Long-Term Morbidity among Medical Imaging Workers in Republic of Benin through a Retrospective Cohort Study from 1972 to 2019

Introduction: A large number of studies indicated that ionizing radiation exposure is a risk factor for some cancers and non-cancer diseases. However, hypothesis supported by the literature of knowing whether protracted exposure to external ionizing radiation like in radiology services could induce other cancers and non-cancers diseases is unclear. The aim of this study was to assess the long-term morbidity among medical X-ray workers in Republic of Benin, from 1972 to 2019. Methods: Exposed (335) and unexposed workers (193), first employed between 1972 and 2019 were included in a cohort study in 2019 at Republic of Benin. Information on morbidity, personal and medical history, lifestyle, and socio-professional characteristics was retrieved from self-reported data. Spearman and Chi-square test were used to analyze the distribution of demographic characteristics in cohort. Cox proportional hazards regression was used to estimate hazard ratios (HRs) for the development of eye diseases (ED) and skin mass, adjusting for age, sex, smoking, alcohol drinking, occupational time, and year of employment. Results : The exposed workers had a higher risk of occurrence of ED and skin mass with the adjusted HRs (aHR) of 2.3 (95% CI = 1.4 - 3.9) and 3.3 (95% CI = 1.2 - 12.7) respectively, after adjusting for relevant variables. Heavy alcohol drinking had an increased risk of skin mass compared to those who did not drink (aHR, 7.6; 95% CI = 2.2 - 22.5). Conclusion : Association between radiation exposure and ED and skin mass was significant. Radiation exposure on the skin mass formation provides a basis for further studies.

• Morbidity
• Long Term
• Medical Imaging Professionals
• X-Ray
• Benin

1. Introduction

Overall, there are over 2.3 million medical radiation workers, and during half of their work time they are exposed to human-made sources of low-dose radiation [1] . Radiologists and radiotherapists were one of the earliest occupational groups to be exposed to external radiation, according to Berrington [2] . This external radiation is the cause of some health effects. The health effects of acute, moderate to high radiation doses are well characterized [3] , and detailed in the basis of data from the Japanese atomic bomb survivors and for patients treated with radiotherapy [4] . But according to study carried out by [5] Azizova et al., the risk estimates remain unclear for prolonged exposure at low dose rates (Azizova et al. 2018), as medical workers. In additional, uncertainties persist regarding quantification of risks of adverse events associated with protracted exposure to low doses at low dose rates of radiation, which are typically encountered in environmental and occupational settings [6] . Within radiology, occupational health and safety are important issues because of the very large number of exposed workers [7] . Few studies non cancer diseases hazards of human induced by low radiation doses, had been summarized by UNSCEAR [8] and other authors [9] . However, there is an association between exposure to ionizing radiation and health events such as cataracts [10] and opacities of the lens [11] .

In Africa, they are a limited number of epidemiology studies about effect’s radiation ionizing among medical workers. Maalej [12] in Tunisia, carried out studies which showed radio-induced late effects with exposures at ionizing radiation doses, such as squamous cell carcinoma. In Republic of Benin, the only article found was this of Dossou et al. [13] which concluded an increasing of chromosome aberrations in different shapes from radiographers in medical imaging centres. Therefore, knowledge about the long term effects of ionizing radiation among medical workers in Republic of Benin is not yet fully-explored.

The present study aimed to assess long term morbidity among radiology medical workers in Republic of Benin.

2. Methods

2.1. Population

The study population from private and public centres included 335 medical X-ray workers and a group of 193 medical workers from twelve (12) departments of Benin, not exposed to X-ray equipment employed at the same centre, who worked in Republic of Benin between 1972 and 2019 (47 years) and were born between 1937 and 1997. The list of centers private and public was obtained from the Ministry of Health.

2.2. Design Process Description of Data Collection

The present retrospective cohort study, exposed and non-exposed, was based on self-reported questionnaires and required contact with members of the cohort. Republic of Benin’s health system does not take into account universal health insurance for all citizens. Therefore, health information was not available in a searchable file health insurance. A list with contacts had been withdrawn from professional associations (radiologists, radiographers…) for exposed workers. But, for unexposed workers, questionnaires were administered to those who were present at the time of the survey. The survey was carried out in 2019 and collected 81.96% (250/305) and 87.34% (345/395) response rates out of 305 and 395 questionnaires administered ( Figure 1 ) to unexposed and exposed workers, respectively. The questionnaire included some information as sociodemographic characteristics, number of children, such as described at Online Resource B. The questionnaire had been validated by an occupational physician and based on feedback from past studies [14] . The investigation standards have been elaborated to unify and facilitate the data collected.

Figure 1

Figure 1. Flowchart selection process (Inclusions and exclusions in the analytic cohort) of study’s subject for risk of disorders, in Benin, 1972-2019.

A retrospective cohort study involving healthcare workers was conducted in 12 departments of Republic of Benin. It is composed to radiologists, radiographers and physicians assistants at diagnostic radiology for exposed workers; and physicians, physician assistants at others services and administrative workers for unexposed workers. Telephone consultations were carried out with healthcare workers who had already left the national territory at the time of the survey. The minimum of duration of employment to be included in study was one year [15] [16] . In order to be an eligible disease case, the disease must be declared after the first employment as occupational exposed workers or occupational unexposed workers. The study cohort included all alive occupational exposed workers of the medical imaging departments of Republic of Benin. In all, 10 occupational exposed workers and 57 occupational unexposed workers were excluded because the occupational exposed workers did not make the minimum of duration of employment which was one year ( Figure 1 ). The final subject cohort was comprised of 528 participants including 335 occupational exposed workers and 193 occupational unexposed workers. The retrospective cohort follow-up started with a date at first employment at the establishment and continued till the dates of survey.

