The science behind US's 'cancer alley' and the chemical plant at the center of the controversy

The 85-mile stretch of land along the Mississippi River between New Orleans and Baton Rouge has been infamously nicknamed cancer alley owing to the high concentration of chemical plants, and the region's cancer cases


                            The science behind US's 'cancer alley' and the chemical plant at the center of the controversy

Over three years ago, residents living near a chemical plant in St. John the Baptist Parish—part of an area known as "Cancer Alley" in Louisiana—were told by the US Environmental Protection Agency (EPA) that they faced the highest risk in the country of developing cancer from air pollution.

However, it is only recently that Louisiana health officials announced that it would conduct a study by visiting every house within 2.5 kilometers of the controversial Denka chemical plant in LaPlace to find out how many people in the neighborhood have developed cancer.

What is 'cancer alley'

The 85-mile stretch of land along the Mississippi River between New Orleans and Baton Rouge has been infamously nicknamed cancer alley owing to the high concentration of chemical plants, and the region's cancer cases. 

More than 150 chemical plants and oil refineries dot this stretch of land, where most communities are predominantly black, and many residents attribute seemingly staggering levels of cancer and other illnesses to toxic air emissions from industry. 

A series, conducted by The Guardian, describes that while Louisiana has the most toxic air in America, along the Mississippi River is an area some call 'Cancer Alley', where residents face the highest risks.

The article says the EPA findings in December 2015 not only confirmed the existence of a "profoundly higher risk" of cancer throughout the region but it "pinpointed Reserve, a working-class town of about 10,000, at the bullseye." Reserve is located in St. John Parish. 

It further says, "nestled in the middle is the community of Reserve where the risk of cancer is the highest in the country, 50 times the national average."

In the May 2019 article, Mary Hampton, a resident of Reserve, told The Guardian: "Almost every household has somebody that died with cancer, or that's battling cancer. It's the worst thing you'd ever want to see: a loved one, laying in that bed, pining away, dying. Just to sit and look at them, and know you can't do anything about it."

The chemical plant at the center of the controversy

The Denka plant is the only one in the country that produces chloroprene, a chemical that was classified as "likely to be carcinogenic to humans" by the EPA in 2010. The toxic emissions in Reserve primarily come from this plant. 

Chloroprene is a chemical used in the production of neoprene. Neoprene has a variety of uses, such as wetsuits, gaskets, hoses, and adhesives. Chloroprene is classified as a likely carcinogen by several agencies, including EPA. 

The Denka plant in Louisiana is the only one in the country that produces chloroprene, a chemical that was classified as "likely to be carcinogenic to humans" by the EPA in 2010. (Getty Images)

The EPA says that short term exposure to high concentrations of the chemical can affect the nervous system. It may also affect the lung liver, kidneys, and the immune system. The EPA says long-term exposure to chloroprene has also been associated with an increase in the risk of developing cancer.

According to a report, released in July 2019 by the University Network for Human Rights (UNHR), the St. John plant's neoprene manufacturing unit -- owned by DuPont until its sale to Japanese company Denka Performance Elastomer in November 2015 -- has been pumping the toxic chemical chloroprene into a predominantly Black community since 1969.

"Residents had long felt that there was too much illness in the area—far beyond what could be considered normal. One resident with whom we spoke recalled the words of her niece, shortly before she passed away of cancer: 'We're just sitting here, waiting to die,'" says the study.

According to an analysis by ProPublica and The Times-Picayune and The Advocate, the plant is in the heart of Louisiana's industrial corridor, "which already has some of the most toxic air pollution in the nation, and where a "wave of new petrochemical plants is expected to worsen air quality in already overburdened areas."

EPA's take on the issue

The EPA's National Air Toxics Assessment (NATA) seemed to confirm the residents' suspicions.

The NATA map released by EPA in 2015, showed "an elevated risk for cancer in the area around the Denka plant. The referenced risk is an incremental estimate of the increased probability of developing cancer over a lifetime as a result of a continuous exposure to chloroprene," says Louisiana Department of Environmental Quality.

According to the most recent NATA, the risk of developing cancer from air pollution in the census tract closest to the Denka neoprene facility is nearly 50 times the national average due to emissions of chloroprene, say UNHR experts. 

"The EPA advocates a significant reduction in chloroprene emissions from the Denka facility, such that air concentration of the chemical does not exceed 0.2 micrograms per cubic meter (µg/m³), the maximum concentration that would keep cancer risk from air pollution within the EPA's upper limit of acceptability," says the paper.

Although the EPA has affirmed its confidence in the scientific validity of its chloroprene assessment, Denka continues to challenge the EPA's findings on chloroprene toxicity, claim experts from UNHR.

Denka signed a voluntary agreement to reduce emissions in January 2017 and finished installing emissions reduction technology by the end of that year. However, the EPA's air monitoring data continue to show high levels of chloroprene emissions—well over the 0.2 µg/m³ guideline -- in the neighborhoods around the Denka facility, say UNHR experts.

What the numbers say

A team of researchers collected health data from a large sample of residents who live within 2.5 kilometers of the plant. Cancer prevalence among those surveyed is unusually high, say experts from UNHR, who conducted the study. 

According to a study by UNHR, which conducted a study of people who live within 2.5 kilometers of the plant, cancer prevalence among those surveyed is unusually high. (Getty Images)

They found that the cancer prevalence among the respondents was 9.7%. "The odds that cancer prevalence would be this high in a population with the same race, sex, and age demographics is only 0.6%, a little over one-half of one percent. In other words, the cancer prevalence among survey respondents is highly unusual -- there is only a 0.6% likelihood that a cancer prevalence value this high could be due to chance," says the study.

The team found that cancer prevalence among those surveyed is also associated strongly with proximity to the Denka facility. Cancer prevalence among respondents who live closest to the facility (within 1.5 kilometers) is 71% higher than the national rate, says the study. "Cancer prevalence among residents who live closest to the facility (within 1.5 kilometers) is 44% higher than the national rate," says the analysis.

The study, says ProPublica, was criticized for its methodology, in particular for its failure to verify the cancer claims made by residents by examining medical records or through some other source. 

What the planned study hopes to achieve

The ProPublica recently reported that Louisiana health officials "plan to knock on every door within 2.5 kilometers of the controversial Denka Performance Elastomer plant in St. John the Baptist Parish in hopes of determining exactly how many people in the neighborhood have developed cancer."

The scientific inquiry was first announced in August this year. According to the plan, graduate students from the Louisiana State University Health Sciences Center in New Orleans will be sent to every household within a 2.5-km radius, which includes an estimated 1,900 households. The team will collect information on the number of people who have been diagnosed with cancer. The information will be matched with data previously gathered by the Louisiana Tumor Registry. 

The survey is expected to give a clearer picture of cancer rates in the area. "We are trying to collect as much information as they provide, and that data could inform future investigations," Dr. Edward Trapido, associate dean for research at LSU's School for Public Health, told ProPublica.

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