# Direct Impact of the Air on Mutant Cells for Mutagenicity Assessments in Urban Environments

## TL;DR

This study introduces a new method to assess air mutagenicity by directly exposing microbial plates to polluted air, avoiding traditional filter-based methods.

## Contribution

A novel direct method for evaluating air mutagenicity using microbial plates without filter extraction is proposed and validated.

## Key findings

- The new protocol yields repeatable mutagenicity results comparable to traditional methods.
- The method captures the full air pollution mixture, including volatile and semivolatile compounds.
- The approach is simpler, faster, and less expensive than conventional techniques.

## Abstract

Background: Urban air pollution is recognized as a critical problem for public health and is classified as a carcinogen for humans. A great number of studies have focused on the monitoring of urban air mutagenicity. One of the best-known and applied methods for assessing mutagenicity is the Ames test, a bacterial reverse mutation test. The classic protocol for assessing air mutagenicity involves the concentration of particulate matter (PM) on filters and subsequent extraction using organic solvents. This work aimed to develop a method for the evaluation of air mutagenicity directly impacted by air on microbial plates already containing an Ames’ microbial sensor. Methods: A specific six-month sampling campaign was carried out in Turin in a period with high air pollution. Samples were tested for mutagenicity on Salmonella typhimurium strains TA98, TA100, and YG1024 with the traditional method and with the new direct method. Results: The new protocol is able to evaluate the mutagenicity of the sampled air and obtain repeatable results. The final sensitivity is similar to the traditional method (≈10 net revertants/m3); however, the mutagenic response is due to the complete air pollution mixture, including volatile and semivolatile pollutants avoiding the concentration of filters and the following laborious extraction procedures. Conclusions. Despite some critical issues in contamination control, the method is easier, faster, and less expensive than traditional methods.