Endrin

Endrin was developed in 1951 as a stereoisomer of dieldrin with even greater acute toxicity to insects and vertebrates [1]. It was used primarily on cotton, grain, and apple orchards. Unlike its sister compounds, endrin is less persistent than dieldrin because it is more readily metabolized in some environments — but it is far more acutely toxic. Endrin poisoning of the lower Mississippi River ecosystem in 1963–1964 killed an estimated 10–15 million fish when endrin from agricultural runoff (and from an Velsicol Chemical plant in Memphis that was illegally discharging endrin to the river) contaminated the river system [2]. This environmental catastrophe contributed to the growing public demand for pesticide regulation. Endrin was cancelled for most uses in 1979–1991. Like other organochlorines, it persists in soil and sediment at historical use sites [3].

Dietary exposure from food grown on historically treated land and from contaminated water sources is the primary pathway for the general population today [1]. Fish from endrin-contaminated waterways (where historical agricultural runoff or industrial discharge occurred) can carry elevated endrin residues. Residents near former agricultural application areas and sites of historical industrial discharge have soil and potential groundwater exposure [2]. Occupational exposure was highest among agricultural workers and factory workers during the use period [3].

Endrin is one of the most acutely toxic of the cyclopentadiene insecticides — its acute oral lethal dose in rats is about 1/5 that of dieldrin [1]. The primary acute effect is CNS stimulation causing seizures — endrin poisoning presents with headache, dizziness, and then convulsions, sometimes without warning. Multiple occupational poisoning deaths occurred in the US and internationally. Endrin is classified as a possible human carcinogen [2]. The environmental toxicity — demonstrated by the Mississippi fish kills — reflects its extreme potency against aquatic life and bioaccumulation up the food chain [3].

People who consume fish from the lower Mississippi River system and tributaries that received historical endrin discharge face dietary exposure [1]. Residents of agricultural areas in the South where cotton was treated with endrin from the 1950s–1970s may have soil residues. Former agricultural workers with endrin exposure should be aware of the cancer and neurological risks [2].

Follow fish consumption advisories for the Mississippi River system and Gulf Coast waters, which address multiple organochlorine pesticide residues including endrin [1]. Test soil if you are growing food on historically treated cotton or grain farmland in the South [2]. There are no unique protective measures for endrin beyond the general organochlorine exposure reduction strategies [3].