (2020).

The bulk of emissions come from material production and processing, while a little over 20% comes from the consumer side, and 6% from transport and retail. 

In order to comply with the 1.5°C pathway, McKinsey’s report proposes the following:

This essentially consists of replacing all upstream energy sources with renewable-generated electric power. This alone covers 63% of the emission reduction needed. 

The key lever here is reducing oversupplying shops, often leading to markdowns or disposals. Technology investment for producing better forecasts and stock management would deliver.

This one concerns more of us so I will go into further detail. Circular business models, like fashion rentals, re-commerce, repair and refurbishment (think thrift stores) are essential to a sustainable fashion industry. Reduced washing and drying is also important. Consider: by skipping one in six washing loads, washing half loads at below 30 degrees, and substituting every sixth dryer uwsage with open-air drying, we would reduce consumer emissions by more than half.

The rise of renewables makes clean energy transitions in large industries quite likely, though it remains to be seen how fast it happens. For the appropriate infrastructures to reach production regions might take some time, and their governments are behind on incentivizing renewables. As for brands, their operations might benefit from the democratization of machine learning applications that can be very powerful for forecasting demand and the like.

Beyond this, it is incredibly empowering to know that much of the onus falls on us as individuals, and that our actions can indeed make a difference. By making the right decisions and educating those around us, we can reverse the trend of fast fashion and relieve the pressure it puts on the environment. 


This article was written by Owen Mulhern . Cover photo by Rio Lecatompessy on Unsplash.

You might also like: The History and Future of Air Pollution in Manchester

Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in Manchester to better understand the current situation, and where things may be heading. 

Manchester is known as being one of the most polluted cities in the United Kingdom. But how did this come to be? In order to understand, let’s go back to the late 18th century when Manchester was a collection of interconnected towns undergoing industrialization.

The agglomeration’s population grew sevenfold in the 18th century, and continued to grow rapidly during the following one as the textile industry boomed and steam power came about. Manchester became the cotton textile hub of the nation, which itself was the cotton textile hub of the world during the 19th century. 

It wasn’t long before the people began reporting the nuisances of heavy industry. In 1800, the Commissioners of Police in Manchester created a committee to oversee the problem; it found that “the increase of steam engines as well as smoak issuing from chimnies used over stoves, foundries, dressers, dyehouses and bakehouses are become a great nuisance to the town”. 

This was only the beginning of course, as the following century saw the appearance of engineering, chemicals and metal working, sulphuric acid and naphthalene production and many more noxious affairs. Reports from local or foreign writers passing through are vivid, like Alexis de Tocqueville’s commentary: “These vast structures keep air and light out of the human habitations which they dominate; they envelop them in perpetual fog; […] A sort of black smoke covers the city. The sun seen through it is a disc without rays.”

The first scientific measurements and analyses of the situation were carried out by R.A. Smith who, in his 1852 paper, described and coined the term “acid rain”. He found that sulphur pollution around Manchester mixed with precipitating water and dropped its pH from the usual ~5.5 to 3.5. He also described its negative effects on the surrounding vegetation, and noted the disappearance of some species from the region, such as the sphagnum mosses. 

The next 50 years saw a succession of local initiatives, like that of the Salford Noxious Vapours Abatement Society that obtained black smoke emission regulations, to the Smoke Abatement Society of Manchester, founded in 1909 and precursor to the Smoke Abatement League of Great Britain.

Around the same time, the first deposit gauges were set up around the city. These rudimentary sulphur deposit measurements often read 170 kilograms per hectare (100 x 100 meter square) per year.   

Better measurement techniques came about during the second World War, and their readings came up with mean sulphur dioxide concentrations of 586 micrograms per meter cube (mg/m3), compared to the 20 mg/m3 WHO guideline value today. Of course, with the sulphur were other pollutants like particulate matter, only these were harder to identify, isolate and measure. 

