Has the burden and distribution of PCBs and PBDEs changed in European background soils between 1998 and 2008? Implications for sources and processes

Background soils were collected from 70 locations on a latitudinal transect in the United Kingdom and Norway in 2008, ten years after they had first been sampled in 1998. The soils were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCs), to see whether there had been any change in the loadings or distributions of these persistent organic pollutants (POPs). The same transect has also been used to sample air between the mid-1990s and the present, so the air and soil spatial and temporal trends provide information on air-soil transfers, source-receptor relationships, long-range atmospheric transport (LRAT), and recycling phenomena. Comparisons of the 2008 and 1998 data sets show a general decline for PBDEs in surface soil, and a smaller averaged net decline of PCBs. Changes between the years were observed for total POP concentrations in soil and also for correlations with site and sample characteristics assumed to affect those concentrations. POP concentrations were correlated to distance and strength of possible sources, a relationship that became weaker in the 2008 data. Fractionation, a commonly discussed process for the global cycling of POPs was also lost in the 2008 data. As in 1998, soil organic matter content continues to have a strong influence on the loadings of POPs in surface soils, but changes in the PCB loads were noted. These factors indicate an approach to air-surface soil equilibrium and a lessening of the influence of primary sources on POP concentrations in soil between 1998 and 2008.

Investigating intergenerational differences in human PCB exposure due to variable emissions and reproductive behaviors

BACKGROUND

Reproductive behaviors--such as age of childbearing, parity, and breast-feeding prevalence--have changed over the same historical time period as emissions of polychlorinated biphenyls (PCB) and may produce intergenerational differences in human PCB exposure.

OBJECTIVES

Our goal in this study was to estimate prenatal, postnatal, and lifetime PCB exposures for women at different ages according to year of birth, and to evaluate the impact of reproductive characteristics on intergenerational differences in exposure.

METHODS

We used the time-variant mechanistic model CoZMoMAN to calculate human bioaccumulation of PCBs, assuming both hypothetical constant and realistic time-variant emissions.

RESULTS

Although exposure primarily depends on when an individual was born relative to the emission history of PCBs, reproductive behaviors can have a significant impact. Our model suggests that a mother's reproductive history has a greater influence on the prenatal and postnatal exposures of her children than it does on her own cumulative lifetime exposure. In particular, a child's birth order appears to have a strong influence on their prenatal exposure, whereas postnatal exposure is determined by the type of milk (formula or breast milk) fed to the infant.

CONCLUSIONS

Prenatal PCB exposure appears to be delayed relative to the time of PCB emissions, particularly among those born after the PCB production phaseout. Consequently, the health repercussions of environmental PCBs can be expected to persist for several decades, despite bans on their production for > 40 years.

Evidence for major emissions of PCBs in the west African region

In previous studies unexpectedly high air concentrations of polychlorinated biphenyls (PCBs) were observed in ship-based measurements made ∼400 km off parts of the West African coast. To investigate further (i) samples were taken on board the RV Polarstern during a cruise from Germany to South Africa in October-November 2007; (ii) samples were obtained on Cape Verde Island during the same period to monitor airflows from Africa; and (iii) passive samplers were deployed in four West African countries to try to characterize potential sources on land. Results were as follows: on Cape Verde and on the ship air masses came predominantly (∼ 95%) from the African continent; the shipboard Σ29PCB concentrations off West Africa ranged from 10 to 360 pg m(-3) and from 6 to 99 pg m(-3) in Cape Verde; the highest land-based concentrations were observed in Ivory Coast and the Gambia (up to 300 pg m(-3)) and the lowest was observed in Ghana (9 pg m(-3)). Taken together, these and previous studies indicate there are more major emission(s) of PCBs and different source types in parts of West Africa than accounted for in current global atmospheric emissions estimates. Results from the FLEXPART model and PAH measurements show that emission inventories and biomass burning cannot fully explain the high PCB concentrations. Potential sources of the high PCB levels to the African regions are discussed, namely illegal dumping of PCB containing waste with release via volatilization and uncontrolled burning, and the storage and breakup of old ships.

Quantification of sources of PCBs to the atmosphere in urban areas: a comparison of cities in North America, Western Europe and former Yugoslavia

We present estimated emission source strengths of seven polychlorinated biphenyl (PCB) congeners for Banja Luka, a city that was affected by the civil war in Bosnia and Hercegovina (former Yugoslavia) in the 1990s. These emission estimates are compared to PCB emission rates estimated for the cities of Zurich, Switzerland, and Chicago, USA using an approach that combines multimedia mass balance modeling and measurement data. Our modeled per-capita emission estimates for Banja Luka are lower by a factor of ten than those for Zurich and Chicago, which are similar. This indicates that the sources of PCB emissions in Banja Luka are likely to be weaker than in the Western European and North American cities which show relatively high PCB emissions. Our emission rates from the three cities agree within a factor of ten with emission estimates from a global PCB emission inventory derived from production and usage estimates and emission factors.

Trends in European background air reflect reductions in primary emissions of PCBs and PBDEs

Data are presented for polychlorinated biphenyls (PCBs) and polybrominated diphenyls ethers (PBDEs) in passive air samplers (PAS) collected along a rural/remote latitudinal transect from southern UK to northern Norway during 2004-2008. This study is part of an ongoing campaign, using semipermeable membrane devices (SPMDs) as PAS over two year intervals since 1994. Absolute sequestered amounts of selected PCB congeners have decreased in a first order fashion between 1994-2008, with the average time of 8.4+/-3.2 years for atmospheric concentrations to decline by 50%. PCBs have continued to fractionate with latitude during this period. PBDE concentrations declined by 50% between 2000 and 2008 every 2.2+/-0.4 years. Results are discussed in terms of sources, long-range atmospheric transport, global fractionation, and clearance processes. It is concluded that the spatial and temporal trends in background European air mainly reflect the strength of primary diffusive emissions of these compounds and subsequently their ongoing declines. The direct evidence for this is similar rates of decline at all the sites; similar rates of decline for all congeners; no systematic change in the fractionation pattern since 1994. The latest results indicate a reduction in the rate of decline for PCBs (and hence in primary emissions).

Atmospheric monitoring of organic pollutants in the Arctic under the Arctic Monitoring and Assessment Programme (AMAP): 1993-2006

Continuous and comparable atmospheric monitoring programs to study the transport and occurrence of persistent organic pollutants (POPs) in the atmosphere of remote regions is essential to better understand the global movement of these chemicals and to evaluate the effectiveness of international control measures. Key results from four main Arctic research stations, Alert (Canada), Pallas (Finland), Storhofdi (Iceland) and Zeppelin (Svalbard/Norway), where long-term monitoring have been carried out since the early 1990s, are summarized. We have also included a discussion of main results from various Arctic satellite stations in Canada, Russia, US (Alaska) and Greenland which have been operational for shorter time periods. Using the Digital Filtration temporal trend development technique, it was found that while some POPs showed more or less consistent declines during the 1990s, this reduction is less apparent in recent years at some sites. In contrast, polybrominated diphenyl ethers (PBDEs) were still found to be increasing by 2005 at Alert with doubling times of 3.5 years in the case of deca-BDE. Levels and patterns of most POPs in Arctic air are also showing spatial variability, which is typically explained by differences in proximity to suspected key source regions and long-range atmospheric transport potentials. Furthermore, increase in worldwide usage of certain pesticides, e.g. chlorothalonil and quintozene, which are contaminated with hexachlorobenzene (HCB), may result in an increase in Arctic air concentration of HCB. The results combined also indicate that both temporal and spatial patterns of POPs in Arctic air may be affected by various processes driven by climate change, such as reduced ice cover, increasing seawater temperatures and an increase in biomass burning in boreal regions as exemplified by the data from the Zeppelin and Alert stations. Further research and continued air monitoring are needed to better understand these processes and its future impact on the Arctic environment.

