If the scant residual amount of oxalic acid remaining on the inside of well rinsed cookware concerns you, you might want to consider cutting a lot of vegetables out of your diet, too.
Oxalic acid/100g food
Parsley (1.7 g)
Chives (1.48 g)
Purslane (1.31 g)
Cassava (1.26 g)
Amaranth (1.09 g)
Spinach (0.97 g)
Beet leaves (0.61 g)
Carrot (0.5 g)
Radish (0.48 g)
Collards (0.45 g)
Beans, snap (0.36 g)
Brussels sprouts (0.36 g)
Garlic (0.36 g)
Lettuce (0.33 g)
Watercress (0.31 g)
Sweet potato (0.24 g)
Chicory (0.21 g)
Turnip (0.21 g)
Broccoli (0.19 g)
Celery (0.19 g)
Eggplant (0.19 g)
Cauliflower (0.15 g)
Asparagus (0.13 g)
Endive (0.11 g)
Cabbage (0.1 g)
Okra (0.05 g)
Onion (0.05 g)
Pea (0.05 g)
Tomato (0.05 g)
Turnip greens (0.05 g)
Parsnip (0.04 g)
Pepper (0.04 g)
Rutabaga (0.03 g)
Cucumbers (0.02 g)
Kale (0.02 g)
Squash (0.02 g)
Coriander (0.01 g)