Stephen K. Brown

Implications for Community Health from Exposure to Bushfire Air Toxics

Environmental Context. Significant bushfires have recently occurred in Indonesia (1997), Europe (2002), Australia (2000–2001) and the USA (2003), and burned large areas over extended periods of time. They cause widespread and serious air pollution through the release of respirable particles and other toxic air contaminants. These large fire events have shown clear impacts on community health and have caused increasing concern about the impact of bushfire smoke, whether from accidental or planned fires, on the health of surrounding communities. Abstract. Bushfires can cause widespread air pollution through the emission of high levels of toxic air contaminants that affect the health of surrounding communities. This review of studies that have evaluated the health impacts of bushfires in North America, Australia and South-East Asia shows that the primary pollutant consistently exceeding air quality guidelines is particulate matter. Elevated levels of respirable particles are likely to be the major cause of the higher number of hospital visits and admissions for respiratory and/or cardiovascular treatment, increased mortality, and elevated respiratory-related symptoms that were observed in communities after major bushfire events. Morbidity effects were found to be mostly short-lived and reversible after exposure ceased, and were more prevalent among susceptible groups such as asthmatics, children, the elderly, and people with pre-existing respiratory and/or cardiac illnesses. Implications of such exposures to the Australian population will be discussed in relation to existing (urban) air quality measures and options for community response to bushfire events.

Asbestos Exposure During Renovation and Demolition of Asbestos-Cement Clad Buildings

External asbestos cement (AC) claddings become weathered after many years by the gradual loss of cement from exposed surfaces; as a result, loosely bound layers enriched with asbestos fibers are formed. This effect usually appears pronounced with roof cladding but slight with wall cladding. Asbestos fibers on such weathered surfaces may be mixtures of chrysotile with amosite or crocidolite. Renovation and demolition of old AC clad buildings could cause asbestos fiber emission, but this has not been investigated in the past. The exposure of workers to asbestos dust during these operations and precautions to minimize exposure now have been investigated at several building sites. Asbestos dust concentrations during water jet cleaning or painting of weathered AC roofing were approximately 0.1 to 0.2 fibers per milliliter (f/ml.). Limited results suggest that concentrations may be reduced substantially by avoiding abrasion of surfaces. Concentrations during AC roof replacement averaged approximately 0.1 f/mL and were reduced markedly by employing more careful work procedures (e.g., by careful handling of sheets or by wet stacking of sheets). Asbestos dust concentrations during demolition by removal of whole sheets averaged 0.3 to 0.6 f/mL for roofs and less than 0.1 f/mL for walls, reflecting the significant differences in extent of weathering between these elements. Suppression of asbestos emissions from roof sheets by wetting or sealing of weathered surfaces was not predictable because of the occurrence of asbestos fibers in dust trapped under sheet laps. Precautions such as respiratory protection and clothing decontamination are considered to be essential for the demolition of roofing containing amosite or crocidolite by the procedures investigated.

Automatic detection of clustered microcalcifications in digitized mammogram films

The existence of clustered microcalcifications is one of the important early signs of breast cancer. This paper presents an image processing procedure for the automatic detection of clustered microcalcifications in digitized mammograms. In particular, a sensi- tivity range of around one false positive per image is targeted. The proposed method consists of two main steps. First, possible micro- calcification pixels in the mammograms are segmented out using wavelet features or both wavelet features and gray level statistical features, and labeled into potential individual microcalcification ob- jects by their spatial connectivity. Second, individual microcalcifica- tions are detected by using the structure features extracted from the potential microcalcification objects. The classifiers used in these two steps are feedforward neutral networks. The method is applied to a database of 40 mammograms (Nijmegen database) containing 105 clusters of microcalcifications. A free response operating character- istics curve is used to evaluate the performance. Results show that the proposed procedure gives quite satisfactory detection perfor- mance. In particular, a 93% mean true positive detection rate is achieved at the price of one false positive per image when both wavelet features and gray level statistical features are used in the first step.

Development of a Multi-Feature Cad System for Mammography

Routine screening mammography for the early detection of breast cancer in women over the age of 50 is now widespread in many countries including Australia. The introduction of these screening programs has stimulated research into computer systems which may assist radiologists examining these mammogram images.

Enhancement and identification of microcalcifications in mammogram images using wavelets

In this paper, we describe an algorithm for enhancement and detection of microcalcifications in digital mammograms. The microcalcifications are first enhanced by a undecimated wavelet transform and segmented by a classification based method. After spatial features are extracted from the segmented images, a neural network and a Bayes classifier are used to identify clustered microcalcifications. We have tested this algorithm on 40 regions-of-interest images extracted from the database provided by the University Hospital of Nijmegen.

CHARACTERIZATION OF THE FIBER DIAMETER DISTRIBUTIONS OF SYNTHETIC MINERAL FIBER PRODUCTS AND THEIR DUSTS

Procedures to measure the fiber diameter distributions of bulk synthetic mineral fiber products in order to characterize product differences and the diameters of airborne fibers emitted from them have been investigated. Bulk fibers were prepared for size measurement by two methods--one that gently teased fibers apart and another that lightly ground them in a liquid slurry. Bulk products exhibited different contents of respirable fibers, but these were significantly greater when products were prepared by grinding rather than teasing. This was established to result from preferential breakdown of finer fibers into shorter lengths with the former method. Airborne fibers emitted during work operations with products had diameter distributions similar to those of ground fibers, indicating that similar breakdown of finer fibers into shorter lengths occurs for dusts emitted during such operations.

Optimisation of a screening procedure for house dust mite numbers in carpets and preliminary application to buildings

The relative performances of the mobility and heat escape methods for measuring house dust mite numbers in carpet has been evaluated. The optimum method was found to be the mobility method for 24 hours at ambient temperatures which exhibited a mite collection efficiency of approximately 30%. Measurements in three dwellings showed that the method should be applied to carpet at several locations in the living room and/or bedrooms as a general sampling procedure, or adjacent to loungeroom seating to determine the worst case scenario. Carpets using different types of fibre within the same dwelling should be assessed separately. For the limited number of dwellings investigated, wool carpets were found to exhibit higher mite numbers than nylon carpets, even when the former had been insect-resist treated. No house dust mites were found in the wool carpets of an office building which was mechanically ventilated and heated and achieved low indoor humidities in winter.

Automatic detection of clustered microcalcifications in digital mammograms based on wavelet features and neural network classification

The appearance of clustered microcalcifications in mammogram films is one of the important early signs of breast cancer. This paper presents a new image processing system for the automatic detection of clustered microcalcifications in digitized mammogram films. The detection method uses wavelet features and feed forward neural network to find possible microcalcifications pixels and a set of features to locate individual microcalcifications.

EVALUATION OF EROSION RELEASE AND SUPPRESSION OF ASBESTOS FIBERS FROM ASBESTOS BUILDING PRODUCTS

Test methods have been developed to measure the release of asbestos fibers from the surfaces of a range of asbestos building products when subjected to an airstream (air erosion) or to light brush contact (brush erosion). The tests allowed discrimination of differences in fiber release from the products and assessment of the effectiveness of encapsulants in suppressing fiber release. Application of “good” encapsulants (by using tough binders and optimum application rates) reduced fiber release to very low or nondetectable levels for all products tested.

A lack of influence of permethrin treatments of wool carpet on habitation by house dust mites

Wool carpet samples, untreated and treated with commercial levels of permethrin, were placed on a mite-inhabited carpet in a Melbourne house for 14 months. The levels of live house dust mites in the samples were found to be high at the end of this period and to exhibit no differences according to the presence of permethrin in the carpets.