UC Berkeley Nuclear Engineering Air Monitoring Station for food, water, air
Berkeley Radiological Air and Water Monitoring Team
Food Chain Testing
Food Chain Sampling Results (grass, spinach, etc.)
Tap Water Sampling
Milk Sampling
Rain Water Sampling
Strawberry Creek Run Off Results
Description of Water Collection Experimental Setup
Air Sampling
Description of Air System A Experimental Setup
Description of Air System B Experimental Setup
Questions and Feedback
Results Log
4/6 (7:30pm): Air measurements have been updated through 4/4. The uptick observed on 4/3 in all isotopes has not lasted -- the levels have decreased for all isotopes.
4/6 (6:20pm): Our first food chain tests are now posted. So far, we have measured spinach, cilantro, grass, and mushrooms. We have detected I-131, Cs-134, and Cs-137 in these samples, but the levels are very low -- consuming 403 kg of spinach could give you a radiation dose equivalent to a roundtrip flight from San Francisco to Washington, DC. Not all isotopes are present in all samples, and the levels vary widely.
4/6 (1:00pm): The new milk results are now posted. Iodine-131 is detected at lower levels than previously measured, but Cs-134 and Cs-137 are now being detected as well. We are interested in watching these trends in the coming days, so we will continue monitoring the milk levels.
Thanks for everyone's patience as we set up and calibrated a new liquid testing station using a germanium detector loaned to us by ORTEC/AMETEK.
Creek water and tap water measurements were also updated. No radioisotopes are detected other than natural background.
4/5 (9:25am):
Response to some misleading claims about our measurements
Some claims have been made recently that our data shows that Bay Area water exceeds EPA regulations by a factor of 181 -- sometimes this has been reported as 18,100% higher, or erroneously as a factor of 18,100 higher. This claim is misleading. Specifically, the reports refer to the I-131 activity of 20.1 Bq/L measured in rainwater on 3/23. The EPA limit for I-131 is 3 pCi/L, or 0.111 Bq/L. There are a number of things wrong with this claim.
First, the measurement we made was of rainwater, not drinking water, so the drinking water limit does not apply. We instead should be discussing tap water, in which we detected a small amount of I-131 (0.024 Bq/L). This is a factor of almost 1,000 below the rainwater measurement and a factor of 4.6 below the EPA limit.
It should also be noted that the EPA limit assumes the water is ingested over the course of an entire year. That is, someone drinking 3 pCi/L water for an entire year would reach the EPA dose limit of 4 millirem, which is a very small dose. The tap water measurement of 0.024 Bq/L on 3/29 is our only detection of I-131; on subsequent days it could not be detected, probably due to the radioactive decay of I-131. So this tap water could have been ingested for at most 1 day, giving the public a dose 365 times smaller than if one assumes an entire year of ingestion. That means the tap water is effectively a factor of 1,700 below the EPA limit.
Finally, we believe that the clear decay in all isotopes shown in our air filtration measurements is an indication that water activity levels are declining at least for now.
4/4 (8:20pm): Thank you all for your participation in our public forum! In response to your feedback, we have decided to update our Frequently Asked Questions page. In particular, there has been a lot of interest in understanding radiation dose and the health effects from low radiation exposure. We have compiled answers for these topics that we hope will provide more information for the discussion. Here are the questions we have updated and addressed:
- What does radiation do to your body?
- What steps would you recommend members of the public take to avoid the radiation?
- How do your measurements compare to regulatory limits from the EPA or other government agencies?
- Is there a health risk from low doses of radiation, such as the levels you are measuring?
- What risk model do you assume in your calculations?
- Is it valid to compare doses from these radionuclides to a cross-country plane flight?
- What is total effective dose equivalent (TEDE)?
4/4 (7:45pm): Air measurements through 4/3 are now posted here. There is clearly an ongoing decay in all species, with even iodine-131 dipping very close to our minimum detectable levels.
4/4 (12:30pm): Over the weekend, another measurement of tap water was posted, showing no detectable radionuclides. In addition, creek water data was added, in which I-131 and Te-132 are seen at low levels, but Cs-137 was below the limit of detectability. We haven't had any rainfall here, so no changes have been added to the rainwater page.
Today there are a few things on the agenda: a few new air measurements from the weekend will be posted later today. We are also catching up on milk measurements and need to perform a calibration of the new system we are running to measure milk now. Lastly, we are revising our FAQ page to include some of the questions from the forum. This log will notify everyone when these updates are made.
3/31 (8:00pm): Our first preliminary tap water samples have been analyzed. The only isotope we have detected besides background is I-131, at low significance: 0.024 ± 0.014 Becquerels per liter. This level is much lower than our rain water measurements by a factor of approximately 300, and lower than our milk measurement by a factor of 30. We will be continuing measurements of tap water to confirm this result; the level is so low it is approaching the threshold of detection.
