About 20 years ago , I finish sanded 600 ,that's right Six Hundred... Black Walnut pot calls for me and my dads call company - needless to say I wasn't wearing a respirator or filter and I overloaded my lungs with Walnut Dust - It took 2 months to get rid of the congestion
I'm not overly sensitive to Coco-bolo I will wear a wet T- shirt over my face if I sand or cut that stuff if a filter is not available -not taking a chance