The fully salt-water load bank dates from an earlier, less regulated and litigious era. To pass current safety legislation requires more enclosed designs.
They are no more dangerous than electrode heaters, which work on the same principle, but with plain water, or electrical immersion heaters, provided the correct precautions are used. This requires connecting the container to both ground and neutral and breaking all poles with a linked over-current circuit breaker. If in the open, safety barriers are required.