Ruth E Wiggans (REW): A 52-year-old man was referred with chronic cough of increasing severity over the last 4 years. The cough was productive of green sputum and he experienced coughing attacks weekly. He reported no other respiratory symptoms. He had a sore throat following coughing bouts but denied other upper airway complaints. He was otherwise well with no systemic symptoms. His cough had improved following a 2-week summer holiday, and subsequently deteriorated following his return to work.

A chest X-ray organised in primary care was normal. Three years earlier, his general practitioner increased his lansoprazole from 15 to 30 mg once daily for cough. This had not helped although treatment continued. His past medical history included treated obstructive sleep apnoea and hypertension for which he took bendroflumethiazide and losartan; the latter substituted for his ACE inhibitor 3 years earlier. He recalled no personal or family history of asthma or atopy and was a lifelong non-smoker. He had kept budgerigars until 6 months previously when the last bird died.

He had worked for 12 years as a computer numerical control (CNC) machine setter and operator, machining metal parts used to make tools for woodworking. He machined bronze, brass, leaded mild steel, high-speed steel and aluminium pieces to the desired specification. He operated five machines in a single area of the factory, adjacent to where ash handles were turned. He was the sole CNC operator turning metal components in the factory and was not aware of any colleagues reporting respiratory symptoms.

Water-based metalworking fluids (MWFs) were used on all five machines. Each machine collected and recirculated MWFs via its own sump. For the last 4 years, the fluids had occasionally become ‘foul smelling’ and sometimes changed colour from a translucent blue to a chocolate brown. The worksite did not perform dip-slide fluid analysis or use biocide contrary …