Major hazards—Thinking the unthinkable

It is a common experience that public administrations tend to shy away from the explicit acknowledgment of quantitative risk levels. Faced with extreme concentrations of population and of industrial activities, including LPG and liquid chlorine storage, within a very small land area, Hong Kong has faced up to the issue of major man-made hazards by “thinking the unthinkable” and adopting explicit risk guidelines. This article describes how these guidelines were developed and the arguments that led to their adoption. It is emphasized that the risk guidelines are not rigid standards but simply a method of focusing decision making and ensuring that any decision to contravene the guidelines is taken at an appropriately senior level in the administration. The way in which the guidelines have been incorporated intimately into the planning and decision-making process is described and details are given on how this has led to the implementation of a variety of measures that have greatly reduced both societal and individual risk from certain types of chemical storage and chemical processing installations in Hong Kong. The opinions in this paper represent the views of the authors and not necessarily those of the Hong Kong Government.     

Rapid interphase analysis for prenatal diagnosis of translocation carriers using subtelomeric probes

Interphase fluorescence in situ hybridization (FISH) has become an accepted laboratory technique for the rapid and preliminary prenatal assessment of chromosome aneuploidy. The introduction of subtelomeric FISH probes now allows for the molecular–cytogenetic analysis of terminal chromosome rearrangements. In a prospective study, we examined the prenatal use of subtelomeric probes on interphase cells to rapidly detect the carrier status of a fetus when a parent carried a known reciprocal or Robertsonian chromosome translocation. Three of the cases were identified as being abnormal. All cases were confirmed by routine cytogenetic analysis. These findings clearly demonstrated the utility of this technique and these probes to rapidly and correctly identify balanced and unbalanced chromosome anomalies of a fetus that could result from parental translocations. Copyright © 2002 John Wiley & Sons, Ltd.     

Prenatal measurement of the fetal cerebellum and cisterna cerebellomedullaris by ultrasound

The fetal cerebellum can be visualized with ultrasound throughout the second trimester. We describe a technique for measuring the transverse and anteroposterior cerebellar diameters and the measurement of the cisterna magna in the same plane between 14 and 32 weeks gestation. Nomograms for these measurements against gestational age showed good correlation, and narrow confidence limits for the transverse cerebellar diameter. The transverse cerebellar diameter was also measured directly in 79 fetuses after mid-trimester abortion and the measurements obtained were compared with the ultrasound TCD nomogram. Good correlation, was obtained between the post mortem measurements and the ultrasound TCD nomogram. Routine use of these measurements and nomograms should prove valuable in the diagnosis of congenital abnormality of the posterior fossa and may also be of use in assessing the effect of severe intrauterine growth retardation and other insults on cerebellar growth and development. The narrow confidence limits obtained with the TCD nomogram should enable it to be used with confidence in clinical practice.     

Effectiveness of mandatory license testing for older drivers in reducing crash risk among urban older Australian drivers

Most licensing jurisdictions in Australia maintain mandatory assessment programs targeting older drivers, whereby a driver reaching a specified age is required to prove his or her fitness to drive through medical assessment and/or on-road testing. Previous studies both in Australia and elsewhere have consistently failed to demonstrate that age-based mandatory assessment results in reduced crash involvement for older drivers. However studies that have based their results upon either per-population or per-driver crash rates fail to take into account possible differences in driving activity. Because some older people maintain their driving licenses but rarely if ever drive, the proportion of inactive license-holders might be higher in jurisdictions without mandatory assessment relative to jurisdictions with periodic license assessment, where inactive drivers may more readily either surrender or lose their licenses. The failure to control for possible differences in driving activity across jurisdictions may be disguising possible safety benefits associated with mandatory assessment. The current study compared the crash rates of drivers in Melbourne, Australia, where there is no mandatory assessment and Sydney, Australia, where there is regular mandatory assessment from 80 years of age onward. The crash rate comparisons were based on four exposure measures: per population, per licensed driver, per distance driven, and per time spent driving. Poisson regression analysis incorporating an offset to control for inter-jurisdictional road safety differences indicated that there was no difference in crash risk for older drivers based on population. However drivers aged 80 years and older in the Sydney region had statistically higher rates of casualty crash involvement than their Melbourne counterparts on a per license issued basis (RR: 1.15, 1.02-1.29, p=0.02) and time spent driving basis (RR: 1.19, 1.06-1.34, p=0.03). A similar trend was apparent based on distance travelled but was of borderline statistical significance (RR: 1.11, 0.99-1.25, p=0.07). Collectively, it can be inferred from these findings that mandatory license re-testing schemes of the type evaluated have no demonstrable road safety benefits overall. Further research to resolve this on-going policy debate is discussed and recommended.     

