This article was produced in partnership with The Times-Picayune and The Advocate, which is a member of the ProPublica Local Reporting Network.

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The industrial stretch of the Mississippi River between Baton Rouge and New Orleans, a region known as “Cancer Alley,” is one of the most highly polluted areas in the country. A ProPublica analysis using a scientific model developed by the Environmental Protection Agency shows that some of the neighborhoods where new plants are being built already have very high concentrations of toxic chemicals. But Louisiana continues to approve the building of these new plants and the expansion of existing ones.

The EPA model ProPublica used, known as Risk-Screening Environmental Indicators, or RSEI, calculates the estimated chemical concentrations from toxic industrial plant emissions across the country, down to 810-by-810-meter blocks. We then used that model to find where toxic levels of cancer-causing chemicals are highest in the seven parishes.