This paragraph I found online from a play sand manufacturer helped me to put things in perspective:
"The sand typically used for sandboxes or playgrounds is granular in nature and is non-respirable. Granular sand sizes are expressed by the term "Mesh". Play sand, including that sold by U.S. Silica Company, is typically a 70-Mesh product, which is equivalent to 212 micrometers, well above the respirable dust size. And, while we have never measured "exposures" in a sandbox, it is only reasonable to conclude that sandbox "exposures" (if they exist at all) are far below those experienced in industrial setting, because (1) play sand is not respirable, (2) playing in play sand does not make it respirable, (3) sandboxes are outside, (4) children do not play in sandboxes 40 hours a week, 50 weeks a year, for 20 or more years. The scientific studies to date have examined the potential adverse health effects
associated with occupational exposure to crystalline silica. Occupational exposures to crystalline silica can be experienced by workers in foundries, ceramics manufacturing facilities and other industries that use crystalline silica, and are higher than environmental or ambient exposures to silica. All the published scientific literature contains no evidence that silicosis or silica-related lung cancer occurs among people with non-occupationally related exposures at beaches, backyards, or sandboxes."