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Table of Contents   
ORIGINAL ARTICLE  
Year : 2017  |  Volume : 10  |  Issue : 5  |  Page : 1260-1264
Evaluation of risk factors impact on cataract development for uranium industry workers


1 Chair of ENT and Eye Diseases, JSC Medical University of Astana, Astana, Republic of Kazakhstan
2 Institute of Radiobiology and Radiation Protection, JSC Medical University of Astana, Astana, Republic of Kazakhstan

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Date of Web Publication6-Nov-2017
 

   Abstract 


The abundance and rough relative risk of cataract among 544 workers at the hydrometallurgical plant of Stepnogorsk Mining and Chemical Combine, depending on the total integrated dose of external irradiation, taking into account non-radiation factors, was studied. The conducted studies showed a statistically significant high abundance of ophthalmic pathology, including cataracts among workers in the main group compared with the control group. A statistically significant trend in the increase of cataracts with an increase in the total integrated dose, smoking index of more than 20 packs/year, increase in body weight and persons suffering from hypertension. As a result of a multivariate analysis of risk factors connection to cataract, we revealed that the cumulative dose and length of exposure are the main indicators predicting the development of cataracts for uranium industry adult workers. It is known that age is a key risk factor for many diseases, including cataracts. Lens opacity is a pluricausal manifestation, which is based on the mechanism associated with the course of time.

Keywords: Cataracts, ionizing radiation, ophthalmopathology, small doses

How to cite this article:
Dautbayeva ZS, Ahmedyanova ZU, Kazymbet PK. Evaluation of risk factors impact on cataract development for uranium industry workers. Ann Trop Med Public Health 2017;10:1260-4

How to cite this URL:
Dautbayeva ZS, Ahmedyanova ZU, Kazymbet PK. Evaluation of risk factors impact on cataract development for uranium industry workers. Ann Trop Med Public Health [serial online] 2017 [cited 2019 Oct 14];10:1260-4. Available from: http://www.atmph.org/text.asp?2017/10/5/1260/217498



   Introduction Top


Cataractogenic effects of ionizing radiation have been studied by many authors, but their results on the development of cataract with low-intensity exposure to radiation and a threshold dose are ambiguous. In most studies, the threshold dose for the development of radio-induced cataract is 0.5 Gy, regardless of the dose frequency and the nature of the irradiation.[1],[2],[3],[4],[5],[6],[7],[8]

According to the results of Ukrainian/American Chernobyl Ocular Study, the relationship between cataract development and the accumulated dose of irradiation has been revealed.[3] In a number of other publications, the results of participants' ophthalmologic examination for liquidators of Chernobyl disaster (Chernobyl nuclear power plant) are controversial.[9],[10],[11]

As a result of water system radioactive contamination, residents of onshore population of Techa River were exposed to long-term irradiation. Among 30,000 people, the most frequently observed vision pathology is cataract (26%). Analysis with correction for potentially interfering factors did not reveal the statistical significance of the prolonged effect of irradiation on the development of cataract.[12]

The authors of various scientific works on the development of cataract in interventional cardiologists summarize the increased risks of radiation-induced cataract development and radiation dose.[13],[14] At the same time, French scientists within the framework of the multicenter study Occupational Cataracts and Lens Opacities in Interventional Cardiology deny the connection between the statistically significant prevalence of cataract in the main group and the dose load.[15]

There are few contradictory studies on the effect of low-level irradiation for the development of cataracts among workers in uranium industry. Some studies deny the relationship between the accumulated dose of radiation and the development of radio-induced cataracts.[16],[17] However, the results of other studies have identified an increased risk of cataract development and revealed the relationship between accumulated radiation dose and cataract.[18],[19]

The goal of this study is to evaluate the risk of cataract for workers at the Stepnogorsk mining and chemical combine (SMCC), depending on the total integrated dose (TID) of external irradiation, taking into account the nonradiation factors.


   Materials and Methods Top


The study uses data from 544 male employees of SMCC and 503 male employees of “Stepnogorsk Teploelektrotsentral” LLP and Stepnogorsk Bearing Plant (SBP), received during the period of compulsory periodic medical examination of workers in 2015.

Information on previous and chronic diseases, alcohol, and tobacco use, professional activities (position, length of service, characteristics of harmful production factors, degree of professional capacity loss, presence of disability in connection with occupational disease) were collected by direct questioning.

An in-depth ophthalmological examination was carried out using modern instrumental and functional methods of examining visual organ for verifying the diagnosis. The information obtained from the ophthalmologic examination and from social survey of professional activity was put in register of information system of “Medical examination map of workers in uranium mining plant” of Radiobiology and Radiation Protection Institute of “manipulation under anaesthesia” for further analysis.

To evaluate radiation dose of the main group, the data from the timetable for measuring the dose rate of external and internal irradiation was used, obtained by calculation from the date of employment.

The control group consisted of 351 workers at the thermal power station and 152 workers in the main production department of SBP. The choice of the control group was determined by the level of medical care comparable with the main group of workers in terms of age and sex, as well as by production harmful factors, with the exception of radiation compound absence. All workers of the basic and control groups live in Stepnogorsk and in suburb. The average age in the exposed group was 44.5 ± 12.4 years (95% confidence interval [CI] 43.48–45.66), in the control group 44.1 ± 12.3 years (95% CI 43.01–45.17). The majority of employees from two companies had a level of secondary and secondary technical education. The length of service between the groups did not have a statistically significant difference: the average length of service in the main group was 10.4 ± 10.0 years (95% CI 9.53–11.28) and in the control group 11.1 ± 10.1 years (95% CI 10.24–12.01) [Table 1].
Table 1: Comparative characteristics of research subjects

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The examination of visual organ was carried out according to the detailed scheme, which allows to study the basic visual functions, state of membranes and refracting eye medium, visometry with correction of ametropia, subjective and objective refractometry, tonometry according to Maklakov, perimetry, biomicroscopy, direct and reverse ophthalmoscopy, and determination of color perception.

