The study, published this week in the Proceedings of the National Academy of Sciences, analyzes a few key points.
- First, researchers at the University of Minnesota pinpointed what products and services were created with a byproduct of air pollution (e.g. factories or transportation).
- They then looked at what demographics were buying or benefiting from these goods and services.
- Next, they located areas that experienced the most air pollution and broke those areas down by demographics to determine who was exposed to the most pollution.
By combining these pieces of information, researchers could see that there was a difference between the groups whose consumption habits indirectly contributed to air pollution, and groups that lived in areas with the highest amount of air pollution.
How do you determine who's 'responsible' for air pollution?
The study broke down the flow of air pollution like this:
A factory, for instance, creates air pollution, but it is the consumer demand for whatever good is produced that necessitates the factory's operation.
The same logic can apply to planes, trains and any other service or good that produces air pollution when a demand is met.
So, no, it's not quite accurate to say a consumer necessarily causes pollution. But these sources of pollution are surprisingly wide-ranging and directly tied to lots of everyday goods and services.
"While the consumption of energy and products is driven by the consumer, that pollution is coming from the system that produces our electricity and produces our food and gets our goods around the country," said David Reichmuth, a senior engineer with the clean vehicles program at the Union of Concerned Scientists who worked on the study. "The pollution is coming from the systems we use, not the consumers. It's coming from electricity generation, coal, fossil fuels and even fertilizer and animal waste."
In order to figure out who was using what, researchers separated "end-use" categories into seven groups, including electricity, food, goods, information and entertainment, services, shelter and transportation.
They also separated the consumers of these products into three ethnic groups: white, Hispanic and black, as well as a separate category for government (i.e. non-individual) consumption.
They found that, between 2003 and 2015, personal consumption by white consumers contributed more to air pollution.
How can some people be more affected by air pollution?
There is more than one type of air pollution, and this study focused on what is called "fine particulate matter," a type of pollution that is especially harmful to humans.
"When you think about particulate matter, you might first think about dust, but we're talking about particles that are much smaller," says Reichmuth. "It gets deep into your lungs and bloodstream. It literally shortens people's lives."
Unfortunately, the way this particulate matter is made, where it ends up in the atmosphere and who it ultimately affects is a complex process. Reichmuth explained that some of this particulate matter is actually made in the atmosphere when different chemicals and gasses combine.
"So, for instance, even if you don't see gasoline coming from a tailpipe, it is still producing nitrous oxide," he said. "It's still producing components that can later produce particulate matter."
The study calculated ground-level pollution concentrations and mapped them to different demographic population areas. The result showed that more of this dangerous pollution was concentrated in areas with high black and Hispanic populations.
This pollution "is disproportionately induced by the racial-ethnic majority and disproportionately inhaled by racial-ethnic minorities," the study said.
"On average, non-Hispanic whites experience a 'pollution advantage': They experience ∼17% less air pollution exposure than is caused by their consumption. Blacks and Hispanics on average bear a 'pollution burden' of 56% and 63% excess exposure, respectively, relative to the exposure caused by their consumption."
Why, exactly, minority populations experience more air pollution than they cause is a complex metric that takes into account local geopolitics, patterns of social behavior and class history.
Some of it has to do with direct exposure to pollution. So, for instance, living close to freeways or factories would put one at risk of higher pollution exposure.
When Reichmuth worked on a study of pollution exposure of different racial groups in California, he found that white Californians were exposed to less pollution than Hispanic and black Californians.
"Part of the reason is, it's just where populations in the state are. Part of it is where people live and where we put these sources of pollution. Historically, it's where we have put freeways, where we have encouraged and discouraged groups from living."
In his California study, Reichmuth also saw that weather, geography and atmosphere played into where pollution ended up. The basin area of Los Angeles, for instance, was well-suited to trap pollution.
What can be done?
This research, and the commonly held idea that pollution disproportionately affects minority populations, is not designed to demonize personal consumption, the study says. Rather, it is to provide a model and a method for policy changes that will help alleviate pollution damage for all people.
"Our analysis shows for the first time how pollution inequity is driven by differences among racial-ethnic groups in both exposure and the consumption that leads to emissions. Still, questions remain about the spatial context of pollution inequity, its underlying causes, how best to address it, and its generalizability," the study reads.
There is some good news: The study concluded that, despite this disparity, levels of fine particulate matter pollution have fallen across the country overall between 2003 and 2015 -- something everyone can benefit from.
"This study points out that air pollution has real consequences," Reichmuth said. "It's not just number on a spreadsheet, or who gets to enjoy blue skies. There are some individual choices we get to make, about what we buy or how we get around, but a lot of the big decisions are made at levels we don't have control over. So that's where we really need smart policies and regulations that help clean up the air. And if they take into account the current inequities in the system, it will benefit everyone."
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