Cautious parents may want to read the label on play sand purchased for use in playgrounds and sandboxes. Some brands of play sand may contain particles that could sicken children, including silica and tremolite asbestos. Crystalline silica dust from the engineered sand is considered a hazard to respiratory health.

The material is regulated by the Occupational Safety and Health Administration in industrial settings. However, silica is present in some types of play sand. It should be noted, however, the silica is considered most dangerous when inhaled repeatedly, such as in an work environment.

Despite the fact that there are no documented cases of children becoming ill from silicosis, asbestosis, lung cancer or mesothelioma from playing in sandboxes, some parents are avoiding sandboxes, or filling them with premium play sand guaranteed not to contain silica, quartz, or tremolite. Quikrete and other brands marketed as play sand have been found to contain not only crystalline silica but traces of the mineral tremolite.

Tremolite is a form of asbestos. In the state of California, bags of play sand are required to be sold with a warning label that states that the product has the potential "to cause cancer, birth defects and reproductive harm." Quikrete recommends that parents keep the sand damp in order to minimize the amount of airborne particles.

For parents who are concerned about the presence of tremolite and other potential hazards in play sand, here are two options for purchasing premium sand:

• Safe Sand, (415) 971-1776, is tremolite-and silica-free. Cost: $60 for a 50-pound box.

• Sandtastik Classic Play Sand contains no silica, quartz or tremolite. It is sold on amazon.com in 25-pound boxes for $21.92. Call (905) 734-7340 for more information.