The result was a high incidence of respiratory disease throughout the 20th century. In December 1930, a December like any other, there were 137 respiratory disease deaths in Manchester. The following year, a severe smog engulfed the city for 9 days and 592 people died of respiratory disease. Catastrophe is often the impetus for change, and following this one, negotiations for the creation of a smokeless zone were launched. Mancunians had to wait for the City to acquire private powers to implement the zone in 1946. Six years later, the great London Smog caused an uproar, leading to the Clean Air Act of 1956.

air pollution manchester

Source: Douglas, Ian, Rob Hodgson, and Nigel Lawson. “Industry, environment and health through 200 years in Manchester.” Ecological Economics 41.2 (2002): 235-255.

As you can see, the Clean Air Act was highly effective in reducing sulphur dioxide (SO2), smoke deposits, and thus bronchitis in the City of Manchester. It is important to note, however, that this was greatly helped by the decline of heavy manufacturing and the substitution of coal with electricity, gas and oil. 

You’ll also notice the subsequent peak in lead (Pb) levels in the mid 1980s. Lead was actually added to fuels in the 1930s, and became progressively more widespread until its extremely negative health effects became apparent. It’s late appearance in the graph is due to a lack of record prior to the first data point, similarly to NO2 (nitrogen dioxide). It can be hard to rein in NO2 because of the amount of vehicles so the road in large agglomerations; still, fuel switching and a range of pre-treatments have helped control it. 

Today, standards are better informed by science, and we able to take things one step further: precise air pollution mapping is possible, both in Manchester and cities around the world. Making this information publicly accessible would allow all to understand what they are exposing themselves to, and possibly make better decisions for their family’s health and their own.

Berkeley Earth made a PM2.5 to cigarette equivalence that has allowed us to map air pollution in Manchester in terms of cigarettes smoked per week.

manchester air pollution pm2.5 cigarettes map

Air pollution mapping in Manchester. PM2.5 data from NASA-SEDAC (2016).

This snapshot of Manchester’s PM2.5 puts things into perspective – what is considered to be a fairly low amount of pollution on the global stage is still equivalent to about 3 to 4 cigarettes per week. The point is, no level of air pollution is good, and the WHO’s guideline of 10 mg/m3 of PM2.5 is just a relatively acceptable level. It is likely we will one day get rid of pollutants (close to) entirely and look back on these times as dangerously and unnecessarily unhealthy. 

Manchester’s Director of Public Health for Air Quality, Eleanor Roaf, says, “We estimate in Greater Manchester that air pollution is the biggest environmental cause of poor health. Up to 1,200 deaths each year are contributed to by poor air quality.”

manchester air pollutiono graph berkeley earth

Source: Berkeley Earth.

On average, PM2.5 is close to the WHO guideline level (green), but the many spikes are the days when hospitalizations for asthma and the like become more likely, especially for children. 

One of the ways the City intends to fight this is by enabling pedestrian and bicycle circulation. They’ve already created one of the largest pedestrian-cycling networks in Britain, covering 1,800 miles. 

Additionally, Manchester was one of the first cities in the UK to declare a climate crisis in July 2019, signaling its intention to assume a leadership role in reducing carbon emissions and ecological footprint. 


This article was written by Owen Mulhern.

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Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look at air pollution mapping in Sao Paulo to better understand the current situation, and where things may be heading. 

Since the Industrial Revolution toward the end of the 18th century, energy-intensive tools have spread across the globe and ushered in a new age of exponential growth and technological progress. Unfortunately, because our energy sources are “dirty”, or non-renewable and polluting, we now find ourselves facing the consequences of accumulated particles and gases in our atmosphere: excessive warming and unhealthy air.

While global warming from fossil fuel emissions is more of a long-term problem that will take decades to fix even if we do everything right, air pollution and health can be seen as more of a short-term issue. It has been accumulating and causing death and morbidity for over a century in many places, long noticed yet ignored for lack of hard evidence it was dangerous, and once this was acquired for business interests over public health. 

