Electrical work during construction and retrofit projects often involves exposure to toxic dusts. One common source is welding; another is the grinding that goes with it.
Ensuring adequate ventilation is the first line of defense. If you feel the ventilation isn't adequate, tell your supervisor. If welding or grinding dust is present, use a suitable respirator so you don’t breathe the particles that ventilation doesn't remove.
Ensuring that you don't breathe toxic dusts is good, but you also need to defend against skin irritation. Rather than scratch an itch (and thus drive the toxins deeper into the skin), rinse the affected area in cold water. If possible, change clothes at the end of your shift so you don't bring the dust into your car and/or home. Transport clothes in a sealable plastic bag or similar container.
To avoid swallowing toxic dusts, don't bring food or beverages into areas where they are likely to be present.