Google Inc's Street View cars have captured the world's roads, highways and back alleys for years. Now they are being used for something entirely different: detecting the thousands of natural gas leaks blighting major U.S. cities.

 

Google cars fit with air monitors have taken millions of readings along the streets of Boston, New York and Indianapolis over the past two years as part of a program run by the non-profit Environmental Defense Fund to help reduce methane emissions.

 

The results, announced by the fund on Wednesday, reveal how common leaks are in highly populated areas that until now have not been quantified. In central Boston, leaks were discovered every few blocks.

 

While the leaks were small and did not appear hazardous, they have prompted concerns about methane whose global warming impact is 20 times greater than carbon dioxide, according to the U.S. Environmental Protection Agency. The leaks also raise questions about the safety of old pipelines carrying natural gas in growing volumes across North America.

 

Methane leaks have previously been detected, but this new method, which involved 15 million readings taken over thousands of miles, revealed the volume of gas leaking in each area.