A form of harmful air pollution that often can't be plainly observed is now being tracked with a groundbreaking new tool developed by scientists that allows residents to see where it's coming from.

The late-afternoon air near Crissy Field in San Francisco was enjoyed recently by locals who squeezed in the last minutes of sunlight for a game of fetch with their dogs, windsurfing, or simply building a sandcastle. Among those hands deep in the sand was resident Vanessa Braunstein and her son Nicholas.

"I grew up in Los Angeles, so I feel the air in San Francisco is almost so much better," remarked Braunstein

"And it feels cool," added her 5-year-old child.

But when it comes to air quality, there's a lot more than meets the eye. There's growing concern over a tiny airborne threat - a pollutant known as fine particulate matter, or PM 2.5.

"Particulate matter is like 30 times smaller than your hair," said Dr. Tanya Payyappilly CEO of Breathe California, a San Jose-based nonprofit that focuses on clean air and healthy lungs. "And that goes deep and penetrates the lungs, and it stays there."

The particles are created by combustion, including the burning fossil fuels. Research shows they are the most dangerous form of air pollution, causing inflammation. They play a role in heart disease, respiratory disorders, lung cancer, neurological disorders, infertility, and more.

Now for the first time, a groundbreaking new tool visualizes this often-invisible health threat. Climate TRACE (Tracking Real-Time Atmospheric Carbon Emissions), an independent group that monitors and publishes greenhouse gas emissions, has launched an interactive map that measures the airborne clouds containing these particles, which are known as plumes. 

The tool uses satellite technology and advanced atmospheric modeling to track the plumes from over 660 million sources worldwide. The map currently contains data for more than 2,600 major urban areas around the world, including the San Francisco Bay Area. 

"We think this will really help people realize it's much more common than you think to be exposed to dangerous levels of air pollution," said Gavin McCormick, co-founder of Climate TRACE. "You can see your neighborhood, by your house, maybe where your kids go to school, you can see how much pollution is happening there, and where it is coming from, and what can be done about it."

The idea of mapping emissions to create an accurate database began at the University of California, Berkeley. McCormick and other researchers participated in a hackathon with some Google and Facebook engineers, and they realized that if everyone used electricity at certain times, there would be no carbon footprint.

McCormick and the other U.C. Berkeley scientists decided to get into the business of using data and statistics to figure out the best times and founded a nonprofit called WattTime.

At one point, they decided to create a database that would pinpoint the cleanest suppliers of raw materials that are much lower emitting than others. They then hit upon the idea of using satellites and AI to measure all the power plants in the world.

"Then Al Gore calls, and he says, 'I've been waiting since the 1990s for technology like this! This is amazing,'" recounted McCormick.

That led to Climate TRACE, with former Vice President Gore as a co-founder, and a coalition of 150 different nonprofits and universities. The group monitors and publishes greenhouse gas emissions and now has a global map that shows plumes of particulates.

"If your child has asthma or a member of your family has difficulty breathing for other reasons, you can see exactly where it's coming from," explained Gore.

The Climate TRACE plumes map of the Bay Area, listed under "San Jose Urban Area, United States," is an eye-opener. There are numerous sources of particulate plumes, but one major source is domestic and international shipping.

The likely paths of the plumes are directed by the wind and weather. However, the quantifiable health impacts are yet unknown. Climate TRACE said that it is seeking to partner with public health institutions to connect the exposure data with established health outcome models.

"We see a lot of tanker ships come in and out of the bay," Braunstein observed from her spot at Crissy Field. "I understand that it is a big city and we need to bring things in and out, but maybe there is a way we can do it in a way that doesn't hurt the air."

McCormick said Climate TRACE will soon release some updates and solutions, with the hopes that we can all breathe easier.