In our study showing the exposure to chrysotile fibres in a friction materials producing plant through urinalysis for fibres, it was shown that smaller chrysotile fibres were indeed absorbed and if shorter than 1-2 µm could also be transported in the urine (1). This property could explain effects also in other sites than respiratory tract.

Exposure can also be demonstrated by an electron microscopic analysis for fibres in the nasal lavage liquid. Thus we were able to show individual exposure to refractory ceramic fibres, the nature of which could be ascertained by X-ray diffraction technique in the same samples (2).

Thus, it seems that exposure to, and absorption of, fibres harmful to health can be determined at an individual level. Cohorts thus constituted could prove the ideas presented in this excellent paper (3).

Heikki Savolainen

1. Savolainen H, Cosca-Sliney R, Guillemin M. Detection of
occupational exposure to inorganic fibres by urinary fibre analysis. Occup Hyg 1996; 3: 351-357.

2. Linnainmaa M, Kangas J, Makinen M, et al. Exposure to refractory
cermaic fibres in the metal industry. Ann Occup Hyg 2007; 51: 509-516.

3. Loomis D, Dement J, Richardson D, et al. Asbestos fibre dimensions
and lung cancer mortality among workers exposed to chrysotile. Occup
Environ Med 2010; 67: 580-584.