The University of Tennessee's Center for Clean Products and Clean
Technologies has developed a hazard evaluation system for TRI chemicals that produces separate rankings for ecological effects and human health
effects, as well as a total hazard score that integrates information
about a chemical's toxicity to humans and ecosystems with information
about chemical characteristics that influence the likelihood of exposure
to a substance.
WHAT DO THE SCORES MEAN?
UTN human health effects scores indicate how a chemical compares with others in terms of its capacity to harm human health. The graphic shows where a compound's hazard score falls relative to all chemicals that have been ranked using this system, indicating whether it is more or less hazardous than most chemicals. Chemicals that score at the far right end of the scale are significantly more hazardous (in the worst 10% of all chemicals according to this scoring system).
All chemicals scored by a system have been placed in "bins" defined by
percentiles (e.g., a chemical's score is in the least toxic 25% of
chemicals scored by a system). The graphic illustrates
which bin a chemical falls in according to each scoring system in
Scorecard. Looking across these different systems, it is possible to
identify chemicals that consistently score as high or low hazards, as
well as chemicals that score high on some measures (such as human health
hazards) but low on others (such as ecological hazards).
STRENGTHS AND WEAKNESSES OF THIS TYPE OF SCORING SYSTEM?
UTN human health scores are based only on toxicity considerations, and
have important limitations because they do
not consider variations in exposure potential across chemicals. However,
the UTN system is an improvement over most "toxicity only" systems
because it considers a variety of health endpoints rather than just one.
For example, UTN human health effect scores are based on a chemical's
acute toxicity, chronic toxicity and indications that a chemical can
cause multiple adverse health effects. In contrast, TRI toxicity
weights do not take acute toxicity into account, and are based on
whatever single toxicity concern underlies a regulatory risk assessment
value for a chemical.