Micro-exposure event modelling

When the EPA considered exposures to insecticide residues in the home they identified at least six possible sources and routes these are given in Table 2.6. Their original approach apportioned the acceptable daily intake (ADI) between the various routes but it soon became clear that this was unrealistic because an individual was unlikely to be exposed via all routes on any one day. The EPA s present strategy is to develop an approach called micro-exposure event modelling. Micro-exposure event modelling is based on statistical data on the frequencies and levels of contamination of food, water, etc. and on behavioural information about the frequency of use of lawn/pet/timber treatments, etc. The combined data are assembled in a probabilistic model called LIFELINE which is able to predict the frequency and level of exposure to a group of hypothetical individuals over their lifetime.12 The model is also able to take account of the relative proportions of different types of accommodation, the incidence of pet ownership or any other data that will affect real levels of exposure. The output from the LIFELINE model allows the exposures of individuals in a population to be modelled over any interval from a single occasion to a lifetime. 

Micro-exposure event modelling combined with probabilistic modelling provides a great opportunity to assess real aggregate exposures in the real world. However, the method is highly dependent on the availability of complete and accurate information about levels of contamination and human behaviour. Whilst some of this is available, particularly in the context of pesticides, for other chemicals it may be a long time before this approach can be employed. 

Understanding the Variables Involved in Assessing Dermal Exposure Assessment Macro- and Micro-Event Modeling... 

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