Environmental Effects of Heavy Spillage from a Destroyed Pesticide Store near Hargeisa (Somaliland) Assessed During the Dry Season, Using Reptiles and Amphibians as Bioindicators

Abstract.

A pesticide store near Hargeisa (Somaliland) was damaged by bombing in May 1988, and subsequently looted by local people, who removed and drained drums of chemicals. Assessment of the effects of resultant spillage during the dry season, March/April 1993, established that pesticides, mainly organochlorines (dieldrin and products and BHC isomers) and organophosphates (fenitrothion and malathion) had contaminated 3700 sq m of soil at up to 3728.0 (geometric mean 149.0) ppm (5180.0 g/m³) total insecticides. Reptiles avoided contamination above 1 ppm, and were absent above 10 ppm. Experimental contact with highly contaminated soil caused death in lizards—Hemidactylus parkeri and Mabuya s. striata—after 26.5 and 33.5 h, respectively (residue levels elevated over 2000-and 149-fold), and 100% mortality within 65 min in frogs Tomopterna cryptotis (geometric mean residue level elevated 168-fold). Sediment 350 m downstream of the spill contained dieldrin at 0.50 ppm (0.03–0.05 ppm after 1.6, to 9.0, km). Whole body residues of spillage vicinity lizards were up to 1.52 ppm wet weight (193.6 ppm lipid) total insecticides. Geometric mean of 0.36 ppm was elevated fivefold above mean background level of Hargeisa lizards in the valley below. Dieldrin and products was highest; the level of BHC isomers was also significantly higher than DDT. Geometric mean total insecticide level in Chalcides ragazzii and H. parkeri was four times higher than in surface-dwelling Pseuderemias smithi. Reptile species richness was habitat-influenced. Frogs without abnormalities present in mud of river-bed wells indicated uncontaminated ground water (organochlorine residues undetected). Low levels in frogs, and of M. s. striata in the vicinity of wells [geometric means 0.09 and 0.07 (ranges 0–0.48 and 0.01–0.31) ppm, respectively], implied that by 2.7 km downstream of the spill few residues were entering food chains.