Large metropolitan areas are usually hotspots for air pollution case studies since they concentrate both industrial activity and transport (the main sources) along with a high density of people who might suffer from it. Sao Paulo is one of these metropolises, having undergone rapid growth in the second half of the 20th century from around 1 million to over 22 million inhabitants.

Its industry boomed between the 1950s and 1980s thanks to the car industry in particular, but also those of chemicals, steel, textile, food and many others. Sao Paulo’s simultaneous urban expansion meant residential and industrial areas often coincided, leading to many complaints in the 60s and 70s. 

The government responded, setting up air pollution control programs which also coincided with less sulfur-heavy fuel, and the rise of hydroelectric and natural gas power plants, resulting in effective pollution reduction. 

As Sao Paulo continued to grow, so did the number of vehicles on the street and the time spent in congestion; industrial emissions were soon overtaken, and vehicular emissions remain Sao Paulo’s largest source of air pollution today. 

Research began linking air pollution to disease burdens in the 80s, but the scopes were not large enough to spur a change in policy. In the last two decades however, evidence has accumulated thanks to studies correlating precise particulate matter (PM) or vehicle traffic density to elderly and child hospitalizations and mortality from respiratory illness. Despite its progress in controlling air pollution, this kind of evidence makes it the government’s responsibility to curb it to the most benign possible levels.  

Today, standards are better informed by science, and we able to take things one step further: precise air pollution mapping is possible, both in Sao Paulo and cities around the world. Making this information publicly accessible would allow all to understand what they are exposing themselves to, and possibly make better decisions for their family’s health and their own.

Berkeley Earth made a PM2.5 to cigarette equivalence that has allowed us to map air pollution in Manchester in terms of cigarettes smoked per week.

air pollution pm2.5 Sao Paulo

Air pollution mapping in Sao Paulo. PM2.5 data from 2016 (most recent gridded global dataset).

The situation has kept improving in Sao Paulo and now fluctuates between “Good” (under 10 micrograms per m3), “Moderate” (under 40 mg/m3) and “Unhealthy” (40 to 60 mg/m3) depending on the season.

air pollution Sao Paulo

Source: Berkeley Earth

Indeed, despite the local authorities’ best efforts, smoke regularly wafts over from the Amazon and Cerrado regions to contribute to the poor air quality in Sao Paulo. In fact, a 2020 study found that around 10% of PM2.5-induced premature deaths are attributable to fire smoke pollution.


Air pollution levels and environmental policy go hand in hand, and in Brazil this is truer than anywhere else. They have made great progress but the truth is that air pollution alone has cost the city of Sao Paulo over USD111 million between the years of 2008 and 2017 in medical costs alone, without accounting for the productivity loss of those who were ill. Even from an economical point of view, it is absurd to let the situation continue. Furthermore, Brazil’ wealth of ecological resources gives it unparalleled responsibility as the warden of our last, largest rainforest. We must all set examples where we are in order to change the global standard. Avoid single use plastics and vote. 


This article was written by Owen Mulhern.

You might also like: The History and Future of Air Pollution in Lagos


Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in Lagos to better understand the current situation, and where things may be heading. 

Lagos became the capital of the British-controlled protectorate of Nigeria in January 1914, and has since become the largest city in West Africa, with an estimated metropolitan population of nearly 15 million. 

Naturally, its transformation came along with, and thanks to industrialization. From the year 1943 to 1959, pre-independence, a number of industries based around raw materials were flourishing, followed by the production of consumer goods like beer, soft drinks and cigarettes. Coal was the main source of energy until oil and gas were discovered in the early 1950s, and as is always the case, ignorance and hasty development led to damaging levels of pollution. .

Since then, sources of pollution have multiplied and magnified. Taking fine particulate matter (PM2.5) as a reference, the main emitters are road transport, heavy dependence on inefficient diesel and gasoline generators, poor waste management, construction and dirty fuels for household stoves. 

