Case 7: Tremolite Asbestos Fibers in Children's Play Sand

tremolite in play sand
SEM micrographs of filter preparation from aqueous sedimentation sample and from glove box aerosol sample showing fibers typical of those counted in this study.
tremolite fiber with EDS spectrum
EDS spectrum of typical fiber confirming the elemental composition of tremolite.
potential aerosol fiber concentrations from play sand fiber length vs. aspect ratio
pouring play sand play sand "smoky" cloud play sand residual airborne particulates

Photographs of glove box with tyndall beam illumination taken during (top, middle) and approximately 15 minutes following (bottom) a single pouring of approx. 200g of play sand from one container to another. Note the extremely dense "smoky" cloud of fine particulates during pouring and the residual fine particulates 15 min. later.

Health hazards of asbestos fiber inhalation are well recognized. Particularly of concern with regard to long term effects are exposures occuring at a very young age. Therefore, the finding of potential and actually aerosolized asbestos fibers in the biologically hazardous size range occurring in a consumer product specifically aimed at young children initiated this study.

ABSTRACT presented at American Thoracic Society meeting in 1988 [Abraham, J.L., Cohen, K.S., Powell, B. and Merritt, C.: Analyses of Bulk and Aerosolized Asbestos Fibers from Children's Play Sand Reveal a Potential Health Hazard. Am. Rev. Resp. Dis., 137:94, 1988].

A commercially sold children's play sand released a dense cloud of "smoky" fine dust when poured into a sandbox. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) of measured aliquots of supernatant from 1 gram of untreated sand (suspended in filtered water, shaken, and allowed to settle for 5 min.) revealed approximately 100,000 to 1,000,000 long (greater than 5µm), high aspect ratio (greater than 10 to 1) tremolite asbestos fibers per gram of original sand. Many fibers exceeded 20µm length and 100 to 1 aspect ratio. Since the mass of an individual fiber is approximately 10-12 gram, the estimated mass fraction of such fibers is on the order of 1 ppm (or 0.0001%). Since such respirable fibers, if all aerosolized, could yield concentrations of 1 fiber/ml if fibers from 1 gram of sand were aerosolized in 1 m3, a simulated sand box sampling was performed in a 91,000 ml glove box. Approximately 1 cup (200g) of sand was gently sifted once or twice per minute from a height of 10cm. Standard calibrated air sampling was done, with filters counted by phase contrast microscopy (PCM) and by SEM/EDS. Up to 17 fibers/ml were found by PCM and from 1 to 6 fibers/ml by SEM (only long, high aspect ratio fibers were counted). This conservative simulated sandbox demonstrated potential exposure above even occupational limits. Samples of several other dolomitic "play sand" products contained similar, easily found tremolite asbestos fibers. Current EPA regulations require asbestos warning labels on products only if they contain greater than 1% asbestos by weight. Testing of several of these sand products by polarized light microscopy (PLM) had been reported negative, emphasizing that PLM is not sufficient to rule out the presence of asbestos fibers too thin to be counted by PLM, but easily found by SEM. It appears that current regulations and testing requirements (which do not require electron microscopy) are inadequate to protect children and other consumers from potentially hazardous asbestos fiber exposure from such products.

Historical Perspective

The results of this study were summarized in an abstract of a poster presented at the ATS meeting in 1987. This saga is posted in part for historical documentation. The manuscript reporting this investigation was submitted to JAMA but rejected. One of the documented reviewers for JAMA (AML) was also a consultant to the industry potentially affected, as well as to the Consumer Product Safety Commission (CPSC). Dr. Yamate, a scientist at IITRI, who did extensive analyses for the CPSC, refused to comment further or to testify at the CPSC hearings held on this issue. His results in his reports were similar to those from our lab. When the lead investigator (JLA) arranged an informal visit to the CPSC to share his observations on the Play Sand, he found at that meeting, in addition to the CPSC staff, two additional scientists: Dr. Arthur Langer (present as a CPSC consultant) and Robert Glenn (a retired NIOSH scientist then working as a lobbyist for the National Stone Association). At the hearing, Dr. Langer testified on his results, which were based on analysis of only a few fibers, in contrast to the hundreds of fibers analyzed by Dr. Yamate's laboratory and ours.

Additional internal CPSC staff documents obtained through Freedom of Information Act request:

This report on Play Sand became the basis (in response to a request by Dr. Abraham) for the formation of the ATS Tremolite Committee, which reported its findings in an official ATS document [American Thoracic Society (Weill, H, Abraham, JL, Balmes, JR, et al.) Official statement. Health effects of tremolite. Am Rev. Respir Dis, 142:1453-1458, 1990]. Curiously, the section of the report describing the Play sand analytical findings from our lab, which were replicated independently by two other ATS Committee member's laboratories (A. Churg and P. Sebastien) was deleted from the final published report by the ATS Board -- ostensibly because the results had only been reported as an abstract.

As a result of all these events behind the scenes, products containing asbestos such as this Play Sand were NOT recalled by the CPSC, and remain unregulated sources of potential early childhood asbestos exposure. This does not imply that many commercially available play sands are contaminated with asbestos [this is an unknown], but that IF they are produced from a mineralogical source containing asbestos, there is no testing or regulation in place.

tremolite in play sand
tremolite fiber with EDS spectrum
potential aerosol fiber concentrations from play sand
fiber length vs. aspect ratio
pouring play sand
play sand "smoky" cloud
play sand residual airborne particulates
play sand residual airborne particulates
play sand residual airborne particulates
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