title: Comparison of respiratory morbidity between present and ex-workers of quartz crushing units: Healthy workers' effect.
abstract: BACKGROUND
  Quartz stone grinders are one such group of workers who are exposed to silica and thereby at risk of developing silicosis. However due to increased campaigning against silicosis the scenario has changed.
  
  
  OBJECTIVE
  To compare the respiratory morbidities among the present quartz stone workers and the ex-quartz stone workers who have left the job.
  
  
  METHODS
  This cross-sectional study included, 134 ex-workers and 182 current workers of quartz grinding units. All these subjects were subjected to chest radiography and pulmonary function tests.
  
  
  RESULTS
  For 134 ex-workers, the mean age was 31.77 ± 9.99 years and the mean duration of exposure was found to be 2.74 ± 1.65 years while for the present workers, the mean age was 26.74± 7.12 years while the mean duration of exposure was 1.36 ± 2.68 years. The study revealed silicosis in 24 (17.9%), radiological suspected tuberculosis in 17 (12.7%) and silico-tuberculosis in 33 (24.7%) ex-workers while in present workers, radiological suspected tuberculosis in 10 (5.5%) subjects and silicosis grade 1/1 in one subject were found. Among the ex-workers, 14 (10.4%) had a combined type of pulmonary function impairment while 8 (6.0%) and 28 (20.9%) were having restrictive and obstructive type of pulmonary impairments, respectively. Among the present workers, pulmonary function testing revealed the combined type of functional impairment in 1 (0.5%), restrictive type in 13 (7.1%), and obstructive type of functional impairment in 17 (9.2%) subjects.
  
  
  CONCLUSIONS
  The high prevalence of respiratory morbidity in ex-workers as compared to current workers can be attributed to the out-of-the-job healthy workers' effect.
authors: National Institute of Occupational Health, Ahmedabad, India.
authors: Rajnarayan R
authors: RR
authors: Tiwari
authors: Raj
authors: R
authors: Narain
authors: Y K
authors: YK
authors: Sharma
authors: Sunil
authors: S
authors: Kumar