synergistic effect of toxic substances 1. A state in which the combined effect of two or more substances is greater than the sum of the separate effects. 2. An effect whereby two toxic substance together have more of an impact than anticipated
toxic waste Refuse posing a significant hazard to the environment or to human health when improperly handled; includes carcinogenic, mutagenic, teratogenic or phytotoxic wastes, or wastes harmful to aquatic species, or poisonous wastes