CHEMICAL PROFILES|Ecological Effects Scores (UTN)

The UTN system assigns hazard scores between 0 and 100 based on the following algorithm:
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 policy choices.

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 this system.

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.