Risk Assessment Of Fluoride Bone Injury Caused By Occupational Exposure

Fluoride (F) bone injury is a complicated disease involving many risk factors, such as fluoride intake, genetic factors, social factors and lifestyles. The prevention of F bone injury should focus on the susceptible population. The identification of susceptible people, depend on the risk assessment method, which is the integration of various factors. Currently, few researchs focused on risk assessment of F bone injury. We selected F exposed workers as our subjects, and analyze their general condition, F burden, and calcitonin receptor gene polymorphisms. In the basis, established the risk assessment model of F bone injury to determine the susceptible people and provide the basis for the prevention strategies. This study is composed by the following three parts:Part I Study on the fluoride burden and relative factors in the occupational fluoride exposure populationObjective To investigate the relationship between the blood fluoride level, urine fluoride level and age, work category, work years, smoking and drinking habits in the occupational exposure population.Methods 245 workers exposed to environmental fluoride of one aluminum plant were selected as the subjects, air fluorine, serum fluorine, urine fluorine levels were detected, work category, age, work years, smoking, drinking and the relative factors of the subjects were investigated.Results The air fluoride concentrations of electrolytic plant and aluminum pole are (2.31±1.01) mg/m3and (0.26±0.10) mg/m3, which are higher than the machine repair shop, the differences are significant(P<0.05). The serum and urine fluoride concentrations of the workers at the electrolytic plant are (0.32±0.06) mg/L and (7.96±8.41) mg/L, while they are (0.30±0.07) mg/L and (4.39±5.21) mg/L at the aluminum pole. These statistics are higher than the workers in the machine repair shop [(0.19±0.04) mg/L, (2.69±2.01) mg/L], the difference is significant (P<0.01). The serum and urine fluoride concentrations of the elder group [(0.32±0.08) mg/L, (5.10±4.01) mg/L] are higher than the younger group [(0.29±0.05) mg/L, (4.27±4.92) mg/L], the differences are evident (P<0.05, P<0.01). The serum and urine fluorine concentrations of the long work years group [(0.36±0.07) mg/L, (6.01±7.05) mg/L] are higher than the middle work years group [(0.30±0.06) mg/L, (4.24±5.13)mg/L] and the short work years group [(0.30±0.06) mg/L, (3.22±4.32) mg/L], the differences are significant (P<0.05, P<0.01). The serum fluorine concentrations of regular smokers group (0.32±0.04) mg/L and occasional smokers group (0.31±0.06) mg/L are higher than the nonsmokers group (0.19±0.05) mg/L, the differences are obvious (P<0.05); the urine fluorine concentration of regular smokers group (5.73±4.92) mg/L is higher than those of occasional smokers group (4.81±4.86) mg/L and nonsmokers group (4.33±3.96) mg/L, the differences are significant (P<0.05, P<0.01); the urine fluorine concentration of occasional smokers group (4.81±4.86) mg/L is higher than nonsmokers group (4.33±3.96) mg/L, the differences are evident (P<0.05). There is no obvious difference between the several drinking groups at the field of serum fluorine and urine fluorine concentrations (P>0.05). Conclusion The serum and urine fluoride concentrations of workers at electrolytic plant and aluminum pole are significantly higher, in addition, age, work category, work years and smoking are connected to the increasing of F burden.Part II Interactive effect of fluoride burden with calcitonin receptor gene polymorphisms on the risk of F bone injuryObjective This study aims to examine the interactive effect of fluoride (F) burden with calcitonin receptor (CTR) gene polymorphisms on the risk of F bone injury, and provide the basis for determination of F bone injury risk factors.Methods In this case-control study, a total of 119 cases and 126 controls were enrolled from 2 aluminum plants in Hubei province. F burden (UF) was measured by F ion-selective electrode method. The CTR gene polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Logistic regression analysis was used to estimate multivariate-adjusted odds ratios, 95% confidence intervals (CI).Results The odds of developing F bone injury for participants in the moderate F burden group versus the mild F burden group were 4.1 (95%CI: 1.9, 8.7); the heavy F burden developing F bone injury for participants with the TC&TT genotypes versus the CC genotype were 2.6 (95%CI: 1.4, 4.7). The interactions between TC&TT genotypes and moderate, heavy F burden were significant (OR=14.4; OR=40.3).Conclusion The interactive effect of F burden and CTR genotype was significant, which increased the F bone injury risk.Part III Creating and application of risk assessment model for F bone injuryObjective To create a risk assessment model for the people at high risk of F bone injury.Methods Case-control study was used to investigate and collect the data of 245 workers from aluminum plants. At first, single factor analysis ( Independent-sample T Test for scale variables, Chi-square Test for nominal variables) was used in 14 variables including smoking habits, drinking habits, age, working years, systolic pressure, diastolic pressure, pulse, urinary fluoride, blood fluoride, osteocalcin, calcitonin, ALP, BAP and CTR genotypes. Multiple logistic regression was used in the selected variables by SPSS16.0. Finally, the Logistic regression equation for forecasting F bone injury was set up: P=ExpΣBiXi/l+ExpΣBiXi, and the odds ratio was calculated:OR=Exp (B). Meanwhile, the accuracy, sensitivity and specificity of the predictive model were evaluated individually.Results Nine variables are selected by single factor analysis, including age, pulse, urinary fluoride, osteocalcin, calcitonin, ALP, BAP, drinking habits and CTR genotypes. By entering such variables into multiple logistic regression analysis, it was revealed that 7 of 9 factors are significant for F bone injury in diminishing sequences as drinking habits (OR=2.346), pulse (OR=0.281), urinary fluoride (OR=3.186), osteocalcin (OR=3.000), calcitonin (OR=3.681), BAP (OR=3.295), and CTR genotypes (OR=0.113). The risk assessment model is:P=-6.359+0.853X2-1.271X4+1.159X5+1.099X6+1.303X7+1.193X9-2.180X10. The accuracy, sensitivity and specificity are 85.3% (209/245), 84.0 (100/119), 86.5% (109/126) respectively.Conclusion Drinking habits, pulse, urinary fluoride, osteocalcin, calcitonin, BAP and CTR genotypes are relevant factors of F bone injury. The logistic regression model based on these factors is reliable in forecasting F bone injury.