Ames test improvements for the assessment of urban air mutagenicity

The release in the atmosphere of greenhouse gases and other pollutants severely affects the Earth’s climate, ecosystems and human health. In order to reduce emissions and find new solutions to face the problems, the ONU proposed the 2030 agenda for sustainable development: 17 interconnected points to achieve better life conditions. In the same direction, the European commission adopted the “European Green Deal”, which is a set of proposals aiming to reach zero-net emissions by 2050. About 7 million people die prematurely due to air pollution every year. The new 2021 WHO guidelines mostly concern six pollutants, which exposure was demonstrated to be harmful for human health: particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO). The exposure to pollutants is correlated to the occurrence of several diseases like cancer, ischemic heart disease, obtrusive pulmonary disease but also metabolic disease such as diabetes (Kampa et al., 2008). As illustrated in the EEA Report No 22/2018, pollution’s impact is higher in children, who can suffer serious long-term impact on the development. Thus, it is vital to characterise the different pollutants and their degree of risk modulation. The determination of whether a substance poses a health risk to humans is based on clinical, epidemiological, and/or animal studies which demonstrate that exposure to a substance is associated with health effects (Kampa et al., 2008). Toxicity includes a complex range of effects. One of the most discussed toxicity aspects associated with air pollution is mutagenicity and carcinogenicity. A classical technique to study the mutagenicity of a substance is the Ames Test, an in vitro method that uses bacteria to test whether a given chemical can induce DNA mutations in a bacterial model organism. Since its introduction (1973) it has been applied not only in the pharmaceutical and chemical industries as preliminary mutagenicity test on new compounds, but also in environmental toxicology to assess the mutagenicity of pollutants present in the different matrices (water, soil, air...) (Kauffman et al., 2020). Bacterial mutation tests have been vastly used to determine the presence of specific classes of mutagens and for doing site- or source comparisons for relative levels of airborne mutagens. The problem is that it is still impossible to analyse and assess all the toxicants both particulate and volatile present in the airborne. Therefore, it is necessary to optimise the Ames test in order to identify, quantify and compare mutagenicity of the totality of the airborne, allowing a better understanding of the real impacts on human health.