Abstract
A model based on the concept of reduction in life expectancy (RLE model) as a result of long term exposure to toxicant has been developed which has normal life expectancy (NLT) as a fixed limiting point for a species. The model is based on the equation (LC50 = a ln(LT50) + b) where a and b are constants. It was evaluated by plotting ln LT50 against LC50 with data on organic toxicants obtained from the scientific literature. Linear relationships between LC50 and ln LT50 were obtained and a Calculated NLT was derived from the plots. The Calculated NLT obtained was in good agreement with the Reported NLT obtained from the literature. Estimation of toxicity at any exposure time and concentration is possible using the model. The use of NLT as a reference point is important since it provides a data point independent of the toxicity data set and limits the data to the range where toxicity occurs. This novel approach, which represents a departure from Haber's rule, can be used to estimate long term toxicity from limited available acute toxicity data for fish exposed to organic biocides.
Highlights
Toxicity is a function of both exposure time period and concentration or dose [1,2,3,4]
There are a variety of organic compounds with different mechanisms of action but the relationship of LC50 and ln LT50 was linear with all toxicants
All plots irrespective of toxicant type had negative slopes indicating that lethal toxicity is related to exposure time and LC50 required to cause toxicity decreases consistently in a systematic pattern
Summary
Toxicity is a function of both exposure time period and concentration or dose [1,2,3,4]. Most of the toxicological data are based on the quantitative relationship between concentration or dose and adverse effect without consideration of the exposure time period [5,6,7]. Often imprecise terms such as acute, subacute, subchronic, and chronic are used to describe the exposure time [8]. There have been studies where exposure time has been evaluated as a quantifiable variable of toxicity [7, 10,11,12] and the relationship between exposure time and dose has been evaluated [6, 13,14,15,16] In these studies the exposure time is relatively short. Information regarding the long term effects of exposure time with environmental chemicals is scarce [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
