Polyvinylchloride (PVC) resins are widely used in industry. Asthma due to the thermal degradation products of PVC are well documented. In this first case of occupational asthma due to unheated PVC resin dust the patient was exposed to PVC resin dust during the mixing of chemicals used for making plastic seals for bottle caps.Meatwrappers' asthma and asthma due to the thermal degradation products of polyvinylchloride (PVC) are well documented.'4 Pneumoconiosis'9 and interstitial pneumonitis'°among workers exposed to PVC dust have been reported. Respiratory symptoms and abnormalities of lung function and of the chest radiograph have been described in surveys of workers exposed to PVC dust." 12 We report the first case of asthma induced by occupational exposure to unheated PVC resin dust. Case reportA 32 year old man worked for 14 years in a factory manufacturing bottle caps. Each metal cap was lined with a plastic seal on its inner surface. Both the fabrication of the metal caps and the injection moulding process of making plastic seals were carried out in the main production hall ofthe factory. The PVC resin mixture for the injection moulding process was prepared in a fairly large air conditioned room that was separated from the main production hall. For the past eight years the patient worked in this mixing room where he was exposed to PVC resin dust and other chemicals during mixing.He started to have episodes ofcough and breathlessness about five years after working in the mixing room. Initially, the frequency of symptoms was once in three to four months. During the past year, however, his symptoms had occurred almost daily and he had to depend on a ventolin inhaler for relief. He worked a five day week from 0730 to 1630. His symptoms usually started at about 0200 or 0300. Symptoms improved on weekends and holidays. Accepted 22 December 1988 There was no associated rhinitis. He had no history ofasthma or atopy. His sister had a history ofasthma. OCCUPATIONAL EXPOSUREThe preparation of PVC resin mixture in the mixing room was observed and the exposure dust concentration monitored. Three types ofchemicals were blended together to form the mixture: (i) PVC resin, a white powder, (ii) dioctylphthalate or Di-2-ethylhexylphthalate(DOP), a plasticiser in the form of a clear oily liquid, and (iii) a paste containing azodicarbonamide (a plastics blowing or foaming agent), colouring agent, and stabilisers. The PVC resin itself was a mixture of three grades of PVC resin: types A, B, and C. Type A was an emulsion resin with no stabilisers added, type B an emulsion resin that had been stabilised against heat, and type C a suspension resin with no stabilisers added. The ratio of A:B:C was 3:1:0-7. The paste containing azodicarbonamide and the liquid DOP were first placed in a tank, then five bags (120 kg) of PVC resins were manually poured into the tank. The pouring process was visibly dusty and took about 10 minutes. No local exhaust ventilation was provided.A quartz crystal microbalance cascade impactor was u...