Human health risk assessment quantifies the human or environmental toxicological effects deriving from the release of a contaminant at a source and its migration towards exposed receptors. Essentially, this entails a quantitative description of the relations in the system “source – pathway – receptor”. The procedure of risk assessment (RA) consists in a sequence of steps, starting from site assessment investigations, through the definition of a conceptual model (i.e., identification of potential receptors and migration and exposure pathways, selection of constituents of concern), the determination of concentrations at the point of exposure, actual risk calculation, to a risk management decision making stage (i.e., uncertainty assessment, risk acceptability evaluation, determination of the maximum acceptable concentration levels at the source and the selection of appropriate interventions).

The risk assessment itself can be carried out at an increasing degree of detail, through a tiered approach. The first tier essentially consists in comparing the site contamination with screening concentration values. It is a qualitative assessment that aims at identifying the potential need for emergency interventions. The second tier consists in simplified risk assessment, in which part of the input data are derived from targeted on-site investigations, whereas missing information is obtained from validated and up-to-date databases or from the literature, favoring conservative data in order to ensure that calculations promote environment and human health protection. The third tier represents an even more detailed appraisal of risk, based on more sophisticated computational methods (mainly numerical and probabilistic models).

Risk assessment standard procedures applied to particle release in the environment

The GW Group deals with the development of conceptual models that identify the contaminants migration in the subsoil, their exposure pathways and their potential receptors. In particular, the group develops analytical models for the second tier assessment and numerical models for the third tier assessment.

The GW Group also deals with the risk assessment of emerging contaminants, specifically with the potential health issues associated to the diffusion of nanoparticles (NP) in the environment. Since nanomaterials are characterized by a polydisperse particle size distribution, the human health risk induced by a NP contamination cannot be assessed through the ASTM procedure commonly used for chemicals. The GW Group proposed a general approach to adapt the ASTM procedure to NP contaminated aquifers and expanded the second tier RA analytical solutions to account for NP transport mechanism.


Sethi, R., & Di Molfetta, A. (2019). Groundwater Engineering. Springer, Cham. DOI 10.1007/978-3-030-20516-4 link

Tosco, T., & Sethi, R. (2018). Human health risk assessment for nanoparticle-contaminated aquifer systems. Environmental Pollution, 239, 242-252. DOI 10.1016/j.envpol.2018.03.041 link

Bianco C, Tosco T, Casasso A, Marchese F, Sethi R. (2019) Extension of human health risk assessment procedure to nanomaterial contaminations in aquifer systems. Geoingegneria Ambientale Mineraria 158(3):4-10 link