The LD50 of methyl methacrylate in rates is 7-10 g/kg. In comparison, the LD50 of table salt in rats is 3 g/kg. So it's not a highly toxic chemical.

It's neurotoxic, a respiratory irritant, and an eye irritant.

No, if it's injected in your bloodstream it won't immediately kill you, but if you inhale a few milligrams of vapor you'll wish you could cough up a lung.

Also, the vapors are heavier than air, so if you fall in a ditch near the hypothetical blown tank you would likely suffocate and die.

It is however highly flammable and potentially explosive when sealed in a tank, which is the main concern.