Outdoor passive air monitoring of semi volatile organic compounds (SVOCs): a critical evaluation of performance and limitations of polyurethane foam (PUF) disks.

The most commonly used passive air sampler (PAS) (i.e. polyurethane foam (PUF) disk) is cheap, versatile, and capable of accumulating compounds present both in gas and particle phases. Its performance for particle associated compounds is however disputable. In this study, twelve sets of triplicate PUF-PAS were deployed outdoors for exposure periods of 1-12 weeks together with continuously operated active samplers, to characterize sampling efficiency and derive sampling rates (RS) for compounds belonging to 7 SVOC classes (including particle associated compounds). PUF-PAS efficiently and consistently sampled polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and eight novel brominated flame retardant (nBFR) compounds. Low accuracy and lack of sensitivity was observed for most polychlorinated dibenzo-p-dioxins/furans PCDD/Fs and polybrominated diphenyl ethers (PBDEs) (under the conditions of this study), with the exception of some congeners which may be used as qualitative markers for their respective classes. Application of compound specific RS was found crucial for all compounds except PCBs. Sampling efficiency of the particle associated compounds was often low.

Practice transitions--past, present, and future.

Upon their retirement, dentists have gone from simply closing their office doors to seeing the sale of their practice as a means to fund their retirement. Today, other practice transition options are used to the advantage of both the retiring dentist and the dentist just starting out. Options will continue to meet the changing needs of dentists, particularly new dentists who must pay off higher education debts and may not opt for immediate ownership of a practice upon graduation.