A novel synthetic erionite fibre radiolabelled with Co-57

The aim was to produce a radiolabelled fibre suitable for long-term carcino genesis studies. To this end, we have successfully synthesised erionite fib res by a method adapted to incorporate Co-57 into the crystal framework. Mo rphologically the fibres are straight, of median length 2.5 mum, with 11% o f fibres >8 mum long, and median width 0.32 mum. These values are comparabl e to natural Oregon erionite. Autoradiography confirmed that the Co-57 was associated with the fibres themselves, The stability of the radiolabel in v ivo was examined by instilling 1 mg of synthetic erionite into the lungs of F-344 rats. About half of the thoracic content of Co-57 was cleared in the first week, and over the following 5 weeks the remainder was cleared slowl y with a half-time of 120 days. After 6 weeks the urinary excretion of Co-5 7 was only 0.054% of the initial lung content per day. This represented fib re dissolution plus any leaching of Co-57 from the fibres, It can he conclu ded that the Co-57 is bound into the erionite fibres with sufficient stabil ity in vivo for studying their effects in relation to translocation to the pleura. (C) 2001 British Occupational Hygiene Society, Published by Elsevie r Science Ltd. All rights reserved.