Simple Dissimilar Action Response or Effect Additivity, Bliss Independence

2 Simple Dissimilar Action (Response or Effect Additivity, Bliss Independence) 

Simple dissimilar action (simple independent action, independent joint action. Bliss independence, and effect addition or response addition) is also a noninteractive process where the toxic effect of each chemical in the mixture is not affected by the other chemicals present. However, the modes of action of the constituents in the mixture will always differ and possibly, but not necessarily, the nature and site of action also differs among the constiments. Response addition is referred to when each individual of a population (e.g., a group of experimental animals or humans) has a certain tolerance to each of the chemicals in a mixture and will only exhibit a response to a toxicant if the concentration exceeds the tolerance dose. In such a case, the number of responders within the group wiU be recorded rather than the average effect of a mixture on a group of individuals. By definition, response addition is determined by summing the responses of the animals to each toxic chemical in the mixture. 

Three different concepts have been developed for effect/response additivity depending on the correlation of susceptibility of individuals to the toxic agents  

There is a complete negative correlation between the effects of two chemicals if the individuals that are most susceptible to one toxicant are least susceptible to the other. This is the simplest form of response additivity. The proportion (F) of individuals responding to the mixrnre is equal to the sum of the responses to each of the components  

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