Optical microscopy as a new approach for characterising dust particulates in urban environment.

In urban environments airborne particulates (dust) must be managed to ensure that industry and community coexist in a mutually beneficial and sustainable manner. The composition of the dust is a function of the local environment and industry. In general, there is a view by many community members that a significant proportion of inhalable (PM10) and respirable (PM2.5) dust in these environments could be coal. Thus there is a need to have an analytical method that provides a quantitative analysis of the amount and size distribution of the different particulates that can be present in air samples. Australia's national research body, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) has developed a Coal Grain Analysis (CGA) system that uses reflected light optical microscopy to provide a unique visual perspective, a qualitative feeling of the sample and quantitative information on the composition and size of the individual particles greater than 1 µm. Furthermore, semi-automated Optical Dust Marker software uses each individual particle's colour reflectance fingerprint to classify that particle. These markers can currently identify coal, combustion chars, iron, quartz/dark minerals, pyrite/bright materials and particulates of organic origin. This paper presents a case study performed using CGA to evaluate the dust composition and proportion of coal and other particulates and also their size distribution in samples collected in an urban area along a coal rail corridor in Newcastle (Australia). In coastal environments a significant proportion of dust can be water soluble (salt) particulates; the proportion of soluble particulates in those samples varied from 46% to 52.3%. The concentration of insoluble particles in samples varied from 5.9 to 15.5 µg m-3 in the PM2.5-10 fraction and from 0.4 to 0.9 µg m-3 in the PM1-2.5 fraction. All samples consisted predominantly of particles of organic origin (mostly plant and insect remains) - 55.3%-85.3% by mass. Dark material particles of mainly inorganic origin (low reflecting material, mainly stone dust, clay, soot, rubber and soil), combustion char and metal particles (rust and iron oxides) were present in lower concentrations - 0.0% to 19.9% by mass. The amount of coal in the water insoluble fraction of the samples ranged from 5.3% to 19.7% by mass with 2.9%-13.5% by mass of coal particles in the thoracic (2.5-10 µm) and 0.3%-1.2% by mass in the respirable (1-2.5 µm) size fraction.

School league tables: a new population based predictor of dental restorative treatment need.

AIM: To test whether dental restorative treatment need was related to the school league tables and level of social deprivation of the school ward. DESIGN: An ecological study using clinical data aggregated at school level, collected in the school dental screening examinations (1996-97), National Census (1991) and the results of the UK school league tables--Key Stage 2 SATs (1996-97). SETTING: State primary schools in the Greenwich District of SE London, UK (1996-97). SUBJECTS: 12,854 pupils (6-11 years of age) in 62 schools. OUTCOME MEASURE: The percentage of 6 to 11 year old pupils per school requiring dental restorative treatment. RESULTS: Deprivation as measured by the overall Jarman Under Privileged Area Index (UPA) of the school ward was not associated with dental restorative treatment need (p > 0.05). Only two components of the Jarman Index, level of unemployment and the number of lone parent families in the school ward were found to be significantly associated with dental restorative treatment need (p < 0.05). Results of stepwise multiple linear regression analysis showed that the association with the school league table results in all three subjects, English, Mathematics and Science remained statistically significant after adjusting for levels of unemployment and single parents. Results of multiple linear regression analysis showed that a high level of dental restorative treatment need was significantly associated with poor school league table results in English, Mathematics and Science (p < 0.05) after adjusting for the overall Jarman score of the school ward. A separate analysis for the 11-year-old pupils aggregated by school (n = 46 schools) gave similar results. CONCLUSIONS: Aggregate measures of academic achievement may be a potential indicator of dental restorative treatment need.