Frequently Asked Questions

What is the source of Safecast’s data?

Short answer: It is collected by SAFECAST volunteers.
Long answer: There are a number of different kinds of data represented on the SAFECAST website, including crowd sourced measurements and data released from other sources. However the official "SAFECAST data" that we reference and publish for others to use is collected by Safecast volunteers using professional-quality devices, primarily the bGeigie series that we developed. For these devices we have standardized on the same sensor, the LND7317, a 2" pancake GM tube. This is a highly sensitive piece of equipment that is used by radiation professionals all over the world, and we have tested them and are confident in their performance, and stand behind the readings taken with our devices. 
As we've grown we've achieved global reach with crowdsourced measurements from over 100 countries, representing every continent. About 90% of our data has been collected by the most active 10% of our volunteers. Consistency is extrememly important to us, and the vast majority of our data has been gathered by volunteers using the bGeigie Nano detector. We're working very hard to make the variations in the equipment used transparent, and to ensure that all the data we publish is interoperable.

What are differences in the data published by SAFECAST and official/governmental sources?

Short answer: SAFECAST data from the start has had higher resolution geographically and better consistency.
Long answer: We know from our efforts that radiation levels can vary over very short distances, so that simply crossing a street can sometimes yield dramatically different readings. Readings that have been published by official sources in most countries generally do not provide detailed geographic coverage. Official government sources often report radiation data for entire cities based on single readings. We feel this is at best too vague to be useful and at worse intentionally misleading. In the case of Japan since the Fukushima NPP accident, the government has increasingly made more informative radiation data available, but SAFECAST's data for the country provides demonstrably more detailed coverage for most areas, and is easily accessible online and through our iOS app. In particular, we have attempted to map radiation in Japan on a street by street level, with consistency in the devices we use. Finally all Safecast data is freely and openly published using a CC0 designation, in a form which makes it easy for others to generate their own visualizations and data comparisons. At present, many Japanese gov't radiation datasets can be downloaded, but many come with restrictive use agreements, while others are not easily adaptable for independent use or research.
One caveat: How measurements are taken is as important as what the measurement is. It is particularly important to know at what height readings have been taken. Official gov't agencies and many research institutions often use readings taken by devices mounted on rooftops, 10 meters above the ground or more, as well as aerial surveys. SAFECAST volunteers are instructed to take standard environmental readings as close to 1m height as possible, and almost all of the data shown on our maps will be taken from that height. However, Pointcast and Solarcast devices deployed in our fixed realtime sensor network may sometimes be mounted higher on buildings. Details regarding their placement is available on each sensor's detail page at linktext

Is Safecast an anti-nuclear activist group?

Short answer: No
Long answer: Safecast is neither anti-nuclear nor pro-nuclear - we are pro-data. Data is apolitical. Safecast was created because we identified a lack of data and realized we could help fill that gap. Our goal is to provide more information, data where none previously existed, so that people can make more informed decisions based on facts rather than the fear and speculation that comes from uninformed rumor.
One caveat: It's worth noting that data can be interpreted in different ways, and visualized to highlight or downplay different aspects. This is why in addition to our visualizations we make our raw data available for anyone to examine and interpret on their own.

Is Safecast working with the Government?

Short answer: No
Long answer: SAFECAST is independent and has successfully remained uninfluenced by politics of any kind. Because of our jealously-guarded impartiality, SAFECAST has increasingly been viewed as an entity whose information and motivations are trusted on all sides. This has allowed us to function at times as an effective "go-between" for conflicted parties, such as environmental groups and government agencies, and to lobby effectively for increased openness in the process. SAFECAST does not accept government funding, but we welcome the input of sincere and open-minded experts wherever they are found.
One caveat: SAFECAST strives to be completely transparent, and our data, device designs, and software designs are available for use by anyone, including government agencies. To the degree that this would imply that any agency doing this was becoming more like SAFECAST (as opposed to vice-versa), we'd be inclined to consider this a step in the right direction.

Are radiation readings affected by driving?

