Robert G. M. Lee

PCBs in U.K. Urban Air

Atmospheric PCB concentrations were routinely monitored every other week over a 2-year period (1991-1992) in four U.K. urban centers. These sites included the major cities of London, Manchester, and Cardiff and the light industrial town of Stevenage, located ∼60 km north of London. Eight major congeners were measured at all of the sites with a further 22 included at the Manchester and Cardiff sites. Atmospheric ΣPCB (eight congeners) concentrations ranged from 112 to 3850 pg m -3 at the four sites, with the mean in London the highest. Clear seasonal cycling was observed in the urban atmospheres with summer concentrations being higher than winter for all congeners. The relative amplitude change in this cycling pattern was greatest for the higher chlorinated congeners ; summer :winter ratios were 2.0, 1.7, 3.2, and 5.0 for congeners 28, 52, 153, and 180, respectively. A simple box model developed by Pankow (1) was applied to the surface area of Manchester to predict the vapor-phase concentration of the tetra-CB, congener 52. Desorption from various compartments such as vegetation, soil, and urban dust were considered. The release from building air was also estimated. The predicted gas-phase concentrations show the seasonal cycling observed in the ambient air concentrations. The model fit for the three considered compartments (veg/soil/dust) was lower than the observed city air concentrations. The model data reflect background rural concentrations more accurately, perhaps suggesting that elevated concentrations of the vapor-phase component in city air are derived from building air and/or a series of point sources. Even today, many years after restrictions of PCB manufacture and use were introduced in the U.K., cities continue to act as sources of airborne PCBs to surrounding areas.

Gas-particle partitioning of PCDD/Fs in daily air samples

Eight short-term (24–48 h) air samples were taken at Lancaster, UK, to study the gas–particle partitioning of PCDD/Fs. Sampling dates in autumn 1997 were selected with a view to minimising temperature fluctuation during the sampling events. ΣCl4-8DD/Fs (ΣTEQ) for the first 6 samples were 1.1–3.6 pg m−3 (15–44 fg TEQ m−3), typical of a rural site; two other samples had ΣCl4-8DD/Fs of 18 and 7.9 pg m−3, with 320 and 100 fg TEQ m−3. The observed gas–particle distributions varied from 0–34% particle-bound for Cl2/3DD/Fs to >70% for Cl6-8DD/Fs. Measured particle-bound fractions were compared to theoretical estimates of their distribution based on the Junge–Pankow model using three different reported sets of vapour pressures. The best correlation was obtained using vapour pressures derived from measured GC-retention time indices (Eitzer and Hites, 1988). Plotting log partition coefficient (Kp) versus log sub-cooled liquid vapour pressure (pL) gave excellent correlations with slopes of roughly −1 for all homologue groups. 2, 3, 7, 8-substituted congeners showed slopes of −1 for the first five sampling events. It is proposed that kinetic factors at the low ambient temperatures, coupled with additional emissions during the last sampling events resulted in non-equilibrium partitioning.

Temperature dependence of PCBs in the UK atmosphere.

A thermodynamic approach was taken to assess the state of equilibrium between air and the Earth’s surface for PCBs at a variety of sites located in urban and rural areas. The Clausius–Clapeyron equation was applied to atmospheric PCB data, relating PCB partial vapour pressure (ln P) to inverse temperature (1/K); essentially representing the temperature controlled transition between condensed phases and the atmospheric gas phase. The slopes of the resulting plots ranged from −3100 to −8272 for a range of congeners at two city sites, significantly steeper than those generated at two rural locations, where there was little or no correlation between ln P and temperature. It was inferred that advection and variable meteorological conditions mask any localised, temperature dependent, air–surface exchange at these rural locations when weekly or two weekly integrated samples were taken. At a third rural site, close to Lancaster University, an intensive highly time-resolved sampling regime, carried out during very stable meteorological conditions resulted in highly correlated plots (r2>0.6), with slopes ranging from −7151 to −14 148 for different congeners. By reducing meteorological variables in this manner localised temperature controlled air–surface exchange became evident. Enthalpies of phase change generated from the temperature coefficients were similar to literature values for the enthalpy of vapourisation and the enthalpy of phase change from octanol to air. This suggests that, under these stable conditions, equilibrium was achieved as a function of either vapour pressure (P°L) or the octanol–air partition coefficient (KOA).

Persistence and fate of polychlorinated biphenyls (PCBs) in sewage sludge-amended agricultural soils.

Four metal enriched sewage sludges containing different concentrations of polychlorinated biphenyls (PCBs) were applied to two field soils in the UK in 1968. Samples of the sludges, sludge-amended soils and soils from untreated control plots were stored and analysed retrospectively. Sludge concentrations ranged from 1 to 7 mg SigmaPCB kg(-1). The pattern of PCBs was similar in three of the four sludges, with congeners 14, 18, 28 and 52 present at the highest concentrations. The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. SigmaPCB concentrations in control plot soil have declined over the last 20 years, indicating a reduction in atmospheric deposition inputs of PCBs to the soil. SigmaPCB concentrations also declined on the sludge-amended plots, reaching control plot concentrations (30-60 microg SigmaPCB kg(-1)) in the late-1980s. Half-lives ranged from < 1 to 8.5 years for congeners 18, 28 and SigmaPCB. Biodegradation and/or the formation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important loss process on both the control and sludge-amended plots. Using the fugacity approach, congener concentrations in soils at Luddington were predicted still to have not reached equilibrium with the air. Further losses to the atmosphere are likely.

The Doctor's Changing Role in Allocating U.S. and British Medical Services

Until the fourth decade of this century, British and American patients who could afford physician services paid for them out of their own pockets; those who could not relied on charity care or simply went without. Doctors functioned as independent contractor private practitioners in both Great Britain and the United States, allocating medical services in response to paying-patient demand and their own consciences. Beginning in the 1930s, health care financing on both sides of the Atlantic was restructured in dramatically different directions, and physicians’ allocational roles in their respective countries began diverging. Under the National Health Service (NHS), British general practitioners became essentially gatekeepers to health services, funneling patients to appropriate hospital and specialist care. As time went by they came more to resemble lockkeepers, regulating the queue for secondary and tertiary treatment resulting from governmental limits on health care spending and from the limitations and inefficiencies of a system of rationing by waiting. In the U.S., on the other hand, efficiency was not at first a concern. Physicians just became dispensers of relatively unlimited medical services, subsidized uncritically by health insurers. Under the more recent pressures of competition, inflation and technological advance, however, some doctors have begun to acquire the attributes of sellers in commercial markets. I As we move into the 1990s, physicians in both countries may soon find themselves coming from opposite directions, but once again performing a similar allocational job; this time one with administrative characteristics. Health care financers, whether governmental or private, are asserting far more control over the way funds are spent for medical services, and physicians’ professional autonomy has correspondingly declined. How did it happen that in less than 50 years, during which time their respective health care systems evolved in strikingly different ways, British and American physicians may once more come to fulfill an almost identical but significantly less powerful allocational function? Neither of these groups of professionals seems to relish the diminished independence inherent in the shift to a more bureaucratic role, and the impact of this change on patient interests is troublesome. How much does it-or should it alter the nature of physician-patient interaction? This article examines evolution of the British and American physician’s role in filtering clinical need from patient “demand” for health services, and in setting relative priorities among patient needs. It then raises questions about the significance of this change to the physician-patient relationship.