Aggregate means a mixture of rocks, pebbles, sand, or similar hard, inert materials used for such purposes as construction, erosion control, road-building, or making of concrete or mortar. Asbestos means any of the following group of minerals: actinolite, amosite, anthophyllite, chrysotile, crocidolite, or tremolite. The use of aggregate containing evidence of asbestos content greater than one hundred parts per million by volume is prohibited for any purpose. Each supplier of aggregate in this County shall be conclusively presumed to warrant it to be free of asbestos-bearing content greater than one hundred parts per million by volume.