Cumulative exposure to dust causes accelerated decline in lung function intunnel workers

Objectives-To examine whether underground construction workers exposed to t unnelling pollutants over a follow up period of 8 years have an increased r isk of decline in lung function and respiratory symptoms compared with refe rence subjects working outside the tunnel atmosphere, and relate the findin gs to job groups and cumulative exposure to dust and gases. Methods-96 Tunnel workers and a reference group of 249 other heavy construc tion workers were examined in 1991 and re-examined in 1999. Exposure measur ements were carried out to estimate personal cumulative exposure to total d ust, respirable dust, a-quartz, oil mist, and nitrogen dioxide. The subject s answered a questionnaire on respiratory symptoms and smoking habits, perf ormed spirometry, and had chest radiographs taken. Radiological signs of si licosis were evaluated (International Labour Organisation (ILO) classificat ion). Atopy was determined by a multiple radioallergosorbent test (RAST). Results-The mean exposure to respirable dust and alpha -quartz in tunnel wo rkers varied from 1.2-3.6 mg/m(3) (respirable dust) and 0.019-0.044 mg/m(3) (alpha -quartz) depending on job task performed. Decrease in forced expira tory volume in 1 second (FEV1) was associated with cumulative exposure to r espirable dust (p <0.001) and alpha -quartz (p=0.02). The multiple regressi on model predicted that in a worker 40 years of age, the annual decrease in FEV1 would be 25 ml in a nonexposed non-smoker, 35 ml in a nonexposed smok er, and 50-63 ml in a non-smoking tunnel worker (depending on job). Compare d with the reference group the odds ratio for the occurrence of new respira tory symptoms during the follow up period was increased in the tunnel worke rs and associated with cumulative exposure to respirable dust. Conclusions-Cumulative exposures to respirable dust and alpha -quartz are t he most important risk factors for airflow limitation in underground heavy construction workers, and cumulative exposure to respirable dust is the mos t important risk factor for respiratory symptoms. The finding of accelerate d decline in lung function in tunnel workers suggests that better control o f exposures is needed.