Firstly, what is toxicity?
Generally speaking, it is a measure of how much a substance can damage an organism, or a specific part of an organism, such as an individual organ.
In this respect, lamp oil can be considered very toxic, but only under very specific circumsatances and to certian individuals.
Lamp oil is an aspirant, which means that should it enter the lungs it can cause serious damage. However, it can only get into the lungs should someone drink it, regurgitate it, and breathe in the fumes! Even then, the damage caused is only likely to be serious to children under the age of three, who clearly should be allowed nowhere near any sort of chemicals.
If an adult drinks paraffin they would probably need to drink a litre to suffer any ill effects!
Very smal amounts can be hazardous to small children so it is very important they are not allowed near it