That's the stuff I was exposed to on Tuesday.
The good news is that it appears it is extremely odorous. Worse than H2S. According to the RSC, only 0.5g were spilt, leading to concentrations on the order of 10 parts per billion. The smell was very strong in a volume of air about 10,000 cm metres. It would have been detectable over a volume possibly ten times that.
1 part per million would only have contaminated 68 cu metres under ideal conditions. Only 1/360 of a mole escaped.
This was enough though to cause people to flee the buildings because of the overpowering stench. Enough to cause rashes on some, headaches and dizziness amongst others.
The not so good news is that P(C3H7)(C2H5)(C6H5) is a relatively new molecule, and no studies have been conducted as to its toxicity. Breakdown products when exposed to air, water, and UV would include Phenol and Benzene. Carcinogens. Fortunately not dangerous at that concentration.