Aldrin and dieldrin (a metabolite of aldrin as well as a marketed pesticide) are both fat soluble persistent and bio-accumulating organochlorine insecticides. Commercial manufacture began in 1950. They have been widely used in the past, but are now banned in most countries world wide and are included in the Stockholm convention on persistent organic pollutants (POPs) and the United Nations Economic Commission for Europe (UNECE) Convention on long-range transboundary air pollution protocol on POPs. There are still residues of dieldrin in the environment and in human tissues, but the levels have been declining during the last 30 years. In both animals and humans, aldrin and dieldrin are readily absorbed via the gastrointestinal tract. The conversion of aldrin to dieldrin occurs much more rapidly than the subsequent biotransformation and elimination of dieldrin, resulting in the accumulation of dieldrin in lipid rich tissues. The dominant toxic effects are in the nervous system and the liver, the latter mainly following chronic exposure. Aldrin and dieldrin are approximately equally toxic. They are not genotoxic or teratogenic. The transfer rates from feed to milk, eggs and adipose tissue are among the highest found for chlorinated pesticides, making aldrin, and especially dieldrin, highly accumulative compounds. Dieldrin rather than aldrin predominates in feed materials of animal origin. Due to a high level of bioaccumulation in the aquatic food chain, fish derived products, particularly fish oil, were identified to contain the highest levels of dieldrin. The majority of fish oil samples contained dieldrin at levels below 50 mu g/kg. Other fish derived feed material contained dieldrin at levels ten fold lower. Feed products of plant origin occasionally show levels of aldrin and dieldrin above the limit of detection which is mostly in the range of 1 to 10 mu g/kg. The levels found in feed are much lower than the levels which would induce toxicity in farmed animals and pets. Due to the ban on aldrin and dieldrin in the EU, and in most other countries world-wide, human exposure to these two pesticides is steadily decreasing. The levels in samples taken recently are below 10 % of those in samples taken 20 years ago. The daily intake from food for adults and children seems to be in the range of 1 to 10 ng/kg b. w. Thus, the dietary intake is substantially below the provisional tolerable daily intake (PTDI) of 100 ng/kg b.w. established by the JMPR (FAO/WHO Joint Meeting on Pesticide Residues).