Towards an understanding of the link between environmental emissions and human body burdens of PCBs using CoZMoMAN

Different factors affect how organic contaminants released into the environment over time distribute and accumulate, enter various food-chains, and potentially cause toxic effects in wildlife and humans. A sound chemical risk assessment thus requires the determination of the quantitative relationship between emissions and human exposure. This study aimed to assess the extent of the quantitative and mechanistic understanding of the link between environmental emissions and human body burdens for polychlorinated biphenyls (PCBs) in the western part of the Baltic Sea drainage basin and to identify any remaining knowledge gaps. An integrated, non-steady state model calculating human body burden from environmental emissions (CoZMoMAN) was created by linking the multi-compartment environmental fate model CoZMo-POP 2 with the human food chain bioaccumulation model ACC-HUMAN. CoZMoMAN predicted concentrations of seven PCB congeners in 11 key model compartments to typically within a factor of 2 to 4 of measured values, although larger discrepancies are noted for soils and humans. We conclude that whereas the most important processes which link emissions of PCBs to human body burdens are quite well understood in this region, some critical knowledge gaps related to the time trend of historical emissions remain to be addressed.

Patients with high-grade atrioventricular block treated and not treated with a pacemaker

One-hundred and eighty-one patients with chronic and with intermittent high-grade atrioventricular block (AVB) were studied retrospectively. Seventy-one were treated with fixed-rate, 51 with demand-type pacemaker, 59 were treated conservatively. Observation time was three years minimum and 14.5 years maximum. The mean age was about seven years higher, and 8.7% more patients had chronic AVB in the conservatively treated than in the pacemaker-treated group. About 12% more patients had Adams-Stokes attacks in the pacemaker group than in the conservatively treated group. There were 7% more patients with coronary heart disease (CHD) in the pacemaker group, and 10% more with aortic valve disease among the conservatively treated. Totally 4.4% of the patients had a calcification of the mitral annulus fibrosus. The two groups were comparable as regards functional class (NYHA) and heart size. Survival showed 31% more sudden deaths in the conservatively treated than in the pacemaker group. Sudden deaths were not more frequent among the patients with CHD than in those without. Long-term survival showed the more favourable result for the patients with than without pacemaker treatment. There were eight (11.3%) unexplained sudden deaths among the patients treated with fixed-rate pacemaker, only three (5.9%) among those treated with a demand unit. The fixed-rate and the demand units showed a mean longevity of 37.2 and 34.6 months, respectively.

Permanent pacemaker treatment in older age groups

Of 693 patients on permanent pacemaker treatment between 1962 and 1981, 282 (40.7%) were above the age of 75. Of this number, 142 patients were 75-79 years, 95 80-84 years and 45 85-93 (mean 87) years old at the time of the first pacemaker implantation. The patients were followed for 13-154 months (mean 37.1) with special attention being paid to morbidity and mortality after the implantation. Complications occurred in 65 (23%) of the elderly patients, with no significant difference between the three age groups. Excessive threshold rise with stimulation failure (6%) and infections or skin erosions (4.9%) were the most frequent complications. Mortality increased in all age groups during the first 6-12 months compared with the age- and sex-matched Norwegian population. Five-year survival rates were 56, 32 and 25% respectively. We conclude that cardiac pacemaker treatment in the elderly is a safe symptom-relieving therapeutic procedure and that the prognosis for these patients is similar to that for their fellow senior citizens after the first year of treatment.

Sick sinus syndrome treated with permanent pacemaker in 109 patients. A follow-up study

During the last decade implantation of permanent pacemakers has become the treatment of choice for patients suffering from the sick sinus syndrome (SSS). We have followed up 112 SSS patients treated with permanent pacemakers in Haukeland Hospital in the period 1966--76. The pacemakers were later removed from three of the patients. In the remaining 109 patients the SSS was characterized by tachy-bradyarrhythmias (TBA) in 44 and bradyarrhythmias (BA) in 65. Before implantation, 68 patients had syncopes and 27 severe dizziness. After implantation, symptomatic improvement was apparent in 104 patients; only three still had syncopes. During the follow-up period (mean 34.4 months), 29 patients died (yearly mortality 9.3%). There was no significant difference in total mortality between patients with TBA and with BA. Concomitant disturbances in atrioventricular (AV) conduction occurred in 35.8% of the patients. Among 79 of 80 patients still alive, five had developed total AV block, 19 had stable atrial fibrillation, 12 of these were possibly pacemaker-independent (ventricular rate greater than 60/min). Systemic embolization was observed in 16 patients, more frequently in the TBA (12/44) than in the BA group (4/65) (p less than 0.001). It is concluded that permanent pacemakers have an excellent symptomatic effect in patients with SSS. The prognosis is mainly determined by the presence or absence of coronary heart disease and/or heart failure.

Relationships between organic matter, black carbon and persistent organic pollutants in European background soils: Implications for sources and environmental fate

Black carbon (BC) and total organic carbon (TOC) contents of UK and Norwegian background soils were determined and their relationships with persistent organic pollutants (HCB, PAHs, PCBs, co-planar PCBs, PBDEs and PCDD/Fs) investigated by correlation and regression analyses, to assess their roles in influencing compound partitioning/retention in soils. The 52 soils used were high in TOC (range 54-460 mg/g (mean 256)), while BC only constituted 0.24-1.8% (0.88%) of the TOC. TOC was strongly correlated (p<0.001) with HCB, PCBs, co-PCBs and PBDEs, but less so with PCDD/Fs (p<0.05) and PAHs. TOC explained variability in soil content, as follows: HCB, 80%; PCBs, 44%; co-PCBs, 40%; PBDEs, 27%. BC also gave statistically significant correlations with PBDEs (p<0.001), co-PCBs (p<0.01) and PCBs, HCB, PCDD/F (p<0.05); TOC and BC were correlated with each other (p<0.01). Inferences are made about possible combustion-derived sources, atmospheric transport and air-surface exchange processes for these compounds.

Spatial patterns of polybrominated diphenyl ethers (PBDEs) in mosses, herbivores and a carnivore from the Norwegian terrestrial biota

The widespread occurrence of polybrominated diphenyl ethers (PBDEs) in the environment has attracted considerable attention, leading to concerns about the extent and magnitude of wildlife and human exposure. In this work, we focus on the occurrence and fate of PBDEs in a Norwegian air-plant-herbivore-carnivore system. Specifically, we have analysed for PBDEs in moss, livers from various terrestrial herbivores (moose, grouse, and European roe deer) and, for the first time, livers from the top predator lynx. The samples were collected from different sites and time periods (1990-2004) to identify possible spatial and temporal trends in contaminant levels and patterns. The general finding was that PBDEs were found in all (biotic) samples, although at lower concentrations than previously observed in mammals from the marine environment. The PBDE levels in the herbivores ranged from less than 0.5 ng/g lipid weight to 9.4 ng/g lipid weight as the highest. The median PBDE concentration in lynx was approximately one order of magnitude higher than in the herbivores. In the lynx samples there was a predominance of BDE-153 whereas BDE-47 and 99 dominated in the herbivores. This probably reflects different bioaccumulation properties or metabolic transformation processes of the BDE-congeners, and food choice. Levels of PBDEs in both moss and herbivores showed a general decline towards the northern parts of Norway. No clear temporal trends were observed. The PBDE levels observed in this study were low and are probably of limited toxicological significance.

