Radioactivity is confusing at best.
The contaminant of concern according to CRIIRAD is Iodine 131. I131 has a half-life of 8.02 days. The article here http://www.euractiv.com/en/health/radiation-risks-fukushima-longer-negligible-news-503947 discusses level of a risky dose as:
"According to the directive, the impact of nuclear activity can be considered negligible if doses of radiation do not exceed ten micro sieverts (mSv) per year. Beyond this value, possible measures should be considered to reduce exposure, it says.
While radioactive iodine-131 is mostly present in the air in the form of gas, CRIIRAD notes that in the case of the Fukushima fallout, the main issue is to limit ingestion of iodine-131.
CRIIRAD notes that the amount of iodine-131 capable of delivering a dose of 10 mSv varies greatly depending on the age of consumers. Children up to two years old are the most vulnerable and ingestion of 50 becquerel (Bq) is enough to deliver to the body a dose of 10 mSv, according to the institute.
If the foods (leafy vegetables, milk etc.) contain between one and 10 Bq per kg or more, it is possible that the reference level of 10 mSv may be exceeded within two to three weeks, the institute added.
Radioactive iodine-131 values measured by the French Institute for Radiological Protection and Nuclear Safety (IRSN) in recent days show the following, varying levels of contamination: 0.08 Bq/kg in salad, spinach and leeks in Aix-en-Provence, 0.17 Bq per litre in milk in Lourdes and 2.1 Bq per litre in goats milk in Clansayes."
So in summation:
10mSv/year is bad
50 bq can deliver a body dose of 10 mSv in children
1-10 bq/kg food can deliver the reference value of 10 mSv (thats a huge range 1-10)
It is important to note that the relationship between bequerels and sieverts is extrememly hard to understand - here's some info (light reading):
(side note I HATE citing wikipedia but it's the best non-textbook resource for a quick look - please do not quote wiki as it is not properly peer reviewed!)
You can honestly spend hours, days, years, a lifetime coming to understand radioactivity - and the truth as I believe it is that there are not that many people out there that truly understand how radioactive materials affect our world and affect us.
Be cautious and well informed. Pay attention to the news reports - but ALWAYS read the accompanying documentation and try to tease out the important tidbits of info.
Sorry that this isn't super clear - but thats kind of the point. The news media can barely get straight-forward information correct - so please read carefully and research often.