Toxins, which are poisons produced by microorganisms or plants, are classified as 6.1 Poisons. DOT defines an infectious substance or etiologic agent as “a viable (liver) microorganism, or its toxin, that is capable of producing disease in humans.” Included in the DOT regulation are agents listed in CFR 72.3 of the regulations of the DSHS or Any other agent that causes or may cause severe, disabling, or fatal disease. Many materials shipped as infectious substances are diagnostic specimens.