Geographic Exposure to Leaded Gasoline

Tetraethyllead (or leaded gasoline) was sold within the United States from 1921 to the late 1990s (EPA. “EPA Takes Final Step in Phaseout of Leaded Gasoline.”). As the automobile began to take the United States and the world at large by storm, lead exposure, especially within cities, skyrocketed. The rise of the automobile entailed greater pollution in cities. Rapid suburbanization in the Postwar Period promised a better life for some, but did little to solve the pollution problem in the central cities. In fact, it exacerbated the problem. Suburbanites continued to work (and drive) in the urban core, but escaped the worst consequences when they return home. Suburbanization, thus, displaced the environmental costs of transportation to city dwellers.

Segregation in American cities had long racialized environmental inequalities, but white flight, beginning in the 1920s and continuing through modern times supercharged the issue of lead exposure. White flight is a term used to describe white people leaving the inner cities for suburban expansions, and influencing zoning laws and neighborhood associations to only allow white residents in these new areas. Highways connected suburban residents to urban centers, which resulted in disproportionate pollution for increasingly marginalized, non-white, and/or impoverished neighborhoods in city centers. Omaha, Nebraska is an exemplar of these trends. Although the city has always been predominantly white, communities of color suffered disproportionate exposure to lead, especially from gasoline. White flight within Omaha lead to many traffic studies within the city to discover what would be the best placement for new highways and where they were needed as people moved out of the city (Howard, Needles, Tammen & Bergendoff). Many of these studies were completed and the highways that were built contributed to development issues, especially within North Omaha as it was cut off from the city center.

This project is inspired by the work of Dr. Leif Fredrickson, and aims to explore the exposure of urban Omaha residents throughout the time period where leaded gasoline was in use. It employs GIS buffer analyses of historical street and census data, historical articles on the effects of lead (specifically within gasoline), and scholarly studies to examine who has historically been and is currently most affected by historic use of tetraethyl leaded gasoline. 

In the past, diagnosing victims of lead poisoning posed significant challenges, causing confusion and worry. Doctors frequently tested individuals from poor, Black communities for tubercular meningitis, a condition prevalent in those areas. However, this avoided the real issue at hand. The symptoms of lead poisoning closely resembled those of various common ailments such as headaches, constipation, convulsions, colic, dizziness, drowsiness, vomiting, hallucinations, or loss of motor control. However, the introduction of spectroscopy marked a turning point. This test enabled doctors to definitively identify lead contamination, allowing them to distinguish lead poisoning from other health concerns.(Fredrickson, 77.) 

Lead is especially dangerous because it can enter the body in multiple ways: through the skin, digestive tract, or inhalation. Lead-contaminated blood distributes the poisonous metal into the body’s tissues. Its impacts on the brain can lead to serious physiological damage. Lead is most impactful in children, whose bodies are still developing as they take in more than a fully grown body (Hollingsworth and Rudick 349.) Lead damage causes long term issues such as cardiovascular illness, infertility, and psychological development and behavior.  

According to the Agency for Toxic Substances and Disease Registry, tetraethyl entering the body is especially harmful due to how easily it is absorbed or inhaled. More specifically, it is more dangerous than lead consumed through paint chips (Hollingsworth and Rudick 349). It is especially harmful because of how it is easily absorbed/inhaled at low levels of exposure. Any exposure to lead is harmful, but regulations have been set to determine what is tolerable. When leaded gasoline was used, the most common exposure was through inhalation. It was nearly impossible to avoid tetraethyl that polluted the air. People of all ages took in lead through inhalation, dust, and ingestion of soil or food. A Princeton study of the "Elimination of Leaded Gasoline" found that the difference of children exposure was that they took in more from soil and dust ingestion. As leaded gasoline slowly became banned, less exposure to tetraethyl happened through inhalation (Thomas 308.) Nowadays, lead is mainly consumed through soil and paint of old buildings or areas.

When combined with other disproportionate risks due to housing, access to medical care, and other compounding factors, this is a clear case of environmental injustice having an outsized impact on already marginalized communities. There are also many portions of this map which appear to have deceptively low soil lead levels. For example, the Old Market area appears to have very low soil lead levels based on the color of each property in this graph. When looking at an example property, such as 1400 Douglas St, it appears to be shaded very lightly. However, upon closer inspection of the pop-ups, you see that this property was never actually sampled at all, and is ineligible for sampling. Because there is no sample listed, it is given a lead level of 0.0 ppm, even though it is likely to be higher. Much of the Old Market is listed this way, because it has historically been commercial property, and therefore ineligible for testing. When you understand this, it makes it all the more clear that the areas with the highest concentrations of soil lead in the city overlap with areas near the most popular roads in use before leaded gasoline was banned.

While average blood lead levels (BLLs) have likely declined over time in Omaha, this does not mean that there are not lasting effects (Fredrickson, 2017). Instead, it points to the relative success of remediation programs and governmental regulation which have helped lower the average BLL in Omaha, despite continued significant exposure due to its historic use and long life in the environment once deposited.

Understanding road use in Omaha during the era of leaded gasoline use is the corner stone of understanding disproportionate exposure to lead. This is due to the lead pollution within the atmosphere that was increased by automobiles, especially around heavily trafficked roads. As those that lived near busy roads were unable to escape their poor quality of living as a result of redlining policies and low income (Fredrickson, 177).

