Background

Zintec is a cold rolled mild steel electrolytically coated with a thin layer of zinc used in vehicle manufacture to limit rust (different to galvanized steel). We report the first case series of occupational asthma in workers exposed to the fumes of spot welding through Zintec-coated steel.

Methods

All workers with possible occupational asthma referred to our clinic since 2001 were asked to record PEF 2-hourly for 4 weeks at home and work. Those with confirmed occupational asthma with a positive Oasys score were included.

Results

Fifteen workers with work-related PEFs were included. Seven showed late reactions, 7 immediate reactions and one was unclassifiable. Figure 1 shows a late reaction ABC plot from the Oasys program. Twenty percent had pre-existing asthma, 33% has non-specific bronchial reactivity, 77% were atopic and 54% had either a FeNO >25ppb or blood eosinophils >0.15 x 10^-9. The mean latency from first exposure to first symptom was 7 years (SD 7.5). 3/5 had immediate reactions following specific challenge (SIC) with Zinc sulphate or Zinc Chloride.

Figure 1.

Discussion

Fumes from Zintec-coated steel welding are a cause of occupational asthma probably related to zinc in the fume. SIC with zinc salts may not reproduce real life exposures, which are difficult to replicate in the challenge chamber. The replacement of steel with aluminium for car bodies can overcome the problem.