I am trying to understand what steady state LC50 is. I read that steady state LC50 or otherwise called incipient LC50 is the concentration below which 50% of the individuals survive indefinitely. However, my question why is that 50% of the individuals survive indefinitely?. Is it because different fish although they belong to the same species have different rates of uptake and elimination (toxicokinetics) and the threshold value of the remaining 50% fish is never reached that they continue to survive indefinitely. Please clarify
The steady state LC50, also known as the incipient LC50, is defined as the concentration of a chemical at which 50% of the exposed individuals are expected to survive indefinitely. This means that half of the individuals will not die after a certain period of time when exposed to this concentration of the chemical.
The reason why 50% of the individuals survive indefinitely is because of the assumption that at steady state, the uptake rate of the chemical is equal to its elimination rate. At this concentration, the toxicokinetics of the chemical (uptake and elimination) in the exposed individuals are in balance and the chemical concentration in their tissues will remain relatively constant over time.
It is important to note that the steady state LC50 is a theoretical concept that assumes that the conditions remain constant over time and that the uptake and elimination rates remain the same for all individuals. In reality, the LC50 can vary for different individuals within a species and for different species, due to differences in their toxicokinetics and other factors such as size, age, and overall health.
Furthermore, the LC50 is not a static value and can change over time as conditions change and as the uptake and elimination rates of the chemical change in the exposed individuals. Thus, it is important to consider the dynamic nature of the LC50 when evaluating the toxicity of chemicals in aquatic environments.
Ahmad Al Khraisat Could you tell me if once the concentration of chemical in the tissue of an organism for example fish reached a constant value, will it be affected by external factors such as temperature, pH, salinity etc? i.e. for example if we conduct an LC50 test in a lab on fish and if we see that with increasing duration there isn't much change in the concentration of chemical in the fish tissue(steady state), will changing external factors affect this chemical concentration? Since, CBR(critical body residue) = LC50 x BCF, external factors might change LC50 and this might change BCF accordingly but the CBR should not change, is that right?
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