2.3. Exposure Definition, Outcome

The subjects included in the study were divided into two groups—the group exposed to ionizing radiation in diagnostic radiology rooms and the group not exposed to ionizing radiation who work in workplace outside diagnostic radiology rooms. The dependant variables of interest (diseases of the eye and other disorders of skin and subcutaneous tissue) were extracted from the datasets by considering those which were the most representative (Online Resource A, Table A1 and Table A2 , Supplementary Information). All diseases of the eye and other disorders of subcutaneous tissue or skin mass were retrospectively coded according to the International Classification of Diseases tenth revision (ICD-10) [17] .

2.4. Confounding Factors

Several factors were considered as potential confounders which were defined and included in questionnaires (in Online Resource B). Age at initial year of employment was categorized into less than 25 years old, 26 - 30 years and 31-year and over, considering the interquartile range. Smoking (yes/no) and alcohol drinking (none, 1 drink per week, moderate, 1 - 10 drinks per week, high, >10 drinks per week) status [15] were considered given previous evidence of associations with different diseases. The different questions related to confounding factors were developed in questionnaire (in Online Resource B).

2.5. Statistical Analysis

Data were entered by double-entry in Epiinfo version 3.5.4. The data collected were analyzed using SAS® version 9.4. Number and percentage were used to summarize the sociodemographic data for descriptive statistics of exposed or unexposed group. Chi-square tests were used to compare the differences between each group. Bilateral tests were carried out, and a p-value ≤ 0.05 was considered statistically significant. We also estimated the cumulative incidence of morbidities selected (diseases of the eye and skin mass) using follow-up as the timescale and presented Hazard ratio’s (HR) and 95% Confidence Intervals (CI) calculated from crude and multivariable Cox model. Maximum likelihood test was used to obtain parameter estimates for cox regression. Left truncation was carried out by only including subjects who entered the study after occurrence of eye diseases and/or skin mass. Multivariable models with lower Akaike’s information criterion (AIC) and higher concordance statistic were preferred. The multivariable model was carried out adjusted for age at initial year of employment, year of first employment, sex, smoking and alcohol consumption using Akaike’s information criterion (AIC).

2.6. Ethical Consideration

The study was reviewed and approved by Research Ethics Committee of the Institute of Applied Biomedical Sciences (CER-ISBA) in Republic of Benin. The informed consent of occupational exposed workers or occupational unexposed workers was requested and obtained before administering the questionnaires.

Respondents were assured of their information and confidentiality, and they were informed of their right to withdraw from the study at any time.

3. Results

3.1. Characteristics Demographic

The characteristics of the exposed workers and the unexposed worker group are described in Table 1 . The mean age at initial year of employment of the exposed workers was 26 years (range, 21 - 46 years) ( Table 1 ), and 59.7 % were female. In the unexposed workers, the mean age at initial year of employment was 28 years (range, 19 - 46 years) ( Table 1 ), and 53.9 % were female. Age at initial year of employment (p < 0.0001) was significantly different between exposed and unexposed workers.

Table 1

Table 1. Characteristics of the study population at the time of the baseline questionnaire, 1972-2019.

Variables	Exposed n (%)	Unexposed n (%)	p-values*
Status	335 (100.0)	193 (100.0)	-
Sex
Male	135 (40.3)	89 (46.1)	0.19
Female	200 (59.7)	104 (53.9)
Subgroup age at initial year of employment (years)
≤25	233 (69.6)	75 (38.9)	<0.0001
26 - 30	54 (16.1)	53 (27.5)
≥31	48 (14.3)	65 (33.7)
Smoking
No	330 (98.5)	192 (99.5)	0.42
Yes	5 (1.5)	1 (0.5)
Alcohol drinking
None	218 (65.1)	142 (73.6)	0.06
Moderate	109 (32.5)	50 (25.9)
High	8 (2.4)	1 (0.5)
No. of years of work as exposed or unexposed worker (years)
≤1	119 (35.5)	72 (37.3)	0.10
2 - 6	127 (37.9)	85 (44.0)
≥7	89 (26.6)	36 (18.7)
Having Holidays during a career
No	161 (48.1)	104 (53.9)	0.21
Yes	174 (51.9)	89 (46.1)
Period of year of first employment (years)
≤2007	99 (29.6)	47 (24.4)
2008-2016	157 (46.9)	97 (50.2)	0.44
≥2017	79 (23.6)	49 (25.4)
	Mean (min-max)	Mean (min-max)	p-values**
Mean age at initial year of employment (years)	26 (21 - 46)	28 (19 - 46)	<0.0001
Male	25 (21 - 41)	27 (19 - 46)	<0.0001
Female	26 (21 - 46)	29 (19 - 44)	<0.0001
Mean of years of work as exposed or unexposed worker (years)	5.2 (1 - 30)	4.2 (1 - 22)	0.03
Mean of year of first employment (years)	2009 (1972-2018)	2011 (1972-2019)	0.22

*From Chi-2 tests. **from Spearman test.

