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RE: report find radium raises risk of bone cancer in men
I attempted to respond to this last night but evidently my system did
not send it out. If it did, I apologize for covering the same ground
twice.
James Dukelow wrote:
>Regarding the greater concern about private wells:
I need to ask a naive question here. If there is any Ra-224 (3.6 day
half-life) in any water system, there has to be a source of that Ra-224.
For Ra-224, that source appears to be Th-228 (1.91 year half-life). If
the source and the progeny are in equilibrium, then decay of Th-228 will
be replacing those Ra-224 atoms as rapidly as they decay away. Why
should community water systems be any different from private wells with
respect to Ra-224 activity?
Response:
The Ra-224 in the water obtained from the Kirkwood-Cohansey aquifer is
not in equiblibrium with Ra-228. The ratio of Ra-224 to Ra-228 is
between 1 and 2, with an average around 1.4. The "unsupported fraction"
of Ra-224 is believed to be due to the "alpha recoil effect" and the
relatively low pH of the aquifer (typically 3.5 to 5.5).
The water company serving most of the area operates wells in three
aquifers and the water from the wells is mixed in the distribution
system. Radioactivity levels in the other two aquifers are lower than
in the Kirkwood-Cohansey so both dilution and time for decay reduce the
concentration of radium in water system. Virtually all the private
wells are in the Kirkwood-Cohansey and, given the shorter time between
pumping and use, and since no dilution is available, the concentrations
of radium in private wells are generally higher than in the water
company's distribution system. The distribution system is quite
complicated and involves 21 wells and several storage locations.
>Regarding the NJ study:
The 2003 State of New Jersey Department of Health and Senior Services
study is clearly an ecological study with radium levels measured after
the period when the osteosarcomas were registered. There are no direct
measures of exposure of the osteosarcoma cases and non-cases to their
drinking water. The results of similar studies in the literature, as
described in the NJ study, are wildly inconsistent with respect to age
and gender dependence of incidence and mortality rates.
Response:
I agree (with the possible exception of the use of "wildly"... I've
learned over the past ten years or so that "wild" to us is pretty much
par for most epidemiologists).
Regards,
Gerry
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