TECHNICAL DETAILS ON HOW SCORES ARE DERIVED
The UTN system assigns hazard scores between 0 and 100 based on the
Environmental Effects = HVoral LD50 + HVfishLC50 + HVfishNOEL
HVx = Hazard Value for endpoint x.
Three endpoints are used as indicators of environmental effects: one measure of acute toxicity to mammals (LD50 is the dose that kills 50% of organisms in a test) and two measures of toxicity to aquatic organisms (LC50 is the concentration that kills 50% of organisms in an acute test; NOEL is the no observed effect level in a chronic test).
Several policy choices influence the rankings that result from use of
this algorithm. First, it is possible to give equal or different weights
to hazard values for the various endpoints within an effect category
(e.g., to give double weight to compounds that harm aquatic life).
Second, some method of assigning hazard values to parameters that lack
data is required (e.g., to treat the absence of data as indicating the
absence of hazard, or to penalize data gaps). UTN has developed several
alternative chemical rankings based on different versions of these
EDF has selected the simplest approach for incorporating UTN scores into
the Scorecard: equal weights are assigned to endpoints, and chemicals
are assigned a default hazard value of zero when required data are
missing. EDF was unable to extend the UTN system to additional chemicals
because the Scorecard lacks some of data elements that are required by
UTN: Davis, G. et al.Chemical Hazard Evaluation for Management Strategies: A Method for Ranking and Scoring Chemicals by Potential Human Health and Environmental Impacts. EPA/600/R-94/177, Office of Research and Development, Cincinnati, OH. 1994. Values received in Excel file, July, 1998.