Elevated levels of polybrominated diphenyl ethers (PBDEs) in fish from Lake Mjøsa, Norway

Surprisingly high levels of PBDEs (polybrominated diphenyl ethers) in fish from Lake Mjøsa watercourse initialized a more detailed study of PBDE contamination in the Lake Mjøsa region as well as fish from other lakes in southeast Norway. With exception of the fish from Lake Mjøsa, the sum concentration of PBDEs in trout was, on a wet weight (ww) basis, in the range of 0.3-40 ng/g (21-1215 ng/g lipid weight (lw)) in fish fillet and 39-446 ng/g (125-915 ng/g lw) in burbot liver. The PBDE levels in fish from Lake Mjøsa, was found in the range of 72-1120 ng/g ww (2348-16,753 ng/g lw) in trout and 156-2265 ng/g ww (4201-45,144 ng/g lw) in burbot. It was later confirmed that the elevated levels in Lake Mjøsa were mainly caused by the release of PBDEs to the water from a textile manufacturer in the town of Lillehammer. In addition to PBDE levels in fish we also present information on the spatial distribution of PBDEs in air around the Mjøsa watercourse, based on the complementary use of passive air samples and analysis of moss, including data on measured air concentrations. The results confirm the presence of an active source of atmospheric PBDEs in the region of Lillehammer. Although this source appears to have a limited impact on atmospheric levels towards the southern reaches of the lake, it could still be a significant source of PBDEs to the lake as a whole. However, more research is needed to better understand and quantify the relative importance of various sources and pathways for which PBDEs enter Lake Mjøsa in order to support the development of future control strategies.

Global fate of POPs: current and future research directions

For legacy and emerging persistent organic pollutants (POPs), surprisingly little is still known in quantitative terms about their global sources and emissions. Atmospheric transport has been identified as the key global dispersal mechanism for most legacy POPs. In contrast, transport by ocean currents may prove to be the main transport route for many polar, emerging POPs. This is linked to the POPs' intrinsic physico-chemical properties, as exemplified by the different fate of hexachlorocyclohexanes in the Arctic. Similarly, our current understanding of POPs' global transport and fate remains sketchy. The importance of organic carbon and global temperature differences have been accepted as key drivers of POPs' global distribution. However, future research will need to understand the various biogeochemical and geophysical cycles under anthropogenic pressures to be able to understand and predict the global fate of POPs accurately.

Empirical and modeling evidence of the long-range atmospheric transport of decabromodiphenyl ether

Understanding of the long-range atmospheric transport (LRT) behavior of decabromodiphenyl ether (BDE-209) is still limited. Most existing model-based approaches to assessing an organic chemical's potential for LRT have assumed invariant environmental conditions, even though many factors impacting on the atmospheric residence time are known to vary considerably over a variety of time scales. Model estimates of LRT also suffer from limited evaluation against observational evidence. Such evidence was sought from dated sediment cores taken from lakes along a latitudinal transect in North America. BDE-209 was generally detected only in recent sediment horizons, and sedimentation fluxes were found to decline exponentially with latitude. The empirical half-distance (EHD) for BDE-209 derived from surface flux data is approximately half that of the sigmaPCBs. A dynamic multimedia fate and transport model provides further insight into the temporal variability of processes that control LRT for BDE-209 and PCBs. The variability of precipitation, and in particular, the occurrence of time periods without precipitation coinciding with strong winds, influences the LRT potential of chemicals that combine a sufficiently long atmospheric half-life with very low volatility. Likewise, the forest filter effect may be important for a wider range of chemicals than believed previously, because models assuming constant precipitation fail to account for the impact of differences in dry deposition on days without rain. Chemicals that are both sorbed to particles and potentially persistent in the atmosphere, such as BDE-209, may have a larger potential for LRT than anticipated on the basis of earlier model evaluations. Still, the EHDs illustrate that the model seems to underestimate atmospheric loss processes of potential significance to BDE-209, illustrating the need to critically compare predictions of LRT against observations. Processes that need to be understood better in order to improve predictions of LRT for BDE-209 include particle dry deposition, precipitation scavenging, and photolysis in the sorbed state.

Evaluating the environmental fate of pharmaceuticals using a level III model based on poly-parameter linear free energy relationships

We recently proposed how to expand the applicability of multimedia models towards polar organic chemicals by expressing environmental phase partitioning with the help of poly-parameter linear free energy relationships (PP-LFERs). Here we elaborate on this approach by applying it to three pharmaceutical substances. A PP-LFER-based version of a Level III fugacity model calculates overall persistence, concentrations and intermedia fluxes of polar and non-polar organic chemicals between air, water, soil and sediments at steady-state. Illustrative modeling results for the pharmaceuticals within a defined coastal region are presented and discussed. The model results are highly sensitive to the degradation rate in water and the equilibrium partitioning between organic carbon and water, suggesting that an accurate description of this particular partitioning equilibrium is essential in order to obtain reliable predictions of environmental fate. The PP-LFER based modeling approach furthermore illustrates that the greatest mobility in aqueous phases may be experienced by pharmaceuticals that combines a small molecular size with strong H-acceptor properties.

Illustrating sensitivity and uncertainty in environmental fate models using partitioning maps

Variations of model predictions of the environmental fate of organic contaminants are usually analyzed for only one or at most a few selected chemicals, even though parameter sensitivity and contribution to uncertainty are widely different for different chemicals. A graphical method is introduced that allows for the comprehensive investigation of model sensitivity and uncertainty for all persistent organic nonelectrolytes at the same time. This is achieved by defining a two-dimensional hypothetical "chemical space" as a function of the equilibrium partition coefficients between air, water, and octanol (KOW, KAW, KOA), and plotting sensitivity and/or uncertainty of a specific model result to each input parameter as a function of this chemical space. The approach is illustrated for the bulk phase concentrations in air, water, soil, and sediment calculated by a level III model. Colored contour maps facilitate the identification of those input parameters that cause a high output variation of hypothetical and real chemicals. They also allow for the easy categorization of chemicals in terms of common parameter sensitivities, and thus comparable environmental behavior. Sensitivity varies with the mode of emission and the degradability of the chemicals, making it necessary to develop multiple sets of contour maps. Comparison of these sets of maps in turn allows the investigation of how parameter sensitivities change as a result of changes in mode of emission and persistence. The presented method can be used for investigating the sensitivity of any prediction obtained with any linear fate model that characterizes the partitioning behavior of organic chemicals with KAW, KoW, and KOA. Once the sensitivity maps have been constructed for a given environmental scenario, it is possible to perform a sensitivity analysis for a specific chemical by simple. placement of the substances' partitioning combinations within the chemical space. The maps can further contribute to the mechanistic understanding of a model's behavior, can aid in explaining observations of divergent environmental behavior of related substances, and can provide a rationale for grouping chemicals with similar model behavior, or for selecting representative example chemicals for a model investigation. They can also help in deciding when accurate and precise knowledge of physical chemical property data is crucial and when approximate numbers suffice to conduct a model investigation.

Modeling the fate of polychlorinated biphenyls in the inner Oslofjord, Norway

A dynamic, segmented, multimedia fate and transport model has been developed, evaluated, and applied to gain insight regarding the behavior of seven polychlorinated biphenyl (PCB) congeners in the Inner Oslofjord (Norway). A comparison with a dated sediment core reveals that the model is not capable of reproducing some key features of the observed, historical, long-term trend in sediments, although better agreement is observed for six of seven PCB congeners over the last two decades. The model also underestimates the concentrations of PCBs in surface sediments in areas adjacent to the city of Oslo (Norway). In general, deviations between modeled and observed concentrations indicate that the historical emissions and discharges of PCBs are not sufficiently characterized and described. Net fluxes predicted by the model suggest that several congeners may have experienced a reversal of air-water and seawater-sediment exchange during the last decade or even earlier. The present study further suggests that the benefit of the proposed removal of the most contaminated sediments of the Inner Oslofjord needs to be assessed, with consideration of the relative contribution of current atmospheric inputs as well as the leaching of PCBs from less contaminated sediments.

