Indoor-outdoor relationship for airborne particulate matter of outdoor origin in exposure assessment: a review of recent studies.

Personal exposure to ambient airborne particulate matter is composed by exposure to indoor particulate matter(PM)of outdoor origin and direct outdoor exposure.After penetrating into indoors,outdoor PM generally showed changed characteristics, including mass concentration,size distribution as well as components,which are contributing to the exposure measurement errors when ambient concentrations are used as real exposure for human epidemiological studies.This paper reviewed adopted methods in studying indoor-outdoor relationships for PM and its various components,mainly including mass balance model,statistic model and receptor model for source apportionment,to better understand existing exposure error and improve exposure-risk assessment of ambient particulate matter.Meanwhile,several factors influencing indoor PM concentration of outdoor origin were pointed out by parameter analysis.In addition,nested source apportionment technique was introduced to offer a new option for further study on indoor PM sources.