A lack of governmental leadership on the issue has resulted in a paucity of data concerning air pollution in Nigeria. With no official measurement stations nor standardized methods, it is difficult for officials to take informed and decisive action. Still, a number of independent operations have given indicative values for organizations to work with, and a few studies monitored PM2.5 over year-long periods in a few representative locations in Lagos. 

The result is an average 68 micrograms of PM2.5 per meter cube (mg/m3), around 7 times the WHO guideline value and in the range of other highly polluted megacities like Beijing and Cairo. Air pollution is very pernicious, because people living in it get used to the way the air feels and its effects manifest as a range of respiratory and cardiac disease, making it quite elusive. The truth is it’s health cost in Lagos alone was US$2.1 billion in 2018, or around 2.1% of Lagos State’s GDP. 

That translated to about 11,200 deaths in 2018 (the highest in West Africa), 60% of which were children under five years old. While they suffer mostly from lower respiratory tract infections, adults deal with heart disease, lung cancer and chronic obstructive pulmonary disease.

PM2.5 and cigarettes have very similar effects on human health, which is why Berkeley Earth calculated their equivalence, which we used to map the situation in Lagos. 

air pollution lagos pm2.5 particulate matter

Air pollution mapping in Lagos. PM2.5 data from NASA-SEDAC (2016).

The worst of its pollution is spread over less densely populated areas, but in the city center, people are still breathing in the equivalent of over 5 cigarettes per week each year. 

It is imperative for such avoidable death and morbidity to be stopped, so let’s take a look at the sources and what can be done about it.

Road transport is the worst source of ambient air pollution in Lagos, unsurprising considering most vehicles are over 15 years old with old emission technologies and sulfur heavy fuels. The fix here is to implement vehicle emission standards with a progressive rollout to allow the population to adapt. Improving public transport also goes a long way. 

Industrial emissions are the second largest source. Zones with cement, chemical, furniture, refinery and steel activities are concentrated have wildly unhealthy levels of pollution – a PM2.5 concentration of 1,770 mg/m3 was once recorded over 24h in Odogunyan. This can be addressed by switching fuels, using modern energy recycling like combined heat and power, and recycling materials. Of course, this is expensive and requires heavy commitment. 

The next biggest problem is the fact that 50% of energy generation comes from private, diesel-powered generators because of how unreliable the energy grid is. This very poor combustion of gasoline and oil produce a lot of noxious fumes, especially when used indoors. Once again, this can be solved but requires a revamp of the grid, and therefore is more about money and commitment than anything else. 

The World Bank’s Pollution Management and Environment Health Program is campaigning to offer incentives and policies in collaboration with the Lagos State Government to help tackle the problem. There are opportunities for innovative investing in the area too thanks to initiatives like the IFC’s Breathe Better Bond that creates climate-friendly infrastructure projects. Still, it is the government’s job to take the lead, improve monitoring and take action for its citizens well-being. 


This article was written by Owen Mulhern.

You might also like: The History of Air Pollution in Tokyo

Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in Tokyo to better understand the current situation, and where things may be heading. 

Because air pollution is directly linked to industrialization, this article will take a historical look at the advent of Japanese industry and its development during the last few centuries. 

In 1843, Japan had long been a closed-off economy, only allowing foreigners to trade in the port of Nagasaki. This is why the arrival of four modern American warships in Tokyo Bay, with armament technology far more advanced than that of the Japanese, was a reality check. In the words of Shimazu Nariakira, “if we take initiative, we can dominate;  if we do not, we will be dominated”, much like their Chinese neighbors had been by the English. 

The country underwent a brief civil war between the reformist Meiji, who championed a western-style modernization of the country, and the conservatives who wanted to maintain the shogunate. The reformists came out victorious in 1869, ushering in a new era of industrialization, political reform, and pollution. 

