Health Hazard Scoring (HHS)

(Source:  Hertwich et al., Evaluating the environmental impact of products and production processes: a comparison of six methods. Science of the Total Environment, 1996 Vol. 196, Issue 1, 13-29.)

This system utilizes the analytical hierarchy process (AHP) to weight workplace toxic effects and accident risks. The primary focus of the HHS System is on occupational health and risks of accidents that might lead to injury or pollution releases. The HHS score is determined as the dot product of two vectors, the health hazard vector HP and the site-specific vector F:

The seven elements, representing oral and inhalation toxicity, eye irritation, dermal irritation, carcinogenicity, reactivity, and flammability, have been included in each vector. HP vector calculated as the product of the chemical hazard H and the phase matrix P:

The value of the elements of H can be anyway from 0-9. For example, for the oral toxicity score, H is a product of the effect (three for lethal, one for mild effect) and the dose range producing this effect (1 for above 500 mg/kg and 3 for below 50 mg/kg). The rules for carcinogenicity scoring assign a proven human carcinogen a score of 8 or 9. H is then multiplied by the phase score P.

The HHS score provides an ordinal measure of hazard. The scoring of toxic strength by orders of magnitude shows that the HP vector is not linear, and some researchers argue that AHP is of a non-linear nature. Due to its ordinality, the system does not permit to determine per-kilogram HHS score and a subsequent scaling of that score by mass flow.

The HHS attempts to quantify potential occupational health hazards and accident risks. The strength of HHS is its simplicity and the availability of the required data. Toxicity values can be obtained from material safety data sheets, which are a necessary requirement in many countries. Due to simplicity and easy understanding, every design or safety engineer is capable of conducting an HHS scoring without having to go through extensive training. In our assessment, the most severe shortcomings of HHS are its ordinality, its limited scope, and its ambiguity in valuation.