Quick updates on our other samples: Rainwater results have been updated to be current as of the last rainfall on Saturday 3/26. Air filtration will be posted this evening to be current to 3/30. A sample of milk from before Fukushima has been added to the milk sampling results.
One additional note: There was some confusion about the dating of the milk data. Yesterday we listed the date incorrectly as "Purchased on" but the date was in fact the "Best By" date. The date itself was wrong -- the sample listed yesterday as 3/25 was actually 4/4. The background sample posted today was 3/25. Apologies for any confusion.
3/30 (5:30pm): Our milk sampling results are now posted. The only isotope we have detected besides background is I-131, at 0.70 Becquerels per liter. This level is lower than our rain water measurements by a factor of approximately 10, while higher than our creek water measurements by a factor of 10. One would have to drink roughly 3,800 liters of milk to receive a radiation dose equivalent to a round-trip cross-country flight.
3/29 (11:35am): Our air results and rain water results have both been updated. The isotope amounts in both have leveled out, which means that we might not be observing a downward trend at this point. We are continuing these tests so that we can observe the eventual expected decline in activities.
3/28 (2:24pm): Latest Air and Water Results data/spectra is now posted. We note decreased levels from previous peaks. This could be due to a number of reasons to include the lack of rain in the past 48 hours to an actual lower amount of particles in the air. Note, this is not a trend unless we see a sustained reduction. We are heading into a period of high pressure in the Bay Area and the jet stream will shift away from our area and this may cause even lower readings. We continue to test run-off creek water, tap water, and milk.
3/27 (2:00pm): Strawberry Creek run off results posted. We do observe all signatures in the run off creek water, but the dilution is from ~2% for I-131 to 15% for Cs137. However, Cs137 and Te132 are just below minimum detectability for our system and the real dilution is most likely closer to 2-5%. Reservoir and tap water sampling begins next week. These activities are factors of 10 to 50 below rain water results.
3/26 (6:20pm): Rain water sample results posted for 3/24 - 3/25. I-131 and Te-132 activities are lower than previously observed (3.12 and 0.27 Bq/L resp.) while Cs137 remains near the high point at ~0.5 Bq/L.
3/26 (10:45am): Air sampling results posted for 3/22 - 3/24. We have observed correlated increasing trends in Cs-137 and I-131 with the water sampling results. Te-132 seems to have increased more in air than in the rain water. Full understanding of the these trends may not be understood for some time until we start to combine this data with other information. Levels remain extremely low, but we are maintaining a close watch on these trends.
3/26 (9:45am): Rain water results posted for the past few days. Delay was due to testing of new data analysis chain script that will make posting results more efficient. We have observed a sharp up-tick in Cs-137 levels from around 0.2 Bg/L to 0.55 Bq/L. I-131 had a sharp rise on 3/23 of I-131 concentration from 6 Bq/L to 20 Bq/L. I-131 levels returned to 6 Bq/L on 3/24. Reasons for the I-131 spike is still unknown. Te-132 and I-132 levels remain relatively constant.
3/24 (2:40pm): Our new air sampling results are now posted. These results should be considered preliminary because we are trying to learn more about the efficiency of our 0.3 micron HEPA filters for capturing the particles of interest (we have assumed 100% efficiency for our current calculations). We thank everyone for their patience as we worked to ensure we had the correct calibration for these measurements. According to our measurements, the exposure to the public is very low -- at the highest levels we measured, breathing the air for 2,000 years would increase one's radiation dose by the same amount received by taking a cross-country airplane flight.
3/23 (2:00pm): Our rainwater data has been revised to account for the half-lives of the different isotopes we are measuring. This has led to slight increases in our previously posted activity levels. Details on the correction can be found here.
3/23 (9:00am): Rain water sampling results from 3/20 are posted. A decrease in the I-131 and Te-132 activity is noted. We expect Te-132 to decay by 1/2 every 3 days and I-131 to decay by 1/2 every 8 days. Cs-137 activity remains extremely low and constant. Air samples for the last 3 days will be posted today as we have calibrated our system. Estimated limits of detectability will also be posted today for both water and air sampling systems.
3/22 (3:05pm): Rain water sampling results from the evening of 3/19-3/20 are now posted. We continue to observe elevated levels of radioisotopes originating from the Japanese reactors. Some trends in activity are starting to emerge, such as a slow increase in the activity of I131, and a decrease and then increase in the activity of Te132. Cs137 activity may be constant. We will continue to monitor these trends. Our measured activity levels remain extremely low and exposure to the public is insignificant.
3/21 (12:35pm): Rain water sampling results for precipitation from 3/19 10:15am to 9:45pm are posted. Slight increase in activities are noted which may be due to many reasons from actual increase from Japan to differing atmospheric chemistry effects. Activity levels remain extremely low and exposure to the public is insignificant.
