What Is Cancer Alley? Louisiana’s Toxic Corridor

Cancer Alley is the informal name for the roughly 85-mile stretch of the Mississippi River corridor between Baton Rouge and New Orleans, Louisiana, where more than 200 petrochemical plants and oil refineries sit alongside predominantly Black and low-income communities. The name reflects decades of concern that emissions from this dense industrial cluster raise cancer rates and inflict other health harms on the people living nearby. Recent mobile-laboratory measurements have found cancer risks in some census tracts along the corridor that far exceed federal safety thresholds, lending hard data to a name that residents have used since at least the 1980s.

How the Corridor Took Shape

The Mississippi River between Baton Rouge and New Orleans has been attractive to heavy industry for straightforward logistical reasons. Deep-water shipping access, abundant freshwater for cooling, and flat riverside land made the region ideal for refineries and chemical plants starting in the early twentieth century. After World War II the petrochemical boom accelerated, and facility after facility was built along the river’s banks. Many of these plants were sited on or adjacent to former sugarcane plantations, placing them directly next to the small, historically Black communities that had grown up around those same plantations after emancipation.

Today the corridor spans nine Louisiana parishes and is home to a cumulative population of roughly 1.5 million people. The facilities produce a wide range of products: plastics, synthetic rubber, fertilizers, industrial solvents, and fuel. Each plant may operate within its individual permitted emissions limits, but the sheer density of facilities means that residents are exposed not to the output of one factory but to the combined output of dozens.

What Mobile Laboratories Found in the Air

For years, estimates of cancer risk along the corridor relied on the EPA’s modeling tools, which use reported emissions data and atmospheric dispersion models rather than on-the-ground air measurements. A 2025 study changed the picture by driving a mobile laboratory equipped with fast-response instruments through 15 census tracts along an 81-kilometer stretch of the Baton Rouge-to-New Orleans corridor, directly measuring 17 cancer-causing volatile organic compounds in the air.

In 14 of those 15 tracts, the researchers’ cancer risk estimates came in higher than the EPA’s own 2020 screening assessment. The median estimate was about five times what the EPA had modeled, and the maximum tract-level estimate reached 560 excess cancer cases per million people, well above the upper bound of the EPA’s acceptable risk range of 100 per million.¹ In other words, when researchers actually measured the air rather than modeling it from emissions inventories, the picture looked considerably worse than official estimates suggested.

A separate spatial analysis that mapped air-toxin concentrations and cancer incidence across all of Louisiana found that the highest risks were clustered in and around Cancer Alley, with one area reaching roughly 826 excess cancer cases per million, more than 27 times the EPA’s acceptable threshold of 30 per million.² These are modeled lifetime risk estimates based on measured or reported pollutant levels, not observed cancer counts, but they illustrate the scale of the potential threat.

The Chemicals Driving the Risk

Three compounds dominate the cancer risk along the corridor. By far the largest contributor is ethylene oxide, a gas used to sterilize medical equipment and as a chemical intermediate. In the mobile-laboratory study, ethylene oxide accounted for between about 40% and 92% of the total estimated cancer risk across the 15 tracts surveyed.¹ That enormous range reflects how much the contribution varied from tract to tract depending on proximity to emitting facilities and wind patterns.

Ethylene oxide earned its outsized role in cancer risk calculations after the EPA revised its toxicity assessment in 2016, concluding that the chemical posed far greater cancer risk at low ambient concentrations than previously believed. Measuring it accurately in outdoor air remains technically challenging; researchers have noted that existing measurement techniques need further development to reliably assess near-source cancer risk from the compound.³ That measurement difficulty partly explains why EPA modeling may have underestimated the risk for so long.

Chloroprene, used to manufacture neoprene synthetic rubber, is the second major contributor. It accounted for up to about 37% of tract-level cancer risk in the mobile-lab study.¹ A single facility in St. John the Baptist Parish, operated by Denka, has been the focus of intense community activism over chloroprene emissions. Animal studies clearly show chloroprene is carcinogenic, though industry-funded research has argued that humans may be less sensitive than the mice used in those studies due to differences in how the chemical is metabolized.⁴ That debate over how to translate animal results to human risk has given the facility and its defenders a talking point, but it hasn’t satisfied the community, which points to its own elevated illness rates.

