Seasonal Variations of Children's Personal Exposure to Ultrafine Particles in Different Microenvironments in Bhutan

The health impacts of air pollution are driven by exposure to pollutants, which is a function of time spent and pollutant concentrations in different microenvironments. There are only a handful of studies on exposure assessment to ultrafine particles (UFP greater than 0.1 m), particularly in developing countries. Available studies on human exposure to air pollution have mostly focused on particle mass and relied on data from fixed monitoring stations and area measurements. While such studies may be useful, it can lead to gross miscalculation of exposure. Real-time personal monitoring combined with individuals time activity patterns provide an accurate assessment of exposure and identification of high-risk microenvironments. This study characterized childrens daily personal exposure to UFP using real-time personal monitors, during wet and dry seasons in rural Bhutan.45 village children, with age range of 9 to 13 years and attending two primary schools participated in the study. All children carried personal monitors attached to their waists for 24 hours and air was sampled continuously from the breathing zone. An activity diary was used to track childrens activity patterns and time spent in different microenvironments. Children received higher daily UFP exposure during the dry season (mean = 4.19 104 particles/cm3) than wet season (mean = 1.13 104 particles/cm3), respectively. The highest UFP exposure resulted during cooking/eating, contributing to 51 % of the total daily exposure during the wet season and 73 % during the dry season. This is despite children spending only 7 % (during the wet season) and 13 % (during the dry season) of the total daily time in the microenvironment where this activity was conducted. The lowest UFP exposures were during the hours that children spent outdoors at schools. Results of this study highlight substantial contribution of household air pollution to childrens personal exposure, thus potentially presenting a significant environmental health hazard.