Is it likely that an alkyd varnish contains lead?
Most responsible countries know the hazards of using lead that my become air born causing health issues if inhaled. The surest way to know is to read the label of ingredients on the container  or any suggested warnings from the manufacturer.
Most varnishes are made with resins and some kind of solvent. Inhaling the dust when sanding or the vapor while applying it can cause health problems related mostly in the lungs. Ingesting lead is much more detrimental especially to children where it effects brain function.