Doctors express “deep concern” about Fukushima impacts on Canada, Vancouver Observer, April 1, 2011:

[Emphasis Added]

… “Physicians for Global Survival  is deeply concerned about the long term health of populations exposed due to accidental or planned releases of radioactivity from Fukushima…”

“The US uses a system of RadNet monitors,” the release said, adding that:

Radiation monitors are “point source” monitors, meaning that the radioactive element or ray must actually strike the monitor to be measured.  They are unlikely to detect radiation as close as twenty five feet above or beside them.  Apparently there are only about 125 of these monitors for the entire continental United States, Hawaii and Alaska. …

“News reports mention Iodine-131 and Cesium-137, not because they are the only radioactive elements discharged from the stricken reactors in Fukushima, but because they are the easiest to detect and measure,” the report added.  …

Alpha and beta radioactivity are more difficult to measure.  RadNet measures them by  “vacuuming” the air and passing it through a filter.  The amount on the filter is then measured.  Sources are contradictory about amount of time between detection, measurement and speed at which the public can be informed.

Read the report here.