3.2. Outcome

Based on one questionnaire, 186 health events have been declared by 113 (21.4%) workers (in Online Resource A, Table A1 , Supplementary Information). The predominant ailments were eye diseases (100/186) and skin mass or subcutaneous mass (26/186) (in Online Resource A, Table A2 , Supplementary Information). The proportion of eye diseases (p = 0.02) and skin mass (p = 0.01) were significantly different between exposed and unexposed workers ( Table 2 ). Four cases of cataracts have been reported among eye diseases (in Online Resource A, Table A2 , Supplementary Information).

A total of 84 and 26 cases of diseases of the eye and skin mass ( Table 3 ) were identified after a median follow-up of six years for the both, [interquartile range (IQR) 2 - 11] and [IQR, 3 - 12], respectively ( Table 2 ). The median follow-up in cases only was eight (08) years [(IQR) 2 - 13] and eight and half (8.5) [(IQR) 4 - 12] for eye diseases and skin mass respectively ( Table 3 ).

Table 2

Table 2. Survival characteristic and summary of most representative diseases developed by exposed (n = 335) and unexposed (n = 193) group in the study population at the time of the baseline questionnaire, 1972-2019.

Outcomes (Diseases)	Exposed n (%)	Unexposed n (%)	p-values*	Follow up Median (IQR) Years
Diseases of the eye and adnexa (ICD-10 classification)				6 (2 - 11)
No	272 (81.2)	172 (89.1)	0.02
Yes	63 (18.8)	21 (10.9)
Skin mass				6 (3 - 12)
No	312 (93.1)	190 (98.5)	0.01
Yes	23 (6.9)	3 (1.5)

*From Chi-2 tests; skin mass = Other disorders of skin and subcutaneous tissue related to radiation according to ICD-10 classification.

Table 3

Table 3. Diseases of the eye and adnexa and skin mass outcome of the study population at the time of the baseline questionnaire, 1972-2019.

Variables	Whole cohort	Retained health events
		Diseases of the eye and adnexa	Skin mass
All	528	84	26
Age attained (years) (mean, min; max)	-	36.7 (22 - 66)	36.4 (25 - 57)
Median follow up for cases (years) (median, IQR)	-	8 (2 - 13)	8.5 (4 - 12)
	n (%)	n (%)	n (%)
Sex
Male	224 (42.4)	33 (39.3)	5 (19.2)
Female	304 (57.6)	51 (60.7)	21 (80.8)
Subgroup age at initial year of employment (years)
≤25	308 (58.3)	42 (50)	15 (57.7)
26 - 30	107 (20.3)	19 (22.6)	3 (11.5)
≥31	113 (21.4)	23 (27.4)	8 (30.8)
Smoking
No	522 (98.9)	82 (97.6)	24 (92.3)
Yes	6 (1.1)	2 (2.4)	2 (7.7)
Alcohol drinking
None	360 (68.2)	47 (55.9)	11 (42.3)
Moderate	159 (30.1)	33 (39.3)	11 (42.3)
High	9 (1.7)	4 (4.8)	4 (15.4)
No. of years of work as exposed or unexposed worker (years)
≤1	191 (36.2)	27 (32.1)	3 (11.5)
2 - 6	212 (40.2)	26 (31)	10 (38.5)
≥7	125 (23.7)	31 (36.9)	13 (50)
Having Holidays during a career
No	265 (50.2)	35 (41.7)	10 (38.5)
Yes	263 (49.8)	49 (58.3)	16 (61.5)
Period of year of first employment (years)
≤2007	146 (27.7)	46 (54.7)	17 (65.4)
2008-2016	254 (48.1)	29 (34.5)	8 (30.8)
≥2017	128 (24.2)	9 (10.7)	1 (3.8)

% = n/all; skin mass = other disorders of skin and subcutaneous tissue related to radiation according to ICD-10 classification.

3.3. Cumulative Incidences and Risk Factors for Diseases of the Eye

Cumulative incidences of diseases of the eye in the whole cohort and by change in exposure status were shown ( Figure 2(a) and Figure 2(b) ). The overall cumulative incidence at the 7 years of follow-up after the initial year of employment was 9.9 % (95% CI 7.3 to 13.3) ( Figure 2(a) ) and exposed workers were at a higher risk of developing diseases of the eye at the 7 years of follow-up after the initial year of employment the cumulative incidence was 12.2 % (95% CI 8.7 to 16.9) while for unexposed workers, this was 5.9 % (95% CI 3.0 to 11.4) ( Figure 2(b) ). Unadjusted and adjusted Hazards Ratio (HRs) and 95% Confidence Intervals (CIs) of eye diseases are shown in Figure 3 . From univariable models, we found that, exposed workers had a significant risk of eye diseases (HR, 1.9 [95% CI, 1.2, 3.2]), compared to unexposed workers. Compared to workers who have started working before 2007, workers who have started working from 2017 (HR, 3.1 [95% CI, 1.2, 7.9]) had a high risk of eye diseases. The stratified analysis among exposed workers revealed a risk of eye diseases that was significantly increased for workers of Oueme-plateau departments (HR, 3.1 [95% CI, 1.3, 8.9]) and Atlantique-littoral (HR, 3.4 [95% CI, 1.5, 9.3]) (in Online Resource A, Table A3 , Supplementary Information).

After adjustment for sex, age at initial year of employment, alcohol drinking, year of first employment, departments of Republic of Benin the risks of occurrence of eye diseases were statistically significant increased for exposed workers (HR, 2.3 [95% CI, 1.4, 3.9]) and for workers who have started working after 2017 (HR, 3.5 [95% CI, 1.3, 9.1]). While the reduced risk of eye diseases was borderline significant for sex (P = 0.058). Sensitivity of analysis carried out with as time scale age attained revealed association between eye diseases and ionizing radiation exposure (HR, 2.5 [95% CI, 1.5, 4.3]) after adjustment for sex, age at initial year of employment, alcohol drinking, year of first employment, departments of Republic of Benin (in Online Resource A, Table A4 and Table A5 , Supplementary Information).

