What are the major patterns that stand out?
Several key patterns that stand out from this analysis.
Louisiana has far more emissions than Mississippi. While this might be apparent to people who know these states well, the significant difference reveals the heavily industrialized nature of Louisiana. In many other ways, the two states are relatively similar. Louisiana and Mississippi are relatively similar in geographic area, have similarly sized populations, similar cultures and similar histories. The significant difference between Louisiana and Mississippi lies in the heavily industrialized nature of Louisiana’s economy.
Louisiana's industrial emissions are concentrated in two major areas. One area is the Lake Charles region in Calcasieu Parish, in southwest Louisiana. For many greenhouse gases and air pollutants, Calcasieu Parish is the parish with the highest total emissions. The second area of concentrated emissions stretches from the northern edge of Baton Rouge along the Mississippi River to south of New Orleans. This is the region that is often called, "Cancer Alley." These two areas contain many large facilities like oil refineries, power plants, and chemical manufacturing plants.
Concentrated emissions occur in other parts of the region. Other parts of Louisiana and Mississippi also have significant emissions. Large industrial facilities are located outside of the two industrial centers, including places like Brame Energy Center, a large power plant in Rapides Parish, Louisiana, Chevron’s Pascagoula Refinery on the Mississippi coast, and the Caledonia Power Plant near Columbus, Mississippi. Sections of rural areas of Mississippi have significant emissions of ammonia and non-methane volatile organic carbon (NMVOCs) which are likely the result of agricultural practices.
The time series show different patterns in emissions across the region; some gases have decreased, some have increased, others have stayed the same.
Some air pollutants, like SO2, have decreased substantially in many parishes and counties. These emissions reductions are likely the result of laws, most notably the federal Clean Air Act, which directly addresses SO2 pollution. In some parts of Louisiana, SO2 reductions are linked to a period in the late 1980s and early 1990s when Paul Templet, the Secretary of Environmental Quality under Governor Buddy Roemer, took a particularly active role in addressing air pollution.
The decrease in SO2 does not mean air pollution is improving across the region. In some parishes along the lower Mississippi River, emissions of non-methane volatile organic carbon (NMVOCs) have changed little since 1970. This could be important to residents in the region concerned about cancer risks from air pollution because NMVOCs include toxic and cancer-causing chemicals like formaldehyde, benzene, and ethylene.
Emissions of some chemicals, particularly greenhouses, are increasing. These increased greenhouse gas emissions are common in the heavily industrialized regions along the Mississippi River and Lake Charles.
Ascension Parish, which is located along the Mississippi River between New Orleans and Baton Rouge, shows these three major patterns. In the years since 1970s, SO2 emissions have decreased, NMVOCs have stayed roughly constant, and CO2 emissions have increased.
Demographic patterns are linked to modern patterns of industrialization and historical factors- including enslavement. One of the largest areas with high emissions, the Mississippi River Industrial Corridor also has a large population of Black residents, and many of whom live near areas where their ancestors were enslaved. The data presented here show a clear link between industrialization along the lower Mississippi River and air pollution. However, the link between demographics and emissions can vary from place to place. For example, Louisiana's Calcasieu Parish- home to many industrial facilities- also has a large white population.
The Mississippi Delta, a broad area of northeast Louisiana and west Mississippi that surrounds the Mississippi River is a clear signal in this analysis. The Delta is home to a large Black population, many of whom live near or below poverty levels. As scholars and residents have known for centuries, the experiences of the people in this area are closely tied to the history of enslavement, segregation, plantation economy, and discrimination. This study shows large industrial facilities are largely absent in this region, and the fingerprint of industrial pollution is lower in the Delta than in other comparable areas.