Respiratory effects of two types of solder flux used in the electronics industry.

Fumes from solder flux have been shown to cause asthma among solderers in a British electronics factory. In the present study, questionnaires and lung spirometry were administered to 104 U.S. electronics workers (93 women, 11 men) who soldered printed circuit boards. Two types of solder flux were used: 68 subjects had worked only with a rosin-core (colophony) solder; 36 had changed from rosin- to an aqua-core ("phosphorous hexate") solder 15 months before the study. Symptoms of eye, throat, and nose irritation occurred in nearly half of the total group. Lower respiratory tract symptoms, including cough, phlegm production, and wheezing, also occurred with increased frequency, compared with reported rates among a general population. Similar symptom rates were observed among the aqua- and rosin-core groups. That these symptoms were work related was indicated by the subject's improvement on weekends or during vacation periods. On average, lung spirometry performed before starting work on Monday mornings showed no impairment in lung function; over the course of the work day there were small decrements in the forced expiratory volume at 1 s (mean, -21 +/- 11 [SD] ml) and forced vital capacity (-30 +/- 145 ml), but these decrements were unrelated to the individual amounts of solder used during the same period. Among the white female workers (N = 83), several multivariate analyses indicated that an increase in the amount of soldering had a beneficial effect on lung function, particularly among those who currently smoked. This paradox probably resulted from a "healthy worker effect" resulting from some individuals with lower than average lung function who left the industry early in the course of their employment.