3.4. Cumulative Incidences and Risk Factors for Skin Mass

Cumulative incidences of skin mass in the whole cohort and by change in exposure status were shown ( Figure 4(a) and Figure 4(b) ). The overall cumulative incidence at the 4 years of follow-up after the initial year of employment was 1.8% (95% CI 0.9 to 3.7) ( Figure 4(a) ) and exposed workers were at a higher risk of developing skin mass at the 4 years of follow-up after the initial year of employment the cumulative incidence was 2.1 % (95% CI 0.9 to 5.0) while for unexposed workers, this was 1.2 % (95% CI 0.3 to 5.0) ( Figure 4(b) ). As for diseases of the eye, unadjusted and adjusted HRs, and 95% CIs of skin mass are shown in Figure 5 . From univariable models, we found that, exposed workers had a significant risk of occurrence of skin mass (HR, 3.8 [95% CI, 1.4 - 14.2]) and heavy taking drinks of alcohol (HR, 8.6 [95% CI, 2.6 - 24.4]) increases also significantly the risk of occurrence of skin mass ( Figure 5(a) ). After adjustment for sex, age at initial year of employment, alcohol drinking, year of first employment, departments of Republic of Benin, the risks of occurrence of skin mass were statistically significant increased for exposed workers (HR, 3.3 [95% CI, 1.2, 12.7]) and for workers who took heavy alcohol (HR, 7.6 [95% CI, 2.2 - 22.5]) ( Figure 5(b) ).

Figure 2

Figure 2. The cumulative incidence curves of diseases of the eye and adnexa (a) in cohort (exposed and unexposed) and stratified by exposure status (b) between 1972 and 2019.

Figure 3

Figure 3. Hazard Ratios of diseases of the eye and adnexa in univariable (a) and multivariable (b) events analysis by confounders factors.

Figure 4

Figure 4. The cumulative incidence curves of skin mass (a) in cohort (exposed and unexposed) and stratified by exposure status (b) between 1972 and 2020. Skin mass = other disorders of skin and subcutaneous tissue related to radiation according to ICD-10 classification.

Figure 5

Figure 5. Hazard Ratios of skin mass in univariable (a) and multivariable (b) events analysis by confounders factors. Skin mass = other disorders of skin and subcutaneous tissue related to radiation according to ICD-10 classification.

Note for Figure 3 and Figure 5 :

Age at initial year [26 - 30] period of age at initial year of employment (year); Age at initial year [≥30] period of age at initial year of employment (year); Year work [2008-2016] period of year of first employment; Year work [≥2017] period of year of first employment; Having Holidays Having Holidays during a career (yes or no); Occupational time [2 - 6] No. of years of work as exposed or unexposed worker (years); Occupational Time [≥7] No. of years of work as exposed or unexposed worker (years).

Hazard ratios (HRs) were estimated from a single Cox proportional hazards multiple regression model.

( Figure 3(b) ) Adjusted for sex, age at initial year of employment, alcohol drinking, year of first employment; departments of Benin; Survival time (Entry = date of first entry into the workplace, Out = date of events) for events and (Entry = date of first entry into the workplace, Out = date of survey) for no events;

Proportional hazards assumptions verified for age at initial year of employment (year), occupational time, having holidays, year work patterns.

4. Discussion

To our knowledge, this is the first evaluation of the risk non cancer diseases among medical imaging workers in Republic of Benin. Our analyses showed associations between medical X-ray workers and diseases of the eye and skin mass. At the same time, Heavy alcohol drinking had an increased risk of skin mass.

4.1. Diseases of the Eye

Diseases of the eye (HR, 2.3 [IC 95 %, 1.4 - 3.9]) were significantly associated to exposure ionizing radiation ( Figure 3 ). It is evidence that exposure to ionizing radiation may be harmful to the lens of the eye and increases the long-term risk of cataract formation (Chodick et al. 2008) [18] . Certainly, several other studies showed the association between cataract (Hiller et al. 1986) [19] ; Picano et al. 2012; Little 2013) [20] , opacities of the lens (Ainsbury et al. 2021) [11] , and protracted exposure to ionising radiation. Moreover, epidemiological studies, many years ago, established the association between exposure to sun (ultraviolet radiation) and development of cataracts Wright and Norval, 2021) [21] . Although there are several other eye ailments in this outcome not described by the literature recognized as radiation-induced, many of them could be related to opacification of the lens and which could involve cataract in its advanced stages. The workers who have started working after 2017 (HR, 3.5 [95% CI, 1.3, 9.2]), have a statistically significant higher risk of diseases of the eye from the multivariable model and were statistically significant. This could be explained by the fact that young workers performed more examinations than older workers, who are generally assigned to administrative work in the centres. The availability of dosimetry data could have supported this explanation and proved the dose-response trends of radiation on eye diseases. The median latency period of eight (08) years ( Table 3 ) shown in this study was not entirely similar to those reported in the literature. Because, according to study’s Chodick [17] , the latency period for cataract formation is probably longer for smaller doses and may reach 30 - 45 years (Wilde and Sjostrand, 1997) [22] .

