Ecological Toxicology Chemical A and Chemical B are discharged to the river by a
ID: 1712361 • Letter: E
Question
Ecological Toxicology
Chemical A and Chemical B are discharged to the river by a factory. Chemical A reaches an average in-stream concentration of 10 ug/l, while chemical B reaches an average in-stream concentration of 100 ug/l. We want to know if there is reason for concern for these concentrations in the stream. We conduct aquatic bioassays using rainbow trout with the following results:
Chemical A Chemical B
Conc. (ug/l) %Mortality Conc. (ug/l) % Mortality
0 0 0 0
1 10 1 0
5 25 5 5
10 50 10 7
80 75 80 9
100 100 100 10
150 100 150 50
200 100 200 100
D. Why is Bench Mark Dose Modeling considered better than using NOEC and LOEC for describing toxicity of a chemical?
Explanation / Answer
The disadvantages of using NOEC and LOEC to determine RfDs and RfCs are
But the BMD approach defines a starting point of departure (POD) for the computation of a reference value (RfD or RfC) or a cancer slope factor. An upper bound, approximating a 95% confidence limit, on the increased cancer risk from a lifetime exposure to an agent. This estimate, usually expressed in units of proportion (of a population) affected per mg/kg-day, is generally reserved for use in the low-dose region of the dose-response relationship, that is, for exposures corresponding to risks less than 1 in 100. (CSF) that is more independent of study design. Using BMD methods involves fitting mathematical models to dose-response data and using the different results to select a BMD that is associated with a predetermined benchmark response (BMR), such as a 10% increase in the incidence of a particular lesion or a 10% decrease in body weight gain
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