The severity level of an average pollution-related case of CB (relative to that of the case described by Viscusi, et al.).
All pollution-related cases, especially those regarding CB, are relative to no other cases. 
mnli hypothesis: All pollution-related cases, especially those regarding CB, are relative to no other cases.  premise: The severity level of an average pollution-related case of CB (relative to that of the case described by Viscusi, et al.).