[Early effects of low-level long-term occupational chromate exposure on workers'health]

Objective: To explore the effects of low-level long-term occupational exposure to chromate on the health of workers, and the potential biomarkers of early health effects in terms of lung function, immune toxicity and genetic damage.

Methods: A total of 22 chromate contact workers and 44 non-chromate contact workers from an electroplating enterprise with long-term occupational environment monitoring in line with the national standards in Inner Mongolia were investigated. The questionnaire survey was conducted to collect the basic situation, the history of smoking, drinking, diseases and so on. The portable lung function instrument, inductively coupled plasma mass spectrometry and cytokinesis-blocked micronucleus test were performed to measure the chromate contact workers'lung function, whole blood Cr (WB-Cr) and micronuclei frequency (MNF) of peripheral blood lymphocytes respectively. The cytometric bead array was used to detect the levels of IL-1β, IL-6, IL-8, IL-10, IL-12P70 and TNFα in the serum among the two groups. The effects of chromate exposure on the above-mentioned indexes involved biological exposure, lung function, immune response and genetic damage, and their correlation were analyzed with different statistical methods.

Results: (1) the average length of service for chromate contact workers was 31 years, and their concentration of WB-Cr was 1.11-4.19 μg/L. They were divided into high and low exposure groups according to the median of 1.72 μg/L. The WB-Cr in the high exposure group (2.17 μg/L) was higher than that in the low exposure group (1.58 μg/L) as well as the reference value of the healthy population (1.74 μg/L, P<0.05); (2) the lung function test showed 10 (45.45%) chromate exposure workers had single or multiple abnormal lung function indexes, among which large airway injury index PEF, and small airway injury indexes MVV and FEF25%-75% were all negatively correlated with WB-Cr (r=-0.53, P<0.05; r=-0.52, P<0.05; r=-0.44, P<0.05); (3) IL-1β, IL-6, IL-8 and TNFα in the serum of chromate contact workers were higher than those in the control group (P<0.05), and there was a positive correlation between TNFα and WB-Cr, and among these cytokines (P<0.05); (4) the average lymphocyte MNF in chromate contact workers was 1.341%, higher than the reference value of the general population (0.436%, P<0.01). Poisson regression analysis showed MNF in thehigh exposure group was higher than that in the low exposure group, OR (95%CI) =1.323 (1.049, 1.669); (5) multiple linear regression analysis showed that the lung function index FEF25%-75% decreased with the increase of TNFα (P<0.05), no significant correlation was found between other cytokines, MNF and lung function indexes.

Conclusion: Long-term low-level occupational exposure to chromate can cause the decline of lung function, immune inflammatory reaction and genetic damage in workers, in which local or systemic inflammatory response is associated with decreased lung function. Lung function indexes PEF, FEF25%-75% and MVV, serum cytokines IL-1β, IL-6, IL-8, and TNFα, and peripheral blood lymphocyte MNF may be used as early health effects biomarkers of chromate exposure.