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.

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