Biomedical subjects

Nick J Farrar

Publications and source records attributed to Nick J Farrar.

4 recordsLinked to original sources

PubMed2006

Continental scale passive air sampling of persistent organic pollutants using rapidly equilibrating thin films (POGs).

A novel design of rapidly equilibrating passive air sampler was deployed at 38 sites across 19 European countries to investigate short-term spatial variability of persistent organic pollutants (POPs). Devices were sealed in airtight containers to eliminate the possibility of contamination during transit and couriered to recipients with deployment instructions. Exposure times of 7days permitted the use of back trajectory analysis to further understand the factors responsible for influencing the large-scale spatial distribution of PCBs, PBDEs, PCNs, PAHs, lindane and HCB. Following sampler harvest, devices were sealed and returned for analysis. Comparison of sequestered levels showed that PAHs exhibited the greatest spatial variability (by a factor of 30) with higher levels often associated with greater population density. In contrast, HCB values were much more uniform, reflecting its well mixed distribution in the atmosphere. Spatial variation was strongly influenced by air mass origin, with lower levels being observed at most sites impacted by maritime air masses.

Air Movements↗

PubMed2004

Passive air sampling of PCBs, PBDEs, and organochlorine pesticides across Europe.

This study presents concurrently sampled ambient air data for a range of persistent organic pollutants at the continental scale. This was achieved using a passive air sampling system, deploying polyurethane foam disks, which was prepared in one laboratory, sealed to prevent contamination, sent out by courier to volunteers participating in different countries, exposed for 6 weeks, collected, resealed, and returned to the laboratory for analysis. Europe was the study area--a region with a history of extensive POPs usage and emission and with marked national differences in population density, the degree of urbanization and industrial/agricultural development. Samplers were deployed at remote/rural/urban locations in 22 countries and analyzed for PCBs, a range of organochlorine pesticides (HCB, alpha-HCH, gamma-HCH, ppDDT, ppDDE), and PBDEs. Calculated air concentrations were in line with those obtained by conventional active air sampling techniques. The geographical pattern of all compounds reflected suspected regional emission patterns and highlighted localized hotspots. PCB and PBDE levels varied by over 2 orders of magnitude; the highest values were detected in areas of high usage and were linked to urbanized areas. HCB was relatively uniformly distributed, reflecting its persistence and high degree of mixing in air. Higher gamma-HCH, ppDDT, and ppDDE levels generally occurred in South and East Europe.

Agriculture↗

PubMed2004

Passive air sampling of polycyclic aromatic hydrocarbons and polychlorinated naphthalenes across Europe.

This study presents concurrently sampled ambient air data for a range of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated naphthalenes (PCNs) at the continental scale. This was achieved with a passive air sampling system, by deploying polyurethane foam disks, which were prepared in one laboratory, sealed to prevent contamination, sent out by courier to volunteers participating in different countries, exposed for six weeks, collected, resealed, and returned to the laboratory for analysis. The study area was Europe, a region with a history of extensive persistent organic pollutants usage and emission, and with marked national differences in population density, the degree of urbanization and industrial and agricultural development. Samplers were deployed at remote, rural, and urban locations in 22 countries. Calculated air concentrations were broadly in line with those obtained by conventional active air sampling techniques, for both compound classes and for compounds existing predominantly in the gas and particle phases. The geographical compound distribution reflected suspected regional emission patterns and highlighted localized source areas. Both PAH and PCN levels varied by more than two orders of magnitude. The implications for sources are discussed.

Air Pollutants↗

PubMed2003

Characterization of polymer coated glass as a passive air sampler for persistent organic pollutants.

The use of thin-film polymer-coated glass surfaces or POGs as passive air samplers was investigated during an uptake experiment in an indoor environment with high levels of gas-phase polychlorinated biphenyls (PCBs). POGs consisted of a micron thick layer of ethylene vinyl acetate (EVA) coated onto glass cylinders. The uptake was initially linear with time and governed by the air-side mass transfer coefficient and surface area of the sampler. This was followed by a curvilinear region and finally a constant phase when equilibrium was established between air and EVA. The high surface area-to-volume ratio of the POGs allowed rapid equilibrium with gas-phase PCBs; equilibration times were on the order of hours for the low molecular weight congeners. The equilibrium concentration was dependent on the EVA-air partition coefficient, K(EVA-A), which was shown to be very well correlated to the octanol-air partition coefficient, K(OA). When POGs of varying thickness were equilibrated with air, the amount of PCB accumulated increased with increasing thickness of the EVA, indicating that uptake was by absorption into the entire polymer matrix. A wind field of 4 m s(-1) resulted in an increased uptake rate by a factor of approximately six compared to uptake in relatively still air. This wind speed effect was diminished, however, when POGs were housed in deployment chambers consisting of inverted stainless steel bowls. Relationships based on the air-side mass transfer coefficient and K(EVA-A) were developed for PCBs that describe the entire uptake profile and allow air concentrations to be determined from the amount of chemical accumulated in the POG. It is believed that these relationships are also valid when POGs are used to detect other classes of persistent organic pollutants.

Adsorption↗