PBDEs in European background soils: levels and factors controlling their distribution

Surface soils (0-5 cm) from remote/rural woodland (coniferous and deciduous) and grassland locations on a latitudinal transectthrough the United Kingdom and Norway were analyzed for polybrominated diphenyl ethers (PBDEs). Concentrations ranged between 65 and 12 000 sigma(ALL)PBDE ng kg(-1) dry weight. PBDE-47, -99, -100, -153, and -154-the major constituents of the penta-BDE technical product-dominated the average congener pattern of the soils. Indeed, the average congener composition and distribution measured in these European background soils closely matched that reported in the technical penta-BDE product. This is interpreted as evidence that transfer of the congeners present in penta-BDE-treated products from source-air-soil occurs with broadly similar efficiency, perhaps because there has been little weathering/degradation/alteration of the congener source pattern by processes operating during atmospheric transport or within the soil itself. BDE-183, a marker for the octa-BDE mix, was detected at concentrations ranging from <9 to 7000 (median approximately 50 ng kg(-1)). In most soils, it made a minor contribution to the sigma(ALL)PBDE concentration, but it was a major component in some samples from northern England. Forest soils tended to have higher concentrations than grasslands. Underlying the average soil composition, some differences in the congener pattern were observed. Notably, there was evidence of latitudinal fractionation, with the relative contribution of PBDE-47 and lighter congeners to the sigmaPBDE increasing northwards (with increasing distance from source areas), while the proportion of PBDE-99 and heavier congeners decreased. Plots of concentration against percentage soil organic matter had different slopes for different congeners. Higher slopes were generally seen for the lighter PBDEs (e.g., PBDE-47), indicating that they have undergone some air-surface exchange (hopping), while the slopes of heavier congeners (e.g., PBDE-153) were close to zero, indicating that they are retained more effectively by soils after deposition.

Primary sources of selected POPs: regional and global scale emission inventories

During the last decade, a number of studies have been devoted to the sources and emissions of Persistent Organic Pollutants (POPs) at regional and global scales. While significant improvements in knowledge have been achieved for some pesticides, the quantitative understanding of the emission processes and emission patterns for "non-pesticide" POPs are still considered limited. The key issues remaining for the non-pesticide POPs are in part determined by their general source classification. For industrial chemicals, such as the polychlorinated biphenyls (PCBs), there is considerable uncertainty with respect to the relative importance of atmospheric emissions from various source categories. For PCBs, temperature is discussed as a potential key factor influencing atmospheric emission levels and patterns. When it comes to the unintentional by-products of combustion and industrial processes (PCDD/Fs), there is still a large uncertainty with respect to the relative contribution of emissions from unregulated sources such as backyard barrel burning that requires further consideration and characterisation. For hexachlorobenzene (HCB), the relative importance of primary and secondary atmospheric emissions in controlling current atmospheric concentrations remains one of the key uncertainties. While these and other issues may remain unresolved, knowledge concerning the emissions of POPs is a prerequisite for any attempt to understand and predict the distribution and fate of these chemicals on a regional and global scale as well as to efficiently minimise future environmental burdens.

Expanding the applicability of multimedia fate models to polar organic chemicals

Reliable estimates of environmental phase partitioning are essential for accurate predictions of the environmental fate of organic chemicals. Current fate and transport models use single-parameter linear free energy relationships (SP-LFERs) to quantify equilibrium phase partitioning. The applicability of such SP-LFERs is limited because no single parameter is able to describe appropriately all the molecular interactions that contribute to environmental phase distribution processes. Environmental partitioning coefficients predicted by SP-LFERs may thus have errors of up to an order of magnitude. Ranges for several environmental partitioning equilibria are identified, where such errors can result in significantly different fate predictions for individual bulk model compartments. We propose that it is possible to reduce such errors and uncertainties by implementing polyparametric LFER (PP-LFER) approaches in multimedia fate models. A level III fugacity model was modified such that the partitioning properties of chemicals are characterized by five linear solvation energy parameters rather than vapor pressure, water solubility, and octanol-water partition coefficient. A comparison of modified and unmodified models for a set of organic chemicals shows that the approach chosen to simulate environmental phase partitioning can have a large impact on model results, including long-range transport potential, overall persistence, and concentrations in various media. It is argued that PP-LFER based environmental fate models are applicable to a much wider range of organic substances, in particular those with polar functional groups. Obstacles to the full implementation of PP-LFER in multimedia fate models are currently the lack of solute descriptors for some chemicals of environmental concern and suitable regression equations for some important environmental phase equilibria, in particular for the partitioning between gas and particle phase in the atmosphere.

Global distribution and budget of PCBs and HCB in background surface soils: implications for sources and environmental processes

This paper presents data from a survey of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) concentrations in 191 global background surface (0-5 cm) soils. Differences of up to 4 orders of magnitude were found between sites for PCBs. The lowest and highest PCB concentrations (26 and 97,000 pg/g dw) were found in samples from Greenland and mainland Europe (France, Germany, Poland), respectively. Background soil PCB concentrations were strongly influenced by proximity to source region and soil organic matter (SOM) content Most (>80%) of the estimated soil PCB burden remains in the "global source region" of the Northern Hemisphere (NH) temperate latitudes (30-60 degrees N) or in the OM-rich soils just north of that %SOM correlated with PCB and HCB in the global data set, with the correlation coefficients being greater for HCB and the lighter PCBs than for heavier homologues. OM-rich soils in the NH consistently contained the highest burdens; such soils are a key global compartment for these compounds. Evidence for global fractionation of PCBs was found in the subset of soils from latitudes north of the global source region but was not discerned with the global data set The full data set was used to estimate the burden for individual congeners/homologues in surface background soils and a global soil total PCB burden of 21,000 t. The significance of the inventory is briefly discussed in relation to the latest estimates of global production and atmospheric emission.

The global re-cycling of persistent organic pollutants is strongly retarded by soils

'Persistent organic pollutants' (POPs) are semi-volatile, mobile in the environment and bioaccumulate. Their toxicity and propensity for long-range atmospheric transport (LRAT) has led to international bans/restrictions on their use/release. LRAT of POPs may occur by a 'single hop' or repeated temperature-driven air-surface exchange. It has been hypothesised that this will result in global fractionation and distillation-with condensation and accumulation in polar regions. Polychlorinated biphenyls (PCBs)--industrial chemicals banned/restricted in the 1970s--provide a classic illustration of POP behaviour. A latitudinally-segmented global PCB inventory has been produced, which shows that approximately 86% of the 1.3 x 10(6) tonnes produced was used in the temperate industrial zone of the northern hemisphere. A global survey of background surface soils gives evidence for 'fractionation' of PCBs. More significantly, however, very little of the total inventory has 'made the journey' via primary emission and/or air-surface exchange and LRAT out of the heavily populated source regions, in the 70 years since PCBs were first produced. Soils generally occlude PCBs, especially soils with dynamic turnover of C/bioturbation/burial mechanisms. This limits the fraction of PCBs available for repeated air-soil exchange. The forested soils of the northern hemisphere, and other C-rich soils, appear to be playing an important role in 'protecting' the Arctic from the advective supply of POPs. Whilst investigations on POPs in remote environments are important, it is imperative that researchers also seek to better understand their release from sources, persistence in source regions, and the significant loss mechanisms/global sinks of these compounds, if they wish to predict future trends.