Things went fast, and within two decades, the country was hardly recognizable. Samurai now worked in local shops, western political and economic institutions had taken over, factories were everywhere, and the environment began to suffer. 

Tokyo’s population was already above a million, and its urbanization and industrialization resulted in many environmental issues. Along with Osaka and a few other hotspots, it suffered from cholera, urban filth, black smoke, and offensive odors from animal processing plants. Ironically, heavy smoke emissions related to industry were often seen as a symbol of prosperity, and therefore rarely garnered complaints. 

Still, there were a few air pollution cases around the time, like that of the Asano Cement Company. It moved to Tokyo in 1883 and its dust emissions began visibly covering the local neighborhood. Angry citizens demanded the removal of the plant, but the government did not intervene, leaving the citizens to endure until Asano introduced an electric dust collector in 1917 (32 years later). 

This example is illustrative of the Japanese priorities concerning the “growth or green” problem, which each country faces throughout its development. In other words, how fast the government acts to mitigate the inevitable environmental damage that comes with industrialization. 

Like many other cases (including but not limited to New York City, Melbourne, London and Johannesburg), early public protest in Japan resulted in weak legal measures, often short-scoped and poorly enforced. Tokyo and Osaka were the first to see a forced relocation of factories to designated industrial areas, with the term “kogai” (environmental pollution) appearing in written law around the same time (1882). The industrial areas were rapidly surrounded by houses again due to continuous urban expansion – signs of a growing awareness, yet of a lack of concern.

Not much happened on the air pollution control front until 1913, when the first Japanese smoke abatement committee appeared in Osaka. However, it’s attempts to impose regulation lost out to business interests for another 20 years, meaning industrialization went completely unchecked for 50 years. 

Tokyo began its first air pollution monitoring program in 1927, which is a key step forward since data provides robust arguments for action. The city’s police force was also recording sharp increases in the amount of complaints at the time, yet regulatory apathy continued. 

It took no less than the Second World War to shake things up, partly thanks to the rewritten constitution’s Local Autonomy Law in 1947. Local-level authorities were finally allowed to take matters into their own hands, and naturally they would be more responsive to their citizen’s pleas. 

Communities began to combine the forces of government, university and industry to implement the first truly effective pollution control programs in the years between 1945 and 1969. Unsurprisingly, a strong wave of anti-insutrialism had formed by this time, and militants were able to exert more influence on a local scale. As a result, more regulation came through, like the decades-late (compared to other countries) Smoke and Soot regulation Law of 1962 – effective for controlling black smoke and heavy deposited matter, but leaving others like sulfur dioxide (SO2) out of its scope. 

The balance was finally shifting, punctuated by the successful cancelling of a planned petrochemical industrial complex in 1964. Companies were now expected to be using the most effective pollution-reducing technology available, incentivizing other companies to research and develop better tech. 

National air quality standards were finally set in 1967 with the Basic Law for Environmental Pollution Control Measures, and two years later, these were integrated into the energy supply program. Regulations were sequentially tightened and improved over the next decade, with the essential vehicle emission standards coming through in 1972.

The ensuing 70s and later 90s saw major breakthroughs in desulfurization technologies and low-sulfur oil, helping the country to satisfy SO2 standards by 2012. 

The 70s were also the first decade in which the damage from photochemically produced air pollutants, that is new molecules formed by atmospheric reactions after an initial pollutant is released, was reported. It became clear that the scope of law had to expand, and regulations for all sulfur and nitrous oxide emitting sources were enacted. It was difficult to keep nitrous oxides in check since they are produced mainly by combustion and not directly from fuel content, and automobiles were multiplying. Still, many small changes like more fuel efficient vehicles, better urban planning and traffic control, along with other technological measures helped reduce emissions to an acceptable level. 

The worst and most widespread form of pollution is that of fine particulate matter, oor PM2.5. It gets deep into our lungs and has deleterious health effects similar to those of cigarettes, including increased respiratory and heart disease occurrence. 

