**4. Conclusions**

In the present study, an assessment of the total daily dose in terms of submicron particle surface area received by children living in different Italian areas and attending different schools located in different urban contexts (rural, suburban and urban area), was performed. The study aimed at investigating the children daily doses received in different microenvironments (both school and non-school environments) also taking into account the impact of the outdoor concentration levels on the received dose. To this end, an experimental analysis using portable instruments able to measure the concentrations at personal scale of the children was performed.

The findings of the study shown that the contribution of the school environment to the overall daily dose of the children is quite limited although they spent a significant time fraction of the day therein. Such dose is mainly affected by the outdoor concentrations; thus, schools placed close to main outdoor sources (e.g., trafficked roads) may results in higher rates of exposure and related doses then rural ones.

Outdoor and transport microenvironments present an almost negligible contribution to the children daily doses, whatever the investigated sites, due to the reduced exposure time in such environments. Therefore, a child's daily dose is mainly affected by indoor non-school environments, e.g., homes. In particular, the contribution of non-school indoor microenvironments to the children's daily dose account for more than 70% of the data from the children and school locations. Such a high contribution is led by "cooking & eating" and other "indoor day" microenvironments. Indeed, the "cooking & eating" microenvironment contributes up to 36% of the daily dose despite the reduced time spent therein: this is due to the high levels of exposure from high-emitting cooking activities.

In conclusion, the results of the study demonstrate that a proper evaluation of the submicron particle dose received by children cannot be performed only relying upon outdoor concentration data and that despite the location of the school and home, the contribution of indoor non-school environments is essential to properly assess the dose received by children.

**Author Contributions:** Conceptualization, G.B. and S.R.; methodology, A.P.; investigation, A.P. and L.S.; data curation, L.S and A.P.; writing—original draft preparation, A.P.; writing—review and editing, L.S and G.B.; funding acquisition, S.R. and G.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the ANTER association and the company NWG Energia Srl Società Benefit.

**Acknowledgments:** The authors want to thank the children and their families for their key contribution in the successful experimental campaign.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
