Warehouses add 17.9% more nitrogen dioxide to their communities
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Key takeaways:
- The study examined nitrogen dioxide levels around 149,075 warehouses in the United States.
- Communities with warehouses had 69.5% more Black residents compared with the national median.
Communities with warehouses were exposed to an average of 17.9% more nitrogen dioxide than other communities, according to a study published in Nature Communications.
These communities have disproportionately large minority and marginalized populations, Gaige Hunter Kerr, PhD, assistant research professor, department of environmental and occupational health, George Washington University, and colleagues wrote.
“As a team of air pollution researchers, we heard concerns from air quality regulators and community-based organizations about the growing warehousing industry and the potential for this industry to negatively impact local air quality,” Kerr told Healio.
“Yet there were no nationwide studies documenting the potential air pollution associated with warehouses and the heavy-duty vehicles that frequent them,” he continued. “Thanks to NASA support, we were able to investigate this important research question.”
NO2 around warehouses
“Nitrogen dioxide is a health-harming pollutant regulated under the Clean Air Act,” Kerr said. “Exposure to nitrogen dioxide has been linked with asthma onset and exacerbation, other respiratory disease, even premature death.”
Using the 2021 CoStar dataset of 149,075 warehouse locations across the contiguous United States, the researchers analyzed satellite data tracking nitrogen dioxide (NO2) within about 7 km of these facilities from the European Space Agency’s TROPOspheric Monitoring Instrument.
Nearly 20% of these warehouses could be found in just 10 counties (0.3%) in the United States. Also, the total number of warehouses increased by 117% between 2010 and 2021, the researchers said, adding that these new facilities were significantly larger and could accommodate much more traffic than their predecessors.
“We found that, on average, an earth-observing satellite was able to detect a 20% increase in the traffic-related air pollutant nitrogen dioxide,” Kerr said.
Comparisons of urban and rural locations found local increases in NO2 near warehouses that ranged from 4.3% to 21.5%. Warehouses that stood alone were associated with an average increase of 11.5%. The largest clusters of warehouses were associated with an average increase of 23.1%.
The number of loading docks and parking spaces that each warehouse had as well as warehouse clustering were associated with significant and nearly monotonic increases in NO2 across environments with low and medium density, the researchers said.
“Some warehouses had more loading docks, therefore increasing their ability to accommodate traffic, and some warehouses were located next to other warehouses in dense clusters,” Kerr said.
“Near these warehouses, we found more heavy-duty traffic activity and more satellite-measured nitrogen dioxide pollution,” he continued.
The strongest association between NO2 and warehouses came with clustering, the researchers continued, accounting for nearly 40% of the increase in NO2 when warehouses were in environments with low population densities.
Environments with higher population densities had weaker relationships between NO2 and loading docks, parking spaces and clustering, the researchers said, probably because these areas have more complex mixtures of nitric oxide and NO2 sources.
There were further associations between increased truck traffic near warehouses and larger warehouse clusters, more loading docks and more parking spaces, the researchers said.
Each additional loading dock within a census tract was associated with a 1,456 km increase in truck vehicle kilometers traveled (VKT), and each additional warehouse was associated with a 485 km increase of truck VKT, within the near-warehouse area.
As near-warehouse truck traffic increased across different population density environments, the researchers continued, near-warehouse NO2 increased significantly as well.
When the researchers excluded other potential sources of nitric oxide and NO2, they found that warehouses still accounted for NO2 increases that ranged from approximately 5% to 30%, with smaller increases in areas that had emissions with less intensity.
For example, the researchers said, areas with low levels of on-road emissions may indicate warehouses with long-term storage instead of last-mile facilities, driving these differences.
Community populations
“Warehouses tend to be located in communities of color throughout the United States and census tracts with the largest number of warehouses had several hundred percent more Hispanic and Asian residents than nationwide average values,” Kerr said.
In comparison with national medians, census tracts with warehouses had 59.7% more Hispanic residents; 69.5% more Black or African American residents; 50.9% more Asian, Native Hawaiian or Pacific Islander residents; and 31.5% more residents of other or two or more races.
Proportions of racial and ethnic minorities in these tracts increased as the numbers of clustered warehouses increased as well, the researchers said.
Whereas Hispanic residents account for a median of 8.3% of the total U.S. population, they represent 28.1% of the population of the top 10% of tracts with the most warehouses for a nearly 240% increase.
Similarly, Asian residents account for a median of 1.6% of the total U.S. population and 6.2% of the population of the top 10% of tracts with the most warehouses for a nearly 290% increase.
Generally, the researchers said that larger proportions of racial and ethnic minorities were associated with increases in parking spaces, loading docks and building areas, but this did not persist for each population subgroup.
For example, there were increased proportions of Black or African American residents with increases in loading docks and building area but not with increases in parking spaces, the researchers said.
The researchers also categorized disparities in individual states as largely consistent with their nationwide findings, although tracts with warehouses in a few rural states such as Idaho and Montana had smaller proportions of ethnic and racial minorities compared with their statewide medians.
