Why an 85-Mile Stretch of the Mississippi Became Known as Cancer Alley

Drive west out of New Orleans on River Road and the levee rises on your left like a long green wall, hiding the water it holds back. On the right, in Reserve, Louisiana, a town of a few thousand people in St. John the Baptist Parish, there are modest houses, churches, a school, and then the fence line of a plant that makes neoprene, the stretchy rubber in wetsuits and laptop sleeves. The plant has run here since the 1960s, first under DuPont and, since 2015, under the Japanese company Denka. For most of that time almost nobody outside the parish knew its name. Then, in February 2023, the United States Department of Justice sued it, using an emergency power in the Clean Air Act that lets the government go to court when pollution presents an imminent and substantial danger to public health. Two years later, in March 2025, the same department dropped the case. Between those two dates sits nearly everything worth knowing about the place people call Cancer Alley.

In short: The industrial corridor along the Mississippi between Baton Rouge and New Orleans holds well over a hundred refineries and chemical plants, many of them set beside Black communities founded after slavery. The federal case against the Denka plant in Reserve showed what the law can do when the government uses it, and its dismissal in 2025 showed how quickly that protection can be withdrawn.

A river built for plantations, then for plants

The geography explains the first half of the story. The lower Mississippi is deep enough for oceangoing ships well upriver, flat enough to build on, and lined with fresh water a plant can draw for cooling. Before there were refineries, those same features made the riverbanks ideal for sugar plantations. The long, narrow land parcels that run back from the water today are the old plantation lots, divided the way French colonial surveyors divided them so every owner got a piece of the river.

After emancipation, freed people bought or settled land along the same bends. Many of the small communities strung along River Road were founded by them. They farmed, fished, built churches and cemeteries, and stayed for generations.

The petrochemical industry arrived in force in the middle of the twentieth century. Oil and gas came up the Gulf, the river offered shipping and water, and Louisiana offered something else: a state government eager for industrial investment and willing to pay for it. Louisiana's Industrial Tax Exemption Program, which for decades let manufacturers skip local property taxes on new plants for years at a time, made the riverbank one of the most attractive places in the country to build. The land that was cheapest and easiest to buy was often next to people with the least political power to say no.

That tax program deserves a second look, because it is the quiet engine of the whole corridor. For most of its history the exemptions were approved by a state board in Baton Rouge, which meant that the parishes and school districts losing the property tax revenue had no vote on whether to give it up. A town could host a plant worth billions and still struggle to fund its schools, because the plant's property was off the rolls. In 2016 Governor John Bel Edwards, a Democrat, changed the rules by executive order so that local governments, including school boards, got a say in whether new exemptions were granted. It was a modest reform with a large principle inside it: the people who live with an industry should have some voice in the bargain that brings it.

The pattern that emerges is less a single villain than a set of incentives pointing the same way. Companies wanted the river. The state wanted the investment and offered to pay for it with other people's tax base. Regulators issued permits one plant at a time, each judged on its own emissions rather than on what the air already held. Nobody had the job of adding it all up for the family whose backyard sat between three facilities.

By the 1980s, residents and activists had a name for the stretch of roughly 85 miles between Baton Rouge and New Orleans. It stuck because people kept noticing who was getting sick.

What chloroprene is and why Reserve became the test case

The Reserve plant became the emblem of the corridor for a specific, documentable reason. Neoprene is made from a chemical called chloroprene. In 2010 the Environmental Protection Agency, after a scientific review, classified chloroprene as likely to cause cancer in humans. A few years later, the agency's National Air Toxics Assessment, a national model that estimates cancer risk from air pollution census tract by census tract, put the neighborhoods around the plant at the very top of the country.

Think about what that meant on the ground. Families who had lived in Reserve for generations learned from a federal spreadsheet that the air in their yards carried a modeled cancer risk far above anything the agency considers acceptable. An elementary school sat close to the plant. Residents formed a group, Concerned Citizens of St. John, and began holding meetings, collecting their own stories, and demanding that someone do something.

Denka, for its part, cut its chloroprene emissions substantially after 2015 under an agreement with Louisiana regulators, and it challenged the EPA's science, arguing that the agency's cancer estimate for chloroprene was too high and asking for it to be revised. That is the company's strongest case and it deserves a fair statement: a firm that bought an existing plant, invested in pollution controls and reduced emissions felt it was being singled out on the basis of a number it believed was wrong. The EPA reviewed the request and declined to change its assessment. Meanwhile, monitors near the plant kept recording chloroprene levels well above the level the agency had said would keep lifetime risk within its usual range.

The 2023 lawsuit and what it asked for

When the Justice Department filed suit in February 2023, it was using a tool regulators rarely pick up. Section 303 of the Clean Air Act allows the government to go straight to court when it believes pollution is an imminent and substantial endangerment, without waiting for the slower process of writing a rule or proving a permit violation. The complaint asked a federal court to order Denka to cut chloroprene emissions far enough that the community's risk fell to acceptable levels.

