Not to be "short" in my reply, but there have been several great discussions on this subject. Tap the "search" function in the menu listed just under the header "AWS Online Forum". Type "tungsten safety" and read the post "2% thoriated...radioactive?" by Stephan (our guru from Germany).

Stephan provides in-depth information and discussions about many aspects of welding that are well worth the time to read them. Speaking of which, we haven't heard from Stephan for some time.

Best regards - Al 

Although I've never used them, I've heard that just about anything is better than pure tungsten, in most situations.
I too am a hobbyist, and found that while my local supplier didn't have a good lanthanated selection, eBay had 10 packs for prices similar to 2 sticks locally.
As for the radiation issue . . . I really don't think there is an issue with handling the rods, but I wouldn't get near the dust.  And with the lanthanated prices being comparable to the thoriated online, it was an easy choice for me.  If you had a wet grinder, or some tungsten grinder with dust collection, there's probably no hazard, but for a hobbyist, that kind of stuff is out of reach, and unnecessary.  Since I've only got lanthanated and zirconated electrodes, I just keep a zirconium-carbide (blue) belt sander belt dedicated for tungsten grinding.  I've tried the chemical stuff for pointing, and don't like it.

Now, for aluminum, you might like zirconated electrodes more.  They're supposed to perform better for A/C, and resist balling more.  Almost always a better choice for A/C than pure.  I personally like my lanthanated electrodes for aluminum, in 1.6mm, up to around 75A (if I recall correctly), and use zirconated in 2.4mm if I need more heat.
The lanthanated is still better than pure for aluminum (at least, on my inverter machine).
So, you considering thorium for working with steel?  Yeah, pure tungsten won't be great here.
Supposedly, ceriated tungstens are easier to start an maintain an arc under low currents (think thin sheet), so probably not the best choice for 1/4"
Lanthanated have just about the same properties of thoriated, and are useful over the widest range of situations.

If you go to www.diamondground.com you can free samples of "tri-mix tungsten". These are a non radioactive electrode that is suppose to arc starts equal to that of thoriated.
I figure better safe than sorry. I also heard that if you use thoriated in a tungsten grinder that most manufacturers will not work on them due to the contamination of dust particles that get trapped inside. Not sure if this is true or not but sound feasable.

I believe the caution pertains to particulate matter.

Dear Sir
Thorium is the most abundant radioactive element on Earth.  It has a biological half live of 15 years.  Therefore if
you ingest Thorium, half of it will still be present in your body after 15 years.  It has a tendency to end up in the
liver, causing liver damage.  Wash your hands before eating and after handling Thoriated Tungsten, but then again I'd
recomment that after handling any heavy metal.  Thorium does several things associated with GTAW electrodes.  It ionizes the shielding gas making it easier to produce a strike.  It also raises the melting temperature of the tungsten as an alloy.  It also makes the electrode more risistive to contamination (dipping.  Radioactive speaking,
the amount of radioactive exposure is extremely low.  I used a Ludlum Pancake counter on (10)seven inch long, 3/32,
2% thorium tungsten GTAW rods and got 250 X 10 counts per minute.  whole body expossure was calculated to be
9.1 X 10-6 millirem/hr.  That's extremely low.  Thorium does produce Alphas and gamma rays.  It's not as bad as it
sounds.  Radiation is part of our lives.  Cosmis rays from space bombard our Earth 24/7.  Most TVs produce X-rays.
Your microwave oven produces microwaves.  Your smoke detector also produces some radiation.  Michigan has radon gas
in the soil.  For more information on GTAW rods there is a web page that might be helpful.

Dan Pendell

http://www.orau.org/PTP/collection/consumer%20products/weldingrod.htm