Joseph O. Okeme

Calibration of two passive air samplers for monitoring phthalates and brominated flame-retardants in indoor air.

Two passive air samplers (PAS), polyurethane foam (PUF) disks and Sorbent Impregnated PUF (SIP) disks, were characterized for uptake of phthalates and brominated flame-retardants (BFRs) indoors using fully and partially sheltered housings. Based on calibration against an active low-volume air sampler for gas- and particle-phase compounds, we recommend generic sampling rates of 3.5±0.9 and 1.0±0.4 m(3)/day for partially and fully sheltered housing, respectively, which applies to gas-phase phthalates and BFRs as well as particle-phase DEHP (the later for the partially sheltered PAS). For phthalates, partially sheltered SIPs are recommended. Further, we recommend the use of partially sheltered PAS indoors and a deployment period of one month. The sampling rate for the partially sheltered PUF and SIP of 3.5±0.9 m(3)/day is indistinguishable from that reported for fully sheltered PAS deployed outdoors, indicating the role of the housing outdoors to minimize the effect of variable wind velocities on chemical uptake, versus the partially sheltered PAS deployed indoors to maximize chemical uptake where air flow rates are low.

Organophosphate esters flame retardants in the indoor environment

Concentrations of 13 organophosphate ester flame retardants (OPEs) were measured in air, dust and window wipes from 63 homes in Canada, the Czech Republic and the United States in the spring and summer of 2013 to look for abundances, differences among regions, and partitioning behavior. In general, we observed the highest concentrations for halogenated OPEs, particularly TCEP, TCIPP and TDCIPP, and also non-halogenated TPHP. Differences between regions strongly depended on the matrix. The concentrations of OPEs in dust were significantly higher in the US than in Canada (CAN) and Czech Republic (CZ). CZ had the highest concentrations in window film and CAN in air. ΣOPE concentrations were 2-3 and 1-2 orders of magnitude greater than ΣBFRs in air, and dust and window films, respectively. We found a significant relationship between the concentrations in dust and air, and between the concentrations in window film and air for OPEs with log KOA values <12, suggesting that equilibrium was reached for these compounds but not for those with log KOA>12. This hypothesis was confirmed by a large discrepancy between values predicted using a partitioning model and the measured values for OPEs with log KOA values >12.

Passive air sampling of flame retardants and plasticizers in Canadian homes using PDMS, XAD-coated PDMS and PUF samplers

Passive air samplers (PAS) were evaluated for measuring indoor concentrations of phthalates, novel brominated flame retardants (N-BFRs), polybrominated diphenyl ethers (PBDEs), and organophosphate esters (OPEs). Sampling rates were obtained from a 50-day calibration study for two newly introduced PAS, polydimethylsiloxane (PDMS) or silicone rubber PAS (one with and one without a coating of styrene divinyl benzene co-polymer, XAD) and the commonly used polyurethane foam (PUF) PAS. Average sampling rates normalized to PAS surface area were 1.5 ± 1.1 m3 day-1 dm-2 for both unsheltered PDMS and XAD-PDMS, and 0.90 m3 ± 0.6 day-1dm-2 for partially sheltered PUF. These values were derived based on the compound-specific sampling rates measured here and in the literature for the PAS tested, to reasonably account for site-specific variability of sampling rates. PDMS and PUF were co-deployed for three weeks in 51 homes located in Ottawa and Toronto, Canada. Duplicate PUF and PDMS samplers gave concentrations within 10% of each other. PDMS and PUF-derived air concentrations were not statistically different for gas-phase compounds. PUF had a higher detection of particle-phase compounds such as some OPEs. Phthalate and OPE air concentrations were ∼100 times higher than those of N-BFRs and PBDEs. Concentrations were not systematically related to PM10, temperature or relative humidity. We conclude that both PAS provide replicable estimates of indoor concentrations of these targeted semi-volatile organic compounds (SVOCs) over a three-week deployment period. However, PUF is advantageous for collecting a wider range of compounds including those in the particle phase.