4.2. Skin Mass

Ionizing radiation exposure and alcohol consumption were the main risk factor significatively associated to skin mass, through this study. According to the descriptive mass made by participants, the skin mass was soft tumor, moveable and no pain, probably benign like a lipoma. The lipoma is commonly observed in ordinal clinics (Mashima et al. 2021) [23] . Association of having skin mass with radiation exposure has been scarcely reported by the literature. The risk of having skin mass for exposed workers was high even after adjusting (HR, 3.3 [95% CI, 1.2, 12.7]) and statistically significant ( Figure 5(b) ). The scarcity of cohort studies able to establish the links between radiation exposure and skin mass was a brake in the discussion. The availability of dosimetry data could have supported this explanation and to prove the dose-response trends of radiation on skin mass. Heavy alcohol consumption was significantly associated with a higher factor risk to having skin mass ( Figure 5(b) ). These results comfort us, because Sumi et al. [24] obtained in their study that higher weekly alcohol consumption was strongly and significantly associated with higher abdominal visceral adipose tissue areas and skin mass. In opposite, according to Kim et al. [25] alcohol consumption is associated with decreased skin mass and increased visceral adipose tissue accumulation.

4.3. Strength and Limitation

This study was one of the largest undertaken to date on morbidity among medical imaging workers risk with high size of the baseline retrospective cohort in Republic of Benin. A study strength includes nearly complete data collection, which reduces the possibility of selection bias. The lack of dosimetry data was limitative factor of the study. The dose-response link could not be proven. Nevertheless, some limitations of the study should be considered. Prevalence disorders cases were identified from the self-reported questionnaires without clinical confirmations. We carried out three groups for the participants based on the frequency of alcohol drinking (none, Moderate and High) and did not get the information about alcohol drinking volume. For the smoking, we also performed two groups based on the acceptance or no of smoking and did not get the information about cigarette rods or packs. This lack of precision may have led to bias. We were unable to match the two groups to limit misclassification bias, since the number of subjects was limited. The potential confounders such as diet, medications, and level of physical activity, exposure to solar ultraviolet (UV) radiation, family medical history, might have contributed to an under or overestimation of the different associations. The difference was statistically insignificant between the two groups (unexposed and exposed) for variables sex, smoking, alcohol drinking. Thus, we believe that the bias might be minimal.

5. Conclusions

This first study among x-rays medical workers in Republic of Benin, confirms the known results that ionizing radiation exposure is a risk factor for eye diseases and adds new information by providing risk estimates for the occurrence of skin mass, benign tumors probability which should not be neglected. It provides a basis for further studies on a link between low dose radiation measured and skin mass and eye diseases in this country.

The public health and dosimetry monitoring significance in the prevention of disorders developed likely in occupational environment due to ionizing radiation exposure is emphasized in this study.

Acknowledgements

We are also grateful to Françoise Terrier for her unfailing support and advice.

Data Availability Statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Funding

Funding for this study was provided by the Division for Africa, Department of Technical Cooperation of International Atomic Energy Agency (IAEA).

Ethics Approval

The study was reviewed and approved by Research Ethics Committee of the Institut des Sciences Biomedicales Appliquees (CER-ISBA).

Abbreviations

CI:	Confidence interval
ICD-10:	International Classification of Diseases 10th Revision
HR:	Hazard Ratio
IQR:	Interquartile Range
AIC:	Akaike’s information criterion
UNSCEAR:	United Nations Scientific Committee on the Effects of Atomic Radiation
CER-ISBA:	Research Ethics Committee of the Institute of Applied Biomedical Sciences

Appendix 1: Supplementary Information (Online Resource A)

Table 4

Table A1. Different ailments collected from the study population at the time of the baseline questionnaire, 1972-2019.

	Participants who declared a health event	113/528
		n (%)
Health events	Eye diseases	100 (53.8)
	Skin mass	26 (13.9)
	Infertility	24 (12.9)
	Intra-pelvis mass (Myoma)	20 (10.8)
	Chronic digestive disorders	12 (6.5)
	Thyroid mass	4 (2.1)
	All	186 (100.0)
	Participants who have not declared a health event	415/528

% = n/all; skin mass = Other disorders of skin and subcutaneous tissue related to radiation according to ICD-10 classification.

Table 5

Table A2. According to International Classification of Diseases 10th Revision (ICD-10), classification of different eye diseases developed by exposed and unexposed group in the study population at the time of the baseline questionnaire, 1972-2019.

	Diseases	Exposed n = 75 (100%)	Unexposed n = 25 (100%)
Diseases of the eye and adnexa* (ICD-10 classification)	Glaucoma	1 (1.3)	0 (0.0)
	Cataract	4 (5.3)	0 (0.0)
	Eye irritation and disturbances	21 (28)	7 (28.0)
	Eye redness and disturbances	37 (49.3)	14 (56.0)
Total		63 (84.0)	21 (84.0)
Others diseases declared by participants for eyes**	lacrymal	2 (2.6)	3 (12.0)
	Abscess	10 (13.3)	1 (4.0)
Total		12 (16.0)	4 (16.0)

*These diseases were taken into account in diseases of the eye and adnexa subgroup accprding to ICD-10 classification; **This diseases subgroup was not taken into account by ICD-10 classification.

Table 6

Table A3. Hazard Ratio (HR, 95% CI) of diseases of the eye and skin mass in univariable analysis (Cox regression model) in the study population at the time of the baseline questionnaire, 1972-2019.