Short answer: No
Long answer: Under the radiation conditions we normally encounter, the speed of a moving car (with a geiger counter attached) does not affect the readings taken when compared against readings taken in the same area with a stationary sensor. Safecast has verified this through research collaborations with Keio, Tokyo, and Nihon Universities.
One caveat: Safecast's "bGeigie" system is mounted outside of the car so that readings are not affected by the car itself. Other groups, including the Japanese gov't, have taken mobile readings from inside vehicles, which provides shielding and blocks out a portion of the radiation. It's important to verify how readings are taken.

What kind of Geiger counter should I buy?

Short answer: Something by a “Googleable” brand name, that measures alpha, beta and gamma radiation and fits your budget and needs.
Long answer: Radiation measurement is not as simple as measuring something like temperature. It’s important that any sensor you purchase actually gives you useful information. A rule of thumb is that any device that gives only “”red/green or “safe/unsafe” feedback may not be adequate – it’s important to know more details about the measurement. It’s also worth thinking about how you will actually intend to use it. If you want to measure radiation in the air and on surfaces near you, then a Geiger counter should meet your needs. If you want to measure food or water contamination or check to see if you or your family have been irradiated, a Geiger counter is not the right kind of equipment and will not help you. We also recommend that you stay away from any company that didn’t sell geiger counters before March, 2011.
We recommend the SAFECAST bGeigie Nano, of course, which is our current workhorse design. It features GPS and data logging, and if you want to contribute radiation data to our online database then buying and building one of these kits is the easiest way.

One caveat: After the 3/11 Fukushima Daiichi event the global demand for Geiger counters skyrocketed. This resulted in both a significant backorder time from major and reputable manufactures that lasted over one year, and in an increase in the availability of less accurate or poorly constructed devices. Because of this it’s very important to make sure any device you buy is reliable.

What level of radiation is “Safe”?

Short answer: That’s hard to say.
Long answer: Unfortunately there is very little agreement within the health physics world about what is safe and what is unsafe. While there are some things that are generally agreed upon, that children and pregnant women are at greater risk for example, there is no clear level that is universally agreed to be the cut-off point between “safe” and “unsafe.” One school of thought believes that “any amount of radiation is unsafe,” while others say that while even small amounts of radiation exposure can cause damage to cells, and so to health, current guidelines adequately guard against all but the smallest risks (less than many risks people accept easily). What’s most important is being aware of what you and others are exposed to, and finding information that will help you decide if it is acceptable or not. It’s a fairly complex subject, because risk factors differ depending on age, existing health issues, exposure time, areas of exposure, etc.. Therefore risk is best gauged on an individual basis and not generalized for an entire population.
One caveat: Individual comfort levels should not be discounted, and different people will be more or less comfortable with various levels. One person’s “safe” could well be another’s “run away!”

Alpha, Beta, Gamma?

Short answer: Confusing isn’t it?
Long answer: These are the three kinds of radiation that are most commonly associated with nuclear plants. Gamma is very high energy and gamma particles can pass through walls, buildings, and people. A very high dose of gamma radiation can kill a person almost immediately. Alpha and Beta are lower energy, and can be blocked with a sheet of paper or thick clothing. Alpha and beta pose a greater risk if they are inhaled or ingested. The Cs137 that was released by Fukushima Daiichi is primarily a beta emitter which is why food contamination is such a concern.
One caveat: A lot of readings that are being published are gamma only, which Safecast doesn’t feel tells the full story.

How can I find out the radiation level near me?

Short answer: That’s why we’re here.
Long answer: The best bet from our perspective is to check out the maps we link to above. Hopefully some of these will give you useful information. If not, stay tuned or get in touch with us to see when we might be able to get data from your area.
One caveat: The world is a big place and until recently no one seemed to be concerned with mapping this kind of info, so it’s a big job. But we’re doing what we can.