Towards a global historical emission inventory for selected PCB congeners--a mass balance approach. 1. Global production and consumption

Information on the historical global production and consumption of polychlorinated biphenyls (PCBs) is urgently needed for estimating PCB fluxes to the environment and for interpreting global contamination patterns by these pollutants. This study presents the methodology, principal uncertainties and selected results from an inventory, aiming to quantify the global production and consumption of total PCBs as well as 22 PCB congeners. The available data on the historical production of PCBs and the chemical composition of various technical mixtures have been compiled from the literature. For some producers with less detailed information, the production of individual PCB constituents has been estimated to derive a global estimate for individual homologues and selected congeners. Information on imports, exports and consumption, as well as restrictions on production and imports, has further been compiled for individual countries. These data, along with assumptions on the trade between countries and regions, have been utilised to derive an estimate of the global historical consumption pattern. Although there are substantial uncertainties involved in these estimates, important aspects governing the large scale temporal and spatial patterns are most likely captured in these estimates. In particular, the information on imports and exports for the principal users of PCBs around the time of peak production is considered to be fairly reliable. The estimates account for a reported historical global production of approximately 1.3 million t PCBs, more than 70% of which are tri-, tetra- and pentachlorinated biphenyls. The results further suggest that almost 97% of the global historical use of PCBs have occurred in the Northern Hemisphere.

Towards a global historical emission inventory for selected PCB congeners--a mass balance approach. 2. Emissions

Accurate and complete data on the global atmospheric releases (emissions) of individual PCB congeners are essential to study source-receptor relationships and contamination patterns in remote areas, such as the Arctic. Information on the anthropogenic emissions may also be useful for the interpretation of measured levels and patterns of atmospheric PCBs. This study builds upon an accompanying paper, presenting an estimate of the global historical production and consumption of 22 PCB congeners (Breivik K, Sweetman A, Pacyna JM, Jones KC. Towards a global historical emission inventory for selected PCB congeners--a mass balance approach. 1. Global production and consumption. Sci Total Environ, submitted). Here, a dynamic mass balance model is elaborated, parameterised and applied in an attempt to estimate the historical anthropogenic emissions as a direct result of the widespread usage of PCBs for a period of 70 years. This paper presents details of the mass balance approach, along with a discussion of the major uncertainties. It is shown that the diversity of historical usage, disposal and accidental release pathways makes it an extremely difficult task to bridge the gap between consumption and emissions, resulting in an equally complex and diverse true emission pattern. These results may therefore at best represent order-of-magnitude estimates only and the results in absolute terms should be treated with great caution. In spite of these uncertainties, useful information can still be gained. The results suggest that temperature is an extremely important factor controlling both emission amount as well as the emission pattern of PCBs. In particular, the emissions of the more chlorinated (and persistent) PCB congeners appear to be significantly influenced by (uncontrolled) high-temperature sources. As a consequence, it may prove warranted to undertake further measures to avoid that contaminated materials are subject to elevated temperatures and uncontrolled burning. It is furthermore suggested that efforts should be directed towards a better characterisation and quantification of these potentially important release pathways. In addition, alternative approaches to bridge the gap between consumption and emissions in quantitative terms should be considered in order to improve these estimates.

Mass budgets, pathways, and equilibrium states of two hexachlorocyclohexanes in the Baltic Sea environment

The POPCYCLING-Baltic model, a non-steady-state multicompartmental mass balance model of long-term chemical fate in the Baltic Sea environment, is used to derive a quantitative understanding of the behavior of alpha- and gamma-hexachlorocyclohexane (HCH) from 1970 to 2000. The atmosphere is found to effectively distribute the HCHs within the Baltic Sea environment and beyond, resulting in relatively uniform concentrations in environmental compartments that do not directly receive emissions. This uniformity is the result of a large-scale redistribution of a relatively small fraction of the emitted HCHs from the agricultural systems in source areas to all other environmental compartments throughout the Baltic Sea region. The major fraction of the HCHs is degraded in the soils receiving the pesticide application. In areas where HCH-containing pesticides are used, HCHs evaporate from soils and water bodies and are advected away in the atmosphere. They are deposited to forests and water bodies when they reach remote regions. This redistribution is driven by the inclination of the HCHs to equalize their chemical potential within the environment, which is illustrated through the use of fugacity fractions. The model is believed to provide useful insight into the complex set of interactions that determine the overall fate of an environmental contaminant but which are inaccessible to measurements.

Evaluating a model of the historical behavior of two hexachlorocyclohexanes in the Baltic Sea environment

The POPCYCLING-Baltic model, a non-steady-state multicompartmental mass balance model of long-term chemical fate in the Baltic Sea environment, is evaluated for its capability to simulate the behavior of alpha- and gamma-hexachlorocyclohexane isomers from 1970 to 2000. The model predicts HCH concentrations in air, seawater, marine sediments, and needles well within an order of magnitude, often within a factor of 2, and reproduces major features of the observed differences in space and time. The spatial and temporal patterns of HCHs in the Baltic Sea environment are found to be controlled mostly by chemical input, both through direct emissions within the drainage basin and through advective inflow from adjacent areas, but variable environmental conditions can significantly modify the spatial distribution patterns. Simulations with different boundary conditions, i.e., variable assumptions concerning advective atmospheric inflow, suggest that sources within the drainage basin alone are not capable of explaining the observed HCH levels and that significant transport into the region must occur. Deviations between predicted and measured HCH concentrations can often be explained by uncertain estimates of usage and advective import, illustrating the usefulness of the model for evaluating the reasonability of emission estimates and boundary conditions.

Inter-current and nosocomial infections among visceral leishmaniasis patients in Ethiopia: an observational study

From July 1989 up to September 1997, a total of 247 non-HIV associated visceral leishmaniasis (VL) patients were treated on outpatient basis in rural clinics (195 patients) and hospitalised in the Northern-Omo Regional Hospital (18 patients) and in Addis Ababa referral hospitals (34 patients). Patients treated in the rural clinics and in the Regional hospital originated from the same endemic area and had comparable baseline characteristics. Overall rates of complications (inter-current/concurrent infectious or non-infectious diseases or deaths) in the three categories were 10.7, 38.9 and 61.6%, while case fatality rates were 2.5, 5.6 and 11.7%, respectively. Nosocomial bacterial infections occurred in 16.6% of patients treated in the Regional hospital and 32.3% of patients treated in Addis Ababa referral hospitals, and these infections accounted for 42.8 and 52.4% of the complications seen in the respective categories. Among VL patients originating from the same endemic place and with comparable baseline clinical data, patients treated hospitalised had significantly higher rates of complications than patients treated on outpatient basis (P<0.001). Patients who had complications during the course of VL therapy had significantly lower pre-treatment haemoglobin levels. Considering the extra cost of hospitalisation and risk of nosocomial infections and petavalent antimonial therapy being fairly safe, we recommend that VL patients, unless with serious complications, should preferably be treated on ambulatory basis with follow-up to monitor response and inter-current infections if any.

Long-term follow-up of 1059 consecutive primary and recurrent inguinal hernias in a teaching hospital

OBJECTIVE

To study the early and late outcome of various methods of inguinal hernia repair.

DESIGN

Retrospective study.

SETTING

Teaching hospital, Norway.

SUBJECTS

1059 repairs of inguinal hernias in men and women by 43 surgeons.

INTERVENTIONS

Analysis of patients charts, results of questionnaires concerning 712 hernias (67%) and follow-up consultations when needed.

MAIN OUTCOME MEASURES

Freedom from recurrence and postoperative groin symptoms after repairs of primary and recurrent hernias.

RESULTS

After a median follow-up of 5.5 years, range 3-8, the recurrence rate was 8% for primary repairs and 29% after recurrent hernias. The incidence of permanent pain or discomfort was unexpectedly high, being 11% after primary repairs and 15% after recurrent hernia repairs.

