Re: Contaminated Hosp Pipes

[jtowson@nucmed.rpa.cs.nsw.gov.au (Jocelyn Towson)]

>ANY THOUGHTS ON THIS PLEASE:
>
>Patients receive up to 7.4GBq (200mCi) I-131 for Ca-thyroid radionuclide
>therapy. This is administered on the 6th floor of our hospital.
>
>Excreted I-131 from these patients passes through cast iron waste pipes
>down the building to the main drain. 90% of the administered activity is
>lost via this waste stream. The pipes pass through occupied work areas to
>reach the main drain.

I have a few thoughts on this one, in the light of our own experience. We
treat an average of 4 patients per week in 2 bedrooms with shared
bathroom/toilet, in a very similar setup - 6th floor of a large ward block
with old cast iron stacks. I don't think the external dose rate is the only
thing to keep an eye on - blockage of the stack is another.
Our iodine rooms had to be moved to the 6th floor several years ago, from a
similar suite of rooms directly below on the ground floor and on the same
drainage line where the old bathroom was the last input from the building
to the sewer.    When we moved, the hospital's plumbers pointed out that
the stack services many toilets in the building and they have to deal with
blockages on any floor from time to time - his words were "You'd be
surprised what people try to flush down the toilet sometimes".  Blockages
also occur because the interior of the stack is heavily corroded and
paper/solids etc get trapped.
In the event of a blockage, the plumbers said (i) we would lose the use of
the iodine toilet till the line was fixed, (ii) we would have to deal with
a very contaminated pipe and (iii) iodine waste water flushed into the
blocked line could surcharge out at floors between the 6th and the level of
the block (I'm not sure if this is correct).  So, despite the usual lack of
funds, the hospital put in a parallel and independent PVC drainage line
direct from the 6th floor iodine toilet to the sewer and we have had no
problems.
My guess is that if yours is an old building, the internal choke of the
stack wil be much reduced by corrosion.  I would suggest that you talk to
your plumbers and management about ways of avoiding the possibility of a
significant contamination hazard if the line gets blocked.
Incidentally, we once tried dosing the drain from the bath/shower with
lugol's iodine, following an earlier suggestion on radsafe to saturate the
resident microflora, but it didn't seem to have any obvious effect.
Regards,
Jocelyn Towson

Jocelyn Towson, RSO
Dept of PET & Nuclear Medicine
Royal Prince Alfred Hospital
Camperdown, NSW 2050
Australia

tel [national]  02 9515 8011    [international] 61 2 9515 8011
fax [national]  02 9515 6381    [international] 61 2 9515 6381
email   jtowson@nucmed.rpa.cs.nsw.gov.au