The impact of household air cleaners on the chemical composition and children's exposure to PM metal sources in suburban Shanghai.

Increased public awareness of the health impacts of atmospheric fine particulate matter (PM) has led to increased demand and deployment of indoor air cleaners. Yet, questions still remain about the effectiveness of indoor air cleaners on indoor PM concentrations and personal exposure to potentially hazardous components of PM. Metals in PM have been associated with adverse health outcomes, so knowledge of their sources in urban indoor and outdoor areas and how exposures are influenced by indoor air cleaners would be beneficial for public health interventions. We collected 48-h indoor, outdoor, and personal PM exposure samples for 43 homes with asthmatic children in suburban Shanghai, China during the spring months. Two sets of samples were collected for each household, one set with a functioning air filter placed in the bedroom ("true filtration") and the other with a non-functioning ("sham") air cleaner. PM samples were analyzed for elements, elemental carbon, and organic carbon. The major sources of metals in PM were determined by Positive Matrix Factorization (PMF) to be regional aerosol, resuspended dust, residual oil combustion, roadway emissions, alloy steel abrasion, and a lanthanum (La) and cerium (Ce) source. Under true filtration, the median indoor to outdoor percent removal across all elements increased from 31% to 78% and from 46% to 88% across all sources. Our findings suggest that indoor air cleaners are an effective strategy for reducing indoor concentrations of PM metals from most sources, which could translate into improved health outcomes for some populations.