Diisocyanates Are Not the Leading Cause of Occupational Asthma

Diisocyanates are among chemicals known to cause asthma in the workplace, however the incidence of diisocyanate-related asthma has been decreasing. Despite the fact that diisocyanates do not rank as the leading cause, nor in the top 10 leading causes, of occupational asthma, some articles continue to reference old data. Recent data show a consistent picture of a decline in asthma rates associated with diisocyanates over the last decade even as production rates of diisocyanates have increased. The reduction in diisocyanate-related occupational asthma is primarily due to a variety of industry product stewardship activities, including education and training, enhanced worker awareness, improved work practices, use of less volatile diisocyanate forms (e.g. pre-polymers), improved engineering controls (e.g., containment and/or ventilation) better medical surveillance programs, minimization of peak exposures, and continuing emphasis on compliance with existing exposure standards. These product stewardship efforts are key to further reductions in cases.

decline in asthma rates

According to the NIOSH Work-Related Lung Disease Surveillance System (eWoRLD), in the four U.S. states surveyed (California, Massachusetts, Michigan, and New York) the most recent work-related asthma statistics from 2009-2014 indicate that diisocyanates are not in the top ten categories nor the top 20 exposure agents  (less than 1.0% of work-related asthma cases).

Other national data collection programs on worker exposure and disease incidence reinforce these findings, showing a reduction of diisocyanate-related occupational asthma cases over the last decade in Finland, Ontario, Belgium, France, and the United Kingdom, even as production and use of diisocyanates increase around the world.


Take a look and download the following product stewardship resources related to occupational asthma and diisocyanates:

Asthma in the General Population

There is no scientific consensus on the causation for the increase of asthma in the general population. A large majority of people with asthma have allergies to airborne substances such as tree pollen, grass pollen, weed pollens, mold, animal dander, dust mites, and cockroach particles. Such allergens can act as triggers for asthmatic attacks. The EPA advises that the most common indoor asthma triggers include secondhand tobacco smoke, dust mites, mold, cockroaches and other pests, household pets, and combustion byproducts.

An exposure potential must exist in order for any substance to contribute to asthma rates in the general population. In regards to diisocyanates, it is important to understand that fully cured polyurethane products do not expose adults or children to diisocyanates in everyday life. EPA acknowledges that “cured” polyurethane products are considered “inert” with no exposure potential under intended use.

A study investigated emission and migration from consumer products such as polyurethane foam and diisocyanates were not detected (Vangronsveld, E., Berckmans, S., Spence, M., 2012. Ann Occ Hyg. Measurement of Toluene Diisocyanate (TDI) emission to air and migration to a surface from flexible polyurethane foam.)

In a North Carolina Department of Health and Human Services (NCDHHS) and  ATSDR TDI study, data were collected from ten NC communities in four counties. Half were communities near facilities with reported TDI emissions (target areas) and half were communities where no TDI emissions were reported (comparison areas). State and federal researchers concluded, “We did not find a scientific connection between respiratory problems and exposure to TDI … Overall, we did not find that people living near the plants that emit TDI have recent or current exposure to TDI at levels of health concern.” The full TDI Community Health Report can be found online at: https://epi.dph.ncdhhs.gov/oee/tdi/TDICommunityHealthReport.pdf.

The EPA initiated a School Air Monitoring Project that monitored the air in 22 states around 62 schools located near industrial facilities or in urban areas. Seven schools in six states were selected for diisocyanates air monitoring. The EPA analysis results concluded that diisocyanates were non-detectable, therefore, if present at all, they were well below levels of concern. More information can be found on the EPA website: https://www3.epa.gov/air/sat/.


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