Quantitative mineral phase analysis of dry powders using energy-dispersive X-ray diffraction.

Energy-dispersive X-ray diffraction (EDXRD) spectrometry is being investigated as a means to perform direct on-line quantitative mineral phase analysis on industrial mineral process streams. A laboratory prototype EDXRD analyser has been developed and a preliminary study has been made to determine its suitability for measuring mineral samples. This was carried out by collecting the diffraction spectra of 20 samples each containing six powdered minerals in dry form and using a linear regression analysis model to determine the mass of each mineral component contained in the samples. Using this method it was found that mineral components could be determined to an accuracy of better than 1 wt%.

Comparison of neutron and high-energy X-ray dual-beam radiography for air cargo inspection.

Dual-beam radiography techniques utilising various combinations of high-energy X-rays and neutrons are attractive for screening bulk cargo for contraband such as narcotics and explosives. Dual-beam radiography is an important enhancement to conventional single-beam X-ray radiography systems in that it provides additional information on the composition of the object being imaged. By comparing the attenuations of transmitted dual high-energy beams, it is possible to build a 2D image, colour coded to indicate material. Only high-energy X-rays, gamma-rays and neutrons have the required penetration to screen cargo containers. This paper reviews recent developments and applications of dual-beam radiography for air cargo inspection. These developments include dual high-energy X-ray techniques as well as fast neutron and gamma-ray (or X-ray) radiography systems. High-energy X-ray systems have the advantage of generally better penetration than neutron systems, depending on the material being interrogated. However, neutron systems have the advantage of much better sensitivity to material composition compared to dual high-energy X-ray techniques. In particular, fast neutron radiography offers the potential to discriminate between various classes of organic material, unlike dual energy X-ray techniques that realistically only offer the ability to discriminate between organic and metal objects.

Fast neutron radiography scanner for the detection of contraband in air cargo containers.

There is a growing need to rapidly scan bulk air cargo for contraband such as illicit drugs and explosives. The Commonwealth Science and Industrial Research Organisation (CSIRO) have been working with Australian Customs Service to develop a scanner capable of directly scanning airfreight containers in 1--2 minutes without unpacking. The scanner combines fast neutron and gamma-ray radiography to provide high-resolution images that include information on material composition. A full-scale prototype scanner has been successfully tested in the laboratory and a commercial-scale scanner is due to be installed at Brisbane airport in 2005.

Evaluation and further development of EASE model 2.0.

EASE (Estimation and Assessment of Substance Exposure) is a general model that may be used to predict workplace exposure to a wide range of substances hazardous to health. First developed in the early 1990s, it is now in its second Windows version. This paper provides a critical assessment of the utility and performance of the EASE model, and on the basis of this review, recommendations for the structure of a revised model are outlined. Twenty-seven stakeholders were interviewed about their previous use of EASE, perceived advantages and limitations of the model and suggestions for improvement. A subset of stakeholders was contacted on a second occasion to determine their views on the preferred outputs for an ideal exposure assessment model. Overall, stakeholders felt that the model should be updated to provide more accurate and precise exposure assessments. However, users also expressed the view that the simplicity and usability of the software model should not be compromised. Six studies investigating the validity of the inhalation exposure assessment section of EASE were identified. These showed that the model generally either predicted close to the measured exposures or overestimated exposure; though performance was highly variable. Two studies investigated the validity of the dermal exposure assessment and found that EASE produced considerable overestimates of actual dermal exposure (the amount of a substance that actually lands on the skin). A conceptual model of exposure was developed to investigate whether the structure of the EASE model is appropriate. Although EASE has a number of characteristics that describe exposure, it is a greatly simplified model and does not include all the important exposure determinants. More importantly, EASE can produce estimates of exposure that are ambiguous or incomplete. Our conceptual model may provide a rational basis for developing an improved version of EASE but further consultation is needed to decide the purpose and intended use of any successor to EASE.

Feasibility study for a low-cost 3D gamma-ray camera.

A novel gamma-ray camera is proposed based on Positron Annihilation Compton Scattering Imaging (PACSI). The camera comprises a positron source and a fast, position-sensitive gamma-ray detector. Monte Carlo simulations of the camera have demonstrated that it should be capable of forming 3-D images of objects that can only be viewed from one side. A simple 1-D PACSI camera has been constructed and tested in the laboratory. Prospects for the construction of a full 3-D prototype camera are discussed.

