Based on experiments using animals subjected to single and multiple inhalatory, oral and skincoating dosages, and which are supported by mathematical and analogical methods, the separate permissible standard for concentrations of industrial dibutylphthalate heated above 140C is 0.001 milligrams per liter of atmosphere. The toxicity of dibutylphthalate depends upon the modality of its introduction to the organism. Most toxic are its fumes heated above 140C which penetrate and consume the lungs. The substance is weakly toxic in oral application. It does not possess skin absorptive capability. Dibutylphthalate possesses a highly cumulative effect in inhalation and ingestion. The cumulative coefficient falls just short of one, which explains the hypersensitivity associated with it.