Risk of isocyanate-induced asthma: Exposure, biomonitoring, and results from epidemiological studies

The number of workers that are exposed to isocyanates has increased due to the broad modes of application. The review investigates whether a valid quantitative risk assessment regarding isocyanate-induced asthma is possible on the basis of the available data from epidemiological studies. For this purpose isocyanate exposure in the workplace, hazards due to isocyanates focussing on epidemiological studies on changes in lung function due to isocyanates, and relevant threshold limit values in Germany are presented. Epidemiological studies have contributed to identifying the respiratory diseases due to isocyanates. Risk quantification is hampered by missing individual measurements and analytical problems in the quantification of all isocyanates in all states of aggregation. Apart from inhalation, dermal exposure might induce isocyanate asthma. It cannot be excluded that TDI, MDI, and polymeric MDI are carcinogenic to humans. Based on further development of methods for the quantification of air concentrations and biomonitoring for the estimation of individual exposure including dermal pathways, additional epidemiological studies on changes in lung function, and development of cancer among exposed workers including the study of dose-response-relationships are needed. Apart from research projects, preventive measures have to be enforced in order to protect the exposed workers.