Correlation Between Ionizing Radiation And Occupational Health Of Medical Radiation Workers

Background:At present,radiation technology has become one of the important means of modern medical diagnosis and treatment.Radiation technology is an efficient,safe and painless method,which has important value in the diagnosis and treatment of diseases.However,radiation workers are inevitably exposed to long-term ionizing radiation in the process of work;occupational ionizing radiation is still a potential risk factor affecting the health of radiation workers.Guangzhou is one of the most domestic cities using medical radiation technology in China.With the increase of radiation diagnosis frequency,the radiation dose of workers in medical institutions may increase during the course of work.Health effects of low-dose ionizing radiation on occupational population are worth in-depth study and evaluation in this current situation.Objective:The purpose of this study was to investigate the individual dose level and occupational health status of radiation workers in hospitals in Guangzhou,and to analyze the impact of low-dose ionizing radiation exposure on the health indicators of radiation workers,so as to provide some evidence for evaluating the occupational health status of medical radiation workers in Guangzhou.Methods:Cluster sampling method was used to select radiation workers engaged in radiation diagnosis,radiotherapy,nuclear medicine and interventional radiology staff from 20 hospitals in Guangzhou during 2010to 2019.Combined with the"occupational health examination system"and"personal dose monitoring system"of Guangdong Prevention and Treatment Center for Occupational Disease,the general demographic information,personal dose monitoring data of external irradiation and annual radiation examination results of the subjects were collected,and the database was established.1.Analysis of personal dose level of medical radiation workers in Guangzhou:From 2011 to 2019,a total of 3819 medical radiation workers in Guangzhou were enrolled.Thermoluminescence personal dosimeter（TLD）was used to measure the exposure dose of the subjects.The trend of total annual effective dose was analyzed by simple linear regression method.Kruskal-Wallis test was used to compare the difference of individual dose level between types of work and gender groups.2.Analysis of occupational health status of medical radiation workers in Guangzhou:Using the cross-sectional survey design,a total of 1804 medical radiation workers in Guangzhou were enrolled.According to the median annual effective dose in 2018,the subjects were divided into two groups:group A（annual effective dose=0.12m Sv,n=991）,group B（annual effective dose>0.12 m Sv,n=813）;the differences of blood routine,thyroid function,liver and kidney function,blood pressure,blood glucose,blood lipid and the results of lens and electrocardiogram were compared between different dose groups.Binary logistic regression model was used to analyze the effect of radiation dose on abnormal physical examination indexes.3.Changes of thyroid hormones in a cohort of medical radiation workers:A retrospective cohort study was conducted with2946 radiation workers of during 2010～2019.The first physical examination time was taken as the baseline,and the last physical examination time was taken as the departure time.The subjects were divided into four groups according to occupation:radiation diagnosis group（n=1267）,radiotherapy group（n=613）,nuclear medicine group（n=252）,and interventional radiation group（n=814）.The individual dose of external exposure is monitored by TLD.Dose level was represented at an average annual effective dose.Thyroid stimulating hormone（TSH）,triiodothyronine（T3）and thyroxine（T4）were measured by chemiluminescence immunoassay.Generalized estimating equation（GEE）was used to evaluate the changes and influencing factors of TSH,T3 and T4 parameters over time.Results:1.Personal dose:From 2011 to 2019,3819 participants in Guangzhou were included,and a total of 20208 person years were monitored.The proportion of people with annual effective dose>5 m Sv in each year was less than 1.00%.The median annual effective dose（interquartile interval）of participants decreased from 0.21（0.28）m Sv to 0.15（0.13）m Sv from2011 to 2019;the annual effective dose showed a general downward trend and in a very low level,and the highest was among nuclear medicine staff.Except for 2011,2012 and 2014,the annual effective dose of male radiation workers was slightly higher than that of female.2.Occupational health survey:There were no significant differences in RBC,WBC,Hb,and PLT levels among different dose groups.In terms of serum thyroid hormone:T3 level of the group B was higher than that of the group A（P<0.001）;ALT level of group B was higher than that of group A.In all subjects,the rate of lens opacity,thyroid dysfunction,electrocardiogram changes and hypertension was 9.53%,2.66%,27.76%,and 14.63%,respectively.There was no correlation between dose level and abnormal risk of hemogram indexs,thyroid hormones,lens,electrocardiogram,blood pressure,blood glucose,blood lipids,livers’and kidney function related indicators.3.Changes of thyroid hormones in a cohort of medical radiation workers:Multi-factor GEE analysis showed that the years of radiation work were negatively correlated with the levels of T3 and T4.[β_T3=-0.015,95%CI:（-0.018,-0.012）nmol/L;β_T4=-2.294,95%CI:（-2.426,-2.162）nmol/L;taking female radiation workers as the reference group,the regression coefficientβand 95%confidence interval of TSH,T3 and T4 levels in male radiation workers were-0.133（95%CI:-0.215,-0.052）×10^-3U/L,0.127（95%CI:0.106,0.148）nmol/L and 1.401（95%CI:0.103,2.700）nmol/L,respectively（P<0.05）.The T3 level of radiation workers in the highest annual effective dose group was higher than that in the lowest group（P=0.008）According to gender stratification,the T4 level of female radiation workers engaged in radiation diagnosis,radiotherapy and interventional radiology was 4.951 nmol/L,6.741 nmol/L and 5.191nmol/L higher than that of nuclear medicine radiation workers,respectively（all P<0.05）.Conclusion:1.From 2011 to 2019,the annual effective dose of radiation workers in the Class 3A hospitals in Guangzhou was always at a low level and showed a downward trend,which may be related to the improvement of radiation protection work and personal protection awareness of radiation;the annual effective dose of radiation workers engaged in nuclear medicine was higher than that of other radiation workers,which indicates nuclear medicine workers are the key group of radiation protection in medical institutes.2.Cross-sectional survey shows that based on the current low level of individual dose monitoring of occupational external radiation,occupational low-dose ionizing radiation may not cause obvious damage to the health of medical radiation workers.The occupational health status of this population in Guangzhou was good.3.A retrospective cohort study found that the T3 and T4 levels of participants decreased with the increase of years of radiation work,suggesting that long-term radiation work may affect the thyroid endocrine function of medical radiation workers.T4 level of female engaged in nuclear medicine radiation work was lower than that of other radiation work,which is considered to be related to the high risk of radiation exposure in nuclear medicine work,and sensitivity of female thyroid abnormalities to radiation.Education of radiation protection should be strengthened for medical radiation workers.Long-term personal dose and occupational health monitoring should be continued.