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Invisible Stars: Mapping America’s Rural Light Pollution

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Rural light pollution map of United States

Invisible Stars: Mapping America’s Rural Light Pollution

From the bright lights of Times Square to the high-powered flood lights of a suburban Walmart, we expect our cities to give off a certain amount of light pollution. Even though our view of the universe is largely blotted out around city centers, there’s a measure of comfort in knowing an inspiring view of a starry night is only a short drive away.

Increasingly though, economic activity in America’s rural spaces is casting a glow into the sky, and now four out of five people in North America cannot see the Milky Way at night.

Today’s map, from geographer and journalist, Tim Wallace, is a different perspective on light pollution in the United States. The map was created by subtracting population from light output, which highlights areas that throw off more light than predicted given their population density.

On this style of map, it isn’t the glowing metropolitan centers of New York and Los Angeles that stand out, but regions like the oil-rich corner of South Dakota or the final leg of the Mississippi River. Let’s zoom in and investigate what’s happening in these unexpected illumination zones.

Oil & Gas

Some of the most prominent patterns on the map appear in regions where shale oil is being extracted.

texas north dakota gas flares

In a relatively short amount of time, America became the largest oil producer on the planet. One of the major factors that fueled record production for shale oil producers was the proliferation of multi-well pad drilling — when multiple wells are drilled from a single drill site. From the air, it’s easy to spot these well formations spreading across the landscape, but the effect is even more pronounced at night.

At times, oil production is so strong that drillers flare the excess natural gas. In North Dakota alone, there are nearly 14,000 producing wells, and the resulting flares are what create the distinctive grid patterns on the map.

One of the brightest areas per capita in the country is Loving County, Texas. The county has around 100 residents, but more than 6,000 drilled wells.

Industrial Activities

Another point of interest on the map is Louisiana’s “petrochemical corridor”, running between New Orleans and Baton Rouge. An overhead view of Southern Louisiana in the daytime will be punctuated by the “ribbon farms” flanking the Mississippi River — a nod to the region’s history of French settlement.

petrochemical corridor louisiana

At night though, a different scene emerges. Over 100 sprawling petrochemical facilities run by companies like Dow Chemical and Union Carbide dot the landscape, a patchwork of highly-illuminated plots.

Commercial Sprawl

Some types of infrastructure are typically located away from the city center. Airports, power stations, and racetracks, for example, need a lot of space and aren’t the most popular neighbors.

Another type of facility has been replacing farmland in recent years — logistics hubs. Many of the bright spots on the map outside cities show the warehouses and sortation centers that feed our growing demand for e-commerce.

economic logistics sprawl

In the example above, companies like Amazon, Home Depot, Dollar Tree, and Ikea have all clustered their facilities in the sparsely populated farmland south of Joliet, Illinois. This trend is repeated around the country, resulting in the “halos” of light that ring most cities on the map.

Flipping the Switch on Light Pollution

Though light isn’t toxic or overtly damaging to the natural landscape, it can still have a serious impact on wildlife, as well as blunting the beauty of the night sky.

The good news is that light is one of the easiest forms of pollution to prevent. New technologies and lighting techniques aren’t just good for our night skies, they’re generally more energy efficient as well.

Just as economic incentive lured buildings and infrastructure to America’s natural spaces, it may be energy efficiency that helps us return more of the night sky to its natural state.

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Environment

The Most Polluted Cities in the U.S.

What are the most polluted cities in the U.S. according to data from the American Lung Association’s 2024 State of the Air Report?

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Teaser image for an infographic showing the most polluted cities in the U.S. according to the American Lung Association's 2024 State of the Air report.

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The following content is sponsored by National Public Utilities Council

The Most Polluted U.S. Cities in 2024

According to the World Health Organization, air pollution is responsible for 7 million deaths annually, and could cost the global economy between $18–25 trillion by 2060 in annual welfare costs, or roughly 4–6% of world GDP.

And with predictions that 7 in 10 people will make their homes in urban centers by mid-century, cities are fast becoming one of the frontlines in the global effort to clear the air.

In this visualization, we use 2024 data from the State of the Air report from the American Lung Association to show the most polluted cities in the United States.

What is Air Pollution?

