Particles from the air sample viewed by transmission electron microscopy, demonstrating both asbestiform fibres and cleavage fragments. Particles from the air sample viewed by transmission electron microscopy, demonstrating both asbestiform fibres and cleavage fragments. (A) An intact asbestiform asbestos fibre. (B) A cleavage fragment. The elongated mineral particle is identified as a cleavage fragment because of non-parallel edges. Hsiao-Yu Yang et al. Occup Environ Med doi:10.1136/oemed-2013-101404 ©2013 by BMJ Publishing Group Ltd