Refining aggregate exposure: example using parabens.

The need to understand and estimate quantitatively the aggregate exposure to ingredients used broadly in a variety of product types continues to grow. Currently aggregate exposure is most commonly estimated by using a very simplistic approach of adding or summing the exposures from all the individual product types in which the chemical is used. However, the more broadly the ingredient is used in related consumer products, the more likely this summation will result in an unrealistic estimate of exposure because individuals in the population vary in their patterns of product use including co-use and non-use. Furthermore the ingredient may not be used in all products of a given type. An approach is described for refining this aggregate exposure using data on (1) co-use and non-use patterns of product use, (2) extent of products in which the ingredient is used and (3) dermal penetration and metabolism. This approach and the relative refinement in the aggregate exposure from incorporating these data is illustrated using methyl, n-propyl, n-butyl and ethyl parabens, the most widely used preservative system in personal care and cosmetic products. When these refining factors were used, the aggregate exposure compared to the simple addition approach was reduced by 51%, 58%, 90% and 92% for methyl, n-propyl, n-butyl and ethyl parabens, respectively. Since biomonitoring integrates all sources and routes of exposure, the estimates using this approach were compared to available paraben biomonitoring data. Comparison to the 95th percentile of these data showed that these refined estimates were still conservative by factors of 2-92. All of our refined estimates of aggregate exposure are less than the ADI of 10mg/kg/day for parabens.