[ RadSafe ] FW: Reporter's question about lower limits of detection

DAMcClureAtlanta 404.694.4036 mcclure-da at comcast.net
Sat Aug 6 17:50:08 CDT 2011

I love it. Thanks Stu! 

stewart farber <SAFarber at optonline.net> wrote:

>Hello all,
>Firstly, it's important for Chris Busby to read what a person writes
>carefully before criticizing it, and to keep in mind the concept of
>comparing Apples vs. Oranges.
>My remarks yesterday which Busby criticized, made in my comment to a
>question from reporter Matt Wald of the NYTimes,  never mentioned the levels
>of Cs-137 in air in Japan after the accident, rather the levels of airborne
>radioactivity measured in the US following the accident. I made a general
>comment, not a distorted point, about airborne levels of Sr-90 IN THE US
>having been much higher in the 1960s than they have been IN THE US since the
>accident in Japan.
>My comment is completely irrefutable based on data derived from proper
>sampling techniques used by the USEPA, and the US Environmental Measurements
>Lab,  and analytical measurements performed using calibrated geometries in
>counting airborne particulate samples gathered in the US after the accident
>following the earthquake and tsunami which severely damaged the Fukushima
>nuclear complex.
>Busby provides a calculated value for airborne Cs-134 at several locations
>in Japan based on his collecting and analyzing several auto air filters
>while guessing at the volume of air sampled. The numbers he quotes for
>airborne Cs in Japan are meaningless based on the major uncertainty of the
>sampling technique employed, the uncertainly in many variables like filter
>efficiency, and no details on how the auto air filter was configured for
>counting in a calibrated geometry. In any case, I wasn't saying anything
>about Cs airborne levels in Japan, so any data there no matter how gathered,
>is simply irrelevant to my comment yesterday--- Apples.
>The US EPA made excellent measurements of airborne Cs-137 in the US released
>from Fukushima after the accident. Air particulate samples were taken all
>over the USA by the EPA. Based on calibrated Hi-Vo samplers and calibrated
>counting geometry for air filters, the highest levels of Cs-137 in air
>measured were seen in HI, CA, AZ, NV. Cs-137 levels were reported as
>[picoCuries per cubic meter]:
>Minimum: 0.000238 pCi/m^3
>Maximum: 0.116
>Average: 0.0189
>The above EPA data can be seen at:
>Open air testing of 500 nuclear bombs by the US and Soviets, ending in 1963,
>led to many years of significant ongoing nuclear fallout from the mid 1950s,
>reaching a peak level of total terrestrial deposition in 1968. After 1968
>the environmental inventory of Cs-137 and Sr-90 continued to drop steadily
>with minor blips in the US from small nuclear bomb tests by India and China.
>Chernobyl added no more than 1% to the environmental fallout inventory in
>the US.
>During the MANY YEARS of nuclear test fallout airborne Cs-137 in essentially
>the entire Northern Hemisphere, including the US, was roughly about 0.1
>pCi/m^3. Peak levels of airborne Cs-137 during the period of open air
>testing were commonly measured at 0.5 pCi/m^3 and higher.
>As noted above, the EPA measured a SHORT TERM average of airborne Cs-137 in
>the US from Fukushima of 0.0189 pCi/m^3  in those states having the highest
>measured concentrations. 
>The LONG-TERM average level of airborne Cs-137 in the US during the many
>years of atomic bomb fallout during and for a few years after open air
>testing ended was about 5 times higher than the average SHORT TERM peak
>levels of accurately sampled and measured airborne Cs-137 seen in the US
>from Fukushima [based upon a few measurements fading away to essentially
>nothing after a short time].
>Given that what is important in calculating total radiation dose is the
>ratio of the time integrated concentration of airborne exposure to Cs-137 in
>this case,  the total exposure of people in the US from open air testing
>fallout is at least 500 times greater than the total exposure from
>short-term peak airborne Cs-137 in the US measured after the Fukushima
>accident [in looking at the areas in the US that had the highest recent
>airborne Cs-137 levels].
>And yes, I consider total time-integrated exposure to Fukushima airborne
>Cs-137 and Sr-90 in the US that is about one part in 500  [or less] of the
>time integrated radiation exposure from nuclear bomb test fallout in the US
>to be trivial. -Oranges
>Cheers as is often said.
>Stewart Farber, MS Public Health
>-----Original Message-----
>From: Busby, Chris [mailto:C.Busby at ulster.ac.uk] 
>Sent: Friday, August 05, 2011 5:46 PM
>To: safarber at optonline.net; The International Radiation Protection (Health
>Physics) Mailing List; 
>Dear Radsafers,
>This is a reply to Stuart Farber who talks about trivial levels from
>Fukushima. I have measured Cs137 in air filters from cars driving for known
>periods of time 100km from Fukushima and in one case in Chiba which is East
>of Tokyo. I have used NaiTl and also had the labs at Harwell do high
>resolution counting.  Activity of Cs134 in these Filters was between 120 and
>This can be shown (from the cubic capacity of the engine, the rpm and the
>mileage after Fk) to give levels of Cs137 of about 1-3Bq/cubic metre.
>Northerm hemisphere peak activity of Cs137 was about 2 to 3mBq
>(milliBecquerels, Yes) Cs-137 per cubic metre as measured in Harwell UK at
>the peak opf the fallout in 1963. I just say this to advise you that the
>Fukushima releases are not trivial. About 1000 times higher than the peak
>fallout levels.
>Post excerpt [sent 05/08/11 18:57]
> by S. Farber to Radsafe to which Dr. Busby commented above
>"During the days of open air testing of nuclear weapons by the US and
>[thru 1963] and after 1968 when most of this nuclear bomb released
>radioactivity had left the stratosphere and come to deposit on the earth's
>surface, Sr-90 and every other fallout radionuclide was much, MUCH higher
>than levels one would measure today in almost all sample media. Levels of
>Sr-90 in surface water, and air, and fish and other biota were much higher
>than today. People [and the media] who have panicked recently from trivial
>levels [in terms of radiation dose and risk] of measurable contamination in
>the US from Fukushima, overlook the fact that during the days of open air
>nuclear testing,  levels of radioactivity were hundreds to thousands of
>higher in some cases. The amazing thing about measuring radiation is you can
>measure a few atoms of some isotope decaying with accuracy and precision,
>vs. the best chemical contaminant analytical technique requiring
>countess[sic- should read countless] "billions and billions" of atoms as
>Sagan so enjoyed saying.
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