Byproducts from many industries have the potential to be used as construction materials, but some means is required to determine if the material is environmentally benign. Foundry sands are produced in many states and can be useful as in transportation projects. However, INDOT currently requires the use of the MICROTOX test to assess the potential toxicity of the sands, and this requirement is viewed as an unnecessary impediment by the producers of foundry sands and is a requirement not encountered in other states. Therefore, the goal of this project was to review current requirements for testing of recycled materials, determine the availability of MICROTOX testing, and to make recommendations concerning the continued use of MICROTOX as an assessment tool. Strictly from viewpoint of environmental protection, the inclusion of Microtox makes sense. The test has the sensitivity to detect potentially toxic agents in recycled sand that might escape chemical analysis. The test, therefore, provides a layer of assurance that otherwise would be absent. From the perspective of the foundry industry, the Microtox test is an unneeded hurdle that could potentially block the beneficial use of spent foundry sand. Cost is one consideration, but the lack of local analytical facilities for the Microtox is particularly troublesome. Our recommendation is that the Microtox test be retained by INDOT, but we suggest the following:

a) Minimize the number of samples of foundry sand that must be tested possibly by reducing the frequency of sampling and testing.

b) A consistent, readily available laboratory needs to be established to ensure rapid turn around of analyses and reduced costs. Currently, the demand is low and some dedicated equipment is needed to perform the test.

One of the potential outcomes of this project discussed during the negotiations for this project was a possible follow-up project in which we would investigate the modifications to the bioassay. This might include exploring alternatives to Microtox or simplifications of the Microtox test. We remain open to this possibility, but from the scientific point of view, such a follow-up may not be necessary. Of all the bioassays we reviewed, Microtox seemed to be the most widely used (though not for foundry sands), and we found no evidence that other bioassays were being offered routinely at commercial labs.

Report Number



Foundry sand, MIRCOTOX, toxicity, recycle, byproducts, SPR-3276

SPR Number


Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version