|Year : 2013 | Volume
| Issue : 1 | Page : 58-62
Neurobehavioral, respiratory, and auditory disorders among mercury-exposed fluorescent lamp workers
Gaafar M Abdel-Rasul, Mahmoud A Abu-Salem, Manal A Al-Batanony, Mervat M Al-Dalatony, Heba K Allam
Department of Public Health and Community Medicine, Faculty of Medicine, Menoufiya University, Al-Menoufiya, Egypt
|Date of Submission||20-Feb-2013|
|Date of Acceptance||17-Mar-2013|
|Date of Web Publication||26-Jun-2014|
Heba K Allam
MSc, Department of Public Health and Community Medicine, Faculty of Medicine, Menoufiya University, Gamal Abdel Nasser Street, Shebin Al-Kom, Al-Menoufiya 32111
Source of Support: None, Conflict of Interest: None
The aim of this work was to study some of the health disorders resulting from occupational exposure to mercury among workers in a fluorescent lamp factory.
With the fast market growth of fluorescent lamps, the associated emissions and risk of mercury, which is an essential component in all types of fluorescent lamps, have received increasing public attention worldwide. Low doses of mercury exert toxicity on various human organs, including the central nervous, renal, respiratory, reproduction, immune, cardiovascular, skin, and motor systems.
A cross-sectional study was carried out on 138 workers in a fluorescent lamp factory and a nonoccupationally exposed group of 151 individuals. An environmental study of mercury and noise levels was carried out. Neurobehavioral tests, spirometric measurements, and audiometric examination were performed. Urinary mercury level was also measured for all participants.
In the exposed group, the mean value of urinary mercury level (µg/g creatinine) was significantly increased among those who showed behavioral changes and hearing loss or had other manifestations related to mercury toxicity. With increasing duration of employment in years or with increasing urinary mercury level, the performance of neurobehavioral test battery and spirometric measurements deteriorated. Prominent symptoms among mercury-exposed workers included tremors, emotional lability, memory changes, neuromuscular changes, and performance deficits in tests of cognitive and/or motor functions.
The neurobehavioral test battery must be used to study subclinical central nervous system dysfunction because of mercury toxicity, especially to evaluate the severity of the effects of mercury in epidemiological studies. This study also reinforces the need for effective preventive programs at fluorescent lamp industry workplaces, especially in developing countries with the most unhygienic ill-ventilated conditions.
Keywords: audiometry, neurobehavioral test battery, occupational mercury exposure, spirometry
|How to cite this article:|
Abdel-Rasul GM, Abu-Salem MA, Al-Batanony MA, Al-Dalatony MM, Allam HK. Neurobehavioral, respiratory, and auditory disorders among mercury-exposed fluorescent lamp workers. Menoufia Med J 2013;26:58-62
|How to cite this URL:|
Abdel-Rasul GM, Abu-Salem MA, Al-Batanony MA, Al-Dalatony MM, Allam HK. Neurobehavioral, respiratory, and auditory disorders among mercury-exposed fluorescent lamp workers. Menoufia Med J [serial online] 2013 [cited 2020 Feb 17];26:58-62. Available from: http://www.mmj.eg.net/text.asp?2013/26/1/58/135428
| Introduction|| |
Mercury is an essential element in the earth and is the only metal that is liquid under standard conditions for temperature and pressure 1. Mercury and its compounds are known to be potentially hazardous materials and are rated among the top environmental pollutants. Mercury can exert significantly adverse effects on human health, especially the kidneys, liver, respiratory, and nervous systems 2. Mercury is used in fluorescent lamps 3.
With the fast market growth of fluorescent lamps, the associated emissions and risk of mercury, which is an essential component in all types of fluorescent lamps, have received increasing public attention and concerns worldwide 4. A fluorescent lamp typically consists of electrodes at both ends of a phosphor-coated glass tube, a small amount of mercury, partly in vapor form, and an inert gas (usually argon) sealed in the tube. The mercury vapor is excited when current is applied to the electrodes, and the ultraviolet radiation emitted by the excited mercury is converted by the phosphor coating to visible light. Mercury vapor is impinged onto the glass, the phosphor powder, and the metal components during lamp operation 5. A fluorescent lamp or a fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor 6. A fluorescent lamp tube is filled with a gas containing low-pressure mercury vapor and argon, xenon, neon, or krypton 7. Mercury is introduced into the lamp in a variety of ways; although in some areas mercury is added manually, the predominant method is automatic. Mercury remains the material of greatest concern during fluorescent lamp making, although the exposure is relatively low – except around the exhaust machines, to mechanics working near these machines, and during cleanup operations 8.
Elemental mercury may exert a variety of adverse effects. Neurological effects, renal effects, cancers, respiratory effects, cardiovascular effects, gastrointestinal and hepatic effects, effects on the thyroid gland, effects on the immune system, effects on the skin, reproductive and developmental effects, and genotoxicity have been observed following exposure to mercury vapor 9,10. Specific symptoms may be found in the central nervous system and the kidney.
