Abstract

We present the first case of occupational asthma to colophony-free solder wire containing an adipic acid flux, previously only reported in a pharmaceutical factory worker who was in contact with spiramycin powder 1. The 43-yr-old female presented with rhinitic symptoms in 1992. She had worked as a solderer and desolderer of alternator parts since June 1989. The process used a colophony-free solder wire containing an adipic acid flux from 1996, but, when desoldering, colophony fluxes may still have been present.

From 1998, she experienced a gradual onset of breathlessness and chest tightness, which she noticed was affecting her keep fit. She had had no asthma, hay fever or eczema in childhood and there was no family history of these conditions. She was a lifelong nonsmoker and gave negative skin prick rest results to common environmental allergens. She started to show nocturnal waking and shortness of breath in the morning, feeling better on days away from work, particularly on holiday. She also noticed that she felt better when not soldering at work. She carried out serial peak expiratory flow measurements four times daily for a total of 4 weeks. When plotted using the Oasys program, they showed work related changes, with an Oasys score of 3.1 (probable occupational asthma; a score of > 2.5 has a sensitivity of 75% and specificity of 94% for occupational asthma diagnosis) and an area between the curves (ABC) score of 15 L/min/h (an ABC score of >= 15 L/min/h has a sensitivity of 69% and specificity of 100%). She was admitted for specific inhalation challenge testing to colophony and adipic acid fluxed solder wires. She melted roughly 1m of solder wire (using an iron heated to 170 C over three challenges, totalling 30 min for the colophony containing wire and 12 min for the adipic acid wire. She exhibited a late asthmatic reaction after the adipic acid exposure, with her forced expiratory volume in 1s falling by a maximum of 28% from baseline, She showed no reaction to the colophony fluxed solder wire. Her methacholine reactivity before challenge was 5,450 ug methacholine (normal) using the Yan method, halving following adipic acid wire challenge to 1,729 ug (mildly hyperreactive).

Adipic acid exhibits an asthma hazard index of 0.75 using the chemical hazard assessment program. Substances with indices of >0.5 have a high probability of being an asthmagen. Other non colophony based fluxes, such as palmitic acid and dodecanedioic acid, also have high hazard indices (0.92 and 0.94, respectively).

On follow up, the worker had joined a different company as a toilet cistern assembler. She still showed significant asthma, with occasional nocturnal wakening and a St George's Respiratory Questionnaire score of 50.8. Her methacholine reactivity was normal at >4800 ug.

Thus adipic acid fluxed solder wire is a new cause of occupational asthma.

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