(Uploaded by Plazi for the Bat Literature Project) Purpose We investigated the effects of human-induced disruption in a subterranean stable environment containing valuable Palaeolithic paintings and engravings (Ardales Cave, Southern Spain) using a double analytical approach. Methods An environmental monitoring system was installed in the cave to record temperature, relative humidity, carbon dioxide (CO2) and radon (222Rn) concentrations in air. In the same stations, an aerobiological sampling was conducted to quantify the level of airborne microorganisms. Results The combination of different methods allowed us to detect the extent of human-induced changes, confirming that these can be very hazardous in certain cave areas that should be apparently outside the scope of human disturbances, either by their remoteness to the visitor entrance or by being briefly visited. Conclusions The detection of evident anomalies in the environmental parameters and airborne microorganism concentration in the cave area housing the high density of