Aggregate risk, defined

As mentioned previously, in addition to aggregate risk as.sess-ment, FQPA required EPA to consider available evidence concerning the cumulative effects on infants and children of such residues and other. substances that have a common mechanism of toxicity. Mechanism of toxicity is defined by EPA-OPP(EPA, 1999a) as... 

Cumulative risk assessments evaluate the health risk for aggregate exposures accumulated over time and for multiple contaminants or stressors. In some contexts (e.g. USEPA pesticide risk assessments), cumulative refers specifically to combined exposures to chemicals that share a common mechanism of toxicity (see http // www.epa.gov/oppsrrdl/cumulative/). Populations may be defined by their location relative to sources, their activities and customs, and their susceptibility to exposures. In this context, populations can include different ethnic groups, different communities, or different age groups. Cumulative risk is a very important concept in understanding environmental health risks to children in different settings, particularly in underdeveloped countries where children may be facing multiple stressors. 

Unfractionated heparin (UFH) inhibits platelet aggregation and fibrin formation by accelerating the action of antithrombin, which in turn inactivates factors Ha, IXa, and Xa. The benefit of heparin in UA has been well defined in early trials (48,49). In the RISC trial, a combination of aspirin and heparin reduced the incidence of MI and death during the first five days by 75% when compared with placebo. This result was successfully replicated in several small trials examining the role of heparin in UA. A meta-analysis of these trials revealed a 33% reduction in the combined risk of death or MI in patients treated with aspirin plus heparin compared with those treated with aspirin alone (66). With benefit of heparin clearly established in UA patients, later trials attempted to expand the role of heparin in NSTEMI. 

Quantitative multicriteria analysis defines and applies weighting factors to the environmental profile to permit aggregation of the quantitative part of the inventory table into an unambiguous single score. This score is then used to rate different product alternatives. The advantages with this method are that the decision process is easily reproducible and that product comparison is simplified. The risk is that the method of aggregation may imply a scientific accuracy that not necessarily exists. Qualitative aspects of the impacts can not be included in the obtained score. These must be evaluated separately. 

Incorporating human error in case for safety risk assessment For many years there has been a requirement in the nuclear industry for plants to develop a Safety Case and have it approved by regulators in order to obtain a licence to operate. The Safety Case is, essentially, a very comprehensive quantified risk assessment based on the aggregated probability of an event (for example, the escape of radiation) against a defined benchmark probability. Once the licence has been granted, the Safety Case has to be formally reviewed at defined intervals. 

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