A Canadian high-school student is reported to have found that some kelp from supermarkets is radioactive beyond safe limits.

“Some of the kelp that I found was higher than what the International Atomic Energy Agency sets as radioactive contamination, which is 1,450 counts over a 10-minute period,” she said. “Some of my samples came up as 1,700 or 1,800.”

Are the claims made in here valid, particularly about the counts per minute and the levels being higher than the International Atomic Energy Agency standards?

I'm not putting much stock in it since its a high school project, and the findings of the project itself i have yet to find.

  • 2
    Some of the statements seem a bit of a stretch. It's mentioned that the kelp that was bought from China, not saying exactly where. Even though it's described as "radioactive contamination", it doesn't describe what kind of contamination is involved. (Iodine 131 or cesium?) And she measured it as "counts", and not in sieverts or becquerels. Although she used a $600 Geiger counter, the brand or model isn't mentioned, at least not in the article listed.
    – Velda
    Apr 5, 2014 at 22:22
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    Like @Velda has mentioned, there are many details missing. In this case, it's hard to debunk or confirm a vague claim like this. Radiation exists everywhere, so it'd be useful to know what levels she found, where, how, etc.
    – Alenanno
    Apr 5, 2014 at 23:38
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    Are you asking us to verify whether she found high levels of radiation in some fish in a store? The article does not claim, and she does not claim, that anything she observed was caused by Fukushima.
    – user5582
    Apr 6, 2014 at 3:40
  • @Articuno (Sarcasm) no radiation occurs naturally, ever, so any radiation we detect must be because of Fukushima Dai-ichi. (Sarcasm off) If the article doesn't explicitly state that the radiation is caused by Fukushima Dai-ichi, it heavily implies it.
    – Golden Cuy
    Apr 6, 2014 at 8:26
  • I agree with @Andrew Grimm that the article heavily implies a connection with Fukushima. The motivation of the study seems to be that she was shocked to discover that, in the wake of the 2011 Fukushima nuclear disaster in Japan, the Canadian Food Inspection Agency (CFIA) stopped testing imported foods for radiation in 2012. It would be nice to find a report of her study, the article does not talk about the methodology at all and only vaguely reports the results.
    – nico
    Apr 6, 2014 at 14:38

1 Answer 1


First, the limit for foodstuffs of Cs-134 and Cs-137 is 1,000 Becquerels per kilogram according to the linked page.

The student (or the reporter) says that the IEAE limits are "1,450 counts in 10 minutes" (that seems a strange unit to me), which works out at 0.4027777 counts per second, or 0.4 becquerels. Thus, for her to claim that as the limit, she must be measuring 2.5 tonnes of seaweed!

However, a bit more searching turned up this document from Japan - on page 3 it says:

ICRP : alpha emitters 0.37 Bq/cm2 : beta and gamma emitters 3.7 Bq/cm2

JAERI : alpha emitters 0.4 Bq/ cm2 : beta and gamma emitters 4.0 Bq/ cm2

So, we have our 0.4 Bq figure, perhaps, but per square centimetre, but both Cs's are gamma emitters...

To conclude, I can only say that I suspect she has made some sort of false assumption or misreading of nuclear contamination data somewhere along the way.

[I'm also exceptionally suspicious of the seaweed being from China - who knows what other pollutants might be in that]

UPDATE: I believe this is a better link that includes a photo of her Geiger counter, which is a bog-standard one, not a specialised food-measuring one. She also says:

Radioactivity is measured in becquerels (Bq), and 0.5 Bq per square centimetre is widely considered an actionable level of contamination.

Delacruz said one Bq is equivalent to 1,450 counts over a 10-minute period, and many of her samples tested well over this amount.

There we go. One Bq is one count per second, and last time I checked there were 600, not 1,450 seconds in 10 minutes. Furthermore, she is using a surface contamination figure, as I suspected, so I wonder if the experimental procedure was to cut out a 1 cm square of seaweed and sit it on top of the detector for ten minutes?

My updated conclusion: yes, false assumptions leading to a meaningless experiment. Junk. Here's a detailed description of how to measure surface contamination properly.

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