The bigger the warehouse, the worse the air pollution, NASA-funded study finds

A new study offers a stratospheric bird’s eye-view of air pollution linked to trucks serving Southern California warehouses.

Using satellite imagery, the NASA-funded study published in the scientific journal GeoHealth found that Southern California ZIP codes with large warehouses, or a large number of warehouses, had higher levels of airborne contaminants than those with fewer or smaller warehouses.

Specifically, warehouse-heavy areas had more pollution linked to exhaust from diesel-powered trucks serving Southern California’s sprawling logistics industry, which continues to add warehouses to an Inland Empire dubbed “America’s Shopping Cart” for the volume of goods that arrive through the ports of Los Angeles and Long Beach.

Diesel exhaust contains tiny particles that, when inhaled, are linked to health problems.

“Any increase in concentration causes some health damage,” Yang Liu, a study co-author and environmental health researcher at Emory University in Atlanta, said in a news release from the NASA-owned and Pasadena-based Jet Propulsion Laboratory.

“But if you can curb pollution, there will be a measurable health benefit.”

Paul Granillo, president and CEO of the Inland Empire Economic Partnership, said the logistics industry also is taking steps to curb pollution, including establishing electric vehicle charging hubs for trucks used by distribution centers.

Warehouses are a major Inland Empire employer, and the logistics industry, which grew rapidly in the region while riding an online shopping boom, is credited with helping the Inland region avoid the worst economic damage from the COVID-19 pandemic.

But critics said logistics also brings a seemingly endless armada of exhaust-belching 18-wheelers. The Inland Empire routinely ranks poorly in air quality report cards, with particulate dust in diesel exhaust linked to cancer, heart disease and other ailments.

The study, published Sept. 18, relies on satellite measurements dating to 2000 of elemental carbon and an airborne particulate known as PM2.5, both of which are found in diesel exhaust.

“Satellite observations … were essential because they provided a continuous map of pollution, including pockets not covered by ground-based instruments,” JPL’s release states.

Researchers compared the satellite data with information from a real estate database about the square footage, as well as the number of loading docks and parking spaces, at almost 11,000 warehouses in parts of Los Angeles, Riverside and San Bernardino counties and all of Orange County.

According to the study, ZIP codes in the 75th percentile for warehouse square footage had more PM2.5 and elemental carbon than those in the 25th percentile. ZIP codes with higher concentrations of warehouse loading docks and truck parking spaces also had higher levels of those airborne particles, the study found.

While the overall level of particulate pollution fell from 2000 to 2019 as stricter emission standards took effect, areas with warehouses still had “consistently higher” concentrations of particulate matter than non-warehouse ZIP codes, and the gap widened during the busy holiday shopping season, the study added.

The study comes amid ongoing efforts in California to phase out diesel trucks in favor of those with electric or other non-polluting engines. State-mandated deadlines and programs aim to get diesel-powered trucks off the roads in the coming decades.