Cullinan et al 1 reported six obliterative bronchiolitis (OB) cases with plausible correlation with fiberglass-reinforced plastics (FRP) fabrication. Five of them were boat builders and one worked for a cooling-tower manufacturer. Due to the complexity of the FRP-related boat building processes, the exact agent(s) and process causing OB were difficult to determine. The cooling-tower manufacturing had a simpler manufacturing process, and may help narrow down the actual processes leading to OB. Both industries involved gel coating and manual lamination of FRP.

Recently, we identified an additional two patients with OB and exposure to FRP lamination. The first is a 35-year-old man who has worked in a FRP yacht manufacturing factory for 4 years. He developed persistent dyspnoea 1 year after starting FRP lamination. Lung function shows severe airway obstruction with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) 2.72 and 1.28 litres, respectively. Work exposure included various resins, mainly polyester resin with methyl ethyl ketone peroxide (MEKPO) (as catalyst) and styrene (as active diluents).

The second patient, a 28-year-old man, was a water storage tank repairer for 8 years. His work involved mainly leakage-proof FRP lamination. Dyspnoea developed 2 years after starting on the job; and progressed so badly that he had to quit this year. Chest CT scan revealed air trapping. Lung function showed severe irreversible obstructive ventilatory defect, with FVC 3.56 litres and FEV1 1.55 litres, respectively.

Two points are noteworthy in our second patient. He has never been involved in gel coating processes, and he only used polyester resin (with MEKPO and styrene) as glue at work. These imply that the actual process causing OB was likely FRP lamination, not gel coating. Besides, polyester resin containing MEKPO and styrene could be the responsible agent. Nevertheless, these are indirect evidences. The conclusive identification of the actual causal agent(s) warrants further investigation.