Has SAFECAST found evidence of plutonium or strontium?

answer: No
Long answer: Other organizations and research groups have documented the detection of these isotopes, generally in very small traces (often at levels equal to what existed before the accident), and occasionally at much higher levels. We feel confident in assuming that these isotopes could be detected in many places in Japan and elsewhere if adequately sensitive equipment were used. But to date no samples that SAFECAST has collected and examined have contained them.
One caveat: The SAFECAST team is highly competent and experienced, but we do not have a fully-stocked isotope lab. Because of this some kinds of analysis are beyond our capability, though we have established good relationships with large labs we can occasionally call on for assistance with particularly demanding technical tasks.

Is it safe for me to visit Japan?

Short answer: Most likely.
Long answer: Parts of Fukushima are highly contaminated, but in most of the rest of the country radiation levels are no higher and sometimes even lower than in other major cities around the world. From our own measurements we can say with confidence that Tokyo and Los Angeles have similar radiation levels and that the levels in Hong Kong are even higher than those in Tokyo. One explanation for this is that Japan had lower average background radiation levels overall than many other places before March 11, 2011, so even with a measurable increase due to the accident, the levels generally still lie within the range what is normal worldwide. It’s also worth noting that air travel, especially transcontinental flights, subject passengers to elevated radiation, sometimes 20 times as much as one might experience on the ground, so it’s very likely that a short-term visitor will be exposed to more radiation on the flight to Japan than they will get the entire time they are on the ground there.
One caveat: Food measurements are still largely misunderstood, please see this post for more information about food contamination.

Did the contamination from Fukushima Daiichi spread outside of Japan?

Short answer: Yes.
Long answer: Traces of particles released by the event at Fukushima Daiichi have been found in every corner of the earth where they have been looked for. The world is a giant ecosystem and when a major contamination event takes place evidence of it can usually be found everywhere. It’s worth noting that there are also remaining global traces of previous nuclear events such as Chernobyl, Hiroshima and Nagasaki, and the widespread nuclear testing of the 1950’s and 1960’s- so much so that there is actually a market for iron and concrete produced prior to WWII for the purpose of shielding environments for isotope identification, as all materials produced after WWII are contaminated and have a higher background radiation level.
One caveat: At this point it is generally accepted by researchers that approximately 80% of the radioactive contamination from Fukushima went into the ocean, 18% into Japan, and 2% spread globally.

Are the radiation levels in Japan changing?

Short answer: Yes, they’re decreasing.
Long answer: Particularly in the first year following the accident, occasionally news of a “new hotspot” was reported in the media. In reality, for the most part these hotspots had existed (at least) since the 3/11 event but just hadn’t been detected. Since 3/11 people in Japan particularly have become much more aware of radiation and their immediate surroundings and are doing more measurements on their own, and because of this much more detailed data is being gathered, meaning that hotspots which previously may have gone unnoticed are being discovered more regularly. The major contamination from Fukushima Daiichi is Cs137, which has a 30 year half-life, and Cs134, which has a 2 year half-life. Because of this, and the effect of weathering such as rain, radiation levels have already decreased by about 60% in most affected areas. But the contamination will be a problem for decades.
One caveat: A new event involving a release of further radiation from any of the reactors at Fukushima Daiichi could result in new contamination. Additionally, the weathering referred to above doesn’t mean that contamination is disappearing, but that it is being moved wherever water flows. Most of it ends up in the ocean, but some is deposited in river and lake beds, where it may remain for a long time.

Is Fukushima Daiichi stable?

Short answer: No
Long answer: The best available evidence indicates that the melted fuel has lost enough heat that a new criticality event — a nuclear reaction which would release large amounts of radiation — is unlikely. But much is still unknown about the conditions inside the damaged reactors, and independent confirmation of published reports is often difficult to obtain. SAFECAST volunteers have visited the Daiichi plant on several occasions and our maps include data they collected.
Continuing problems of particular concern include ongoing leaks of radioactive water, the need to move spent fuel rods to safer storage, and breakdowns in the often improvised machinery put in place to maintain cooling and water purification.

One caveat: A lot of information is published by TEPCO and by gov’t agencies, but data about some important efforts and results often goes unreported. SAFECAST continues to call for independent verification of all radiation measurements.