A method for monitoring a regulated emissions concentration C, in the exhaust gas of an internal combustion engine is provided. The method comprises directing the exhaust gas through an exhaust-gas turbocharger, directing at least a portion of the exhaust gas through an exhaust-gas recirculation system, measuring an air ratio λmeas in the exhaust gas with a lambda probe, measuring a rotational speed nT of the exhaust-gas turbocharger with a sensor, and determining the regulated emission concentration Ci based on the air ratio λmeas and the rotational speed nT. In this way, the emission concentration of the exhaust may be determined as a function of the rotational speed of the turbine.