NASA Study Finds Connection Between Population And Pollution
August 20, 2013

NASA Study Finds Connection Between Population And Pollution

Brett Smith for - Your Universe Online

While previous research has linked employment or innovation statistics to urban population density, a new study from NASA scientists has made a connection between pollution and the number of people living in a city.

Using satellite observations, the NASA team was able to calculate air pollution's dependence on population for cities in the United States, Europe, China and India. According to the report, which was published in the journal Environmental Science & Technology, pollution has a direct relationship with population density.

In the study, researchers focused on nitrogen dioxide, or NO2, a pollutant released by the burning of fossil fuels. The gas plays a role in the formation of near-ground ozone found in many cities, which is unhealthy to breathe in high concentrations and can cause respiratory problems – making it a good indicator of urban air quality.

Study data was collected using NASA Aura satellite’s Ozone Monitoring Instrument, which measures atmospheric nitrogen dioxide in the afternoon for various time zones around the world. The data was processed through a computer model to determine the annual average concentration of ground-level nitrogen dioxide in some of the Earth’s major polluting regions. After overlaying pollution concentration onto population density data, the researchers could examine the patterns between the two.

The NASA team discovered that the relationship between pollution and population can vary from region to region. For example, a European city of 1 million people is exposed to six times higher nitrogen dioxide pollution than a city of 1 million people in India.

Different regions showed a wide range of nitrogen dioxide surface concentrations in urban areas of around 1 million people. Europe was ranked highest at over 1.3 parts per billion, while India’s 1-million population cities came in at just over 0.2 parts per billion. For cities with population of 10 million people, the results were similar: 3.9 parts per billion in Europe versus 0.5 parts per billion in India.

"Energy usage patterns and per capita emissions differ greatly between India and Europe," said study researcher Lok Lamsal, of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Despite large populations, Indian cities seem cleaner in terms of NO2 pollution than the study's other regions."

While NO2 concentration approximately doubled for each ten-fold increase in city population in the US, Europe, and India – in China the concentration more than quadrupled for the same increase.

Previous research has shown that larger cities are more energy efficient with lower per-capita emissions. However, more people translate to more pollution and the study revealed some striking differences from region to region.

"Measurement of that relationship is potentially useful for developing future inventories and formulating air pollution control policies,” Lamsal said.

The NASA team suggested that future research should be geared toward understanding the mechanisms behind the regional differences.

Air pollution has been a major issue in China for some time now and the Asian country recently announced plans to combat the problem. According to the country’s National Development and Reform Commission, Beijing is expecting to invest almost $280 billion in clean air initiatives over the next five years.