Study Methodology

Sierra Club analysts obtained from the real estate information firm CoStar a nationwide list of existing and proposed locations categorized as “warehouse,” “distribution,” “light distribution,” and “refrigeration/cold storage,” with “rentable building area” over 100,000 square feet.

Our analysts then used the US EPA’s EJScreen Mapping Tool to overlay demographic information about residents living within a half mile of the warehouses and distribution centers. The analysts queried ambient concentration of PM 2.5 air pollution, National Air Toxics Assessment diesel particulate matter exposure, and total population as well as the percentage of residents who are people of color or low income, provided by the US Census Bureau’s 2013–2017 American Community Survey.