Uptake and Retention of Tritiated Pump Oil in Rats Following Intratracheal Instillation
S.M. Carlisle and P.A. Burchart (AECL, Chalk River, Ontario, Canada)
Saturated hydrocarbon mineral oils in vacuum pumps used in tritium handling facilities often contain significant amounts of tritium (as much as several hundred GBqL-1). These oils require frequent changes due to polymerization. The air around an open pump during such changes may contain hundreds to millions of becquerels of volatile tritiated species per litre. Tritiated pump oils may pose a workplace hazard, especially during pump maintenance, if contaminated oil aerosols and hydrocarbon vapours are inhaled. In the absence of specific data on metabolism, retention or excretion of tritium from tritiated oil aerosols and vapours, radiation doses from tritiated oil aerosols are estimated using inhalation dose coefficients recommended by the ICRP for tritiated organic gases or vapours (ICRP Publication 68, Annals of the ICRP 24 (4): 1994). Several experiments have been carried out to follow tritium retention in rats exposed to intratracheally instilled tritiated pump oil, in order to provide empirical data for establishing dosimetric parameters for this potential workplace hazard. Initial studies indicated that a substantial fraction of the administered tritium (about 30%) was retained for at least 3 weeks in the lungs as organically bound tritium, with no consistent decline in activity over that time period. Further studies, following excretion and organ retention of tritium for up to one year after exposure, are currently underway. Preliminary results from this longer-term study are presented. This research is supported by funding from the CANDU Owners' Group.
