Safety is the state of being "safe" (from French sauf), the condition of being protected from harm or other non-desirable outcomes. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk.
There must be ever present in our minds the fundamental truth that in a republic such as ours the only safety is to stand neither for nor against any man because he is rich or because he is poor, because he is engaged in one occupation or another, because he works with his brains or because he works with his hands.
To understand changes observed in the aerosol layer of the stratosphere, scientists use remote sensing to collect relevant data. EU funded scientists are now 4D modelling aerosol formation and transport, in particular after volcanic eruptions.