CONCLUSIONS

The number of recurrences at long-term follow-up after repairs of primary and recurrent inguinal hernias was unsatisfactory. The extent of postoperative pain was surprising as this was not given enough attention during the learning period. We have introduced a uniform treatment policy with a prospective surveillance programme with the aim of improving results in our teaching programme.

Use of alpha-, beta- and gamma-hexachlorocyclohexane in Europe, 1970-1996

Data on current and historical usage of alpha, beta, and gamma-hexachlorocyclohexane (HCH) in Europe are presented. The data were collected and estimated as a part of a project studying the regional cycling of persistent organic pollutants (POPs) in the Baltic environment (Popcycling-Baltic). Better data on sources, environmental discharges and atmospheric emissions of HCH and other POPs are needed to study, and hopefully reduce, the impact of these pollutants on the environment. Substantial uncertainties are assigned to the estimated data for individual countries and years, but it seems likely that the general trend of usage in Europe is captured. The quality of the estimates is thought to improve in general throughout the period, thus, reflecting the availability of reliable data. The results suggest that 382,000 t of technical HCH and 81,000 t of lindane were used in Europe from 1970 to 1996. This is equivalent to an estimated cumulative usage of 259,000 t alpha-HCH, 235,000 t gamma-HCH and 20,000 t beta-HCH. The usage of technical HCH was the major source of gamma-HCH until the late 1970s, and thereafter lindane became the dominating source of this isomer. The use of gamma-HCH in 1996 was estimated to still be nearly one-third of the European usage in 1970. The pattern of decreasing concentrations in biota follows the pattern of reductions in usage for the studied period within the Baltic area.

Clinical use of low output settings in 1.2-mm2 steroid eluting electrodes: three years of experience

A new generation of tined steroid-eluting leads featuring 1.2-mm2 distal electrodes (CapSure Z, Medtronic Inc., Minneapolis MN, USA) has the potential to reduce battery current drain and enhance pulse generator longevity by means of high pacing impedance and low pacing threshold. Forty patients aged 50-87 years (mean 72.4 years) were implanted with 33 ventricular (models 4033 and 5034) and 30 atrial-J (models 4533 and 5534) leads with 1.2-mm2 electrodes. Low pacing outputs, mainly in the range from 1 V/0.20 ms to 1.6 V/0.36 ms with > or = 3:1 pulse width safety margins (PWSM) applied, were instituted at 3-6 months of implantation and adjusted at subsequent follow-up controls according to changes in thresholds. Cumulative follow-up period of low outputs was 1,512 months (24 months per lead, range 9-36 months), which involved 3.43 follow-up controls per lead (range 2-5). During follow-up, pulse width thresholds (PWTs) at the used amplitudes did not change in 55.5% of the leads; PWTs increased by < or = 100% in 36.5%, by 101%-200% in 1.6%, and by > 200% in 6.3% of the leads. Changes in PWT that would apparently exceed 3:1 PWSM over a 1-year period occurred in one atrial lead where even the nominal 3.5 V/0.4-ms output would not be effective and in one ventricular lead in the aftermath of an acute myocardial infarction (300% PWT rise at 1.6 V). Based on the present observations, pacemaker dependent patients require > or = 4:1 PWSM and other patients > or = 3:1 PWSM with output pulse widths < or = 0.60 ms and annual pacemaker clinic visits. Calculated battery current drain and anticipated longevity associated with a variety of pacing outputs and impedances are provided, compared, and discussed. Correlation between acute and chronic pacing impedances and pacing thresholds was weak, implying that a systematic intraoperative pacing site optimization cannot contribute significantly to the extension of average battery longevity.

An algorithm for automatic measurement of stimulation thresholds: clinical performance and preliminary results

We have developed an algorithmic method for automatic determination of stimulation thresholds in both cardiac chambers in patients with intact atrioventricular (AV) conduction. The algorithm utilizes ventricular sensing, may be used with any type of pacing leads, and may be downloaded via telemetry links into already implanted dual-chamber Thera pacemakers. Thresholds are determined with 0.5 V amplitude and 0.06 ms pulse-width resolution in unipolar, bipolar, or both lead configurations, with a programmable sampling interval from 2 minutes to 48 hours. Measured values are stored in the pacemaker memory for later retrieval and do not influence permanent output settings. The algorithm was intended to gather information on continuous behavior of stimulation thresholds, which is important in the formation of strategies for programming pacemaker outputs. Clinical performance of the algorithm was evaluated in eight patients who received bipolar tined steroid-eluting leads and were observed for a mean of 5.1 months. Patient safety was not compromised by the algorithm, except for the possibility of pacing during the physiologic refractory period. Methods for discrimination of incorrect data points were developed and incorrect values were discarded. Fine resolution threshold measurements collected during this study indicated that: (1) there were great differences in magnitude of threshold peaking in different patients; (2) the initial intensive threshold peaking was usually followed by another less intensive but longer-lasting wave of threshold peaking; (3) the pattern of tissue reaction in the atrium appeared different from that in the ventricle; and (4) threshold peaking in the bipolar lead configuration was greater than in the unipolar configuration. The algorithm proved to be useful in studying ambulatory thresholds.

Clinical performance of steroid-eluting pacing leads with 1.2-mm2 electrodes

To raise pacing impedance and reduce battery current drain, new tined steroid-eluting leads were developed with 1.2-mm2 hemispherical electrodes, instead of conventional 5-8 mm2. Twenty-two unipolar J-shaped atrial leads and 25 unipolar ventricular leads (models 4533 and 4033, respectively) were implanted in 33 consecutive patients and followed for a mean of 25 months (range 18-29). Handling characteristics of atrial leads were found favorable. The leads slipped easily into the right atrial appendage and were easy to position. Handling characteristics of ventricular leads were satisfying, but more efforts had to be applied to cross the tricuspid valve. Special care was taken to avoid perforation of the myocardium due to the small lead tip. Following implantation, four ventricular and one atrial lead exhibited instability of pacing thresholds that resolved spontaneously within 1-3 days of implantation. Except for this, no lead malfunctioned. The reoperation rate was zero. The mean electrogram amplitudes of 15 mV (ventricle) and 4 mV (atrium), and the mean chronic pacing threshold of 0.085 ms at 1.6 V (app. 0.43 V at 0.5 ms) were comparable with the best values seen in the literature on passive fixation leads. The rest of the electrophysiological parameters were enhanced: mean pacing impedances were 984 omega (acute) and 900 Q (chronic), mean slew rates 3.26 V/s (ventricle) and 1.75 V/s (atrium), mean acute voltage threshold at 0.5 ms was 0.25 V, mean current and energy thresholds calculated at 0.5 ms were 260 microA and 32 nJ (acute) and 478 microA and 103 nJ (chronic). The electrical characteristics of these leads provide for increased pacemaker longevity in combination with substantial safety margins for pacing and sensing.

Clinical evaluation of a thin bipolar pacing lead

The main disadvantages of bipolar pacing leads have traditionally been related to their relative thickness and stiffness compared to unipolar leads. In a new "drawn filled tube" plus "coated wire" technology, each conductor strand is composed of MP35N tubing filled with silver core and coated with a thin ETFE polymer insulation material. This and parallel winding of single anode and cathode conductors into a single bifilar coil resulted in a bipolar lead (ThinLine, Intermedics) with a body diameter and flexibility similar to unipolar leads. The lead is tined, polyurethane, with the cathode and the anode made of iridium-oxide-coated titanium (IROX). The slotted 8-mm2 cathode tip is coated with polyethylene glycol, a blood soluble material. We present the clinical evaluation results from four pacemaker clinics, where 47 leads (23 atrial-J model 432-04 and 24 ventricular model 430-10) were implanted in 25 patients and followed for up to 2 years. The lead handling characteristics were found to be very satisfactory. Electrical parameters of the leads were measured at implant and noninvasively on postoperative days 1, 2, 21, 42, and months 3, 6, 12, and 24. Mean chronic pulse width thresholds at 2.5 V were 0.14 +/- 0.05 ms in the atrium and 0.10 +/- 0.02 ms in the ventricle, pacing impedances 443 +/- 104 omega and 520 +/- 241 omega, while median electrogram amplitudes were > or = 3.5 mV and > or = 7 mV, respectively. Pacing impedances and thresholds were found to be slightly but statistically significantly higher in unipolar than in bipolar configuration--the findings are explainable by the lead construction. One of 47 leads failed 3 weeks after implant; the conductors were short circuited due to an error during the manufacturing process. We conclude that the new lead thus far has demonstrated appropriate mechanical and electrical characteristics.