Using Berkeley Earth’s PM2.5 to cigarette equivalence, we mapped what pollution looked like over Tokyo in 2016 (latest PM2.5 dataset) to illustrate the situation.

air pollution pm2.5 particulate matter tokyo

Air pollution mapping in Tokyo. PM2.5 data from NASA-SEDAC (2016).

There has been progress since, and though the levels fluctuate a lot, Tokyo’s average PM2.5 levels are just above the WHO’s guideline (10md/m3) at a solid 12mg/m3

tokyo air pollutiono berkeley earth

Source: Berkeley Earth.

So where do things go from here? The biggest sources of air pollution in Tokyo are still vehicle emissions and factory fumes, with improvable levels of nitrous oxides. The authorities have established a plan to reduce PM2.5 under 10mg/m3 by 2030, mainly through subsidizing electric vehicles and continuing to tighten regulations on diesel vehicles and industry. 

It is an incremental process that will take time, yet is entirely solvable and Tokyo is doing it correctly. 


This article was written by Owen Mulhern.

You might also like: Outsourcing Deforestation: The Local vs. the International Footprint

Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in Manhattan, NYC to better understand the current situation, and where things may be heading. 

After its colonization in the 1600s, New York City rapidly grew into an important trading port due to its strategic positioning. Many historic events took place in the area throughout the 1700s, until it was made the nation’s capital in the latter part of the century.  

The path was cleared for the city to prosper and expand, which indeed it did, growing from 60,000 to 3.43 million over the course of the 19th century.  

During the same period, the Industrial Revolution changed the world, bringing about better means of transportation, production and engineering, but also launching the exponential increase in fossil fuel emissions that we have not yet seen the end of. 

For the first hundred years of the United States’ existence, air pollution issues were settled by legal challenge between the concerned parties, with no specific legislation addressing the problem. It was around 1881 that the first legislation was enacted to specifically declare smoke emissions to be a public nuisance, after which municipal legislations began to multiply. 

Most of the smoke abatement ordinances of the time generally prohibited smoke vaguely defined as “dense”, “black” or “grey”, to a certain number of minutes per hour. The poor definition based on color led to a later definition of smoke density by Ringelmann Chart number or percent opacity.

ringelmann opacity measurements smoke particles air pollution

Around the turn of the century, records show that it became unnecessary to state that air pollution was a public nuisance, as it was self-evident from the smell, soot, and irritated eyes and throats. County-level laws then came about in the 1920s, and the first comprehensive state legislation appeared in 1952, Oregon. 

stern air pollution legislation

Many of the laws included in the table above failed to make a difference because the appropriate oversight, personnel, and/or fiscal means to enforce them were not provided. In fact, most early air pollution measures were ineffective, regardless of the country, possibly due to the fact that it was written into law as a nuisance rather than a threat. Yet the nefarious effects of air pollution on health had been described since the 13th century, when air quality first dropped to abysmal levels in London.

Arthur C. Stern explains that, were it not for a few great men, little would have been accomplished, and he shares his personal hall of fame, included here for your perusal. 

air pollution great men hall of fame

Real attention to air pollution in New York came about with the 1928 installation of Owens-type air paper air filters that captured fine particles. 

owens type air filters owens air filters

Set up in a number of key locations around the city, these provided much needed rudimentary data and gave way to a wave of studies. The main pollutant identified before World War II was sulphur dioxide (SO2) combined with soot from heavy coal combustion for heat and power production. This was addressed through the use of cleaner fuels (natural gas, better forms of coal, oil), higher smoke stacks and industrial gas cleaning in certain areas. However, the rise of the automobile replaced the SO2 with nitrogen dioxides and volatile organic compounds which can react in the air to create photochemical air pollution, the main component of smog. 

These became notorious in the late 40s and early 50s as a common occurrence in Los Angeles, and a rarer albeit deadly one in New York City. 

