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BackgroundAsbestos is a silicate mineral that is naturally generated by geological processes in the Earth's crust. The six types of commercially used asbestos each display the asbestiform crystal habit that is characterized by fibrous aggregates of extremely long, thin crystals. This study provided data that can be used to discriminate asbestiform and non-asbestiform amphiboles contained in landscaping rocks in parks. MethodIn five of the 21 parks, two or more landscaping rocks were found to contain asbestos. These five were selected for additional study. The length and width of fibers being at least 5 ㎛ long and with a minimum aspect ratio of 3:1 were measured using a Transmission Electron Microscope(TEM) and compared to a standard asbestos sample.ResultsThe park samples were thicker than 1 ㎛(average 1.9 ㎛) while the Health and Safety Executive(HSE) reference sample averaged 0.3 ㎛ in width with 100 % thinner than 1.0 ㎛. The average aspect ratios were 7.1 for the park samples and 67.1 for the HSE reference sample. The actinolite contained in the landscape rocks of the five selected parks did not show the typical asbestiform structure that was observed in the standard asbestos sample.ConclusionsBased on these distributions, the amphibole fibers in sampled landscape rocks were found to be thicker and lower aspect ratio than those of the standard sample. The result of this study can contribute to the public policy for managing and controlling of landscaping rocks containing naturally occurring asbestos(NOA) and also to communicate about the possible health risk resulting from NOA contained in landscaping rocks.

This study is purposed to measure airborne asbestos concentrations at demolition sites and surrounding areas of asbestos containing buildings in Seoul and examine whether the measurement results correspond with allowable exhaust standard for asbestos of the Asbestos Safety Control Act. The airborne asbestos concentrations for 37 sites were below the detection limit (7 fiber/mm 2 ) in 101 (35%) out of 288 samples. The whole average airborne asbestos concentration in 37 sites was 0.003±0.002 f/cc (max 0.0013 f/cc) and almost the whole airborne asbestos concentrations were satisfied with allowable exhaust standard for asbestos, 0.01 f/cc, of the Asbestos Safety Control Act. So possibility of asbestos exposure is not yet a major concern at current levels for sites demolished of asbestos containing buildings in Seoul. Looking at each sampling point, the average airborne asbestos concentrations in boundary line of site, entrance of sanitation, around the workplace (in), around the workplace (out), negative pressure units, storage area for waste, outlet for waste and residential area of residents were respectively 0.002±0.002 f/cc, 0.004±0.002 f/cc, 0.004±0.002 f/cc, 0.004±0.002 f/cc, 0.004±0.002 f/cc, 0.005±0.004 f/cc, 0.005±0.003 f/cc and 0.003±0.002 f/cc. As a result, all sampling points of study were satisfied with allowable exhaust standard for asbestos, 0.01 f/cc, of the Asbestos Safety Control Act.

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This study provided data that can be used to discriminate asbestiform and non-asbestiform amphiboles contained in landscaping rocks in recreational parks. The length and width of fibers being at least 5 µm long and with a minimum aspect ratio of 3:1 were measured using a transmission electron microscope and compared to an asbestos reference sample. The park samples were thicker than 1 µm (average 1.9 µm), while the Health and Safety Executive (HSE) reference sample averaged 0.3 µm in width, with 100% being thinner than 1.0 µm. The average aspect ratios were 7.1 for the park samples and 67.1 for the HSE reference sample. Based on these distributions, the amphibole fibers in sampled landscape rocks were thicker and had a lower aspect ratio than the reference sample. These results suggest that actinolite fibers in sampled landscape rocks cannot be classified into commercial-grade asbestos. This study can contribute to public policy for managing and controlling landscaping rocks containing naturally occurring asbestos (NOA) and be used to communicate the possible resulting health risks.