Smartphones monitor air pollution

The portable pollution sensor known as ‘Citisense’ delivers real-time data on air quality to the user’s mobile and home computer.

The sensors detect ozone, nitrogen dioxide and carbon monoxide levels, the most common pollutants emitted by cars and trucks. The user’s smartphone displays a reading based on the Environment Protection Agency’s (EPA) air quality rating where green is good and purple is hazardous.

While the device and app are currently only a prototype, the team from the University of California hope that it could be used to form a network for monitoring air quality in cities as well as for personal use by people whose health is affected by pollutants such as asthma-sufferers. 

“We want to get more data and better data, which we can provide to the public,” says William Griswold, a computer scientist at the University of California, San Diego.

“We are making the invisible visible.”

The team gave the device to 30 members of staff and students at the university’s computer science department who carried them on their daily commute to work. They found that rather than diffusing equally through the air, pollution was concentrated around certain ‘hotspots’ such as main roads and busy intersections.

One of the users, Wendy Chapman, found that when she biked in using the bike path along State Route 56 she was exposed to the most pollution whereas when she drove home along the same road, she had virtually no exposure.

“The people who are doing the most to reduce emissions, by biking or taking the bus, were the people who experienced the highest levels of exposure to pollutants,” says Griswold.  

Armed with information about where they were likely to encounter the most pollution, users were able to take action such as changing their route to travel along less busy streets or if they were commuting by bus, not to queue near the bus’s exhaust pipe.

Griswold and his team believe that the technology in the sensors could eventually form a large network of sensors that feed back into a large centralised computer where they can be analysed and accessed by the health and environment authorities as well as members of the public.  

The EPA currently has only a very small number of sensors monitoring air quality in cities. For example San Diego County has a population of 3.1 million, living over 4,000 square miles, and only 10 stations.