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LOEL: (LOAEL), lowest observed (adverse) effect level. A common term in regulatory toxicology to define the lower limit of toxic or biochemical effects in animal studies. This time-honoured term is a poor and inaccurate way of defining toxicity, because toxicity is not a threshold phenomenon but fades away gradually when the dose decreases. Therefore LOEL depends on the number and size of doses selected, number of animals (the more animals, the lower the LOEL is likely to be), and inaccuracy caused by chance. Errors can be easily an order of magnitude (tenfold) or greater. There is a trend to replace LOEL with a "benchmark dose", which is defined as a dose causing 5 % or 10 % of the maximal effect. It is much more accurate, because it is not based on just one dose but a dose response curve derived from several dose levels. [1]


  1. Jouko Tuomisto, Terttu Vartiainen and Jouni T. Tuomisto: Dioxin synopsis. Report. National Institute for Health and Welfare (THL), ISSN 1798-0089 ; 14/2011 [1]