I'm sure the dust from dry media is just loaded with lead.
You are Absolutely Correct on this item. A cloud of lead dust is suspended for a coupla feet above a vibrating tumbler.
ALWAYS keep the lid on w/dry media.
BTW, it's a good idea to get tested for lead every year w/your annual physical. Hardly costs anything extra, and establishes a baseline for yourself, should you ever need it.
And--assuming your BLL is low (under 10micrograms/deciliter)--it will provide a certain Peace of Mind.