Louisiana - Levels of air toxicity in Louisiana's "Cancer Alley" are even higher than previously thought, a new study has found, amid concerns of environmental racism.

Johns Hopkins University researchers set up a mobile lab for air testing in Louisiana's industrial corridor, stretching from Baton Rouge to New Orleans.

They found the toxic gas ethylene oxide in some areas at 40 parts per billion – a thousand times higher than what is considered safe, according to a study published in the journal Environmental Science & Technology.

The amounts were far greater than projected in estimates by the US Environmental Protection Agency (EPA).

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Ethylene oxide is a human-made gas linked to higher rates of cancers, including leukemia, myeloma, lymphoma, and breast cancer. It is used in the production of other chemicals and in sterilization and fumigation operations.

The bulk of Cancer Alley's industrial facilities – which account for around 25% of US petrochemical production – are concentrated in Black communities, which suffer disproportionately from long-term exposure to toxic air and resulting health impacts.

In an attempt to curb ethylene oxide releases, the EPA earlier this year announced new rules it said would cut sterilizer plant emissions by around 90%.