Formaldehyde rounds out the top three, contributing between about 4% and 15% of total cancer risk across the tracts measured. Unlike ethylene oxide and chloroprene, formaldehyde is emitted by a wider variety of industrial processes, making it harder to pin on any single facility.

Why Official Estimates Keep Falling Short

The gap between what the EPA’s models predict and what on-the-ground measurements find is not a minor discrepancy. The mobile-lab study reported estimates that were, in the median case, five times higher than the EPA’s AirToxScreen assessment for the same tracts.¹ Several factors explain the mismatch.

The EPA’s screening tools rely heavily on self-reported emissions from industrial facilities, which represent averages over time and may not capture episodic releases, leaks, or flaring events. The atmospheric dispersion models then spread those emissions across geographic areas, smoothing out the localized spikes that a person standing downwind of a plant actually breathes. Mobile measurements, by contrast, capture what is in the air at a specific place and time, including the plumes, hotspots, and transient spikes that modeling tends to flatten out. On top of that, facilities sometimes underreport emissions or fail to account for fugitive emissions from valves, flanges, and storage tanks.

The result is that residents in Cancer Alley have often been told their air quality falls within acceptable ranges, while their lived experience of odors, health complaints, and community illness clusters suggests otherwise. The new measurement data lends scientific support to what those communities have been saying for decades.

Environmental Justice and Who Bears the Burden

Cancer Alley is not just an environmental story. It is inseparable from the history of race and poverty in the American South. The corridor’s industrial facilities are disproportionately surrounded by Black residents and low-income households, a pattern that researchers have documented with increasing precision.

A national-scale analysis of cancer risks from air toxics found that people living in low-income census tracts bore about 12% more cumulative cancer risk than those in high-income tracts, and people in predominantly Black areas carried about 16% more risk than those in predominantly white areas.⁵ These disparities hold even after accounting for other factors, and in Louisiana specifically, research has confirmed that a higher burden of air pollution is associated with larger percentages of Black residents and higher unemployment across census tracts.⁶

The reasons are historical and structural. When petrochemical facilities were built in the mid-twentieth century, the cheapest and most politically powerless land was often adjacent to Black communities that had limited economic options and little political representation. Zoning decisions, permitting processes, and economic incentives all tended to concentrate industrial risk in areas where residents had the least capacity to object. Decades later, the pattern has calcified: residents who want to move often cannot afford to, and their property values are depressed precisely because of the industrial neighbors that make the area less desirable.

Activists like the late Wilma Subra and organizations such as RISE St. James have drawn national attention to these dynamics. In 2022 and 2023, proposals for new facilities in the corridor, including a massive Formosa Plastics complex in St. James Parish, became flashpoints for a broader national conversation about environmental racism. Community opposition and legal challenges delayed or altered several projects, but the fundamental industrial footprint of the corridor remains largely intact.

Health Harms Beyond Cancer

The name “Cancer Alley” centers the cancer risk, but the health toll of living in the corridor extends well beyond cancer itself. A study examining birth outcomes across Louisiana found that census tracts classified as severely polluted had 36% higher rates of low birth weight and 25% higher rates of preterm birth compared to unpolluted tracts.⁷ Across the state, the researchers attributed roughly 2,166 low-birth-weight births and 3,583 preterm births each year to pollution exposure.⁷

Respiratory illness, cardiovascular disease, and neurological symptoms also appear at elevated rates in communities near petrochemical facilities, though isolating the contribution of any single pollutant to these outcomes is difficult. Residents frequently report headaches, nosebleeds, skin rashes, and chronic respiratory problems that they link to nearby emissions. These complaints often go unresolved because the symptoms are non-specific and because the regulatory system evaluates pollutants one at a time rather than as the cocktail residents actually breathe.

The Cumulative Exposure Problem

One of the most persistent frustrations for people living in Cancer Alley is that environmental regulation in the United States was built around the idea of evaluating one chemical at a time. A plant’s permit to release ethylene oxide is reviewed separately from another plant’s permit to release chloroprene, and neither permit accounts for the formaldehyde, benzene, or particulate matter also present in the same air. Residents, meanwhile, are inhaling all of it simultaneously.

