Mapped: Which Countries Have the Worst Air Pollution?

View the high-resolution of the infographic by clicking here.

In many parts of the world, blue skies are a rarity. Instead, accumulated levels of air pollution from industrial processes and motor vehicle traffic cloak cities in smog year-round.

But to what extent does air pollution impact the human population around the world?

To answer this question, data scientist Matt Dzugan has created a cartogram that shades each country based on levels of fine particulate matter (PM2.5) air pollution experienced by the population living there.

Carto-What?

First off, let’s talk about the visualization style itself.

Not your everyday map, this unconventional cartogram resizes the borders of countries based on their total populations. In this style, a single square represents 500,000 people. According to Matt Dzugan, the cartogram view is meant to provide a bird’s eye perspective of the impact of air pollution and fine particulate matter (PM2.5) on human lives.

A clear correlation emerges: some of the most inhabited places in the world also experience the most pollution. Highly populated China and India show up the most prominently, while other countries like Australia and Canada seem to disappear off the map entirely.

To put this into perspective, 800 dark brown squares on this cartogram (a PM2.5 concentration of 50 μg/m³) represent 400 million people in India that are exposed to polluted air at levels five times past thresholds set by the World Health Organization.

Top 20 Countries with Cleanest Air

So how do countries on each end of the PM2.5 spectrum shake out? Pulling supplemental data from the WHO, here’s how the top 20 countries with the cleanest air rank.

New Zealand tops the above list. And as you can see, air quality tends to be highest in advanced coastal economies with low population densities—and being an island or bordering less habitable Arctic tundra also helps as well.

That said, there are temporary bouts when air quality can dip in even the best of countries. For example, recent wildfires on the West Coast of the United States and Australia resulted in reddish-orange skies and hazardous levels of air quality for weeks at a time.

The 20 Countries with the Most Air Pollution

On the other hand, it may be surprising that Nepal lands all the way at the bottom of the air quality list. Why is this landlocked country—home to less than 30 million—suffering from hazardous air pollution reaching 100μg/m³?

In short, the emissions from fossil-fuel driven traffic and manufacturing operations are trapped within the Kathmandu valley, which causes air quality issues for people living in the region.

The regions with lower air quality tend to be more landlocked with developing economies, such as some countries in central Africa and Asia, as well as in the Middle East.

Finally, while China is lower on this overall list, it’s worth noting that it is one of the most prominent on the cartogram due to its sheer population size.

Visualizing the Human Impact on the Earth’s Surface

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There is little doubt that human activity has impacted the Earth, but to what extent?

As it turns out, nearly 95% of the Earth’s surface shows some form of human modification, with 85% bearing evidence of multiple forms of human impact.

This map by data scientist Hannah Ker outlines the extent of humanity’s modification on terrestrial land ecosystems.

Measuring the Human Impact

This map relies on the Global Human Modification of Terrestrial Systems data set, which tracks the physical extent of 13 anthropogenic stressors across five categories.

1. Human settlement: population density, built‐up areas
2. Agriculture: cropland, livestock
3. Transportation: major roads, minor roads, two tracks, railroads
4. Mining and energy production: mining, oil wells, wind turbines
5. Electrical infrastructure: powerlines, nighttime lights

Researchers compiled all these stress factors and scaled their impact from 0 to 1. Then, in order to map the impacts spatially, the surface of land was organized into cells of 1 kilometer in length creating “edges” of varying impact.

These impacts are further organized by biomes—distinct biological communities that have formed in response to a shared physical climate.

Digging into the Data

Only 5% of the world’s lands are unaffected by humans, which amounts to nearly 7 million km² of the Earth’s land, and 44% (59 million km²) is categorized as low modification.

The remainder of land has a moderate to high degree of modification: with 34% categorized as moderate (46 million km²), 13% categorized as high (17 million km²), and 4% categorized as very high modification (5.5 million km²). This latter category is the most visible on the map, with portions of China, India, and Italy serving as focal points.

Below is a look at how Earth’s various biomes fare under this ranking system:

Out of the 14 biomes studied, the least modified biomes are tundra, boreal forests, deserts, temperate coniferous forests, and montane grasslands. Tropical dry broadleaf forests, temperate broadleaf forests, Mediterranean forests, mangroves, and temperate grasslands are the most modified biomes.

Dense human settlements, agricultural land uses, networks of infrastructure, and industrial activities dominate the more highly modified biomes. These lands are commonly subject to five or more human stressors simultaneously, threatening naturally-occurring ecosystem services.

What are Ecosystem Services?

An ecosystem service is any positive benefit that wildlife or ecosystems provide to people, and they can be sorted into four categories:

1. Provisioning Services: This is the primary benefit of nature. Humans derive their food, water, and resources from nature.
2. Regulating: Plants clean air and filter water, tree roots help to keep soil in place to prevent erosion, bees pollinate flowers, and bacterial colonies help to decompose waste.
3. Cultural Services: Humans have long interacted with the “wild” and it in turn has influenced our social, intellectual, and cultural development. However, the built environment of a city or town separates man from nature and ancient patterns of life. Ecosystems have long served as inspiration for music, art, architecture, and recreation.
4. Supporting Services: Ecosystems contain the fundamental natural processes that make life possible such as photosynthesis, nutrient cycling, soil creation, and the water cycle. These natural processes bring the Earth to life. Without these supporting services, provisional, regulating, and cultural services wouldn’t exist.

A Delicate Balance

With each encroachment upon habitat, the potential increases for humans to inadvertently upset the careful balance of ecosystem services that have nourished the processes of life on Earth.

As we become more aware of the human impact on the plant, we can make smarter decisions about how our society and economies function—ultimately ensuring that the same ecosystem services are there for future generations.