Aclima: Pollution data shows how much San Diego’s skies have cleared

Air pollution has fallen dramatically in San Diego, California in recent weeks, according to data collected by Aclima‘s fleet of fixed and mobile pollution monitors. Precise measurements show the dramatic effect of work-from-home policies enforced during the pandemic and could prove invaluable in developing strategies to fight pollution on a hyperlocal level, Aclima CEO Davida Herzl said in an interview with VentureBeat.

“The reason that this data is so important is that we’ve never had control data on this scale,” Herzl said. “It’s an unnatural experiment, where you literally turn off the biggest emission sources all at once, in every county, across the state, but also around the world. And so the fact that we are collecting, measuring air quality during this time is an unprecedented experiment.”

Aclima has been working with local governments to provide “hyperlocal” air quality insights, first by measuring local air quality data and then by sharing that information publicly so communities can take action to reduce pollution. It is a potentially disruptive approach to fighting climate change and pollution, Herzl said, but she stressed that the gains we are seeing during the pandemic are not permanent.

“There is a temporary reprieve,” Herzl said. “There are a couple of things that we take away from this. I think we now have a personal experience of what clean air feels like and what it smells like. We can feel the visceral experience. I think that has the potential to really inspire people to new actions on emissions reductions.”

Above: Davida Herzl is CEO of Aclima.

Image Credit: Aclima

The company puts pollution monitors on a fleet of electric cars that drive through the city, and it also has monitors in fixed places, Herzl said. These monitors catch the pollution on every street at the level where we breathe the air, she said. The government, by contrast, only collects small samples from fixed stations, such as a single monitor for the entire city of San Francisco.

“They have very low-resolution data and they extrapolate to a large region. Aclima has published studies with a number of scientific institutions that show that pollution is actually hyperlocal, and it can vary by 5 to 8 times along the single city block,” Herzl said. “And so if you want to understand how a neighborhood experiences pollution, or how an individual might have higher levels of exposure to pollution, you need to understand what hyperlocal pollution looks like.”

The pandemic effect

The silver lining of the coronavirus that has killed more than 100,000 people in the U.S. alone is its dramatic impact on pollution, as shelter-in-place orders have taken cars, trucks, planes, and mass transit out of operation. In February and March, reduced travel correlated with a decline in air pollutant levels around the world.

In San Diego, fine particulate matter dropped 29%, carbon monoxide dropped 20%, and ozone dropped 6% in recent weeks, based on regulatory data from previous years for the Air Quality and Meteorological Information System (AQMIS) database. The company observed drops in air pollutant levels in every county in the state, starting from when the shelter-in-place order was issued through the first week in April. You can verify it by looking out the window in normally polluted cities like Los Angeles.

Above: Black carbon is an important type of particle pollution typically arising from diesel fuel combustion.

Image Credit: Aclima

In mid-April, however, Aclima began to see an increase in air pollutants in parts of California, as measured by both regulatory monitors and Aclima’s mobile sensing network. Changes in air pollutant and greenhouse gas levels can be caused by any number of factors. Many of these overlap — including precipitation, temperature, wind speed and direction, traffic patterns, and changes in human activity — so Aclima is conducting ongoing research to more deeply understand contributing factors during the shelter-in-place order.

The company is looking at the government’s regulatory data going back as far as 2017 to discount any seasonal effects on air pollution. Aclima’s own mobile sensing network has been measuring air pollutant and greenhouse gas levels in regions on a block-by-block basis since the spring of 2019. While average air pollutant levels are still lower than the average of the past three years and are below pre-pandemic levels, the upward trend in parts of San Diego is important to explore further as more people return to work.

Above: Carbon monoxide fell to lows during the lockdown in San Diego.

Image Credit: Aclima

Looking at the hyperlocal data and border areas in San Diego, you can see fluctuations in pollutant levels week over week.

Broader mission

Aclima has been measuring pollutants and greenhouse gases with its mobile sensing network in areas designated as environmental justice communities, as well as along the U.S. border with Mexico. This work supports emissions reduction efforts in parts of San Diego that are disproportionately impacted by air quality issues, including the neighborhoods near the port. “We make it easy to get this kind of environmental data in the hands of more decision makers to accelerate emissions reductions,” Herzl said.

The company said that prior to the shelter-in-place order, major freeways and roads near the coast and the border showed higher levels of the pollutant black carbon than other regions, likely relating to port activity and cross-border trucking traffic. “These front-line communities see much higher levels of pollution, and they have more health impacts,” Herzl said. “During COVID-19, there is an emerging science that shows that communities with more pollution are seeing more impact from COVID-19.”

Above: Black carbon levels are inching back up in San Diego after falling during lockdown.

Image Credit: Aclima

During the shelter-in-place period, black carbon concentrations (often from diesel fuel) fell 33% in San Diego across five weeks. But starting the week of April 12, concentrations of black carbon began to increase with the rise in other pollutants. Ongoing research is required to isolate the impact of combustion emissions versus meteorological influences on black carbon and other air pollutant concentrations.

But Herzl believes the overall message is clear: We need to invest in “decarbonization” efforts now. While such efforts could strain an economy already taxed by the pandemic, she believes we have a new opportunity to create jobs with smart energy investments.

Aclima has 120 employees and has raised $24 million from Social Capital and others.