Blood Leukocyte Counts And Lung Function Changes Induced By Occupational Dust Exposure In Iron And Steel Industry Workers

Objective:Iron and steel industry workers are exposed to high levels of inhalable dust particles that widely existed in the working environment.Productive dust has become the main occupational harmful factor that damages workers’health and causes occupational lung diseases.Currently,cross-sectional studies with small samples have established the associations between industrial dust and lung function of workers in iron and steel workers.However,large-sample studies monitoring the continuous changes of lung function are inadequate.We aim to assess the relationship between long-term occupational dust exposure,systemic inflammation,and longitudinal changes of lung function in iron and steel workers,searching for effective biomarkers and providing a scientific theoretical basis for the prevention and treatment of occupational diseases and precision medicine.Methods:This longitudinal study was conducted on 7,575 workers who were employed at an Iron and Steel Company Limited between January 1,2008 and December 31,2017.Participants were selected to conduct routine blood examination,lung function measurement and other routine health examinations annually.In general,individual participants in this program received medical assessments every other year with medical surveillance workouts recommended by the China Ministry of Health for 10 consecutive years.Time-weighted exposure intensity（TWEI）of dust was quantified based on the percentage of subjects reporting dust exposure,consultation with occupational hygienists,historical personal air sampling data,and epidemiological consideration of sample size within each exposure category for workers with certain job titles.A generalized linear model was used for investigating the influencing factors of the baseline lung function,and a linear mixed-effects model was used for investigating the influencing factors of the decline rate lung function.The relationship among dust exposure,WBC count,and base lung function as well as its decline were conducted with a careful assessment of important covariates,dose-response relationship,and sex stratification at the same times.Data analyses were performed using SAS version 9.4.Results:1.The average annual change of lung function during follow-up was-55.98 m L/s·year in forced expiratory volume in 1 second（FEV1）and-43.49 m L/year in forced vital capacity（FVC）during follow-up.2.Higher TWEI was associated with lower baseline function（-20.89 m L/s for FEV1 and-39.34 m L for FVC,per unit increase of TWEI）and a more slowly decline（3.55 m L/s·year for FEV1 and 6.17m L/s·year for FVC,per unit increase of TWEI）to the adverse effect of occupational dust exposure,but no effect on FEV1/FVC ratio.3.Higher TWEI was associated with a higher level（0.08×10⁹/L,per unit increase of TWEI）and a slow increment（-0.01×10⁹/L·year,per unit increase of TWEI）of neutrophil,a lower level（-0.03×10⁹/L,per unit increase of TWEI）of lymphocyte,a lower level（-0.02×10⁹/L,per unit increase of TWEI）and a slowly decline（-0.001×10⁹/L·year,per unit increase of TWEI）of the mid-range absolute count.4.Higher WBC count and differential counts were associated with lower baseline measurements.An interquartile increase in WBC（2.0×10⁹/L）predicted a significantly 21.45m L/s lower in FEV1 and 21.69 m L/s lower in FVC（P<0.05）.Higher WBC count and differential counts were associated with a more rapid decline of FEV1 and FVC in male workers only,with a characteristic of the dose-response relationship(P_trend<0.05).Conclusions:1.Occupational exposure to inhalable particles containing metal elements prior to baseline evaluation was inversely associated with baseline measurements and a lower decline of FEV1and FVC over a follow-up period of 10 years.2.Iron and steel dust exposure can reduce a high level and a slow increment of neutrophils,a lower level of lymphocyte and a lower level and a rapid decline of the mid-range absolute count.3.Cohort members with high levels of WBC counts and differential had lower baseline measurements and a more rapid decline of FEV1 and FVC in male workers in a dose-dependent increasing manner.4.Our findings strongly support the important role of systemic inflammation in affecting the temporal change of lung function in iron and steel industry workers.