these numbers do not mean much in general, we need to put them into the context
of naturally occurring radioactivity. For example, the concentration of naturally
occurring K-40 was about 4000 Bq/kg in these samples, a factor of 20,000 more
then the Cs-137 observed. By utilizing a chemical preprocessing step and filtering
large amounts of water, the Woods Whole Oceanographic Institution was able to
measure Cs-134 off the Northern California Coast in water [18]. The observed
concentration of 2 mBq/l is a factor 5000 less than the approximately 10 Bq/l of
naturally occurring K-40 observed in the Pacific Ocean [19]. The ongoing releases
of contaminated water off the coast of Japan resulted only in fairly small concentrations, even close to the harbor of the power plant. For example, the water
concentration of Cs-134 in close proximity to the harbor of the Dai-ichi nuclear
power plant is about 20 mBq/l, if detectable at all [19]. While the observation of
Cs-134 in the water does confirm the transport of this isotope via ocean currents, it
is significantly diluted spatially and temporally and—as expected and as with the
other samples mentioned before—never posed a health risk to the public or the
environment.
We are still continuing to conduct environmental and food sample measurements
to-date, including measurements driven by requests from the public. This even
includes materials from Europe with potential contamination from the Chernobyl
accident more than 30 years ago. In addition to real-time air-sampling and sample
measurements performed utilizing gamma radiation, the team set up alpha spectrometers that enable us to measure alpha particle decay in the same samples. The
main goal of this activity is to measure naturally occurring alpha decay, specifically
of Po-210. The fact that there is naturally occurring gamma radiation in the environment is not widely known, and the fact there is naturally occurring alpha-particle
radiation is even less known. However, naturally occurring background radiation is
part of the world we are living in and something that the general public should be
aware, so any new information about radioactive contamination can be put into the
proper context. It is noteworthy that the Po-210 measurements, particularly in fish,
do dominate the radiation exposure, meaning the dose from Po-210 is larger than
the dose due to K-40 [20]. This information should not lead to a decision to avoid
eating fish, as we are exposed to Po-210 all the time as it is part of the radioactive
decay chain starting from U-238. Radioisotopes such as U-238, Th-232, or K-40
have half-lives of billion of years and can be found everywhere in our universe
resulting in some amount of radioactivity even in the smallest quantities of matter.
In addition to the gamma-ray and alpha-particle monitoring performed in the
RadWatch UC Berkeley lab, we have performed so-called neutron-activation
analysis experiments which allow us to measure trace amounts of non-radioactive
matter in our environment and food. Of specific interest are trace metals, such as
mercury or arsenic, which can be commonly found in food and fish. In keeping with
the RadWatch mission, the goal is not to make the public fearful of food or our
environment, but to make them aware of the world we are living in and to ultimately put the observation and risks of radiation in a proper context. All this
information is available online on our Berkeley Radwatch website [15].
The Institute of Resilient Communities
213
of naturally occurring radioactivity. For example, the concentration of naturally
occurring K-40 was about 4000 Bq/kg in these samples, a factor of 20,000 more
then the Cs-137 observed. By utilizing a chemical preprocessing step and filtering
large amounts of water, the Woods Whole Oceanographic Institution was able to
measure Cs-134 off the Northern California Coast in water [18]. The observed
concentration of 2 mBq/l is a factor 5000 less than the approximately 10 Bq/l of
naturally occurring K-40 observed in the Pacific Ocean [19]. The ongoing releases
of contaminated water off the coast of Japan resulted only in fairly small concentrations, even close to the harbor of the power plant. For example, the water
concentration of Cs-134 in close proximity to the harbor of the Dai-ichi nuclear
power plant is about 20 mBq/l, if detectable at all [19]. While the observation of
Cs-134 in the water does confirm the transport of this isotope via ocean currents, it
is significantly diluted spatially and temporally and—as expected and as with the
other samples mentioned before—never posed a health risk to the public or the
environment.
We are still continuing to conduct environmental and food sample measurements
to-date, including measurements driven by requests from the public. This even
includes materials from Europe with potential contamination from the Chernobyl
accident more than 30 years ago. In addition to real-time air-sampling and sample
measurements performed utilizing gamma radiation, the team set up alpha spectrometers that enable us to measure alpha particle decay in the same samples. The
main goal of this activity is to measure naturally occurring alpha decay, specifically
of Po-210. The fact that there is naturally occurring gamma radiation in the environment is not widely known, and the fact there is naturally occurring alpha-particle
radiation is even less known. However, naturally occurring background radiation is
part of the world we are living in and something that the general public should be
aware, so any new information about radioactive contamination can be put into the
proper context. It is noteworthy that the Po-210 measurements, particularly in fish,
do dominate the radiation exposure, meaning the dose from Po-210 is larger than
the dose due to K-40 [20]. This information should not lead to a decision to avoid
eating fish, as we are exposed to Po-210 all the time as it is part of the radioactive
decay chain starting from U-238. Radioisotopes such as U-238, Th-232, or K-40
have half-lives of billion of years and can be found everywhere in our universe
resulting in some amount of radioactivity even in the smallest quantities of matter.
In addition to the gamma-ray and alpha-particle monitoring performed in the
RadWatch UC Berkeley lab, we have performed so-called neutron-activation
analysis experiments which allow us to measure trace amounts of non-radioactive
matter in our environment and food. Of specific interest are trace metals, such as
mercury or arsenic, which can be commonly found in food and fish. In keeping with
the RadWatch mission, the goal is not to make the public fearful of food or our
environment, but to make them aware of the world we are living in and to ultimately put the observation and risks of radiation in a proper context. All this
information is available online on our Berkeley Radwatch website [15].
The Institute of Resilient Communities
213