The precautionary principle in environmental science.

Environmental scientists play a key role in society's responses to environmental problems, and many of the studies they perform are intended ultimately to affect policy. The precautionary principle, proposed as a new guideline in environmental decision making, has four central components: taking preventive action in the face of uncertainty; shifting the burden of proof to the proponents of an activity; exploring a wide range of alternatives to possibly harmful actions; and increasing public participation in decision making. In this paper we examine the implications of the precautionary principle for environmental scientists, whose work often involves studying highly complex, poorly understood systems, while at the same time facing conflicting pressures from those who seek to balance economic growth and environmental protection. In this complicated and contested terrain, it is useful to examine the methodologies of science and to consider ways that, without compromising integrity and objectivity, research can be more or less helpful to those who would act with precaution. We argue that a shift to more precautionary policies creates opportunities and challenges for scientists to think differently about the ways they conduct studies and communicate results. There is a complicated feedback relation between the discoveries of science and the setting of policy. While maintaining their objectivity and focus on understanding the world, environmental scientists should be aware of the policy uses of their work and of their social responsibility to do science that protects human health and the environment. The precautionary principle highlights this tight, challenging linkage between science and policy.

Reenergizing public health through precaution.

The precautionary principle has provoked a spirited debate among environmentalists worldwide, but it is equally relevant to public health and shares much with primary prevention. Its central components are (1) taking preventive action in the face of uncertainty; (2) shifting the burden of proof to the proponents of an activity; (3) exploring a wide range of alternatives to possibly harmful actions; and (4) increasing public participation in decision making. Precaution is relevant to public health, because it can help to prevent unintended consequences of well-intentioned public health interventions by ensuring a more thorough assessment of the problems and proposed solutions. It can also be a positive force for change. Three aspects are stressed: promoting the search for safer technologies, encouraging greater democracy and openness in public health policy, and stimulating reevaluation of the methods of public health science.

Retrospective collection of exposure data from industry: results from a feasibility study in the United Kingdom.

In the United Kingdom the Health and Safety Executive for some years has stored chemical exposure data in their National Exposure Database. However, it has been difficult to persuade industry and other organizations to contribute to this resource. The aim of this project was to devise a cost-effective method of obtaining occupational exposure data on chemicals from U.K. industry and other sources. Five strategies were used to identify data for three different substances: toluene, acrylonitrile, and ethylene oxide. In total, 810 organizations were contacted and over 45 percent responded. However, only 40 had relevant exposure data. Almost equal numbers of acceptable measurements were identified for toluene and acrylonitrile (2,770 and 2,000 respectively) with lesser ethylene oxide data (800). These measurements were drawn from a wide range of industries and are probably representative of measurements made by U.K. industry, although most of the data were from companies employing more than 100 people. During the second phase of the project, more than 3,000 measurements and associated contextual information were collected (499 for toluene, 1,516 for acrylonitrile, and 17 for ethylene oxide, with a further 1,004 measurements for 1 of 27 substances collected simultaneously with one of the above). The costs of identifying and collecting exposure data ranged from l7 to l380 per valid measurement, depending on the source of the data. We suggest that, rather than trying to retrospectively collect data, it is likely to be more cost-effective to enlist a number of occupational hygiene consults and industrial organizations to prospectively provide anonymized exposure measurements for inclusion in the Health and Safety Executives National Exposure Database.

Workshop on harmonization of serving future needs with occupational exposure databases--inhalation modeling, session IIIA.

This workshop was one of several that took place at the International Symposium on Occupational Exposure Databases and Their Application for the Next Millennium held in London from November 1-3, 1999. About 30 delegates participated in the workshop. The agenda for the discussions was provided by a white paper prepared by the organizers. The workshop produced a conceptual outline for a general-purpose prediction model for inhalation exposure, and constructed a list of important input variables for successful model development. Evaluation of prototype models was discussed in some detail, and the workshop concluded with suggestions for taking forward the ideas discussed and maintaining the momentum and interest generated during the symposium.

An on-belt elemental analyser for the cement industry.

