The results of analysis of
mineral fibres in lung tissues from 10 paraoccupational cases of
malignant mesothelioma were compared with analysis obtained from seven cases of
malignant mesotheliomas that had developed in
gas mask workers. Nine of the paraoccupational cases were considered to have developed their tumours because of exposure to
asbestos on their husbands' working clothes and one
cancer developed in the daughter of a man who had died of
asbestosis. The
gas mask workers had direct exposure to
asbestos while working in a factory that produced military
gas masks. The results of
mineral fibre analysis in the paraoccupational cases were variable; six showed high
crocidolite concentrations, seven raised
amosite concentrations and two normal concentrations of all types of
asbestos fibre measured.
Chrysotile was raised in one case but
crocidolite and
amosite were also increased. The
gas mask workers showed a consistent pattern with high
crocidolite concentrations and normal or low concentrations of
chrysotile and
amosite. Fibre lengths for
chrysotile were similar in both groups and predominantly less than 5 microns.
Crocidolite fibres tended to be longer in the
gas mask workers than in the paraoccupational group and longer than
chrysotile in both groups.
Amosite fibres tended to be more variable in width than those of
chrysotile or
crocidolite.