Populations of racial and ethnic minorities living near warehouses experienced higher NO2 levels even relative to overall near-warehouse NO2 levels, the researchers continued. Hispanic populations experienced levels that were 29.1% higher, and populations of residents of other or two or more races saw 28% higher levels, representing the largest differences relative to overall exposures.
Black and African American populations living near greater numbers of warehouses, loading docks and parking spaces experienced 2.1% less NO2 exposure compared with average near-warehouse levels, the researchers said.
But in 43 of 49 states, the researchers continued, Black and African American populations were exposed to higher near-warehouse NO2 compared with the overall near-warehouse population. Removing the six states with lower NO2 exposures yielded a 0.8% increase in NO2 exposures over average near-warehouse levels for these populations.
Conclusions
Based on these findings, the researchers said that warehouses drive increases in NO2 in the communities where they are located, with even greater increases among communities of racial and ethnic minorities.
“The warehousing industry is a growing industry that is likely to stick around,” Kerr said.
But unlike other highly regulated sources of air pollution such as factories and power plants, he continued, warehousing has not seen the same degree of regulations and oversight, even though it represents an indirect source of pollution.
“Our findings are also significant because of the populations that the warehousing industry disproportionately affects,” Kerr said.
These findings may inform policy pertaining to zoning, transportation, the environment, emissions and public health and equity, the researchers said, on the federal as well as on the state, local and corporate levels.
“There are actions that policymakers and corporations can make to protect communities from health-harming air pollution associated with this industry,” Kerr said.
“Policymakers can implement indirect source rules that offset and regulate air pollution around warehouses, pass regulations to tighten vehicle engine standards, and also speed up or expedite permitting for electric vehicle charging infrastructure,” he added.
Also, Kerr said, corporations can commit to phasing out their older, diesel vehicles or electrifying their fleet.
Health care providers can take action to mitigate these effects as well, Kerr added.
“Air pollution as a risk factor has not been emphasized in medical education and disease prevention programs, so physicians could make this environmental risk factor a topic of conversation among their patients in the clinic and peers,” he said.
Providers also should encourage patients, especially those in sensitive groups, to stay up-to-date on air quality alerts and avoid activity during air pollution events, Kerr continued.
“They also could provide these patients with tips on avoidance behaviors, such as those from the American Heart Association,” he said.
However, the researchers also called for further research that would help determine the utility of satellite NO2 data in evaluating the impact that individual warehouse facilities or clusters may have in limited geographical areas.
“Nitrogen dioxide is just one health-harming air pollutant emitted by heavy-duty vehicles,” Kerr said.
“Through work funded by NASA and the Health Effects Institute, we are both exploring how other vehicle-related pollution, like particular matter or black carbon, may also be higher around warehouses and using detailed computer models of the atmosphere to understand how vehicle electrification may reduce air pollution in urban areas of the U.S., including near warehouses,” he said.
Reference:
- Warehousing industry increases health-harming pollutants. https://publichealth.gwu.edu/warehousing-industry-increases-health-harming-pollutants. Published July 24, 2024. Accessed July 24, 2024.
For more information:
Gaige Hunter Kerr, PhD, can be reached at gekerr@gwu.edu.
Perspective
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The findings of this study are significant and are not surprising at all. This study illustrates very clearly the effects of large amounts of commerce traffic combined with a significant amount of idling in areas of warehouses. I appreciate the fact that the study is able to quantify the increases in pollution in those areas and illustrates the disproportionate impact of this air pollution in underserved communities.
As a pediatrician in southern California who deals with asthma, these results confirm my own subjective observations that children who live near significant warehouse traffic are more likely to have asthma and are more likely to have worse respiratory illness than children who live in an area with less air pollution.
In much the same way that physicians screen for level of exercise, depression, access to healthy food and other factors that can impact the health of a patient, physicians should be aware of where a patient is living. The environmental risk factors in the area where a patient lives, particularly air pollution, should be reviewed with the patient.
Also, education should be given to the patient regarding best times to exercise, how to avoid air pollution, and what can be done in the house to help reduce indoor air pollution, keeping in mind the financial and social resources of the patient. I urge physicians to speak up at local government meetings to share their experiences regarding the effects of this type of pollution on their patients as well.
Approval of warehouse facilities should be done in consideration of the nearby populations and other factors such as air patterns in the area. This type of data may help to compel government agencies to consider placing warehouses of this type in areas that are less populated.
The next step in this research is to correlate the prevalence and severity of disease in the areas affected by warehouse traffic. Since this air pollution can affect every system in the body and can have a wide range of associated illness from asthma to cancer, the research should measure all disease prevalence (and severity) in those areas, such as cancer rates, asthma rates, rates of birth defects, and prevalence and rates of cardiovascular disease.
Warehouses and commerce are important to the economy and to the livelihood of many families in this country, but we cannot sacrifice the health of the population by constructing these facilities close to large communities.
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