New temporary atrial and ventricular pacing leads for patients after cardiac operations

We have studied two new temporary pacing leads (Medtronic 6491 and 6492) intended for pacing after cardiac operations. The conductor has stainless steel strands coated with polyethylene connected to a 4' mm2 surface area, stainless steel, smooth, tapered electrode. A soft 4-0 coiled polypropylene fiber served as as fixation mechanism in the heart. The study included 15 children (aged 3 months to 7 years, body weight 4.4 to 20 kg) with a variety of congenital heart defects and 15 adults (aged 45 to 78 years) with coronary artery disease (n = 13) and aortic valve disease (n = 2). A pair of leads each was placed in a bipolar fashion in the right atrial wall and nonsystemic ventricle in the children (median implant duration 12 days) and in the right atrial wall only in the adults (median implant duration 9 days). The atrial current threshold values in children increased from 0.61 +/- 0.34 mA immediately after implant to 2.08 +/- 1.86 mA at explant (p < 0.002). In the adults the threshold values increased from 0.95 +/- 1.44 mA immediately after implant to 2.76 +/- 2.76 mA at explant (p < 0.002). In the ventricle the threshold values increased from 0.38 +/- 0.13 mA immediately after implant to 2.22 +/- 1.63 mA at explant (p < 0.002). Tissue resistance immediately after implant measured 809 +/- 182 omega at explant (children, p = not significant). Corresponding values in adults were 778 +/- 190 omega and 599 +/- 91 omega (p < 0.004). In the ventricle resistances changed from 1019 +/- 143 omega to 876 +/- 137 omega (p < 0.05). P wave amplitudes measured 1.8 +/- 1.5 mV immediately after implant and decreased to 1.6 +/- 1.2 mV at explant (p = not significant, children) and 2.0 +/- 1.3 mV to 1.8 mV (p = not significant, adults). R wave amplitude were 13.1 +/- 3.0 mV immediately after implant and fell to 8.7 +/- 4.5 mV at explant (p < 0.005). Thus, threshold values, tissue resistances, and electrogram and pliable amplitudes assured a safe pacemaker function. The small diameter and pliable texture of these leads provided a smooth surgical handling. They were found particularly suitable in children.

Dilation of the internal mammary artery by external and intraluminal papaverine application

Three methods for prevention of perioperative spasm of the internal mammary artery were compared in 78 patients undergoing coronary artery bypass grafting. In group 1, internal mammary artery pedicles were divided distally, clamped, and placed under the upper sternum submerged in papaverine solution (1.5 mg/ml). In group 2, as in group 1 but before clamping, 2 ml of heparinized blood with 1.5 mg/ml papaverine added was injected into the vessel lumen. In group 3 treatment was as in group 2, but heparinized blood with papaverine was injected a second time just before extracorporeal bypass was begun. In a univariate analysis free flow from dilated internal mammary arteries was not significantly different among the groups (group 1, 58 ml/min; group 2, 82 ml/min; group 3, 68 ml/min; p < 0.1). When free flow from dilated internal mammary arteries was the dependent variable in a regression analysis, the use of intraluminal papaverine, high blood pressure during flow measurement, and high initial blood flow were predictors of high flow (all p < 0.01). Morphometric measurements on the resected distal portion of the dilated internal mammary arteries disclosed less folding of the internal elastic lamina and a larger luminal area in groups 2 and 3 compared with respective findings in group 1 (1.21 mm2 and 1.42 mm2 versus 0.77 mm2; p < 0.02). Mechanical vessel wall injury occurred in 8 of 52 internal mammary arteries treated with intraluminal papaverine. Intraluminal papaverine solution injected once or twice in addition to external papaverine exposure therefore provides a better blood flow rate and distal dilation than mere submersion in papaverine solution, but at a considerable risk of mechanical wall injury.

[Infantile hypertrophic pyloric stenosis]

We present 40 patients operated consecutively for pyloric stenosis during an 8-year period (1981-88). The most common symptom was projectile vomiting, which occurred in 92.5% of the cases. On examination only three patients had a palpable hypertrophic pylorus. In 39 patients, a preoperative x-ray examination with contrast was necessary to confirm the diagnosis. A pyleromyotomy was performed in all patients. We discuss the diagnostic routines and the results of our treatment.

Mental and physical capacity and consumption of neuroleptic drugs in residents of homes for aged people

The mental and physical capacity of all residents in homes for aged people were estimated, and their neuroleptic drug consumption and duration of stay were registered. One third was moderately to severely mentally impaired and 38% demanded more extensive nursing care. Physical dependence was significantly associated with mental decline, and less with age. One quarter of severely mentally impaired people had stayed for less than one year; 23% of the residents received neuroleptic drugs. Treatment was more common in physically incapacitated people together with wandering and aggressive ones. Lack of psychogeriatric services may enhance the use of neuroleptic drugs in homes for aged people.

Assessment of the work capacity and relationship between rate response and exercise tolerance associated with activity-sensing rate-responsive ventricular pacing

The relationship between rate response and exercise tolerance was studied by measuring the symptom-limited maximum treadmill time (MTT)both during fixed rate VVI pacing and during VVI + activity mode pacing (RRP) in 15 patients (mean age, 73 years) who had received rate-responsive ventricular pacemakers. Their indications were atrioventricular block, sino-atrial block, and atrial fibrillation with slow ventricular response. Basic rate was programmed to 60 ppm in both pacing modes; rate response and activity threshold were programmed to 5 and medium, respectively. The order in which the two pacing modes were tested was randomly determined. The MTT was, on average, 29% longer in RRP than in VVI mode with a mean of 12 minutes in VVI and 14.8 minutes in RRP (p less than 0.001). For the subgroup of eight patients with paced-only rhythm the average increase in MTT was 38% with a mean of 9.5 minutes in VVI and 12.8 minutes in RRP (p less than 0.01). Seven patients who showed episodes of spontaneous rhythm, increased their average MTT by 17% (mean in VVI, 14.9 minutes; in RRP, 17.1 minutes; p less than 0.02). During RRP, a significant positive correlation existed between MTT and the increase in heart rate (N = 15; r = 0.83; p less than 0.001). In 12 patients with paced-only rhythm, the pacing rate remained at the programmed basic rate when the patients were lying, sitting, and standing and increased to 86 +/- 4 ppm during casual walking, and to 101 +/- 4 ppm during jumping up and down with the pacemaker programmed to the above-mentioned parameters. The maximum pacing rate during jumping corresponded with the maximum pacing rates measured from Holter recordings during normal daily activities.

Dementia and work load evaluation of the elderly

Dementia and work load were estimated in 4736 elderly home-nursed or institutionalized persons. Mental status was estimated by means of the Clinical Dementia Rating scale (CDR), and work load by means of a traditional work load scale. Approximately one third of elderly over 85 years were living in an institution. 4.6% of the population over 65 years of age were moderately to severely and 1.8% mildly demented. Work load increased with increasing dementia. In homes for the aged 40% and in nursing homes 85% of the residents create a heavy work load. 14.5% of the estimated population are considered misplaced, the majority of whom should be transferred to a higher care level. Dementias cause a major problem on every care level. Services which are lacking for this group and necessary rehabilitation facilities should be provided.

