The Problem: What Was in the Water
For decades, Jefferson Parish and much of the New Orleans metro area drew drinking water directly from the Mississippi River. A landmark 1975 study by Dowty, Carlisle, and Laseter detected an alarming mixture of chemicals in that finished tap water, including chloroform and bromodichloromethane (both byproducts of the chlorination process itself), as well as benzene, trichloroethylene (TCE), tetrachloroethylene (PCE), and multiple chlorinated benzenes. These were not just river contaminants — several were created or concentrated by the very treatment process meant to make the water safe. Residents of Jefferson Parish who drank this water over years or decades were unknowingly consuming a cocktail of compounds that science has since linked to cancer.
What the Science Says About Cancer Risk
Research has established credible connections between the specific chemicals found in this water and multiple cancers. Trihalomethanes like chloroform and bromodichloromethane — formed when chlorine reacts with organic matter in the river — have been linked in pooled international studies to a 24–44% increase in bladder cancer risk with long-term exposure. TCE, also detected in New Orleans tap water in 1975, is now classified a “known human carcinogen” by the U.S. Department of Health and Human Services, with the strongest evidence pointing to kidney cancer — one residential exposure study found a 78% increased risk after 15 years. Benzene, present at high concentrations in the 1975 samples, is a confirmed cause of leukemia. The chlorinated benzene derivatives (mono-, di-, and trichlorobenzenes, also found in the water) add liver, kidney, and endocrine system risks that benzene alone does not produce — and unlike benzene, these compounds bioaccumulate in body fat over years of drinking, effectively amplifying the true biological dose.
Louisiana parishes served by Mississippi River water were documented to have some of the highest cancer death rates in the entire U.S. during 1950–1969, prompting a major case-control study that found statistically significant elevated mortality for rectal cancer, with upward trends for kidney and breast cancers as well.
Jefferson Parish and the Limits of Certainty
Jefferson Parish sits squarely in the 11-Parish Industrial Corridor along the Mississippi River, drawing from the same water source studied in these reports. Paradoxically, some summary statistics show Jefferson Parish cancer rates below Louisiana’s state average — but Louisiana’s statewide rates are themselves significantly above national averages across every demographic group, making this a poor baseline for reassurance. Isolating drinking water as a cancer cause is methodologically difficult because smoking, industrial air pollution, diet, and occupational exposures are hard to separate in population studies. What the science does clearly support is that the specific chemicals detected in Jefferson Parish’s water supply are individually capable of causing cancer, that residents were exposed to all of them simultaneously for decades with no mixture safety standard in place, and that the chlorinated benzene derivatives bioaccumulate — meaning years of low-level drinking-water exposure may produce a higher effective dose than any single water test would suggest. For anyone with a long history of drinking Jefferson Parish municipal water, particularly before modern filtration upgrades, this body of research represents a scientifically grounded basis for concern.
Unabridged Article
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