TR 058 : Assessment of Non-Occupational Exposure to Chemicals | May 1994
The main objective of the work described in this report is to review the assumptions and equations used to assess non-occupational exposure to chemicals. The approach recommended in this report to assess consumer exposure and indirect human exposure has been evaluated for several representative chemicals with different properties and use patterns.
A step-wise approach is recommended to assess consumer exposure. The first step consists of an initial evaluation to establish whether a potential exposure exists. If the substance itself is a consumer product or if the substance is contained in a preparation/article which is a consumer product, direct exposure of the consumer is possible. It is then necessary to estimate the extent, frequency and duration of exposure. The assessment of extent, duration and frequency requires an understanding of the substance and/or product use category and use scenario. Information on the use and function of the substance/product should therefore be provided in the dataset to allow a meaningful exposure assessment. Typical product use scenarios are discussed for common consumer products such as cosmetics, household products, aerosol products, paints and plasticisers. Recommendations are made for typical quantities per application, and frequencies of application. The second step consists of an evaluation of all potential exposure routes (oral, dermal, inhalation) to allow the estimation of the total exposure of the consumer to a particular substance. Comprehensive consumer exposure assessments require measured data to assess the extent of dermal, oral and inhalation exposure to products and their components. Realistic exposure assessments can also be achieved using reasonable calculations and justifiable assumptions for key exposure parameters. In this report some practical approaches are described to predict uptake via oral, dermal and inhalation routes taking into account the bioavailability of the substance. Use of default values in the absence of data may often lead to an overestimation of the exposure dose. A check for realism in the exposure assessment is therefore recommended to ensure that the final assessment is realistic and not overly conservative.
Similarly to the consumer exposure assessment, a step-wise approach is recommended to assess indirect human exposure. The first step (screening phase) consists of an initial evaluation to establish whether air, water or soil compartments are likely to be exposed to the substance (i.e. environmental exposure assessment) and whether human exposure via air, water, soil and food intake is likely to occur (i.e. indirect exposure). It is recommended that if environmental exposure occurs at a regional level, indirect exposure of the public can be expected and should be assessed. Environmental exposure can be estimated if it is known how and in what quantity a substance enters the environment and how it is subsequently distributed and transformed in these receiving compartments (i.e. air, water, soil). The proposed environmental exposure scheme to obtain release estimations and environmental concentrations for water, air and soil at the regional level has been discussed in detail in ECETOC Technical Report No. 51 “Environmental Hazard Assessment of Substances” (1993a) and is further developed in a forthcoming ECETOC Technical Report on “Environmental Exposure Assessment” (1994a).
If indirect exposure is likely to occur, then it is necessary to estimate the relation between the concentration in each contact medium (air, water, soil) and transfer to food products and drinking water. In addition, it is necessary to assess dietary characteristics and food sourcing for the average individual. Comprehensive indirect exposure assessments (investigative phase) require measured concentration data for air, water, soil and food products, and measured data on ingestion (food, water, soil) and inhalation rates. In the absence of measured data, some practical approaches (screening phase) are described to predict the concentrations in air, water and soil at a regional level, and to assess transfer of chemicals from these media to drinking water and food products. Quantitative structure activity relationships (QSARs) are discussed to relate partition between water, soil and plants, and between animal diet, lipid tissue, and food product. In addition, average food baskets for all EC member countries have been compiled to estimate the potential dose to which the average adult or child may be exposed.
The total non-occupational exposure (consumer and indirect) or resulting total estimated intake for the average individual can then be used in the human health risk assessment and compared with intake criteria, such as acceptable and tolerable daily intakes.