Industrial application of moisture cure polyurea coatings: Assessing potential exposure to airborne isocyanates

The Challenge

Our client intended to apply moisture cure polyurea coating products using specialised spray equipment, and they wanted to ensure that the risk of isocyanate exposure to their workers was adequately controlled.

Isocyanates are a primary component of these products and can also be found in a number of construction products including polyurethane paints, coatings, foams, glues and flooring. Certain tasks, such as spraying, can produce very high exposure to isocyanates.

Isocyanates can affect your health in a number of ways. They can cause:

• irritation of the eyes, nose and throat
• dermatitis - for more information on the effects of dermatitis see this video, worker's story and pictures
• occupational asthma - this is a significant risk for workers spraying isocyanates

The Control of Substances Hazardous to Health (COSHH) Regulations states that employers must protect workers against the risks of isocyanates and, in Great Britain, a workplace exposure limit (WEL) of 20 µg/m³ (8-hour time weighed average) has been set.

Moisture cured polyurea coating products are formulated with a range of polymeric isocyanates and some also contain high levels (>50%) of a powdered metal to provide anticorrosion properties. Although polymeric isocyanates are less volatile than monomeric isocyanates, significant airborne levels can still be generated depending on the application method. Consequently, measuring exposure can be challenging, particularly as current biological monitoring methods only measure monomeric isocyanate and material safety data sheets may only identify polymeric species generically. Underestimates of isocyanate exposure are possible.

The Solution

In discussion with the client, a phased programme of work was agreed to ensure that they would have the relevant information to carry out a thorough risk assessment for application of the new proposed coating.

Firstly, our analytical team analysed four different coating products. Two contained high levels of a metallic powder, which was found to interfere with the analysis, so a method was developed to remove interferences. The safety data sheets only provided generic information about the isocyanate present within each sample. MDHS 25/4 methods were therefore used to characterise the specific polymeric species within the bulk samples. Confirmation that all the isocyanate (as the chemical group -NCO) was accounted for was determined by titration.

Secondly, following successful characterisation of the bulk materials, a spray booth was set up to model the client's spray application under controlled conditions, to evaluate likely exposures. The client's specialised spray equipment was used under their guidance to make the scenario as representative of real world conditions as possible.

The Outcome

For each of the four moisture cured polyurea coating products tested, airborne isocyanate was measured at levels in excess of the WEL. A significant health risk was identified not only for the person carrying out the spraying but also for those close by.

Because we used the client's own spray equipment and worked closely with them to ensure the appropriate application scenario was used, we were confident that the measurements provided an accurate assessment.

Our client was then able to review their risk assessment, consider exposure controls and assess the practicalities around application of the MCU products to ensure compliance with regulations and to protect the health of their workforce.

For more information about how we could do something similar for you, email our Sample Registration team or contact us via the enquiry form.