PARC has published a new deliverable on aggregate exposure, showing how methods and tools can better assess combined chemical exposures across both general and occupational environments. Bringing together 36 institutes from 16 Member States, the work supports more integrative risk assessment and management by addressing how different exposure sources and routes can be considered together, in line with current European efforts to strengthen cross-sectoral approaches to chemical safety (ex: EFSA ExpoAdvance project and European Comission Chemicals Strategy for Sustainability). They called for harmonisation and policy coordination on the level of sectorial legislations, which creates the need to further develop integrative modelling approaches (EU Commission and Parliament 2020).

Human exposure to chemicals may occur from multiple sources, and routes from general and occupational environments. The exposure pathways are often complex as, it is often a combination exposure at the workplace, exposure arising from the use consumer product and materials, and indirect exposure from several sources (industry, agriculture, waste treatment facilities, etc) releasing chemicals to the environments affecting on their turn several exposure sources (food, indoor and outdoor air, dust, drinking water, etc.). Aggregating chemicals exposure from multiple sources and routes, integrating the fate of the substances from its emission sources could highlight the relative contributions of the different exposure sources and thus enrich risk assessment and inform the risk management context.

CThis deliverable presents how the roadmap and strategy developed during the first years of PARC (see deliverable AD6.3) were implemented in the PARC Model Network (in collaboration with T8.3) and details its application into case studies.

The strategy for performing aggregate exposure starts with the investigation of which are relevant routes and sources to aggregate, allowing negligible sources and routes to be excluded from the aggregation. Hereto, a quantitative decision tree was developed to identify relevant exposure sources in the context of aggregate exposure. A case study for spray applications, focusing on joint exposure to a specific chemical in a consumer product through domestic use of hairspray, and exposure at the workplace involving surface spraying, such as spray application of paints was performed to illustrate.

Further, the strategy and roadmap for aggregate exposure are based on the modelling of the contaminant transfer and migration in the different compartments, from their emission sources to the exposure sources in contact with the human body, such as indoor/outdoor air and dust, food, consumer products and articles, etc. Hereto, an inventory, scoring, selection and connection of the relevant exposure models was made. The next step in aggregation involves summing chemical concentrations in the different exposure sources by route (ingestion, inhalation, dermal contact) and to combine occupational and general life environments. Applying PBK models or proxy like absorption factors, excretion factors, steady-states developed in the T6.2.2 PBK model project enables to aggregate routes of exposure and simulate internal concentration in the different biological matrices. Internal simulated doses are then compared with HBM data in connection with T4.1 of PARC.

The case studies consider relevant exposure sources for different population groups (children and adults) and address exposures occurring in key settings, including occupational and general environments. For the general environment, a range of exposure levels was investigated where relevant, from background diffuse pollution to highly contaminated environments such as polluted sites (hotspots). For each case study, an in-depth assessment of available data was carried out, including literature searches. Data were stored in dedicated databases such as the ones for chemical cadmium and PFAS concentrations in consumer products to be used in the case studies.

Case studies on metals for the general population include exposure from soil, dust, diet, drinking water, air, consumer products, and specific exposure sources for children (dust in playground) and for adults (cigarette and occupational exposure in metal industry). Six partner countries were actively involved in modelling cadmium aggregated exposure, with France already delivering first results. Initial results from France and Switzerland indicated that food intake and smoking (for smokers) are the two main contributors to daily internal cadmium exposure. In Belgium, and Slovenia, similar modelling activities were currently underway, while in Spain and Portugal, model selection and data collection were still in progress. For occupational environment, professions that can lead to metals exposure have been identified. Power plant boiler workers, manual glass manufacturers, silver-cadmium welders and electronic waste workers were selected for cadmium, and chrome platers, spray painters of aircrafts, welders and steel factory workers for chromium. Exposure scenarios were then developed and performed in occupational exposure models.

Case study on PFAS exposure for the general population includes exposure from soil, dust, diet, air, consumer products. For an environmental hotspot in Belgium, exposure via locally grown foods, notably chicken eggs and to a lesser extent vegetables from private gardens, was a dominant exposure source. Further work on aggregate exposure to PFAS modelling is currently ongoing in four countries: France, Spain, Switzerland, and Belgium. This activity will continue during Y5-Y7 of PARC. Regarding occupational exposure to PFAS, the following professions were identified as relevant for potential PFAS exposure: chrome platers, ski waxers, fluorochemical plants workers and firefighters Exposure scenarios were set up and modelled for ski waxers and chrome platers.

Progress on other case studies, notably on aggregate exposure to phthalates and pyrethroids is reported in the deliverable. These case studies continue in Y4, and results will be published in scientific papers.

The outputs of this activity will contribute to a better understanding of the main exposure sources and routes in both general and occupational environments. By integrating modelling of the fate of substances from their emission sources to the relevant exposure sources and routes, this work aims to support European agencies in the development of effective exposure and risk management measures. The proposed developments, tools, and results can be practically used by European agencies and provide a foundation for structuring future collaborations, thereby strengthening synergies between PARC and EU agencies in the development of aggregate exposure assessment.