I agree with Cas,
Here's some info, but do stay away from play sand. Your health ain't worth the savings!
Warning: Abrasive blasting with sand containing crystalline silica can cause serious or fatal respiratory disease. Exposure to crystalline silica may cause silicosis (a serious lung disease), cancer and death. Exposure to aluminum oxide (a dust generated from material removing processes) can result in eye, skin and breathing irritation. Always use a NIOSH (National Institute for Occupational Safety and Health) approved respirator and safety goggles. Avoid skin exposure. Proper ventilation in the work area is required. Read and understand the 10 recommended measures below to reduce crystalline silica exposures in the workplace and prevent silicosis and silicosis related deaths.