3/20 (4:15pm): Rain water results show trace levels of radioactive iodine (I131,I132), cesium (Cs134, Cs137), and tellurium (Te132). The amounts show that the activity we are observing originated from any of the three operating reactors that was shut down since I-131 and Te132 half-lives are less than 10 days and the spent fuel from unit 4 had not operated for > 130 days. The calculated exposure to the public is so low that the consuming of ~500 liters of this water would only increase dose by the same amount received by taking a cross-country airplane flight.
3/19 (8:37 pm) Initial analysis of first rain water sample has been completed. Peer review of concentration amounts and radioactivity is in progress. We expect to post results of multiple samples tomorrow. We apologize for the delay.
3/19 (10:34am): Rain fall from 3/17-2pm to 3/18-12:15pm. Preliminary results show trace amounts of radioactive iodine (I131, I132), cesium (Cs137, Cs134), and tellurium (Te132) which are not naturally occurring elements and are assumed to originate from the Fukushima nuclear site. In context, we also see Be-7 (cosmogenically produced) and Pb-212 (radon daughter) which are naturally occurring isotopes that also show up normally in rain water. Preliminary analysis show levels remain well below that which would cause health effects. We are currently awaiting better calibration of our detector system to publish amounts.
3/18: Due to the rainfall overnight and throughout the day, we expect an amount of "scrubbing" of the atmosphere as particles attach to rain drops. We have collected many liters of rainwater and are currently shifting our focus to sampling and testing the rainwater. Rainwater samples taken today will be counted overnight with results to be posted tomorrow morning. In addition, we are increasing our flow rate for air sampling and will not post air sampling results until Sunday night. However, due to the expected moderate levels of precipitation over the weekend we expect greater sensitivity within the rainwater samples.
The UC Berkeley Department of Nuclear Engineering is currently performing measurements to detect a potential increase in radiation here in Berkeley that could be associated with the release of radioactive materials in Japan. We perform this measurement by sampling air flowing through a particle filter mounted at the top of Etcheverry Hall. We first calibrated the monitor to account for normal background radiation levels. After a period of 8-12 hours of particle collection, we take the filter down to our counting station in our laboratory and, using highly sensitive detection instruments, can determine the concentration of target radioactive elements within the air sample collected by counting gamma-ray photons emitted. This is to determine if any radiation signatures are present above normal background radiation levels.
The detection instruments we are using are not only able to measure the amount of radiation in the sample, but also its energy. More specifically, we measure gamma rays and their energies in our detector, which provides a unique fingerprint of a specific radioisotope. By measuring the energy of the gamma rays with high precision, we can not only determine the amount of radiation due to a specific radioisotope, but we can distinguish it from the natural background radiation we measure as well.
For example, we can measure gamma rays from isotopes of Cesium (Cs) such as Cs-134 or Cs-137, Iodine (e.g. I-131), or Tellurium (e.g. Te-132), which we would expect to see from the release due to the fission products in Japan.
It is important to realize that all because we can detect radiation does not mean it is harmful. Our instruments are so sensitive that we can measure radiation far below the levels of the natural background radiation we live in day to day. For example, even if we are able to observe a tens of counts per hour of I-131 or Cs-137, we have to compare that to a natural background radiation level of > 300000 counts per hour when expressed in these terms. Therefore, even if we were able to observe these small amounts of radiation, it will only lead to a very small increase in the radiation we are exposed to due to the natural radiation and will have no measurable health effect.
We express the biological effect of radiation in terms of doses and dose rates expressed for example in terms of millirem (mrem) or milli-Sievert (mSv) per hour, day, or year. One millisievert is equivalent to 100 millirems. The average dose of a person living in the U.S. is about 620 mrem (6.2 mSv) per year. This can be broken down into about 300 mrem per year due to natural background, such as radon and ultraviolet rays from the sun, and 320 mrem per year due to artificial exposures, such as X-rays or Computed Tomography (CT) scans. One Chest-CT scan produces about a 1,000 mrem dose of radiation exposure, or about three times the level due to just the natural exposure. The radiation levels we expect to measure due to the events in Japan will be 1,000 times smaller than the natural levels of background radiation.
source: MIT NSE Nuclear Information Hub
The maximum measured dose rate at the Fukushima plant has been reported at 11.4 mSv/hr (source and plots) which puts the dose in one hour to be near a full-body CT scan and one-fifth the annual US dose limit for US radiation workers. No health effects have been proven below the 50mSv per year level.
We began the air sampling at 6pm, Wednesday March 16, 2011 and moved the filter to our counting lab at 9 a.m. Thursday, March 17. The chart above presents our first and preliminary results.
The "data" link for each measurement leads to a so-called energy spectrum obtained with our detector, which is a high-purity germanium semiconductor detector. Indicated are features and lines reflecting background radiation from primordial materials such as potassium, thorium and uranium. The number of counts within the various peak regions will be tabulated and compared to normal background to determine if the filter paper contains radioactive materials. What is also indicated are regions where we expect to see specific lines from materials and specific radioisotopes that could be associated with the release of radioactive materials in Japan.