The case was part of a broader push by the Biden administration to treat environmental justice as an enforcement priority rather than a slogan. The EPA had also opened an investigation, under Title VI of the Civil Rights Act, into whether Louisiana's environmental and health agencies had discriminated against Black residents in how they permitted and monitored plants like Denka's. That investigation was closed in June 2023 without a finding after Louisiana sued the federal government and challenged the agency's authority. In April 2024 the EPA also finalized a stronger national rule for chemical plants that emit chloroprene and ethylene oxide, requiring fence-line monitoring and deeper cuts.

So for a moment, three tracks were running at once: a lawsuit aimed at one plant, a civil rights inquiry aimed at a state, and a national rule aimed at an industry.

March 2025 and the dismissal

In March 2025, after the change of administration, the Justice Department moved to dismiss its own case against Denka. The new leadership at the EPA had made clear it intended to wind down the agency's environmental justice work, and the Denka suit was among the most prominent examples. The court case ended without a ruling on whether the plant's emissions were in fact an imminent danger.

Here is where the argument starts, and it should be labelled as argument. Supporters of dropping the case said the government had stretched an emergency power meant for sudden crises to cover a long-running, permitted operation, and that disputes over chemical risk belong in rulemaking, not in a lawsuit against a single company. That is a coherent position about how the law should work. The answer, I think, is that the people of Reserve did not experience their situation as a slow regulatory disagreement. They experienced it as decades of breathing a chemical the government's own scientists flagged as a likely carcinogen, and of waiting for a process that never seemed to reach them. An emergency power that can never be used for a chronic emergency is not much of a power.

The dismissal also teaches something about how fragile enforcement is. A lawsuit filed by one administration can be withdrawn by the next. A civil rights inquiry can be closed. A rule can be reconsidered or delayed. What lasts longer are statutes Congress passes and the organizations residents build for themselves.

The case against calling it a racial story, and the answer

Some people object to the framing of Cancer Alley as environmental racism. They argue that plants went where land, water and shipping were, that the industry employs many local residents, Black and white, and that cancer rates across Louisiana parishes are driven by many factors, including smoking, diet and access to care. Some parish-level cancer statistics do not show the dramatic spikes the nickname suggests, and serious people have pointed that out.

That objection deserves a real answer rather than a dismissal. First, the strongest evidence about the corridor is not raw cancer counts, which are hard to tie to any single source, but measured exposure: what is in the air, how much, how close to homes. On that measure, the corridor's fence-line communities stand out. Second, siting decisions are not neutral just because they follow economic logic. When cheap land and weak political resistance line up with the descendants of enslaved people, the result is a racial pattern whether or not anyone intended one. United Nations human rights experts said as much in 2021, describing the corridor as a form of environmental racism. Third, the jobs argument cuts both ways: residents of the small towns closest to the plants often say the best-paid jobs go to people who commute in from elsewhere.

Progressives can also be honest about where our own side has fallen short. Environmental review processes that were designed to protect communities have sometimes become tools that slow everything, including clean energy and transmission lines. The lesson of Cancer Alley is not that every permit should be harder to get. It is that the people who live closest should have real power in the decision, and that measured pollution, not paperwork, should drive enforcement.

What the corridor looks like now

The plants are still there. New ones keep being proposed, including large plastics and petrochemical projects upriver in St. James Parish that drew years of organized opposition. The national chemical-plant rule finalized in 2024 has itself become a target, with the industry seeking relief from its deadlines and the current administration sympathetic to that request. Residents continue to run their own air monitoring with university partners and advocacy groups, because they no longer trust that a federal monitor will stay in place.

What has changed is visibility. Twenty years ago, a resident of Reserve describing chloroprene would have been talking mostly to neighbours. Today the corridor's name is known across the country, its groups have national allies, and the record of what the government found, filed and then dropped is public. That record will outlast any single administration.

Notice, too, that the people doing this work are not activists by temperament. Many are retirees, church members and parents who started out asking a single question about why so many people on their street were sick. Their persistence is the reason the corridor became a federal case in the first place.

What you can do

You do not have to live on River Road to help the people who do.

• Look up the plants near you. The polluter search shows EPA-regulated facilities in any ZIP code, along with their recorded violations and the penalties they paid. Try the ZIP codes for Reserve and LaPlace, then try your own; most Americans live closer to a regulated facility than they think.
• Comment while rules are open. Air toxics rules, including any rewrite of the 2024 chemical-plant standards, go through public comment. The open comment periods are listed with the soonest deadlines first, grouped by issue, with a plain guide to writing a comment that agencies have to read and answer.
• Call the people who fund and oversee the EPA. Enforcement depends on budgets and on congressional oversight. Use your representatives' contact page to find your member of Congress and senators, their phone numbers and their recent votes, then ask what they will do about enforcement in fence-line communities.
• Back the groups already on the ground. Local organizations in the river parishes have done the monitoring, the testimony and the litigation for years. The organizations directory lists environmental and civil rights nonprofits by state, including Louisiana.
• Keep reading the record. The environmental justice topic page collects current reporting on Cancer Alley and similar communities, so you can follow what happens to the plants, the rules and the people next.

The neighbours in Reserve did the hard part already: they noticed, they organized and they made the country look. The rest of us can make sure looking turns into something more lasting.