Diseases	Variables	Cases/n	Univariable analysis (HR 95% CI)
Diseases of the eye	Departments of Benin (old territorial division)
	Atacora-Donga	5/47	Reference (HR = 1)
	Borgou-Alibori	4/45	0.9 (0.3; 3.1)
	Zou-Collines	3/22	2.7 (0.8; 9.2)
	Mono-Couffo	3/16	1.9 (0.5; 6.7)
	Ouémé-Plateau	15/62	3.1 (1.3; 8.9)
	Atlantique-Littotal	33/143	3.4 (1.5; 9.3)
	p-value		0.01
Skin mass	Departments of Benin (old territorial division)
	Atacora-Donga	3/47	Reference (HR = 1)
	Borgou-Alibori	3/45	1.2 (0.3; 5.3)
	Zou-Collines	0/22	0.3 (0.0; 3.4)
	Mono-Couffo	1/16	0.8 (0.1; 4.8)
	Ouémé-Plateau	4/62	1.1 (0.3; 4.9)
	Atlantique-Littoral	12/143	1.4 (0.5; 5.4)
	p-value		0.92

Table 7

Table A4. Hazard Ratio (HR, 95% CI) of diseases of the eye and skin mass in univariable analysis (Cox regression model) for age attained in the study population at the time of the baseline questionnaire, 1972-2019.

Diseases	Variables	Cases/n	Univariable analysis (HR 95% CI)
Diseases of the eye	Age attained
	≤28	20/139	Reference (HR = 1)
	29-40	38/267	0.3 (0.1; 0.5)
	≥41	26/122	0.1 (0.0; 0.1)
	p-value		<.0001
Skin mass	Ageattained
	≤28	6/137	Reference (HR = 1)
	29 - 40	12/259	0.1 (0.0; 0.4)
	≥41	8/132	0.0 (0.0; 0.1)
	p-value		<0.0001

Table 8

Table A5. Cox regression model Multivariable analyses (HR and 95% CI) of diseases of the eye in the study population at the time of the baseline questionnaire with time scale age attained, 1972-2019.

Covariate	Cases/n	Multivariable analysis (HR 95% CI)
Status
Unexposed	21/193	Reference (HR = 1)
Exposed	63/335	2.5 (1.5; 4.3)
p-value		0.0007
Sex
Male	33/224	Reference (HR = 1)
Female	51/304	0.6 (0.4; 0.9)
p-value		0.04
Age at initial year of employment
≤25	42/308	Reference (HR = 1)
26 - 30	19/107	0.7 (0.4; 1.1)
≥31	23/113	0.5 (0.3; 0.9)
p-value		0.04
Year of first employment (years)
≤2007	46/146	Reference (HR = 1)
2008-2016	29/254	1.9 (1.1; 3.4)
≥2017	9/128	3.2 (1.3; 7.5)
p-value		0.02
Alcohol drinking
None	47/360	Reference (HR = 1)
Moderate	33/159	1.4 (0.9; 2.2)
Heavy	4/9	1.9 (0.6; 4.6)
p-value		0.20

Adjusted for sex, age at initial year of employment, alcohol drinking, year of first employment, departments of Benin; Survival time (Entry = age at first employment, Out = age at events) for events and (Entry = age at first employment, Out = age at survey) for no events; Proportional hazards assumptions verified for sex, age at initial year of employment (year), smoking, alcohol consumption, occupational time, having holidays patterns.

Appendix 2: Questionnaire (Online Resource B)

Part 1

IDENTIFIANT DU TRAVAILLEUR: |__|__|-|__|__|___|

à ne pas renseigner par l’enquêteur)

Nom et prénom:

Numéro de téléphone:

Etude épidémiologique chez les travailleurs exposés aux rayonnements X des centres d’imagerie médicale du Bénin.

Cible: TRAVAILLEURS EXPOSES—Atravailleurs affectés aux travaux sous rayonnements ionisants (ingénieurs, techniciens et aides soignants qui accèdent en zone contrôlée et/ou surveillée)

RENSEIGNEMENTS GENERAUX

Identification du travailleur (ingénieurs, techniciens et aides-soignants qui accèdent en zone contrôlée et/ou surveillée)

01. Numéro: |__|__|-|__|__|__| (à ne pas renseigner par l’enquêteAur)

02. Date: |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

03. Sexe: Masculin ρ0 Féminin ρ1

04. Date de naissance: |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

05. Catégorie socio-professionnelle (Tech/Ing en radiologie ou imagerie médicale/Radiologue/Autres):__________ (Variable autres à créer)

06. Nombre d’enfants: |__|__|

07. Date de première prise de service:

|__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

08. Carrière:

Structure 01	Durée au poste 02	Congés (adm et tech) 03	Temps de travail/jr sous Rx/par poste 04
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire

09. Avez-vous fait valoir vos droits à la retraite?

Non ρ0 Oui ρ1

10. Si oui fournissez la date de mise à la retraite:

|__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

11. Travaillez-vous dans d’autres unités de radiologie après votre admission à la retraite?

Non ρ0 Oui ρ1

12. Si oui renseigner le tableau ci-dessous

Structure 01	Durée au poste 02	Congés (adm et tech) 03	Temps de travail/jr sous Rx/par poste 04
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H Scopie	|__|__| H Radio	|__|__| H Scan	|__|__| H Mamo	|__|__| H Dentaire

RENSEIGNEMENTS SPECIFIQUES

Risque radiologique

13. Avez-vous reçu des cours de radioprotection après votre formation académique?

Non ρ0 Oui ρ1

14. Séjournez-vous en zone contrôlée pendant la réalisation des examens?

Non ρ0 Oui ρ1

15. Séjournez-vous en zone surveillée pendant la réalisation des examens?

Non ρ0 Oui ρ1

16. Portez-vous des Equipements de Protection Individuelle - EPI (tablier plombé, cache-thyroïde, cache-gonade), lorsque vous devez séjourner dans une zone contrôlée pendant la réalisation des examens?