Nevertheless, there is no clear knowledge of the level of exposure at which mercury vapor exerts adverse effects 11. Few Egyptian studies can be found in this field, such as the work of El-Safty et al. 12, who studied the nephrotoxic effects of mercury exposure and smoking among Egyptian workers in a fluorescent lamp factory, and Foda 13, studied memory status among workers exposed to mercury in a fluorescent lamp factory in Alexandria.
Aim of the work
The aim of this work was to study some of the health disorders resulting from occupational exposure to mercury among workers in a fluorescent lamp factory as well as biological and environmental monitoring of workers and environment of the factory.
| Participants and methods|| |
This study was carried out in a fluorescent lamp factory (the industrial zone, Quisna city, Menoufia governorate, Egypt) between February and July 2012. The Menoufia Faculty of Medicine Committee for Medical Research Ethics reviewed and formally approved the study before it began. Approval from the factory was obtained and all participants provided written informed consent before inclusion. A cross-sectional comparative study was designed to study 138 occupationally exposed male workers from the different departments in the factory studied after excluding nonresponders and the application of exclusion criteria, which included individuals with a history of neurological or psychiatric diseases, use of antipsychotic drugs, chronic liver or kidney diseases, chronic drug or alcohol abuse, and chronic auditory or chest disease. A control (unexposed) group of 151 men who were never exposed to mercury at work were matched with the exposed group for age, residence, education, and income. They were chosen randomly from among the relatives of the exposed workers.
Participants were interviewed by trained investigators at the factory clinic during the day shift (between 7:00 a.m. and 3:00 p.m.). At each workplace visit, demographic data, smoking status, and employment history (including years of working in the industry and wearing of protective clothes) were obtained.
Neurobehavioral assessment was performed using the neurobehavioral test battery, which consisted of subtests from the Wechsler Adult Intelligence Scale for adults revised to cover domain cognitive functions of attention and short-term recall (Paired Auditory Serial Addition Test and Digit Span test, forward and backward), visuospatial (Benton Visual Retention test), psychomotor (Symbol Digit and Trail-making part A and B tests), and general intelligence (Vocabulary and Similarities tests) 14. Better performance was evaluated by higher scores obtained on tests of Similarities, Digit Symbol, Digit Span, Vocabulary, Paired Auditory Serial Addition Test, and benton visual retention test; by contrast, lower latencies or time to complete Trail-making part A and B tests indicated better performance.
In addition, the following measurements were made: first, spirometry spirometric measurements were performed using the spirolab (MIR 010) to determine vital capacity (VC), forced vital capacity (FVC%), forced expiratory volume in 1 s (FEV1%), forced expiratory ratio (FEV1/FVC%), and forced expiratory flow during 25–75% of FVC (FEF 25–75%), with the best value of three technically acceptable maneuvers recorded and expressed as percentages of predicted values. Second, using diagnostic audiometer AS 67 (Audiometer, Mod.AS5 V 220 Hz 50 W 10 NoSerie 205; Spain), an air conduction audiometric examination was carried out at different frequencies for the right and left ears separately for exposed workers and the control group. The mean of the intensities of three measurements at 1000 Hz was considered. Third, a 25 ml morning urine samples were collected from each participant before the work shift and were maintained at 0–4°C in a sterile container until analysis. Every sample was analyzed for the presence of inorganic mercury using a cold vapor-atomic absorption spectrophotometer at the institute of measurements and calibration, Cairo, Egypt. Results of the mercury analysis were expressed as µg Hg/g of urinary creatinine in order to minimize problems because of variations in urine osmolality and specific gravity. Finally, environmental measurement of mercury levels was carried out in the factory using a mercury vapor analyzer ELTWI-‘MS’ (Arizona Instrument LLC, Tempe, Arizona, USA), survey mode. The measurements were performed at different places with expected potentially high mercury concentrations such as the exhaust machine, mounting machine, sealing machine, and automatic basing machine; three readings were taken at each site and the mean values were calculated. Also, noise measurement was performed using a sound level meter ANSI type 2 Model 452 (Digital Sound Level Meter, Models 407744 & 407766, Version 2.0; USA) at the locations where the workers usually worked. The apparatus was set up on the fast A scale. Multiple readings were taken from different places of the factory and the mean reading was recorded.
Student’s t-test was used for continuous quantitative parametric variables and the Mann–Whitney U-test was used for nonparametric variables. The χ2-test was used for categorical variables. Partial correlation coefficients were also used to test the association between variables. Comparisons of data were performed with the overall α error set at 0.05 (two tailed). Analyses were carried out using the SPSS v. 13 software (SPSS Inc., Chicago, Illinois, USA) and Epi Info version 3.3, released by Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, in October 2004.
