Ants can serve as "biological sensors" of urban pollution. This is proved by a University of Parma study published in the international journal Environmental Pollution, which presents a novel method for detecting and mapping magnetic particulate matter related with road traffic. The work brings up new possibilities for widespread, scalable, and low-cost biomonitoring systems that complement established monitoring methods. The sentinel organism employed in the study (Ants as bioindicators of urban traffic pollution) was the arboreal ant Crematogaster scutellaris. The sampling included 30 sites in the city of Parma with varied amounts of traffic and four control areas with no vehicle activity. Official traffic flow data collected by the Municipality of Parma in several parts of the city were connected with particles accumulated on the ants' surfaces and those found in the soil. By combining magnetic susceptibility measurements and scanning electron microscopy, the researchers discovered a substantial relationship between traffic intensity and the amount of magnetic particles on the ants; however, the similar relationship was not found in soil samples. In the model, each 1,000 additional vehicles per day resulted in a 1.41-fold increase (about 41%) in the ants' magnetic susceptibility. The particles, which were located largely on the thorax, were high in iron oxides and also contained zinc, copper, and titanium, with sizes and morphologies similar to traffic particles. "The most intriguing discovery is that ants do not merely detect the presence of particles; rather, they offer a local and time-integrated signature of exposure as a result of their nest fidelity, foraging activity, and direct interaction with the environment", the researchers explain. "This is a very concrete example of how biology, ecology, mineralogy, and materials physics can converge to build new tools for interpreting the environment". According to the scientists, "ants do not replace monitoring stations, but they can serve as a very sensitive biological matrix for identifying crucial locations in which to concentrate instrumental measurements and treatments at much finer spatial resolution".