Non ρ0 Oui ρ1

17. Faites-vous de la maintenance préventive pour les EPI?

Non ρ0 Oui ρ1

18. Si oui à quelle périodicité?

1 - 2 ans ρ0 2 - 4 ans ρ1 2 - 6 ans ρ2 >6 ans ρ3

Risque chimique

19. Faites-vous du développement manuel/automatique des clichés?

Non ρ0 Oui ρ1

20. Si oui, pendant combien de temps par jour?

Structure 01	Nombre de jours au poste de développement	Temps développement/jr 02
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H

21. Utilisez-vous des gants en latex pour le développement?

Non ρ0 Oui ρ1

22. Utilisez-vous des cintres pour le développement?

Non ρ0 Oui ρ1

23. Utilisez-vous des masques protège nez spécifiques pour le développement?

Non ρ0 Oui ρ1

Surveillance dosimétrique et médicale

24. Êtes-vous sous surveillance dosimétrique?

Non ρ0 Oui ρ1

25. Si oui ; quelle est la périodicité?

1 mois ρ0 3 mois ρ1 6 mois ρ2 1 ans ρ3

26. Portez-vous un dosimètre passif/opérationnel lorsque vous séjournez en zone surveillée ou zone contrôlée?

Non ρ0 Oui ρ1 Oui mais données non disponibles ρ2

27. Si oui quelles sont les valeurs des cumuls de doses annuelles reçues dans la période pendant laquelle vous avez travaillé au poste actuel? (Créer un autre masque avec le même identifiant)

Structure 01	Année 02	Doses/an (mSv) 03
	|__|__||__|__| Année	|__|__|__|, |__|__|
	|__|__||__|__| Année	|__|__|__|, |__|__|
	|__|__||__|__| Année	|__|__|__|, |__|__|
	|__|__||__|__| Année	|__|__|__|, |__|__|
	|__|__||__|__| Année	|__|__|__|, |__|__|

28. Êtes-vous sous surveillance médicale?

Non ρ0 Oui ρ1

29. Si oui ; quelle est la périodicité?

<6 moisρ0 1 an ρ1 2 ans ρ2 3 ans ρ3 >4 ans ρ4

30. Êtes-vous fumeur?

Non ρ0 Oui ρ1

31. Prenez-vous des boissons alcoolisées?

Rare ρ0 souvent ρ1 toujours ρ2

Morbidité (depuis 1970)

32. Avez-vous contracté des maladies malignes de la peau?

Non ρ0 Oui ρ1

33. Si oui lesquelles?_______________________________________________

34. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

35. Avez-vous contracté des maladies des yeux (cataracte, irritation ou rougeur fréquente des yeux, trouble de la vision)? ou en ressentez-vous les signes?

Non ρ0 Oui ρ1

36. Si oui lesquelles?_______________________________________________

37. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

38. Avez-vous des masses sous-cutanées?

Non ρ0 Oui ρ1

39. Si oui lesquelles? ______________________________________________

40. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

41. Aviez-vous été mis au courant d’une masse suspecte au niveau de la thyroïde au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

42. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

43. Aviez-vous été mis au courant après une consultation que vous avez contracté une maladie liée à l’un des organes?

44. Cœur

Non ρ0 Oui ρ1

45. Si oui lesquelles?_______________________________________________

46. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

47. Les poumons (Cancer, broncho-pulmonaire primitif…)

Non ρ0 Oui ρ1

48. Si oui lesquelles?_______________________________________________

49. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

50. Aviez-vous des troubles digestifs chroniques de causes inconnues?

Non ρ0 Oui ρ1

51. Si oui, Quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

52. Aviez-vous été mis au courant que vous avez contracté une maladie maligne du sang (Lymphome non hodgkiniens, leucémie, myélome multiples…) au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

53. Si oui lesquelles?_______________________________________________

54. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

55. Aviez-vous été mis au courant d’une masse suspecte dans votre organisme au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

56. Si oui lesquelles?_______________________________________________

57. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

58. Avez-vous eu une infertilité primaire ou secondaire?

Non ρ0 Oui ρ1

59. Si oui quelle a été la durée de cette infertilité: |__|__|ans

60. En quelle année est survenue l’infertilité: |__|__|__|__|ans

Part 2

IDENTIFIANT DU TRAVAILLEUR: |__|__|-|__|__|__| (à ne pas renseigner par l’enquêteur)

Nom et prénom:

Numéro de téléphone:

Etude épidémiologique chez les travailleurs exposés aux rayonnements X des centres d’imagerie médicale du Bénin.

Cible: TRAVAILLEURS NON EXPOSES (personnel administratif et d’entretien ; soignants et aides-soignants)

RENSEIGNEMENTS GENERAUX

Identification du travailleur (personnel administratif et d’entretien ; aides-soignants, brancardiers).

