This paper presents a two-stage numerical study of the effects of airborne fine particle pollution on the usability of natural ventilation in three Asian megacities (Beijing, Shanghai and New Delhi), using measured weather and PM2.5 data. The first stage assessed the impact of personal comfort systems on NV availability and their combined effect on HVAC electricity consumption. PCS increase the potential for NV-use from 25-50% to 40-65%, which more than doubles its energy-saving capability, decreasing the HVAC electricity consumption by 13-42%. However, higher NV-use also increases indoor cumulative PM2.5 exposure up to fourfold. The second part of this paper analyses two approaches to decrease occupant exposure: limiting NV-use to moments of low outdoor particle pollution (with two thresholds: 10 and 35 mu gw/m(3)), and using an electrostatic filter to limit PM2.5 penetration in the NV airflow. The first approach reduces the increase in exposure by between half and two-thirds, although it also reduces energy savings. The second approach also reduces the increase in exposure by two-thirds but, due to the filter's low power consumption, upholds NV's energy-saving potential. Overall, NV-use is most beneficial in Shanghai (highest energy savings and lowest PM2.5 levels) and least beneficial in New Delhi. (C) 2017 Elsevier Ltd. All rights reserved.