Ground zero of Cancer Alley is St. Gabriel, a village of 7,300 residents bordering the Mississippi River where two-thirds of the residents are black and the annual per-capita income — just $15,000 — is nearly 30 percent lower than the state average. St. Gabriel has earned the disturbing distinction of having the state’s worst air quality, with residents enduring miscarriages and dying of cancer, the investigation found.

At least 30 large petrochemical plants are located within a 10-mile radius of long-time resident Hazel Schexnayder’s home and another five more major plants await approval. Schexnayder described the air as smelling like “rotten eggs and nail polish,” while Reginald Grace, a career counselor who grew up in St. Gabriel’s Sunshine neighborhood, described a thick mist, “It’d look like raindrops but yellow,” that could form from nighttime chemical releases.

“Out of every 10 houses, there’s a prospect of one or two people that have died of cancer,” resident Terry Frazier told ProPublica reporters.

The state health department and scientists, however, haven’t linked the toxic air to cancer.  

It wasn’t until the early 1990s that toxic emissions data was required to be published and the area’s problems became more widely known. In 1993, industrial plants in Louisiana released about 105 pounds of air pollution and other hazardous materials per Louisiana resident. But in St. Gabriel, the rate was triple that, according to EPA data reported by ProPublica.

According to the Environmental Protection Agency, as reported by the Chicago Tribune, the chemicals that carry the highest cancer risks are ethylene oxide, formaldehyde, and chloroprene. Chloroprene, for example, affects the central nervous system and has been linked to higher rates of lung cancer and skin cancer for decades, according to the Centers for Disease Control and Prevention.

Industrial plants in Cancer Alley spew chloroprene and other harmful chemicals into the air.

Near the Denka neoprene plant, which emits chloroprene, the EPA found that the concentration of the chemical was among the country's highest, according to the ProPublica report. The same is true for an area of St. Charles Parish near where the Union Carbide plant emits ethylene oxide, another known carcinogen.

According to EPA figures as reported by ProPublica, the number of industrial plants in Louisiana that reported toxic releases rose 25 percent in the last three decades — even as national reports fell by 16 percent in the same period.

Although the EPA dictates the range of chemical risk levels that it deems acceptable, the “acceptable threshold” for chloroprene lacks the force of law, as ProPublica notes. States can set their own standards, and Louisiana’s standards are “at the loosest end of that spectrum.”

Louisiana opts to monitor only large-scale polluters, and in most cases, it takes companies at their word on emissions, according to ProPublica. In practice, this means that Louisiana’s benzene standard is more than twice as lax as the standard in Texas, which is more than 30 times more lenient than that of Massachusetts. 

What’s more, while the EPA considers the collective effect of chemicals, Louisiana only considers the impact of one chemical at a time, a method that may underestimate the cumulative toxic effect of multiple chemicals on air quality, as ProPublica noted.

Even so, Bryan Johnston, an air permits administrator at the Louisiana Department of Environmental Quality defended the state’s air-quality standards to ProPublica. His supervisor Chuck Carr Brown, DEQ Secretary of State, told ProPublica that during four years on his watch the DEQ has rejected some bids by chemical-makers to build new industrial plants in select towns because those communities had already “borne their burden.”