Air pollution is a complex mixture of gases, particles, and liquid droplets and can have a variety of sources, including wildfires and cookstoves in rural areas, and road dust and diesel exhaust in cities. 

There are a few kinds of air pollution that are especially bad for human health, including ozone and carbon monoxide, but here we’re concerned with fine particulate matter that is smaller than 2.5 microns, or PM2.5 for short. 

The reason for the focus is because at that small size, particulate matter can penetrate the bloodstream and cause all manner of havoc, including cardiovascular disease, lung cancer, and chronic pulmonary disease. 

The American Lung Association has set an annual average guideline of 9 µg/m³ for PM2.5, however, the World Health Organization has set a much more stringent limit of 5 µg/m³.

The 21 Worst Polluted Cities in the U.S.

Here are the top 21 most polluted cities in the U.S., according to their annual average PM2.5 concentrations:

RankCity, StateAnnual average concentration, 2020-2022 (µg/m3)
1Bakersfield, CA18.8
2Visalia, CA18.4
3Fresno, CA17.5
4Eugene, OR14.7
5Bay Area, CA14.3
6Los Angeles, CA14.0
7Sacramento, CA13.8
8Medford, OR13.5
9Phoenix, AZ12.4
10Fairbanks, AK12.2
11Indianapolis, IN11.9
12Yakima, WA11.8
13Detroit, MI11.7
T14Chico, CA11.6
T14Spokane, WA11.6
15Houston, TX11.4
16El Centro, CA11.1
17Reno, NV11.0
18Pittsburgh, PA10.9
T19Kansas City, KS10.8
T19Las Vegas, NV10.8

Note: The American Lung Association uses Core Based Statistical Areas in its city and county rankings, which have been shortened here to the area’s principal city, or metro area in the case of the Bay Area, CA.

Six of the top seven cities are in California, and four in the state’s Central Valley, a 450-mile flat valley that runs parallel to the Pacific coast, and bordered by the Coast and Sierra Nevada mountain ranges. As a result, when pollution from the big population centers on the coast is carried inland by the wind—cities #5 and #6 on the list—it tends to get trapped in the valley. 

Bakersfield (#1), Visalia (#2), and Fresno (#3) are located at the drier and hotter southern end of the valley, which is worse for air quality. The top three local sources of PM2.5 emissions in 2023 were farms (20%), forest management / agricultural waste burning (20%), and road dust (14%). 

Benefit to Economy

While the health impacts are generally well understood, less well known are the economic impacts.

Low air quality negatively affects worker productivity, increases absenteeism, and adds both direct and indirect health care costs. But the flip side of that equation is that improving air quality has measurable impacts to the wider economy. The EPA published a study that calculated the economic benefits of each metric ton of particulate matter that didn’t end up in the atmosphere, broken down by sector. 

SectorBenefits per metric ton
Residential Woodstoves$429,220
Refineries$333,938
Industrial Boilers$174,229
Oil and Natural Gas Transmission$125,227
Electricity Generating Units$124,319
Oil and Natural Gas$88,838

At the same time, the EPA recently updated a cost-benefit analysis of the Clean Air Act, the main piece of federal legislation governing air quality, and found that between 1990 and 2020 it cost the economy roughly $65 billion, but also provided $2 trillion in benefits

Benefit to Business

But that’s at the macroeconomic level, so what about for individual businesses?

For one, employees like to breathe clean air and will choose to work somewhere else, given a choice. A 2022 Deloitte case study revealed that nearly 70% of highly-skilled workers said air quality was a significant factor in choosing which city to live and work in.

At the same time, air quality can impact employer-sponsored health care premiums, by reducing the overall health of the risk pool. And since insurance premiums averaged $7,590 per year in 2022 for a single employee, and rose to $21,931 for a family, that can add up fast. 

Consumers are also putting their purchase decisions through a green lens, while ESG, triple-bottom-line, and impact investing are putting the environment front and center for many investors.

And if the carrot isn’t enough for some businesses, there is the stick. The EPA recently gave vehicle engine manufacturer Cummins nearly two billion reasons to help improve air quality, in a settlement the agency is calling “the largest civil penalty in the history of the Clean Air Act and the second largest environmental penalty ever.”

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