Long-term comparison of unipolar and bipolar pacing and sensing, using a new multiprogrammable pacemaker system

Over a six-month period a comparison was made between uni- and bipolar myocardial stimulation thresholds and R-wave sensitivity in 15 consecutive pacemaker patients. The patients received a new multiprogrammable Cordis 336 A pulse generator, that could be programmed with either uni- or bipolar circuitry. In addition, rate, output, sensitivity and pacing mode could be noninvasively programmed. The occurrence of myopotential interference at different sensitivity levels was also studied. Cordis 325-161 bipolar endocardial leads were used in all patients. In one patient, the current output sometimes had to be programmed higher bipolarly than unipolarly to capture the ventricles, otherwise no differences in threshold were found. Acutely. R-wave sensitivity was superior in 9 patients (60%) in the bipolar mode. Unipolar and bipolar electrograms were equal in 4 (26.7%), whereas unipolar R-wave sensitivity was best in only 2 (13.3%) of the patients. At a six-month follow-up, the same tendency was found. In 5 patients, bipolar sensing was superior to unipolar, while anti- and bipolar sensitivity was equal in the remaining patients. Myopotential inhibition was never seen in the bipolar mode at highest sensitivity (0.8 mV) even during provocative tests (n = 15) or 24-hour Holter monitoring (n = 12). In the unipolar mode, 14/15 patients (93.3%) showed inhibition during provocative tests and 12/12 patients (100%) during monitoring at a programmed sensitivity of 0.8 mV. No patients had myopotential interference at a sensitivity level of 3.5 mV. All patients have their pacemakers programmed in the bipolar mode after six months. This study confirms earlier acute data that the bipolar pacing mode is superior to the unipolar mode for permanent pacemaker therapy.

Bipolar atrial application of a new temporary pacing lead after cardiac operations

A new temporary pacing lead. Medtronic Model 6400, with a defined electrode surface area of 7.5 mm2, has been clinically and electrophysiologically evaluated during bipolar atrial application in 20 patients after cardiac operations. A silicon disc was used for fixation of the electrodes to the right atrium in 10 patients, and an atrial plication technique was used in the other 10. Myocardial stimulation threshold and resistance were measured throughout the postoperative period. Atrial electrograms were recorded on magnetic tape for computer analysis of amplitudes, slew rates, and signal source impedance. No significant differences (p greater than 0.1) were found in myocardial stimulation threshold between the two fixation modes. During constant-current pacing, median threshold rose from 0.65 mA to 2.3 mA. Stimulation resistance, measured during constant-voltage pacing, fell from 567 to 365 omega, with a subsequent rise to 425 omega before electrode removal. Again no difference was found between silicon disc and plication fixation of the electrodes. P-wave amplitudes were significantly higher with plication than with silicon disc fixation (2.26 versus 0.86 mV, p less than 0.01), as were slew rates (0.34 versus 0.18 V/s, p less than 0.05). Signal source impedance had a magnitude of 6 k omega. The electrodes were used successfully in 12 (60%) of the patients for diagnosis and/or treatment of arrhythmias. We find the new lead well suited for atrial application.

New temporary pacing lead for use after cardiac operations

A newly designed temporary pacemaker lead (Medtronic Model 6400), which has a solid defined electrode surface area of 7.5 mm2, was compared with a multifilamental stainless steel electrode in common use (Davis & Geck, DG). Thirty-nine patients had both types of electrodes inserted intramyocardially in the right ventricle. A DG electrode fastened to the pericardium served as a reference lead. In addition to the standard Medtronic 7.5 mm2 electrode (n = 11), specially made Medtronic electrodes with areas of 5 mm2 (n = 10), 10 mm2 (n = 10), or 7.5 mm2 with platinum-iridium tips (n = 8) were studied. Measurements of myocardial stimulation threshold and resistance were made in both electrodes throughout the postoperative period. The patients' electrograms were recorded on magnetic tape for computer analysis of amplitudes and slew rates. The Medtronic 7.5 mm2 electrodes showed overall better results than 5 and 10 mm2 leads. Maximum stimulation threshold on the Medtronic 7.5 mm2 electrodes was medium 3.4 mA versus 10 mA on DG electrodes (p less than 0.001). The tissue resistance on Medtronic 7.5 mm2 was almost double than on the Davis & Geck electrodes (median 311 ohms versus 164 ohms on the day of minimum resistance, p less than 0.001). There were no significant differences in electrogram amplitudes between the two electrode types studied (5.52 versus 4.68 mV, p greater than 0.1), but the slew rates were significantly higher on the Medtronic (0.56 versus 0.37 V/sec; p less than 0.01). The new lead is an important innovation in temporary pacemaker lead design compared to the commonly used multifilamental leads.

Acute and chronic pulse-width thresholds in solid versus porous tip electrodes

Sixty-one patients given programmable pacemakers at initial implantation have been followed for a mean of 18 months (3-42) with non-invasive measurements of myocardial pulse-width threshold. Fifty of the patients had CPI 0505/0522 (Microlith-P/Microthin-PI) pacemakers with either Cordis 322-462 8 mm2 ball tip (n=12), Cordis 322-620 17.5 mm2 (n=23), or CPI 4116 porous tip electrodes (stimulation area 7.5 mm2 and sensing area 50 mm2) (n=15). Eleven patients had Medtronic 5985 (Spectrax-SX) pacemakers with either Medtronic 6907-R 8 mm2 ring tip (n=7), 6907 11 mm2 (n=3) or 6917 myocardial electrodes (area 12 mm2) (n=1). At acute implant, the ball tip and porous tip electrodes had the lowest stimulation thresholds, but the differences were only statistically significant in comparison with the 17.5 mm2 electrode (p less than 0.01). Chronically there were no significant differences between the various electrodes (p greater than 0.1), but the ball tip electrode tended to give best long-term results, and the porous tip electrode the poorest. Thirty-eight of the 61 patients (62.3%) had chronic pulse-width thresholds of 0.1 ms or less at approximately equal to 5 V output, indicating that pulse-width programming is a useful way to conserve battery energy. However, at some stage of the study, six of the patients (9.8%) had a pulse-width threshold of 0.5 ms or more. Pulse width should therefore not be set too narrow in standard nonprogrammable pacemakers.

Clinical and electrophysiological properties of a new temporary pacemaker lead after open-heart surgery

A new temporary pacemaker lead, Medtronic 6400, with a solid defined electrode surface area of 7.5 mm2, has been implanted in 50 patients after open-heart surgery. One electrode was inserted intramyocardially on the right ventricle, while another was placed extracardially and served as a reference lead. Forty-six of the patients were followed postoperatively with measurements of myocardial stimulation threshold and resistance. In 25 of the patients, electrograms were recorded on magnetic tape for further computer analysis of amplitudes, slew rates, and signal source impedance. During constant current pacing, myocardial stimulation threshold increased from a median of 0.4 mA one hour postoperatively to a maximum value of 2.3 mA. In two patients (4.3%) intermittent pacing failure was seen. Stimulation resistance fell from a median of 875 omega to a minimum of 487 omega, with a subsequent increase of 598 omega before electrode removal. Both mean electrogram amplitude (7.35 mV) and slew rate (0.82 V/s) had their minimum values on the sixth postoperative day. Intermittent sensing failure was observed in 2/25 patients (8%). Signal source impedance was of a magnitude not likely to contribute to sensing failure. No complications were seen from the use of this lead. The new electrode is an important improvement in temporary pacemaker lead design.