human exposure to chemicals

Building the road for assessing aggregate human exposure to chemicals, covering different sources, routes and environments

Thirty-six European institutes from sixteen countries joined forces, under PARC, to propose a more integrative risk assessment and risk management of the human aggregate exposure to chemicals. The work includes development of methods, tools and results to advance knowledge on the combination of the different chemicals’ sources and the different routes of human exposure to them, in regard to general and occupational environments. The application of this integrated approach required harmonization and policy coordination on the level of sectorial legislations, including overcome regulatory silos. This is in line with recent incentives from European agencies (e.g. EFSA ExpoAdvance project) and the European Commission (e.g. Chemicals Strategy for Sustainability).

Diversity of sources  

Human exposure to chemicals involves multiple sources from the general and occupational environments and takes place via different routes. Several sources of chemicals such as industrial emissions, food contact materials, treated indoor surfaces, consumer products may contaminate the food, indoor and outdoor air, dust, drinking water, and anything that humans come into contact with or consume, making the exposure pathways complex to study.  

Addressing the challenge of complexity

The strategy to address the challenge of this complexity involves the “Source-to-Dose” project which aims at improving knowledge and existing models on chemicals’ fate during their transfer from the emission sources to the exposure sources in the general environment with a focus on environmental hotspots and the indoor environment. In addition, the “Aggregate Exposure” project aims at advancing knowledge on the combination of exposures sources and routes from occupational and general environments.  

During the first year of PARC, the development of an intended strategy and its roadmap was accomplished. First the transfer and migration of chemicals to the different environmental compartments, from their emission sources to the exposure sources that the human body comes in contact with, such as indoor/outdoor air and dust, food and consumer products is modelled. Afterwards, the aggregation of exposure sources by route (ingestion, inhalation, dermal contact) is proposed and aggregated levels of the chemicals can be compared to external reference thresholds. Internal chemical doses are also predicted using appropriate toxicokinetic models. Internal simulated doses are then compared with human biomonitoring data collected in the framework of PARC. Another challenge is to combine exposures from the general and occupational environments to perform risk assessment from source-aggregated external exposure and to better explain internal exposures observed in human biomonitoring data for the general population and for individuals in a particular occupational sector.  

In more detail, the implementation of the strategy required the establishment of an inventory of exposure models, extending the previous work performed by the International Society of Exposure Science (ISES), and Working Party on Exposure Assessment of the Organization of Economic Co-operation and Development (OECD). Models were scored to facilitate their selection. The different data (monitoring in the various sources, biomonitoring data, job exposure matrices, exposure factors, etc.) useful to feed the exposure models on general and occupational environments were also identified at country and European levels. Two complementary approaches (population based and worker based) were proposed to combine exposure from general and occupational environments and will be tested through case studies. The case studies account for relevant exposure sources for different population groups (children, adults including workers) and different types of chemicals like metals, perfluoroalkyl and polyfluoroalkyl substances (PFAS), pyrethroids and phthalates. Read more in the report.

The perspective  

The output of this activity will contribute to provide a better understanding of the main exposure sources and routes in general and occupational environments and generate an integrated and harmonised methodology  to support European agencies in proposing effective risk assessment of the human exposure that will lead to efficient risk management measures.