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This study was carried out to determine the distribution of particles in classrooms in primary schools located in the centre of the city of Sari, Iran and identify the relationship between indoor classroom particle levels and outdoor PM2.5 concentrations. Outdoor PM2.5 and indoor PM1, PM2.5, and PM10 were monitored using a real-time Micro Dust Pro monitor and a GRIMM monitor, respectively. Both monitors were calibrated by gravimetric method using filters. The Kolmogorov-Smirnov test showed that all indoor and outdoor data fitted normal distribution. Mean indoor PM1, PM2.5, PM10 and outdoor PM2.5 concentrations for all of the classrooms were 17.6 μg m-3, 46.6 μg m-3, 400.9 μg m-3, and 36.9 μg m-3, respectively. The highest levels of indoor and outdoor PM2.5 concentrations were measured at the Shahed Boys School (69.1 μg m-3 and 115.8 μg m-3, respectively). The Kazemi school had the lowest levels of indoor and outdoor PM2.5 (29.1 μg m-3 and 15.5 μg m-3, respectively). In schools located near both main and small roads, the association between indoor fine particle (PM2.5 and PM1) and outdoor PM2.5 levels was stronger than that between indoor PM10 and outdoor PM2.5 levels. Mean indoor PM2.5 and PM10 and outdoor PM2.5 were higher than the standards for PM2.5 and PM10, and there was a good correlation between indoor and outdoor fine particle concentrations. [ABSTRACT FROM AUTHOR]

This study investigated occupational exposure to silica dust of 48 workers in stone cutting, glass making, ceramic, and sand blasting plants in the north of Iran. Samples were collected from the breathing zone using a personal sampling pump and a size-selective cyclone. Sample filters and blanks were analysed using infrared spectroscopy. The mean sampling period was 4.83 h. Mean exposure of workers to crystalline silica dust in glass making, ceramic, sand blasting, and stone cutting was 0.129 mg m-3, 0.169 mg m-3, 0.313 mg m-3 and 0.318 mg m-3, respectively. As exposure at each of the workplaces is three to 12 times higher than the current national and international thresholds, these workers run a greater risk of lung cancer and mortality. Our findings call for specific ventilation design and personal protection improvements in the four plants as well as stricter enforcement of the existing regulations by the authorities. [ABSTRACT FROM AUTHOR]