Why does rhenium get a pass on being radioactive? Thorium is thought of as radioactive and "dangerous" because its half life is 10 billion years.  However, most rhenium is radioactive with a half life of 40 billion years even though rhenium does have a stable isotope which comprises a minority of natural rhenium atoms.  Why don't we hear more about radioactive rhenium?
 A: So $f=62.6$% of normal Rhenium is $^{187}$Re, decaying with a half-life of 40 billion years. That give a rate $r=\ln(2)/\text{40 Gyr}=7.927448\cdot 10^{-19}$ per second. That means that the decay rate per second is $f r N_A = 298,853$ Bq/mol.
$^{232}$Th has half life 14 Gyr and gives a rate per second as 1,364,005 Bq/mol. So it is about 4.5 times more active. 
More importantly, it decays by $\alpha$ which tends to be nastier (if easier shielded) to biology than $\beta$. Also, it has a bunch of daughter isotopes that are gamma emitters and goes through radon, so they might get into the air. Rhenium just goes to osmium. Plus rhenium is rarely used, so people have not looked much at toxicity or radioactivity risks - they don't come up because rhenium rarely comes up. 
A: Thorium has the same decay energy as uranium with about 4 MeV. With 14 billion years its half live is even longer than uraniums half live of 4 billion years. That means the dose rate you get from thorium is even less than from uranium. 
I see no reason why the radioactivity of thorium could be considered dangerous. Actually it should be safe to handle without much protection.
