Chemical agent resistant coatings (CARC) contain the harmful compound hexamethylene diisocyanate (HDI). RIVM National Institute for Public Health and the Environment has investigated HDI and the effects of occupational exposure to HDI on health.

CARC is a type of paint, a top coating that is applied as the final paint layer on a surface. CARC is also applied as a top coating on the metal surfaces of vehicles because it has the property that biological and chemical agents are hardly able to penetrate a CARC layer.
One specific component of the coating has harmful properties, namely hexamethylene diisocyanate or HDI for short. During maintenance work, employees can be exposed to HDI, which can harm their health. RIVM National Institute for Public Health and the Environment investigated which diseases may be linked to HDI. 

Illness caused by HDI

HDI has been linked to various health conditions. Inhalation of HDI can result in complaints in the eyes, nose and lungs. These symptoms can be caused by irritation or allergy. This can lead to for example itching or weeping eyes (conjunctivitis) or a runny nose (rhinitis). HDI can also trigger asthma, a condition in which people are affected by shortness of breath or difficulty breathing. 
Skin complaints can arise if HDI comes into contact with the skin, which may redden, become itchy or swell up. This condition is referred to as contact eczema and it can be caused by irritation or allergy. 
HDI can cause the lung condition called hypersensitivity pneumonitis (previously also known as extrinsic allergic alveolitis or EAA). This is a rare pulmonary condition that is caused by inflammation. 
There are no indications that HDI can cause cancer.

Occupational exposure to HDI

The risk of becoming ill becomes greater as an employee is in contact with HDI more, more often and for longer. In particular, workers who apply the CARC layer to the equipment can come into contact with HDI. They can breathe in particles that are released during spraying and their skin can come into contact with it too. Employees who apply the top coat with rollers and brushes come into contact with it to a lesser extent. This also applies to employees who process the painted surface, for instance by sanding, sandblasting and welding. Employees whose task is for example to check the sprayed work (such as quality inspectors) can come into contact with the substance indirectly.