Nitrogen removal and nitrate leaching for two perennial,sod-based forage systems receiving dairy effluent

In northern Florida, year-round forage systems are used in dairy effluent sprayfields to reduce nitrate leaching. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentration below the rooting zone for two perennial, sod-based, triple-cropping systems over four 12-mo cycles (1996-2000). The soil is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzip-samment). Effluent N rates were 500, 690, and 910 kg ha(-1) per cycle. Differences in N removal between a corn (Zea mays L.)-bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (CBR) and corn-perennial peanut (Arachis glabrata Benth.)-rye system (CPR) were primarily related to the performance of the perennial forages. Nitrogen removal of corn (125-170 kg ha(-1)) and rye (62-90 kg ha(-1)) was relatively stable between systems and among cycles. The greatest N removal was measured for CBR in the first cycle (408 kg ha(-1)), with the bermudagrass removing an average of 191 kg N ha(-1). In later cycles, N removal for bermudagrass declined because dry matter (DM) yield declined. Yield and N removal of perennial peanut increased over the four cycles. Nitrate N concentrations below the rooting zone were lower for CBR than CPR in the first two cycles, but differences were inconsistent in the latter two. The CBR system maintained low NO3(-)-N leaching in the first cycle when the bermudagrass was the most productive; however, it was not a sustainable system for long-term prevention of NO3(-)-N leaching due to declining bermudagrass yield in subsequent cycles. For CPR, effluent N rates > or = 500 kg ha(-1) yr(-1) have the potential to negatively affect ground water quality.     

REDUCING THE COST OF CONTINUOUS HYDROLOGIC-HYDRAULIC SIMULATION1

ABSTRACT: The use of continuous hydrologic-hydraulic-water quality models is inhibited by their large computer run costs relative to cost incurred with discrete event models. The fixed recurrence interval transfer (FRIT) technique is a means of achieving substantial reductions in computer costs associated with continuous models while retaining their technical advantages. The FRIT technique is applicable where it is reasonable to assume that the recurrence interval of the response of a watershed to a causative meteorologic event is the same for both “before” and “after” conditions. Example applications of the FRIT technique to the hydrologic-hydraulic modeling of floodwater storage, land use changes, and channel modifications are presented to demonstrate the procedure, to suggest the expected accuracy, and to illustrate how computer run costs might be reduced by 99% or more. The FRIT technique is intended for preliminary assessment of the impact of alternative land use conditions and structural water control measures.     

Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change

The use of assimilation tools for satellite validation requires true estimates of the accuracy of the reference data. Since its inception, the Network for Detection of Stratospheric Change (NDSC) has provided systematic lidar measurements of ozone and temperature at several places around the world that are well adapted for satellite validations. Regular exercises have been organised to ensure the data quality at each individual site. These exercises can be separated into three categories: large scale intercomparisons using multiple instruments, including a mobile lidar; using satellite observations as a geographic transfer standards to compare measurements at different sites; and comparative investigations of the analysis software. NDSC is a research network, so each system has its own history, design, and analysis, and has participated differently in validation campaigns. There are still some technological differences that may explain different accuracies. However, the comparison campaigns performed over the last decade have always proved to be very helpful in improving the measurements. To date, more efforts have been devoted to characterising ozone measurements than to temperature observations. The synthesis of the published works shows that the network can potentially be considered as homogeneous within +/-2% between 20-35 km for ozone and +/-1 K between 35-60 km for temperature. Outside this altitude range, larger biases are reported and more efforts are required. In the lower stratosphere, Raman channels seem to improve comparisons but such capabilities were not systematically compared. At the top of the profiles, more investigations on analysis methodologies are still probably needed. SAGE II and GOMOS appear to be excellent tools for future ozone lidar validations but need to be better coordinated and take more advantage of assimilation tools. Also, temperature validations face major difficulties caused by atmospheric tides and therefore require intercomparisons with the mobile systems, at all sites.     

Aortic isthmus Doppler velocimetry: role in assessment of preterm fetal growth restriction

Intrauterine fetal growth restriction (IUGR) is an important pregnancy complication associated with significant adverse clinical outcome, stillbirth, perinatal morbidity and cerebral palsy. To date, no uniformly accepted management protocol of Doppler surveillance that reduces mortality and cognitive morbidity has emerged. Aortic isthmus (AoI) evaluation has been proposed as a potential monitoring tool for IUGR fetuses. In this review, the current knowledge of the relationship between AoI Doppler velocimetry and preterm fetal growth restriction is reviewed. Relevant technical aspects and reproducibility data are reviewed as we discuss AoI Doppler and its place within the existing repertoire of Doppler assessments in placental insufficiency. The AoI is a link between the right and left ventricles which perfuse the lower and upper body, respectively. The clinical use of AoI waveforms for monitoring fetal deterioration in IUGR has been limited, but preliminary work suggests that abnormal AoI impedance indices are an intermediate step between placental insufficiency-hypoxemia and cardiac decompensation. Further prospective studies correlating AoI indices with arterial and venous Doppler indices and perinatal outcome are required before encorporating this index into clinical practice. Copyright © 2010 John Wiley & Sons, Ltd.