Spatial and Temporal Distributions of Organophosphate Ester Concentrations from Atmospheric Particulate Matter Samples Collected across Houston, TX.

Atmospheric particulate matter (PM) samples were collected from four ground-based sites located in the Houston, TX (September 21-28, 2013) and were analyzed for 12 organophosphate esters (OPEs; current-use plasticizers and flame retardants). Samples analyzed included daytime, nighttime, and 24 h PM of <2.5 μm aerodynamic diameter (PM) and total suspended particulate (TSP) samples. PM and TSP atmospheric ΣOPE concentrations varied over an order of magnitude and were statistically significantly different between urban and suburban and industrial sites. Additionally, significant temporal variability was also identified; for example, daytime atmospheric concentrations of 2-ethylhexyl diphenyl phosphate (EHDPP; 610 ± 220 pg m) measured in TSP samples were significantly higher than nighttime concentrations (280 ± 180 pg m; p = 0.03). Detailed discussions of the spatial and temporal distribution are given for Tris-(1-chloro-2-propyl) phosphate (TCiPP), EHDPP, tri-n-butyl phosphate (TnBP), and triphenyl phosphate (TPhP). Correlations to bulk measurements of carbonaceous PM including organic carbon, elemental carbon, and water-soluble organic carbon were used to understand potential sources and urban atmospheric transport. These results highlight the fundamental complexity associated with assessing OPE atmospheric concentrations across a large urban landscape and specific knowledge gaps at the intersection of consumer products and safety with environmental and human health.