This map from a 1956 traffic study shows the most heavily trafficked roads within the Omaha metropolitan area. These maps were created by traffic studiers and funded by the city of Omaha. Their goal was to aid in reducing traffic throughout the city. This was important due to the rapid suburbanization of Omaha during this time period, making immense traffic into the city one of the biggest issues facing Omaha. These studies tracked heavily trafficked roads to determine where highways would lie, but also display what parts of Omaha were most aggressively exposed to lead within gasoline.

They can also be utilized to display exposure of leaded gasoline. Using a buffer analysis of the busiest roads of the time along with census data from the time period, it is possible to examine disproportionate exposure to lead across demographic groups.

The following vector maps were made using QGIS, and used historic maps of Omaha to display the historic roads across different time periods. After this 1955 traffic study, Omaha created a freeway through the city that shifted many of the roads in a slight way over time. This means that the historical roads are no longer where their modern equivalent lies, for example Hamilton experienced a notable shift. As a result, the roads may appear to be out of place, but in reality they are shown where they were historically, making the exposure date more accurate.

First, we examined road placement and usage from the 1930s, when leaded gasoline in Omaha was gaining popularity, and had been in use for some time.

As time has gone on, popular road usage changed, and where people live has changed as more wealthy white citizens moved westward. Omaha city limits were and continue to expand due to the annexation of suburbs and Sanitation Improvement Districts (SIDs). Because of this, traffic use decreased in the urban core, and instead focused on arterial roads used for populations in the suburbs to commute into the city.

To analyze which groups are most exposed to health hazards related to the use of leaded gasoline, we wanted to examine the roads in Omaha that have been most heavily used over the longest period of time when leaded gasoline was in use. Therefore, we compared the location of most heavily used roads from 1938 and 1948 to the locations of different racial groups in Omaha today.

The effects of using lead in gasoline on populations living near busy roads is clear when examined at the time of this pollution, but why do we still care today? Pollution from gasoline-powered cars is a leading contributor to modern urban air pollution, and this was true while leaded gasoline was in use as well (Fredrickson, 2017). However, due to its extremely long half-life in the environment, lead exuded from the exhaust of gasoline does not disappear quickly. Lead's half-life in soil is estimated to be approximately 700 years (Semlali et al., 2004). This means that large amounts of lead can accumulate around roads unless properly remediated, and thus can have serious effects on a community long after lead was phased out of gasoline. Continued suburban expansion, the building of expressways, and efforts to deal with congestion in the urban core frequently caused an increase in lead pollution by allowing more cars to travel the same area every day, often at higher speeds, which deposited more lead that would remain there for years to come (Fredrickson, 2017). Therefore, it is important to examine which communities are in areas most likely to have large buildups of lead due to long-term historic use of leaded gasoline, in order to better prevent and treat the exposure and affiliated symptoms of lead poisoning still taking place today.

We can see here that as mostly white populations moved westward, marginalized racial groups largely stayed closer to the core of the city, to the east. This is important because the core of the city has the oldest roads with the longest continuous heavy use by cars using leaded gasoline. To examine who specifically is most impacted by close proximity to these roads, we performed a buffer analysis using a combined layer of the 1938 and 1948 most heavily used roads:

From this buffer analysis, we find that those living in the closest vicinity to these roads with long-term exposure are disproportionately from marginalized racial groups:

Here, we see that Black people make up almost 30% of those living within the buffer zone. This is significantly higher than the total percentage of Black people in Omaha, which is around 12%. This pattern is also true for both Hispanic and Asian people, though the difference is not as extreme. In contrast, White people are less than 45% of the exposed population, but make up over 70% of Omaha's total population. The result is clear: Marginalized racial groups, and Black people in particular, are at a higher risk of exposure to the hazards of historic use of leaded gasoline in Omaha.

This is especially important when considering other lead exposures in the surrounding area, which result in high levels of lead in soil:

The use of leaded gasoline within automobiles was officially banned in 1996, however the issues of pollution from tetraethyl lead still persist. Soil within Omaha has a notably high lead content, making it unsafe for children to interact with, as well as poor for growing food. Leaded fuel is still used within small aircrafts, specifically piston engine aircrafts. Although there have been recent pushes to ban the use of leaded fuels within these aircrafts, issues still persist. Articles about the negative effects of leaded fuel within aircrafts are written often, the most recent large article coming from the Washington Post on October 18, 2023. This exposure may seem more like an individual chosen hazard for those within the aircraft, but that fails to consider the atmospheric pollution that these aircrafts cause. More lead within the atmosphere is never a good thing, as it leads to more lead within the soil, water, or even the air we breathe.

The use of leaded gasoline had many lasting effects in the Omaha area, but it is clear that it disproportionately affected Black communities. The process of exposure to leaded gasoline is clear: where there are cars, there are emissions of lead in the atmosphere. More importantly, where there is traffic and heavily congested streets, there is even more exposure to and inhalation of tetraethyl lead. As seen on the second map above, areas with Black residents have the highest exposure to leaded gasoline. It's important to note that after many white people moved into suburbs and away from the city congestion, Black communities were left with busy roads and exposure to polluted air. During the time that leaded gasoline was in use from the 1930s-1960s, Black people did not have equal opportunities to respond to the lead epidemic. They lacked access to healthcare, education about the issue, and due to restrictive housing and loan policies, far less capacity to move to healthier environments. Combined with proximity to industrial sources of atmospheric lead and residential exposure in declining housing stock, this created a toxic interplay of exposure difficult to escape in an age of enforced segregation.

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