Particulate matter (PM) contributes to an increased risk of respiratory and cardiovascular illnesses, cancer, and preterm birth complications. This project assessed PM exposure in Eastern Indonesia's largest city, where air quality has not been comprehensively monitored. We examined the efficacy of wearing masks as an individual intervention effort to reduce in-transit PM exposures. Handheld particulate counters were used to investigate ambient air quality for spatial analysis, as well as the differences in exposure to PM2.5 and PM10 (mu g/m(3)) by different transportation methods [e.g. motorcycle (n = 97), pete-pete (n = 53), and car (n = 55); note: n = 1 means 1 m(3) of air sample]. Mask efficacy to reduce PM exposure was evaluated [e.g. surgical masks (n = 39), bandanas (n = 52), and motorcycle masks (n = 39)]. A Monte Carlo simulation was used to provide a range of uncertainty in exposure assessment. Overall PM10 levels (91 +/- 124 mu g/m(3)) were elevated compared to the World Health Organization (WHO)'s 24-hour air quality guideline (50 mu g/m(3)). While average PM2.5 levels (9 +/- 14 mu g/m(3)) were below the WHO's guideline (25 mu g/m(3)), measurements up to 139 mu g/m(3) were observed. Compared to cars, average motorcycle and pete-pete PM exposures were four and three times higher for PM2.5, and 13 and 10 times higher for PM10, respectively. Only surgical masks were consistent in lowering PM2.5 and PM10 (p < 0.01). Young children (<= 5) were the most vulnerable age group, and could not reach the safe dosage even when wearing surgical masks. Individual interventions can effectively reduce individual PM exposures; however, policy interventions will be needed to improve the overall air quality and create safer transportation. (C) 2015 Elsevier B.V. All rights reserved.