01. Numéro: |__|__|-|__|__|__| (à ne pas renseigner par l’enquêteur)

02. Date: |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

03. Sexe: Masculin ρ0 Féminin ρ1

04. Date de naissance: |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

05. Catégorie socio-professionnelle (aide-soignant, technicien de surface, secrétaire, brancardier): (Variable autres à créer)

06. Nombre d’enfants: |__|__|

07. Date de première prise de service:

|__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

08. Carrière:

Structure 01	Durée au poste 02	Congés 03	Temps de travail/jr 04
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H

09. Avez-vous fait valoir vos droits à une retraite?:

Non ρ0 Oui ρ1

10. Si oui fournissez la date de mise à la retraite:

|__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

11. Travaillez-vous dans d’autres unités de radiologie après votre admission à la retraite?

Non ρ0 Oui ρ1

12. Si oui renseigner le tableau ci-dessous

Structure 01	Durée au poste 02	Congés 03	Temps de travail/jr 04
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| Jours	|__|__| H

Renseignements spécifiques

Risque radiologique

13. Avez-vous reçu des cours de radioprotection après votre embauche?

Non ρ0 Oui ρ1

14. Avez-vous accès de manière régulière à la zone contrôlée/surveillée (salle d’examens) pendant la réalisation des examens?

Non ρ0 Oui ρ1

NB: pour une réponse oui prière soumettre l’intéressé (e) à aux questions de la première partie du présent questionnaire.

15. Êtes-vous sous surveillance médicale?

Non ρ0 Oui ρ1

16. Si oui; quelle est la périodicité?

1 an ρ0 2 ans ρ1 3 ans ρ2 > 4 ans ρ3

17. Êtes-vous fumeur?

Non ρ0 Oui ρ1

18. Prenez-vous des boissons alcoolisées?

Rare ρ0 Souvent ρ1 Toujours ρ2

Risque chimique

19. Faites-vous du développement manuel/automatique des clichés?

Non ρ0 Oui ρ1

20. Si oui, pendant combien de temps par jour?

Structure 01	Nombre de jours de développement	Temps développement/jr 02
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H
	|_|_|_|_|_| Jours	|__|__| H

21. Utilisez-vous des gants en latex pour le développement?

Non ρ Oui ρ1

22. Utilisez-vous des cintres pour le développement?

Non ρ Oui ρ1

23. Utilisez-vous des masques protège nez spécifique pour le développement?

Non ρ Oui ρ1

Morbidité (depuis 1970)

24. Avez-vous contracté des maladies malignes de la peau?

Non ρ0 Oui ρ1

25. Si oui lesquelles?_______________________________________________

26. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

27. Avez-vous contracté des maladies des yeux (cataracte, irritation ou rougeur fréquente des yeux, trouble de la vision)? ou en ressentez-vous les signes?

Non ρ0 Oui ρ1

28. Si oui lesquelles?_______________________________________________

29. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

30. Avez-vous des masses sous-cutanées?

Non ρ0 Oui ρ1

31. Si oui lesquelles? ______________________________________________

32. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

33. Aviez-vous été mis au courant d’une masse suspecte au niveau de la thyroïde au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

34. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

35. Aviez-vous été mis au courant après une consultation que vous avez contracté une maladie liée à l’un des organes?

36. Cœur

Non ρ0 Oui ρ1

37. Si oui lesquelles?_______________________________________________

38. Quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

39. Les poumons (Cancer, broncho-pulmonaire primitif…)

Non ρ0 Oui ρ1

40. Si oui lesquelles?_______________________________________________

41. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

42. Aviez-vous des troubles digestifs chroniques de causes inconnues?

Non ρ0 Oui ρ1

43. Si oui, quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

44. Aviez-vous été mis au courant que vous avez contracté une maladie maligne du sang (Lymphome non hodgkiniens, leucémie, myélome multiples…) au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

45. Si oui lesquelles?_______________________________________________

46. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

47. Aviez-vous été mis au courant d’une masse suspecte dans votre organisme au cours d’un examen d’exploration diagnostique?

Non ρ0 Oui ρ1

48. Si oui lesquelles?_______________________________________________

49. Si oui quand? |__|__|/|__|__|/|__|__|__|__| (jj/mm/aaaa)

50. Avez-vous eu une infertilité primaire ou secondaire?

Non ρ0 Oui ρ1

51. Si oui quelle a été la durée de cette infertilité: |__|__|ans

52. En quelle année est survenue l’infertilité: |__|__||__|__|ans

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21. Wright, C.Y. and Norval, M. (2021) Health Risks Associated with Excessive Exposure to Solar Ultraviolet Radiation among Outdoor Workers in South Africa: An Overview. Frontiers in Public Health, 9, Article 678680. >https://doi.org/10.3389/fpubh.2021.678680

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23. Mashima, E., Sawada, Y. and Nakamura, M. (2021) Recent Advancement in Atypical Lipomatous Tumor Research. International Journal of Molecular Sciences, 22, Article 994. >https://doi.org/10.3390/ijms22030994

24. Sumi, M., Hisamatsu, T., Fujiyoshi, A., Kadota, A., Miyagawa, N., Kondo, K., et al. (2019) Association of Alcohol Consumption with Fat Deposition in a Community-Based Sample of Japanese Men: The Shiga Epidemiological Study of Subclinical Atherosclerosis (Sessa). Journal of Epidemiology, 29, 205-212. >https://doi.org/10.2188/jea.je20170191

25. Kim, K.H., Oh, S., Kwon, H., Park, J., Choi, H. and Cho, B. (2012) Alcohol Consumption and Its Relation to Visceral and Subcutaneous Adipose Tissues in Healthy Male Koreans. Annals of Nutrition and Metabolism, 60, 52-61. >https://doi.org/10.1159/000334710