Effect Of Low-dose Ionizing Radiation On Health Of Radiation Medical Staffs:a Prospective Cohort Study

ObjectiveTo evaluate the occupational health among radiation medical staffs exposed low-dose ionizing radiation,explore the effect of cumulative radiation dose on peripheral blood lymphocyte micro-nucleus,cataracts,thyroid hormones,and hematology parameters changing,analyze the dose-response relationship between cumulative radiation dose and health effects changing,and determine biological effects and ionizing radiation dose cutoff value on providing a scientific basis for prevention and control of radiation damaged and improvement basic standards of radiation protection.MethodsA prospective cohort study was used to analyze data of all radiation medical staffs in Dongguan including occupational health and personal dose monitoring,epidemiological investigation and clinical examination in Dongguan Sixth People’s Hospital from 2015 to 2017.A total of 1285radiation medical staffs participated in the study,and 20 subjects were excluded with baseline hematology parameters abnormal;the follow-up servery was completed in June 2019,28 subjects were lost to follow-up,and1237 subjects were finally included.We divided the subjects into four categories including 0.212～2.585 m Sv,2.586～3.316m Sv,3.317～3.757 m Sv and 3.758～31.272 m Sv based on the IQR（2.586-3.757）of the cumulative radiation dose and used 0.212～2.585 m Sv as the reference to evaluate the impact on low-dose ionizing radiation dose on the subjects’health.The generalized linear models were used to analyze risk factors of health effects changing,the restricted cubic spline models were used to fit the dose-relationship between the cumulative radiation dose and health effects changing,and the ROC curve was used to determine AUC which the cumulative radiation dose had an impact in health indicators changing and cutoff value.Statistical analysis adopts two-sided test,and the test level isα=0.05.ResultsBasic information:A total of 1,237 subjects were enrolled,and the follow-up time（（?）±s）was 2.0±0.4 years.The cumulative follow-up was2342 person-years,and the follow-up rate was 97.79%.The median age was35（29-43）years old,and the median radiation servicing was 7.5（3.0-13.5）years.Most of them were males（72.84%）,63.86%of ionizing radiation occupational were physicians,diagnostic radiology was majority among the work types（67.50%）,a small part was primary medical unit（17.46%）and only 25.79%were accustomed to smoking.In the control group,there was 317subjects at 0.212～2.585 m Sv;subjects of 2.586～3.316 m Sv cumulative radiation dose group was 302,311 subjects in 3.317～3.757 m Sv,and 307subjects in 3.758～31.272 m Sv.Baseline observation indicators:The median of basophils percentage,eosinophils,eosinophils percentage,hematocrit,hemoglobin,mean corpuscular volume,mean corpuscular hemoglobin concentration,mean platelet volume,platelet distribution width,platelet hematocrit,platelet,red blood cell and red blood cell distribution width were 0.50（0.30-0.80）%,0.10（0.10-0.20）×10⁹/L,2.00（1.20-3.20）%,44.50（41.20-47.10）%,147.20（135.20-155.20）g/L,29.30（28.10-30.50）Pg,328.60（332.30-336.60）g/L,8.40（7.70-9.20）f L,17.60（16.70-19.30）f L,0.20（0.20-0.20）%,211.80（193.10-258.20）×10⁹/L,5.05（4.70-5.38）×10¹²/L and 12.50（11.20-13.30）%,respectively;the median of free triiodothyronine,triiodothyronine,thyroxine were 4.35（4.01-4.71）pmol/L,1.57（1.42-1.75）nmol/L and 82.80（74.68-91.78）nmol/L,respectively.Health status and factors of radiation medical staffs:Hematocrit[0.80（-0.80-2.50）%],hemoglobin[3.80（-1.11-8.60）g/L],red blood cells[0.10（-0.10-0.29）×10¹²/L]and thyroxine[8.90（-1.23-21.75）nmol/L]had a large change in 3.317～3.757 m Sv during the study period,and the mean corpuscular hemoglobin concentration[4.50（-4.60-10.60）g/L],the platelet distribution width[-0.70（-2.70-0.00）f L]had a large change in 3.758～31.272 m Sv.These indicators were statistically different to the cumulative radiation dose groups（P<0.05）.The multivariate analysis showed that the high medical level was risk factor of increasing on the hematocrit（β=0.466,95%CI[Confidence Interval]:0.053-0.879）,mean corpuscular hemoglobin concentration（β=2.345,95%CI:0.170-4.520）,decreasing on platelet distribution width（β=-0.549,95%CI:-0.905--0.192）and thyroxine（β=-3.364,95%CI:-6.554--0.173）;family history of diabetes were risk factor of decreasing on hematocrit（β=-2.286,95%CI:-4.450--0.122）and red blood cells（β=-0.276,95%CI:-0.519--0.033）;radiation medical staffs was thyroxine increasing with smoking habits（β=2.680,95%CI:0.171-5.189）,the thyroxine of radiation physician（β=-6.660,95%CI:-12.076--1.243）and technician（β=-5.976,95%CI:-11.650--0.301）were reduced compared to other radiation occupation.Dose-response relationship:After adjusting gender,age,servicing,occupation,work types,medical level,smoking habits,family history of hypertension,family history of diabetes,the restricted cubic spline model was used to analyze the cumulative radiation dose and changing of hematocrit,hemoglobin,mean corpuscular hemoglobin concentration,platelet distribution width and thyroxine showing a non-linear dose-response relationship（non-linear test P value<0.05）.Analysis of ROC curve and cut-off values:The AUC of cumulative radiation dose and mean corpuscular hemoglobin concentration,platelet distribution width changing were 0.731 and 0.604,respectively;while the thyroxine changing AUC（95%CI）was 0.857（0.807-0.908）（P<0.001）,the sensitivity was 79.2%,the specificity was 90.9%,the Youden index was 0.701and the optimal cutoff value was 2.225 m Sv.ConclusionThe cumulative radiation dose of low-dose ionizing radiation has an effect on the hematology parameters and thyroid hormones of radiation medical staffs.The high medical level was risk factor for mean corpuscular hemoglobin concentration increasing,platelet distribution width and thyroxin decreasing.Radiation physician and technician were significantly reduced thyroxine.There were non-linear dose-response relationship between the changing of mean red blood cell hemoglobin concentration,platelet distribution width and thyroxine and the cumulative radiation dose.The cumulative radiation dose has the greatest impact on thyroxine changing among these indicators.