No, I don't really do a lot of grimy work on a daily basis but I do put my hands in the water a lot because I do lots of house chores that require water like dish washing. And I have started limiting water contact from my hands since too much water use can strip your hands of moisture and make it dry and flaky which is what my hands have been experiencing. I have been using makeshift gloves i crafted from plastic grocery bags when washing dishes because we don't have any rubber/latex gloves at home at the moment. This information is probably irrelevant though since water is used as a cleanser so it isn't really known for causing build up. But it could be a possible cause and also I touch a lot of oils and butters so maybe that's what's been accumulating under my nails but im not really sure. I do wash under my nails with a tooth brush and soap but the white stuff never washes off.