It is best known for being the situated along the snow-capped mountains of the Himalayas.
But, despite its awe-inspiring landscape, Nepal is actually the most polluted country in the world.
Residents in the landlocked country in South Asia are exposed to 99.73 micrograms per cubic metre (μg) of fine particulate matter (PM2.5), on average, throughout the year, according to Oxford University‘s Our World in Data platform.
Experts called the figure — which is nearly 20-times higher than the World Health Organization‘s guideline limits of 5μg/m3 — ‘alarming’.
For comparison, levels in the UK stood at 10.47μg/m3, while the US logged 7.41μg/m3. It means the nations had the 24th and ninth cleanest air, respectively.
It is measured in particulate matter 2.5 (PM2.5) and can be especially dangerous – it is linked to worsening medical conditions such as heart disease
PM2.5 refers to tiny particles that are less than 2.5 micrometres in diameter — about one ten-thousandth of an inch.
The particles can include dust, soot, metals and other chemicals. This pollution is linked to burning fossil fuels and is released from car engines and factories.
As the particles are so small, they pose a big risk to health, as they can be inhaled deep into the lungs. Swathes of evidence show that long-term exposure increases the risk of severe illness and death due to cardiovascular and respiratory diseases.
As well as harming the heart and lungs, air pollutants also affect the brain, with studies linking exposure to a higher risk of dementia and cognitive decline.
The World Health Organization (WHO) states that annual average concentrations of PM2.5 should not exceed 5µg/m3.
What is PM2.5?
PM2.5 refers to tiny particles, less than 2.5 micrometres in diameter – about one ten-thousandth of an inch.
The particles can include dust, soot, metals, and other chemicals. This pollution is linked to burning fossil fuels and is released from car engines and factories.
The World Health Organisation (WHO) states that annual average concentrations of PM2.5 should not exceed 5µg/m3, while 24-hour average exposures should not exceed 15µg/m3 more than three to four per year.
The air quality data, gathered in 2017 and based purely on levels of PM2.5, is available for 195 countries.
Following Nepal, Niger (94.05μg/m3) and Qatar (91.19μg/m3) had the highest concentration of PM2.5.
The researchers said the high concentrations across North Africa are ‘very high’, partly due to ‘drier conditions with more sand and dust sources’.
Rounding off the top five countries with the poorest air quality is India, where the population of 1.4billion was exposed to 90.87μg/m3 of PM2.5, and Saudi Arabia, where 87.95μg/m3 was logged.
Except for Qatar, each of the top five countries’ PM2.5 levels had increased since 1990 — indicating that efforts to improve pollution levels has been unsuccessful in some nations.
Of the top five offenders, Nepal had the biggest jump in levels of PM2.5, with the figure skyrocketing by 12.13μg/m3. This jump is more than twice the average annual exposure to PM2.5 in Finland.
Egypt (87μg/m3), Cameroon (72.79μg/m3), Nigeria (71.80μg/m3), Bahrain (70.82μg/m3) and Chad (66.03μg/m3) were also among the nations with the poorest air quality.
Dr Raj Tiwari, an assistant professor in climate change data science at the University of Hertfordshire, told MailOnline: ‘Countries like Nepal (South Asia), Niger (Africa) and Qatar (Middle East) are on the top end for PM2.5, with an exposure of more than 90 — which is very alarming.
At the other end of the scale, Finland logged the lowest PM2.5 mean annual exposure (5.86μg/m3). However, this figure is still above the WHO’s safety levels.
It was closely followed by Brunei, a tiny nation on the border of Malaysia, which was exposed to just 5.9μg/m3.
New Zealand (5.96μg/m3), Sweden (6.18μg/m3), Canada (6.43μg/m3) and Iceland (6.48μg/m3) also logged low levels of the air pollutant.
It may come as a surprise that the country with the highest death rate is not Nepal but, in fact, Uzbekistan
Pollution is one of the world’s largest health problems, as it was the cause of 6.67million global deaths in 2019, making it the third biggest killer in the world
Ten most polluted countries
Nepal: 99.73 μg
Niger: 94.05 μg
Qatar: 91.19 μg
India: 90.87 μg
Saudi Arabia: 87.95 μg
Egypt: 87 μg
Cameroon: 75.01 μg
Nigeria: 71.80 μg
Bahrain: 70.82 μg
Chad: 66.03 μg
Ten least polluted countries
Finland: 5.86 μg
Brunei: 5.90 μg
New Zealand: 5.96 μg
Sweden: 6.18 μg
Canada: 6.43 μg
Iceland: 6.48 μg
Estonia: 6.73 μg
Norway: 6.96 μg
United States: 7.41 μg
Maldives: 7.80 μg
The Our World in Data figures also revealed national death rates due to outdoor air pollution in 2019.
Despite Nepal logging the worst levels of PM2.5, it was Uzbekistan that recorded the highest fatality rate.
The Central Asian country, home to 20.5million people, reported 179 deaths per 100,000 people — more than double the 81 seen in 1990.
It is closely followed by Egypt, where the death rate was 161, and Qatar (133).
Dr Tiwari said: ‘Further analysis on death rates from outdoor air pollution is really an eye-opener, as it clearly shows how air pollution is highly linked with the economy of the countries.’
This is due to poorer countries tending to have weaker laws around air pollution, lower vehicle emission standards and higher numbers of coal power stations, according to the UN.
Meanwhile, Finland recorded just three deaths per 100,000 caused by pollution exposure — the lowest in the world.
Pollution is one of the world’s largest health problems, behind 6.67million deaths worldwide in 2019, making it the third biggest killer, according to the WHO.
Taking the top spot for the world’s biggest cause of death in 2019 was high blood pressure (10.85million) which was closely followed by smoking (7.69million), according to a Global Burden of Disease study published in The Lancet.