A 3-year follow-up study of lung function and respiratory symptoms among Japanese toner-handling workers

Introduction
To investigate whether toner dust affects lung function, respiratory symptoms and lung CT findings, we initiated a cohort study of toner-handling workers. This study reports the 3-year changes in their lung functions and respiratory symptoms.

Methods
At baseline in 2004, 317 male toner-handling workers from four plants and 235 reference workers in the same plants who were not exposed to toner dust except normal use of office copiers or laser printers, were recruited and surveyed. Age, sex and smoking status were matched. In 2007, 295 of the toner workers and 224 of the reference workers participated in the follow-up survey (follow-up rates: 93.1 % and 95.3%, respectively). Respiratory symptoms were evaluated by the Japanese version of the self-administered ATS-DLD questionnaire. Pulmonary function tests were also done according to the standardized ATS protocol. In addition, blood cell counts as well as urinary levels of the oxidative stress marker, 8-hydroxy-2’-deoxyguanosine (8-OHdG), were measured. Job-exposure matrices were created by combining each worker’s job history with his or her current average exposure concentration to toner dust.

Results
The toner workers in this study were 35.8 years in age and their average exposure duration at baseline was 11.3 years. Area monitoring of toner dust indicated that the geometric average dust concentration (<4µm) in the toner-handling process was 67.6 mg/m3 *h. No significant differences were detected in 3-year changes in lung function tests such as FVC, FEV1.0, and %FVC. Respiratory symptoms in the two groups were also comparable.

Discussion
No change was detected in this 3-year follow-up with relation to toner dust exposure. A careful follow-up is needed to examine the pulmonary effect of toner dust inhalation, especially focusing on its interaction with smoking.