When I first started woodworking Oxalic Acid was widely used, for example if Oak components touched sash cramps during a glue up they'd likely stain and so you'd do a spot application of Oxalic Acid to cure the problem. You might wear gloves, I can't ever remember anyone using masks, and you'd work with it right at your bench.
But nowadays Oxalic Acid has fallen out of favour due to the health and safety restrictions that now surround it. One workshop I know stipulates that any use of Oxalic Acid will only be done in the spray shop in front of the extractors while being masked up, and that covers both the initial application and any subsequent sanding of the component. I guess in restoration work you don't have a choice, but for furniture making it's all too much faff. Cheaper to take precautions (like using bearers during glue ups) so the problem doesn't occur in the first place and treat any instances in sawn boards as defects to be cut out and scrapped.
Here's what the data sheets say about Oxalic Acid,
Potential Acute Health Effects:
Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (permeator), of eye contact (corrosive). Slightly hazardous in case of skin contact (corrosive). The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe over-exposure can produce lung damage, choking, unconsciousness or death. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering.
Potential Chronic Health Effects:
CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Not available. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. The substance may be toxic to kidneys, the nervous system, mucous membranes, heart, brain, skin, eyes. Repeated or prolonged exposure to the substance can produce target organs damage. Repeated exposure of the eyes to a low level of dust can produce eye irritation. Repeated skin exposure can produce local skin destruction, or dermatitis. Repeated inhalation of dust can produce varying degree of respiratory irritation or lung damage.