On-line control of raw mill feed composition is a key factor in the improved control of cement plants. A new and improved on-conveyor belt elemental analyser for cement raw mill feed based on neutron inelastic scatter and capture techniques has been developed and tested successfully in Adelaide Brighton's Birkenhead cement plant on highly segregated material with a depth range of 100 to 180 mm. Dynamic tests in the plant have shown analyser RMS total errors of 0.49, 0.52, 0.38 and 0.23 wt% (on a loss free basis) for CaO, SiO2, Al2O3 and Fe2O3 respectively, when 10-minute counting periods are used.

Health risks posed by use of Di-2-ethylhexyl phthalate (DEHP) in PVC medical devices: a critical review.

BACKGROUND: Polyvinyl chloride plastics (PVC), made flexible through the addition of di-2-ethylhexyl phthalate (DEHP), are used in the production of a wide array of medical devices. From the late 1960s, leaching of DEHP from PVC medical devices and ultimate tissue deposition have been documented. METHODS: A critical review of DEHP exposure, metabolism, and toxicity data from human and animals studies was undertaken. A brief analysis of alternatives to DEHP-plasticized PVC for use in medical device manufacture was completed. RESULTS: DEHP leaches in varying concentrations into solutions stored in PVC medical devices. Certain populations, including dialysis patients and hemophiliacs may have long-term exposures to clinically important doses of DEHP, while others, such as neonates and the developing fetus, may have exposures at critical points in development. In vivo and in vitro research links DEHP or its metabolites to a range of adverse effects in the liver, reproductive tract, kidneys, lungs, and heart. Developing animals are particularly susceptible to effects on the reproductive system. Some adverse effects in animal studies occur at levels of exposure experienced by patients in certain clinical settings. DEHP appears to pose a relatively low risk of hepatic cancer in humans. However, given lingering uncertainties about the relevance of the mechanism of action of carcinogenic effects in rodents for humans and interindividual variability, the possibility of DEHP-related carcinogenic responses in humans cannot be ruled out. CONCLUSIONS: The observed toxicity of DEHP and availability of alternatives to many DEHP-containing PVC medical devices presents a compelling argument for moving assertively, but carefully, to the substitution of other materials for PVC in medical devices. The substitution of other materials for PVC would have an added worker and community health benefit of reducing population exposures to DEHP, reducing the creation of dioxin from PVC production and disposal, and reducing risks from vinyl chloride monomer exposure.

Democratic participation: a critical element of precautionary public health decision-making.

The precautionary principle is increasingly discussed in debates about threats to health and the environment, particularly when government actions might inhibit free trade. It is gaining recognition as an overarching principle of decision-making, one that underlies efforts for sustainable development. Pronouncements about the precautionary principle have focused generally on the responsibility of government to act in the face of uncertainty and the shifting of burdens onto proponents. This assumes that government will have the resources, knowledge, expertise, and will to act. The role of the public those who may be affected by environmental degradation or their representatives is mostly missing from the discussions. This article outlines a rationale for why participation is critical and explores the theory of citizen participation. The article also describes participatory models used around the world, primarily examples of citizen participation though various models also exist for workers.

Children's environmental health: a case study in implementing the precautionary principle.

The plausible threat to children from environmental exposures and uncertainty as to the magnitude and nature of potentially harmful effects provide a rationale for taking precautionary measures to prevent such exposures. The authors present principles for applying precaution to children's environmental health, and policy tools for implementing them. A stronger focus on primary prevention and a better understanding of the risks are needed.

Determination of the spatial response of neutron based analysers using a Monte Carlo based method

One of the principal advantages of using thermal neutron capture (TNC, also called prompt gamma neutron activation analysis or PGNAA) or neutron inelastic scattering (NIS) techniques for measuring elemental composition is the high penetrating power of both the incident neutrons and the resultant gamma-rays, which means that large sample volumes can be interrogated. Gauges based on these techniques are widely used in the mineral industry for on-line determination of the composition of bulk samples. However, attenuation of both neutrons and gamma-rays in the sample and geometric (source/detector distance) effects typically result in certain parts of the sample contributing more to the measured composition than others. In turn, this introduces errors in the determination of the composition of inhomogeneous samples. This paper discusses a combined Monte Carlo/analytical method for estimating the spatial response of a neutron gauge. Neutron propagation is handled using a Monte Carlo technique which allows an arbitrarily complex neutron source and gauge geometry to be specified. Gamma-ray production and detection is calculated analytically which leads to a dramatic increase in the efficiency of the method. As an example, the method is used to study ways of reducing the spatial sensitivity of on-belt composition measurements of cement raw meal.