Ethylene dibromide (1,2-Dibromoethane, EDB)

EDB was manufactured in large quantities beginning in the 1920s primarily as an anti-knock additive in leaded gasoline, where it served as a lead scavenger to prevent lead deposits in engines [1]. This function meant EDB was in virtually every gallon of gasoline sold until leaded gas was phased out from 1975–1996, depositing EDB into soil at gas stations and fuel storage sites across the country. When EDB's agricultural use as a soil fumigant and post-harvest fumigant for citrus and grain was discovered to have contaminated groundwater in Florida and elsewhere in the early 1980s, the EPA emergency-cancelled most agricultural uses in 1984 [2]. The contamination story is a case study in how multiple uses of a persistent chemical across many decades can lead to widespread environmental legacy: EDB in soil and groundwater persists for decades and has been found in municipal water systems in multiple states [3].

Contaminated drinking water from groundwater near former agricultural fumigation areas, fuel storage sites, and spill locations is the primary community exposure pathway [1]. Florida, California, Georgia, and other major citrus and grain-producing states had significant groundwater contamination following agricultural EDB use. Vapor intrusion from EDB-contaminated soil is a secondary pathway in affected communities [2]. Historical dietary exposure from fumigated grain and citrus products occurred from the 1950s through the 1983 cancellation. Occupational exposure in chemical manufacturing and the workers who applied EDB as a fumigant had significant inhalation and dermal exposures [3].

EDB is a probable human carcinogen (IARC Group 2A), causing tumors in multiple organs in animal studies and showing elevated cancer rates in workers [1]. The mechanism is alkylation: EDB is metabolically activated to episulfonium ions and other reactive intermediates that form DNA adducts and cross-links. EDB is a powerful reproductive toxin, causing testicular atrophy and infertility in male animals and workers, similar to the DBCP effects in the same agricultural worker population [2]. EDB also has neurotoxic effects at high exposures, causing degeneration of peripheral sensory nerves. The groundwater contamination from both EDB and DBCP in California's agricultural valleys represents a legacy exposure for communities that relied on well water during peak use periods [3].

Residents of communities near former citrus fumigation areas (Florida, California), grain storage facilities, and leaky underground fuel storage tanks in agricultural regions face groundwater exposure risks [1]. Workers who applied EDB as a fumigant in the 1950s–1980s carry lifetime reproductive and carcinogenic risk from their occupational exposures [2]. People on private wells in historically fumigated agricultural areas should test for EDB.

Test private well water in areas with historical EDB agricultural fumigation or near fuel storage sites — EDB may not be included in standard well water panels and must be specifically requested [1]. Carbon adsorption and reverse osmosis both remove EDB from drinking water. Check your local water utility's annual quality report if you use municipal water [2]. If you live in a vapor intrusion zone near EDB contamination, contact your state environmental agency for indoor air testing [3].