During recent decades the industrial use of isocyanates has expanded enormously due to the huge product palette with a variety of different properties. As opposed to the fast technical development, there is a delay in the formulation of respective occupational health and safety regulations. Adverse health effects of isocyanates are mainly due to inhalative exposure. In addition, cutaneous contact causes toxic as well as allergic reactions. Oligomeric and polymeric isocyanates that are mostly used in the industry are only regulated in the Technical Rules for Hazardous Substances 430 (TRGS 430), but not by the mandatory occupational medical surveillance directive (Arbeitsmedizinische Vorsorgeverordnung). Although the TRGS 430 facilitates risk assessment (e. g., the aerosol penetration factor is related to the size of aerosols; only the acute irritative effect of oligomeric and polymeric isocyanates as shown in animal studies is taken into consideration in the case of defining a so-called evaluation factor), so far this new regulation has not yet been implemented in practice according to our own findings.