The first nation-wide piece of air pollution legislation, the Clean Air Act, came into play in 1963, meaning states could receive federal funds for their academic institutions, research programs and staff relating to air pollution. 

This Act set the foundation for the next major advances in air pollution regulation including the 1970 National Ambient Air Quality Standard (NAAQS), setting the first health-based limitations on six air pollutants, including:

A side note on lead: 

Lead was introduced as a way to boost fuel efficiency by permitting higher compression ratios, and was sold in the U.S. as a “tiger in the tank” of your car. After being criticized for its potential environmental damage, its noxious effect on human health was also demonstrated, and lead was slowly phased out of gas in the developed world. 

The Environmental Protection Agency took oversight of air pollution control and ushered in a new era of difficult, yet steady improvement in environmental policy. Some of the most notable changes were the use of catalytic converters to reduce carbon monoxide exhaust from cars and the change from ozone depleting chlorofluorocarbons to hydrofluorocarbons. 

More evidence emerged in the following decades proving the danger of even low levels of pollutants, from ozone to fine particulate matter, prompting the EPA to tighten its regulations on all of these. There are now 189 controlled threats on the list, all much better understood than before. 

new york city air pollution berkeley earth PM2.5

Source: Berkeley Earth.

Above, we see the long term PM2.5 levels recorded in New York City, courtesy of Berkeley Earth. The color ranges indicate the level of health risk associated with the PM2.5 according to the WHO’s guidelines, with 10 micrograms per meter cube being the recommended max. 

Using Berkeley Earth’s PM2.5 to cigarette equivalent in terms of health effects, we mapped air pollution over the city to give a more recent perspective on the situation. 

new york city air pollution pm2.5 berkeley earth cigarette equivalent

Air pollution mapping in Manhattan, NYC. PM2.5 data from NASA-SEDAC (2016).

New York’s air pollution remains above the WHO’s recommended limits, and the health effects amount to smoking 3 to 5 cigarettes per week for its citizens. Far from negligible, it is also far from infrequent – over 90% of all humans are exposed to air pollution levels over the guideline limit.

This data pre-dates the COVID-19 pandemic however, so current pollution levels are far lower, although they are expected to bounce back shortly after activity resumes since authorities are more concerned with getting the economy going again than saving what environmental progress was made. 

Not that they are wrong to do so; the pandemic hit New Yorkers hard, but it is a shame to see such environmental healing go to waste when we could use it to rethink how we do things. Of course, that would take more than a year and a half to implement. Things are already moving in the right direction, and the adoption of electric vehicles combined with cleaner energy is making a difference.

This article was written by Owen Mulhern.

You might also like: The History of Air Pollution in Johannesburg


Air pollution is the third leading cause of death worldwide, and most large cities, have fine particulate matter (PM2.5) levels above WHO health guidelines. Here, we take a look air pollution mapping in Johannesburg to better understand the current situation, and where things may be heading. 

Air pollution is tightly linked to a country or city’s stage of economic development, so it is helpful to take a look back at its history to understand why things are as they are today. 

In the late 19th century, South Africa transformed from what was mainly an agricultural society to an industrialized one. Entrepreneurs of the time capitalized on the massive mineral reserves of the region, diamonds and gold in particular. 

Johannesburg was founded as a mining camp of about 3,000 people in 1887, but the gold rush caused it to grow to a town of 100,00 within ten years, then to a city of a quarter million by 1914. Labour force demand was the driving force behind all of this, leading to an extraordinarily compacted, uneven development of the city. Quoted as a place, “of unbridled squander and unfathomable squalor,” large parts of its population found themselves pressured to get by in this runaway urban society. 

The main difference between the pre- and post-industrialized society was the new presence of mass production and huge factories. No matter where these appeared, records remain of the fetid smoke belched out the chimneys and difficult working hours, returning home covered in grease and soot. 