The following quantitative and categorical indicators were taken into account during mathematical processing: age, intensity of smoking, alcohol consumption, glucose level, body mass index (BMI), and characteristics of industrial exposure, length of service with ionizing radiation source, and TID.

The systematization and statistical processing of data was carried out using SPSS 20.0.0 software of IBM Corp. (International Business Machines Corporation USA). The numerical data are presented as “average value ± standard deviation.” Student's test was used to compare the quantitative characteristics of the data, the comparison of qualitative characteristics was made using the 2 × 2 contingency tables with Pearson Chi-square criterion with the Yates' correction and the exact F-test. Spearman's rho (rs) was used to analyze the dependence of the quantitative characteristics of sample data from summation with or without normal distribution. The differences in the data and the correlation between the data for P < 0.05 were considered statistically significant. Statistically significant risk factors were included in multivariate regression analysis (multiple linear regression); for the degree of reliability, the determination coefficient R2 was used.


   Results and Discussion Top


The conducted studies showed a statistically significant high prevalence of ophthalmopathology among workers of the main group in comparison with the control group (χ2 =4.97 P = 0.026). This indicator for 100 workers was 97 cases in the main group and 87 in the control group [Table 2].
Table 2: The prevalence of ophthalmopathology among workers in the study groups (per 100 workers)

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In the structure of ophthalmopathology, lens diseases have a leading place among workers, in both the main group and control group. A statistically significant difference in the index of the lens disease (χ2 = 4.02, P = 0.052) among the contingent of workers in the study groups was revealed. At the same time, the prevalence of the lens disease in the main group is 1.4 times higher than in the control group (95% CI 1.01–1.81).

Cataract has a multifactorial genesis, with the following most significant risk factors: age, length of service, smoking intensity, BMI, TID, average blood pressure, and intraocular pressure of each eye [Table 3].
Table 3: Risk factors for the development of cataract among workers in the study groups

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The risk factors for cataract in the study groups are comparable and there are no significant differences.

Statistical analysis was made on the relationship between the lens disease and the effect of ionizing emission to determine the reasons for the increase in the prevalence of cataracts among workers in the uranium industry. With an increase in TID, there is an increase in cataract development [Table 4].
Table 4: Cataract abundance depending on the total integrated dose of workers in the exposed group

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To determine the possible relationship between the development of cataracts and the influence of occupational exposure with correction for potentially interfering factors, two subgroups were formed depending on the dose level: up to 100 mSv and more than 100 mSv [Table 5].
Table 5: Cataract abundance depending on the total integrated dose of the main group of workers, taking into account nonradiation factors

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A statistically significant trend in the increase of cataracts with an increase in the total integrated dose, smoking index of more than 20 packs/year, increase in body weight and persons suffering from hypertension.

Logistic regression analysis was used to determine the greatest impact of the risk factor on the development of cataracts among workers of SMCC. Age, exposure, TID, BMI, and smoking were added to the statistical model of logistic regression analysis. As a result of a multivariate analysis of risk factors relationship to the presence of cataract, it was found that the main sign predicting the development of cataract in uranium industry workers is TID (R2 = 0.821 P = 0.0007) and the duration of exposure (R2 = 0.809 P = 0.0009). The age index had a high determination coefficient (R2 = 0.972 P = 1.016) but was not statistically significant. The values of BMI (P = 0.095) and smoking (P = 7.141) were statistically insignificant in the development of cataracts.

It is known that age is a key risk factor for many diseases, including cataracts. Lens opacity is a pluricausal manifestation, which is based on the mechanism associated with the course of time. The indexes of the human impact of ionizing emission showed a statistically significant effect on the development of cataract among adult SMCC workers.

In general, the evaluation of lens disease development depending on the prolonged effect of ionizing emission, taking into account other significant factors, was comparable with the results of other studies. A longer period of observation and expansion of the studied group for further research will provide more information about the development of cataract with planned occupational exposure.


   Conclusions Top


  1. In the main group, the overall disease of the organ of vision is statistically significant, including lens diseases (χ2 =4.02, P = 0.052)
  2. A statistically significant increase in the risk of developing cataract was found in the main group (RR = 1.4 95% CI 1.01–1.81)
  3. With the increase of TID, there is an increase in the development of cataract among workers in the uranium industry (χ2 = 29.04 P = 0.000)
  4. Statistical analysis of the relationship between the development of cataract and the dose of radiation, taking into account significant factors, determined a statistically significant trend of increasing cataract with an increase in TID, smoking index, BMI, and suffering from hypertension
  5. Logistic regression analysis revealed that the main signs predicting the development of cataracts in workers of the uranium industry are TID (R2 = 0.965 P = 0.000) and length of service (R2 = 0.868 P = 0.000). The age index had a high determination coefficient (R2 = 0.972 P = 1.016) but was not statistically significant. The values of BMI (R2 = 0.402 P = 0.095) and smoking (P = 7.141) were statistically insignificant in the development of cataracts.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Correspondence Address:
Zhibek S Dautbayeva
Chair of ENT and Eye Diseases, JSC Medical University of Astana, Beybitshilik, 49A, 010000 Astana
Republic of Kazakhstan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ATMPH.ATMPH_175_17

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