Hi Ishaq,

The following papers may help you with this:

Williams, E. S., Berninger, J. P., and Brooks, B. W. (2011). Application of chemical toxicity distributions to ecotoxicology data requirements under REACH. Environmental Toxicology and Chemistry 30, 1943-1954 http://dx.doi.org/10.1002/etc.583

Brain, R. A., Sanderson, H., Sibley, P. K., and Solomon, K. R. (2006). Probabilistic ecological hazard assessment: Evaluating pharmaceutical effects on aquatic higher plants as an example. Ecotoxicology and Environmental Safety 64, 128-135.

Centile is just a shortened version of percentile, and means the same thing.

The screening point value is some measure of toxicity that you choose to decide whether there is a toxic hazard. In the Williams et al. paper, they have chosen the first and fifth centiles as their screening point values.

Risk Assessment Tools by Mayer et al is available from SETAC, is a software program and sensitivity distribution has multiple centimeters levels.

Did not like centimeters so percentiles

Thank you so much Dr Colville, i am following the same papers already you mentioned. But now as u made it clear that centile and percentile are the terms with same meanings. I read both of the papers already and could not get the values of1st and fifth centiles. I want to ask more about this if you take some time for me i wanna inbox you.

Thank you so much for your guidance

Dear Dr Mayer

Thanks for your answer.

I will follow your answer and if i need more help i will ask again.

Thanks