Mobile phones used to track exposure to air pollution in the Big Apple

1 September 2016

Researchers in Trinity College Dublin have collaborated with MIT and Harvard University to devise a new, more sensitive way of tracking human exposure to air pollution in cities. Their method uses mobile phones to track the location and movements of millions of people through cities, which vary in terms of their pollutant concentration by local area.

Considered to be one of the leading causes of death, disease, and illness, particularly for those in urban areas, air pollution exposure has traditionally been measured in city populations that remain static – without taking into consideration the fact that people tend to move to different locations throughout the day.

As a proof-of-concept study that underlines the ability of the technique to improve public health in cities all around the globe, the team conducted research in the city of New York. Their work has just been published here in the journal Environmental Science & Technology.

Assistant professor in civil structural & environmental engineering, Aonghus Mc Nabola, said: "Up to now much of our understanding of the impact of air pollution on population health has been based on the relationship between air quality at fixed locations and mortality/morbidity rates in the population. As these fixed locations are not always an accurate measure of the exposure the population experiences, accounting for the movements of people as has been done here, will improve our understanding of this relationship. The findings will be important for future population health assessments."

It is projected that 70% of the world’s population will live in cities in the year 2050. As urban populations considerably increase, so will the number of people contributing to and being exposed to air pollution, which continues to be a major health concern for cities worldwide. A recent report by the World Health Organization states that more than 7 million premature deaths are attributable to air pollution each year globally; with approximately 3.7 million due to outdoor air pollution.

Around 80% of the global urban population is currently exposed to air pollution levels above the WHO recommended standards, while 50% of the world’s urban population is exposed to levels at least two and a half times higher than those standards.

The active exposure index considers a moving population, based on activity from the mobile phone network. High exposure index districts are more centralised. This knowledge is useful for targeting specific areas in which to attempt to reduce pollution.

Consequences of air pollution exposure include heart and lung-related deaths and illnesses as well as a myriad of other public health problems. However, a number of major environmental epidemiological studies have linked air pollution to these health effects, assuming that everyone remains at the same location throughout the day.

Dr Marguerite Nyhan from Harvard University and formerly Trinity, led the study. She said: “The growing accessibility of vast digital data sets has now enabled researchers to access the movements of entire urban populations, thus enabling scientists the ability to produce more detailed and accurate exposure assessments.”

To trace the large-scale movements of people in New York City, researchers tracked the communication requests sent from millions of mobile phones to thousands of cell phone network antennae dispersed throughout the city’s 71 districts. They then intersected this information with neighborhood air pollution measurements, which enabled them to identify where and when people were most at risk – with major implications for environmental policy and public health.

Rex Britter, Emeritus Professor at Cambridge University and Visiting Scientist at MIT, said: “This study will greatly improve how public health officials understand population exposure to air pollution and how people’s daily movements can impact public health. The work will have ramifications in a diverse range of fields including those that address environmental concerns, digital technologies and mobility, and public health on a large scale.”

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