South Africa’s industry developed later than other countries’, lagging behind England and even Australia, but the result was similar: coal and chemical fume-spouting chimneys popped up everywhere. 

In its early centuries, the environmental issues of most concern were drinking water control and rationing, water and land pollution and the conservation of wild animals. This last one became a big issue in the late 19th and early 20th, while air pollution remained largely ignored. 

Global concern arose with the London disaster of 1952, where thousands died within days after meteorological conditions created a dense blanket of toxic smog over the city. This prompted many to speak out, and a wave of rudimentary studies appeared. One by P.D. Tyson, published in 1959, cites concerns about South African cities’ “smokiness” being as bad, if not worse than that of British cities. With no differentiation of the types of particles, they measured air pollution in units of actual smoke. 

south africa johannesburg UK air pollution in smoke units

Source: P.D. Tyson (1959).

As you can see, Johannesburg was already one of the most polluted cities of the industrialized world, especially in winter. 

As a sidebar: this is an important aspect of atmospheric pollution in general; meteorological conditions will largely dictate whether particles stagnate or get blown away, though of course their amount is also a deciding factor. 

Back to Johannesburg, the problem of air pollution was visible, yet governmental inaction persisted. This could be chalked up to the lack of information on the health impacts of noxious fumes. This data was the missing link between pollution and the constitutional right to a safe environment. 

A few years later, the Atmospheric Pollution Prevention Act of 1965 was the first legislation of its kind in South Africa, though unfortunately it was a largely ineffective piece of legislation. The situation didn’t truly change until 1996 (30 years later!), when section 24 of the South African Constitution robustly enshrined basic environmental rights for its citizens. The National Environmental Management Act (NEMA) came soon after, along with the ratification of the United Nations Framework Convention on Climate Change (UNFCCC). 

Things were finally moving on a global scale, though South Africans still had to wait until 2004 for the Air Quality Act to come into play, setting precise national norms and standards to regulate air quality. Namely, the particles falling under regulation were sulfur dioxide (SO2), nitrogen dioxide (NO2), particulate matter (PM10), fine particulate matter (PM2.5), ozone (O3), benzene (C6H6), lead (Pb), and carbon monoxide (CO).

A few or many of these may be familiar to you, but here we focus on PM2.5, the notoriously small particles that can enter deep into the lungs. They have similar health effects to those of smoking, including but not limited to chronic bronchitis, reduced lung function, cancer and heart disease. Berkeley Earth, a climate-concerned think tank, made a conversion formula from PM2.5 to cigarettes in terms of health effects, which we mapped below.

air pollution in Johannesburg

Air pollution mapping in Johannesburg. PM2.5 data from NASA-SEDAC (2016).

PM2.5 air pollution in Johannesburg is, on average, as bad for you as smoking 12 to 14 cigarettes a week. If you think that sounds like a lot, that’s because it is. Most large cities in  developed countries have dropped the cigarette index to under 3 a week, many in Europe under 1. 

The truth is that Johannesburg’s air quality is lagging behind that of its peers, and its citizens are suffering the consequences. According to a 2019 study, air pollution shaves an average 3 years off the Johannesburger’s life. The combination of vehicle emissions, coal-heavy energy production and forest fires create a serious health hazard which South Africa doesn’t seem ready to take care of. 

Policy is filled with glaring omissions like the lack of a vehicle emissions standard; truly a standard nowadays when they are found from Europe to India. A 2019 study estimated a single energy company called Eskom was responsible for over 300 deaths a year in an industrial zone near Johannesburg, prompting a lawsuit against the government. It is still ongoing today, and little progress has been made. 

South Africa isn’t doing enough to curb its air pollution, but clean technology is becoming more market-competitive everyday and it will soon be the economically preferable choice to improve things. In the meantime, the authorities are racking up a debt with their citizens that cannot truly be repaid, though reparation is certainly due. 

This article was written by Owen Mulhern.

You might also like: Melbourne Air Pollution


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