An exhaust system for a vehicular lean burn internal combustion engine that emits oxides of nitrogen (NOx) and particulate matter (PM) is disclosed. The system comprises a NOx reduction catalyst for reducing NOx in the presence of a reductant, means for introducing reductant into a flowing exhaust gas and a source of hydrocarbon reductant, a nitrogenous reductant, and/or hydrogen, a filter for removing PM from exhaust gas flowing in the exhaust system and a low pressure exhaust gas recirculation (EGR) circuit for connecting the exhaust system downstream of the filter to an air intake of the engine. The EGR circuit comprises a IMOx adsorber catalyst (NAC) comprising a NO adsorbent.