Increased lead concentrations in the hairs of radiographers in general hospitals

This study investigated lead concentrations in the hairs of radiographers working in the radiological departments of general hospitals that used lead shielding for radiation protection. We collected scalp hair samples from 32 radiographers working in four radiology departments with lead shielding and 18 administration personnel in the same hospitals without lead shielding. Samples were analyzed for lead concentrations by inductively coupled plasma mass spectrometry. As a result, lead concentrations in the hairs of the radiological technologists were significantly higher than those in the administration staffs (0.72 ± 0.51 vs. 0.19 ± 0.27 μg/g, P < 0.001). The hair lead concentrations were positively and significantly associated with environmental lead concentrations (r = 0.6, P = 0.001), but not associated with age, working duration, and gender distribution.


Results
The lead concentrations in the hairs of radiographers were significantly higher than those of the administration staffs (0.72 ± 0.51 vs. 0.19 ± 0.27 μg/g, P < 0.001), while age, working duration, and gender distribution were not shown significant difference between the two groups (33.9 ± 8.6 vs. 35.2 ± 11.9 years of age; 8.4 ± 8.3 vs. 5.4 ± 5.4 years of working duration, as shown in Table 1). www.nature.com/scientificreports/ The lead concentrations of the study population were further analyzed by multiple linear regression, with the lead concentration (µg/g) as a dependent variable and associated factors including age (year), gender (male/ female), working duration (year) and environmental lead concentrations (mg/g) as independent variables. As a result, lead concentrations in the hairs of study population were positively and significantly associated with environmental lead exposure (r = 0.599, P = 0.001), but not associated with age, working duration, and gender distribution as shown in Table 2.

Discussion
The average hair growth rate is approximately 400 μm/24 h for Asian 14 , i.e. 1 cm increment per month, so hair samples including hair root less than 12 cm were collected to ensure that lead accumulation within 1 year of radiological working period and rule out possible lead accumulation or dilution beyond 1 year working period.
Any possible lead exposure at the residences and dietaries of all study subjects was ruled out, so higher lead concentrations in the hairs of radiographers may be attributed to potential lead exposure in the radiological departments. Additionally, the mean lead concentration in the hairs of radiographers (0.72 ± 0.51 μg/g) was comparable with that of workers employed in lead-related manufacturing plants (0.91 ± 0.22 μg/g) 15 . Noticeably, lead exposure on the workers could have adverse effects on their health even if their lead levels were within occupational health safety standards 16 . Therefore, the lead exposure was regard as no low limit in terms of health hazard and the lead concentration was recommended to be as low as possible.
A study on lead smelter workers found that lead was originated both from ingestion and environmental exposure; however, direct deposition from the environment was a more important source of lead in hairs 17 . Burns et al. found that 63% of lead aprons had detectable surface lead that was associated with visual appearance, type of shield, and storage method. Lead-containing shields are a newly identified, potentially widespread source of lead exposure in the health industry 18 . Additionally, lead sheets are installed within plasterboards fixed to the walls for shielding radiation in the departments of radiology, cardiology, vascular surgery, orthopedic surgery, neurosurgery, and dentistry 19 . We measured the levels of lead on wipes taken from fixed surfaces within the x-ray rooms of the study hospitals. The levels of lead ranged from 0.23 to 8.92 mg/g, and 3.31 mg/g on average. We speculate that the lead shielding materials disintegrate over time and the lead dusts escape the capillary pores of plasterboards or cracks of aprons and enter the x-ray room environments. Therefore, environmental lead accumulated in the hairs of radiological professionals during working period.
Lead sheet has been frequently and worldwide used to shield radiation in the department of radiology due to its high barrier property of radiation. However, the potential hazards of lead are ignored. This study found for the first time that increased lead concentrations in the hairs of radiographers using lead aprons for radiation protection and working in the space which installed lead shielding. Therefore, ambient lead monitoring, indoor ventilation, or replacements of lead-free shielding 20 are recommended for avoiding such occupational hazards. Table 1. Comparisons between the radiographers and administration staffs. a Not detected or below detection limit.

Conclusions
Significantly increased lead concentrations were found in the hairs of radiographers working in the radiological departments of general hospitals that used lead shielding for radiation protection. Additionally, the hair lead concentrations were positively and significantly associated with environmental lead concentrations. Tai-wan were recruited randomly as the exposed individuals, including 9 men and 23 women who had worked for 8 h/day and at least 1 year in the radiology departments that had installed lead for radiation shielding for more than 10 years. Eighteen administration staffs worked in the same hospital environments without lead shielding were also randomly recruited as the reference group. A questionnaire was completed by all study enrollees to rule out possible lead exposure at their residences and dietary, without hair dyed, permed, bleached, or straightened for at least 1 year before the hair collection. This study was approved by Tzu Chi Hospital Ethics Committee (approval number: IRB108-52-B). All methods were carried out in accordance with relevant guidelines and regulations (Declaration of Helsinki) and written informed consent was obtained from every participant.

Study population. Thirty-two radiographers out of 81 radiological staffs in four general hospitals in
Hair lead concentration analysis. More than 200 mg of scalp hair sample was collected from every participant. The lead concentrations were analyzed using the procedure adapted from Drobyshev et al. 11 . In briefly, 1:200 (v/v) Triton X-100 solutions was used to clean hair samples, followed by acetone, and washed samples twice with deionized water. Clean samples were dried at 75 °C for 24 h in an oven, and then stored in an electronic dry cabinet at room temperature for 12 h or longer until digestion. A dried hair was digested in a microwave with 3 mL of 70% nitric acid and diluted to 10 mL with 1% (v/v) hydrochloric acid. The analyzer mixed 1 mL of the solution, 1 mL of Indium standard solution (as an internal standard) and 8 mL of 1% (v/v) hydrochloric acid to measure lead element using an inductively coupled plasma mass spectrometer (Thermo X Series II) with each sample performed in triplicate.
Environmental lead concentration measurement. Dust wipe samples for lead were taken from the ceilings of x-ray rooms which were rarely cleaned to avoid the difference of clean frequency taking from walls. The lead concentrations of wipe samples were measured by x-ray fluorescence (XRF) spectrometry according to IEC 62321-3-1:2013. Method detect limit (MDL) for lead is 50 ppm.
Statistical analysis. Student's t-test was applied to analyze the differences between lead concentrations in the hair samples of the exposed and the reference groups, with statistical significant level set at P < 0.05. Multiple linear regression analysis was applied to determine the factors associated with lead concentrations in the hairs of the study population. All statistical analyses were performed using IBM SPSS Statistics 19.0 (IBM Taiwan Corp. Taipei, Taiwan).

Sample size calculation.
We were planning a study of a continuous response variable from independent control and exposed subjects. In a previous study the response within each subject group was normally distributed with standard deviation 0.5. If the true difference in the exposed and control means is 0.5, we will need to study 17 exposed subjects and 17 control subjects to be able to reject the null hypothesis that the population means of the exposed and control groups are equal with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05 21 . Sample size calculation was performed using Power and Sample Size Calculation version 3.1.6.