Cumulative risk assessment is the scientific framework designed to address this gap. It aims to examine the combined health effects of simultaneous or sequential exposures to multiple environmental stressors.⁸ In theory, this approach asks three things: which chemical mixtures matter most, how much of each are people actually exposed to, and whether the combination produces health effects that are greater than what you would expect by adding up each chemical’s individual risk. In practice, the science is still catching up. The methods for estimating combined effects of correlated pollutants are statistically tricky, and different modeling approaches can produce meaningfully different answers for the same population.

Researchers have also argued that cumulative risk assessments need to go beyond chemical mixtures and incorporate nonchemical stressors like poverty, discrimination, and limited healthcare access, all of which are present in abundance along the corridor.⁹ A community dealing with high unemployment, poor nutrition, limited insurance coverage, and chronic stress from discrimination is biologically more vulnerable to chemical exposures than a wealthy community breathing the same air. Ignoring those compounding factors produces risk estimates that systematically undercount the harm done to the most affected populations.

What Residents Are Pushing For

Community groups in Cancer Alley have generally coalesced around several demands. First, they want continuous, fence-line air monitoring at major facilities so that emissions data comes from actual measurements rather than self-reporting and models. Some facilities have begun installing fence-line monitors under EPA rules for petroleum refineries, but coverage remains patchy and does not extend to all pollutants of concern. Second, advocates are pushing for cumulative-impact permitting: the idea that when a new facility applies for a permit, the review should account for all existing pollution in the area, not just the incremental addition from the proposed plant. Louisiana does not currently require this. Third, many communities are seeking buyouts or relocation assistance for residents who live within the closest buffer zones of major emitters, modeled on federal programs that have relocated communities near Superfund sites or in flood zones.

The legal landscape has shifted unevenly. A federal judge blocked construction of the proposed Formosa Plastics complex in 2022 on procedural grounds related to the Army Corps of Engineers’ environmental review, though the legal battle continued. The EPA under the Biden administration announced investigations into whether Louisiana’s industrial permitting practices violated civil rights laws, but enforcement actions have been slow and face political headwinds. Industry groups, meanwhile, argue that the corridor’s plants provide thousands of high-paying jobs and that emissions have decreased over time as older facilities have been upgraded.

Threatened Burial Grounds and Cultural Erasure

One dimension of Cancer Alley that often goes unmentioned in discussions of air quality is the threat to historic African American burial grounds along the Mississippi. Many of these cemeteries were originally established on the edges of sugar plantations and date to the era of slavery. Today they occupy small, isolated parcels surrounded by industrial facilities and corporate agricultural operations. Climate change, industrial expansion, uncertain land-tenure records, and the shrinking number of living descendants all threaten their survival.¹⁰

The loss of these sites carries weight beyond the physical. For communities that have lived along the river for generations, burial grounds are tangible links to ancestors and to a history that was systematically obscured during and after slavery. Allowing them to be swallowed by industrial development or neglect extends what researchers have described as a centuries-long process of erasing Black presence and humanity from the American landscape.¹⁰ Preservation efforts, often led by small community organizations with minimal funding, are attempting to document, protect, and restore these sites before they disappear entirely. For many residents, the fight to save a family cemetery and the fight against a neighboring chemical plant are the same fight, rooted in the same question of whether their community’s existence is valued.

The Measurement Gap That Still Exists

Despite the recent mobile-laboratory studies, continuous air-quality monitoring in Cancer Alley remains sparse compared to the scale of industrial activity. The EPA operates a limited number of fixed monitoring stations in Louisiana, and many of them are not positioned to capture the localized plumes that residents experience. The mobile-lab approach demonstrated how much information is missed by fixed stations and modeling alone, but a single research campaign covering 15 tracts over a finite period cannot substitute for the kind of ongoing, granular monitoring that would be needed to hold facilities accountable in real time.

Emerging technologies like low-cost sensor networks and satellite-based remote sensing offer some promise. Several community groups have deployed their own air monitors, and NASA and NOAA satellite data have been used to map plumes from specific facilities. But interpreting data from inexpensive sensors requires careful calibration, and satellite observations have limited spatial resolution for detecting the kinds of ground-level hotspots that matter most to individual neighborhoods. The fundamental challenge is one of political will and funding. The technology to measure what is in the air exists; the question is whether regulators and industry will pay for it and act on what it shows.