A miniature bird-borne passive air sampler for monitoring halogenated flame retardants

Birds have been used intensively as biomonitors of halogenated flame retardants (HFRs), and several studies have reported elevated tissue concentrations and inter-individual variability for these contaminants. While diet is known to be an important exposure pathway for HFRs in birds, it has been suggested that exposure through air may represent an underestimated source of HFRs for certain species. However, a method was not available for measuring the atmospheric exposure of individual birds to HFRs or other semi-volatile contaminants. The goal of this study was to develop a bird-borne passive air sampler (PAS) enabling the determination of individual atmospheric exposure to gas- and particle-phase HFRs using the ring-billed gull (Larus delawarensis) nesting in the Montreal area (QC, Canada). The new miniaturized elliptical-shaped PAS (mean weight: 2.72g) was tested using two sorbent types during three exposure periods (one, two and three weeks). Results showed that PAS using polyurethane foam (PUF) combined with a glass fiber filter collected all major polybrominated diphenyl ethers (PBDEs) and exhibited better performance for collecting highly hydrophobic DecaBDE mixture congeners compared to the PAS using polydimethylsiloxane (PDMS). Emerging HFRs including hexabromobenzene, Dechlorane 604 Component B, and Dechlorane plus (DP) isomers also were sampled by the PUF-based PAS. Sampling rates for most HFRs were comparable between the three exposure periods. This novel bird-borne PAS provides valuable information on the non-dietary exposure of free-ranging birds to HFRs.

Examining the Gas-Particle Partitioning of Organophosphate Esters (OPEs): How Reliable are Air Measurements?

Organophosphate esters (OPEs) in air have been found to be captured entirely on filters of typical active air samplers and thus designated as being in the particle phase. However, this particle fraction is unexpected, especially for more volatile tris(2-chloroethyl) phosphate (TCEP) and tris(chloroisopropyl) phosphate (TCIPP). We evaluated gas-particle partitioning in indoor and outdoor air for OPEs and polybrominated diphenyl ethers (PBDEs) using single-parameter models (Junge-Pankow, Harner-Bidleman) and poly-parameter linear free energy relationship (pp-LFER) models. We also used the pp-LFER to estimate filter-air partitioning in active air samplers. We found that all gas-particle partitioning models predicted that TCEP and TCIPP should be in the gas phase, contrary to measurements. The pp-LFER better accounted for OPE measurements than the single-parameter models, except for TCEP and TCIPP. Gas-particle partitioning of PBDEs was reasonably explained by all models. The pp-LFER for filter-air partitioning showed that gas-phase sorption to glass and especially quartz fiber filters used for active air samplers could account for up to 100% of filter capture and explain the high particle fractions reported for TCIPP, tris(1,3-dichloro-2-propyl) phosphate TDCIPP, and triphenyl phosphate TPhP, but not TCEP. The misclassification of gas-particle partitioning can result in erroneous estimates of the fraction of chemical subject to gas-phase reactions and atmospheric scavenging and, hence, atmospheric long-range transport.

Fixation of XAD-4 power on filter paper using methyl cellulose for the passive air sampling of semi-volatile organic compounds in indoor air

ABSTRACT The sorption capacity of a substrate serving as sampling medium can be enhanced by adding another sorbent to its surface. This is usually achieved through an impregnation process by repeated dipping of the substrate in a slurry solution containing the powder of the sorbent. Because the impregnation process only deposits the sorbent powder on the surface of the substrate, the powder could detach and fall off during field deployment. In this study, a novel approach was explored to fix the added sorbent powder to the surface of the substrate. Methylcellulose (MC) in fine crystal form was selected as the fixing agent to secure the powder of polystyrene-divinyl benzene copolymer resin (XAD-4), with its high sorption capacity, to a cellulose filter paper (CFP). The process involved first mixing XAD-4 and MC in the presence of water to form a milky slurry solution that was then painted on to the surface of the paper and then allowed to dry. The painting technique resulted in a good reproducibility of the applied amount of XAD-MC mixture with a relative standard deviation (RSD) of 12% (n = 5). Scanning electron microscope (SEM) images showed that the XAD-4 powder was held to the surface of the filter paper. No free XAD powder was dislodged from the coated filter paper when coated paper was flicked with a finger. For use as an indoor passive air sampler (PAS), this new sampling medium was placed in a round housing made of electronically polished aluminium material and was tested for uptake of polybrominated diphenyl ethers and phthalic acid dialkylesters. Surface area specific uptake rates (ASUR) of PBDEs ranged from 1.14 to 2.82 m3/(dm2d), while ASUR of phthalates had a wider range from 2.74 to 5.66 m3/(dm2d).