Table 1 Individual studies’ characteristics
Study ID (reporting quality) | Study design | Country | Number of participants | Age (years) | Exposed | Controls | Outcome | Duration of exposure (years) | Variables adjusted for |
|---|---|---|---|---|---|---|---|---|---|
Burge et al. [9] (A) | Case control | UK | 58 | Mean age: 46.5 (±10.9) for workers without symptoms and 39.4 (±11.4) for cases | Solderers and ex-solderers | Never soldered | Respiratory symptoms, lung function | Mean duration: 10.1 years (±4.3) for workers without symptoms and 6.7 (±5.1) for cases | No adjustment |
Burge et al. [24] (C) | Cohort | UK | 45 | Range: 25–62 | Solderers | No control group | Lung function | Not available | No adjustment |
Greaves et al. [26] (A) | Cross-sectional | USA | 104 | Mean age: 41.2 (±14.3) | Solderers, mostly “hand solderers” | No control group | Lung function | Mean duration: 3.7 years (±3.6) | No adjustment |
Courtney and Merrett [10] (C) | Cross-sectional | UK | 1611 | Mean age: 51 for exposed. Standard deviation and age of non-exposed not available | Female solderers and ex-solderers | Female non-solderers | Respiratory symptoms and lung function | No mean duration available. Participants were divided according to whether the duration of exposure was more or less than 6 years | No adjustment |
Gupta et al. [25] (B) | Cross-sectional | India | 197 | Mean age: 34.8 (±0.85) in exposed males, 35.2 (±0.42) in exposed females, 34.4 (±1.05) in male control group, and 32.9 (±0.14) in female control group | Solderers | Participants never involved in soldering | Respiratory symptoms and lung function | Mean duration: 13.3 years (±0.4) | Smoking, atopy |
Lee et al. [11] (B) | Cross-sectional | Singapore | 202 | Mean age: 29.2 (±6.4) in exposed and 28.5 (±5.9) in controls | Full-time “hand solderers” | Administrative staff in industry with no present or past exposure to soldering | Respiratory symptoms and lung function (expressed in liter) | Not available. Participants were divided according to whether the duration of exposure was more or less than 5 years | Smoking |
Palmer et al. [8] (A) | Cross-sectional | UK | 152 | Mean (range): 35.6 (17–63) | Full-time solderers (≥37 h/week) | Part-time solderers (≤20 h/week) | Respiratory symptoms | Median: 5 years | Smoking, atopy |