| Results|| |
The highest mean value of environmental mercury (µg/m3) was found in the exhaust machine (53±0.9), followed by the basing machine (33±0.2) and then the sealing machine (29±0.6) [Figure 1]. The mount machine showed the highest mean value of sound level (82±0.9 dB), followed by the sealing machine (81±1.0 dB) and then both exhaust and washing machines (80±1.2 dB) [Figure 2]. The mercury-exposed group had a significantly higher mean value of urinary mercury level (µg/g creatinine) (44.1±17.5) than the control group (6.1±4.9) [Figure 3]. There was a nonsignificant difference between the exposed and the control groups in sociodemographic data, anthropometric measurements, and vital signs. Chest and auditory manifestations, behavioral changes, manifestations related to mercury toxicity, spirometric measurements, moderate/severe hearing impairment, and deteriorated performance on neurobehavioral tests were significantly frequent among the exposed group than the controls [Figure 4] and [Figure 5]. In the exposed group, the mean value of urinary mercury level (µg/g creatinine) was significantly increased among those who showed behavioral changes or had manifestations related to mercury toxicity [Table 1]. Also in the exposed group, with increasing duration of employment in years or with increasing urinary mercury level (µg/g creatinine), the correlated performance of the neurobehavioral test battery and spirometric measurements deteriorated significantly [Table 2].
|Figure 3: Urinary mercury level (µg/g creatinine) among the studied groups.|
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|Figure 4: Manifestations related to mercury toxicity among the studied groups.|
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|Table 1: Pearson’s correlation between independent variables urinary mercury level (µg/g creatinine) and duration of employment and dependent variables of neurobehavioral tests and spirometric measurements among the exposed group|
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|Table 2: Mean values (±SD) of urinary mercury level (µg/g creatinine) among exposed workers (n=138) with or without manifestations related to mercury toxicity or behavioral changes|
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| Discussion|| |
In this study, the highest environmental mercury concentration was 53±0.9 μg/m3 at the exhaust machine, followed by 33±0.2 μg/m3 at the basing machine; both exceed the Occupational Safety and Health Administration limit of 10 μg/m3 15 and the American Conference of Governmental Industrial Hygienists threshold limit value of 25 μg/m3 16. The noise levels in all sectors of the factory were below the maximal permissible limit of the sound intensity inside working closed areas according to the Egyptian law 4/1994 B appendix 7 17 of 90 dBA; thus, any changes in the auditory manifestations or hearing acuity could be attributed to the ototoxic effect of mercury exposure.
Urinary mercury level was significantly higher in mercury-exposed workers than in the unexposed group. This is in agreement with similar results found in Egypt 18.
Early changes in ventilatory functions in the form of FVC, FEV1, FEV1/FVC%, and FEF 25–75% were observed among exposed workers. Similar results were obtained by Snodgrass et al.19, who reported impaired pulmonary functions, airway obstruction, restriction, hyperinflation, and decreased VC in mercury vapor-exposed workers.
The prevalence of hearing loss was significantly higher in exposed than in unexposed groups. These results are in agreement with those of Cesarani et al. 20, who found a higher prevalence of hearing loss among dentists chronically exposed to mercury vapors.
In this study, exposed workers showed significantly lower performance on all neurobehavioral tests compared with the controls. A meta-analysis carried out by Meyer et al. 21 with results from 12 studies of occupational mercury exposure showed a significantly lower neurobehavioral performance among mercury-exposed workers compared with the control group. Moreover, Zachi et al. 22 reported the same lower performance on the neuropsychological test among former workers at a fluorescent lamp factory compared with matched unexposed controls in Digit Span subsets and Vocabulary test. Also, Moen et al. 23 and Liang et al. 24 showed evidence for neuropsychological decrements and psychosomatic disorders associated with low Hg concentrations on attention, visual perception, memory, and psychomotor speed. However, Fouda 13 found no significant difference between mercury-exposed and unexposed workers in the digit span forward and backward test. This difference may be attributed to the lower urinary mercury concentration among mercury-exposed workers in this study (44.1±17.5 µg/g creatinine) than in Fouda’s study (32±4.1 µg/g creatinine). In this study, a significant adverse association was observed between urinary mercury level and neurobehavioral tests. Echeverria et al. 25 reported significant negative associations between urinary mercury level and neurobehavioral tests, especially the Digit Span Forward and Digit symbol test.
Tremors were prevalent in the mercury-exposed group than in the controls. This finding is in agreement with that of Fawer et al. 26 Piikivi and Hanninen 27. Teeth loss, gum inflammation, and bleeding gums were significantly more frequent among mercury-exposed workers than the controls. These results are in agreement with those of Holland et al. 28, who reported frequent teeth loss and gum inflammation among mercury-exposed workers.
This study shows that with increasing duration of employment, urinary mercury level increases. This result was in agreement with that of Farahat et al. 18 and El-Safty et al. 12.
| Conclusion|| |
This study offers additional evidence that the central nervous system is a highly sensitive target for elemental mercury vapor exposure in the form of performance deficits in tests of cognitive or motor function and focuses on the ability for earlier detection of health effects among mercury-exposed workers using neurobehavioral testing. These tests are an easy, cheap, and effective tool that can be used in different workplaces and different cultures with low levels of education to study subclinical central nervous system dysfunction because of mercury toxicity, especially to evaluate the severity of the effects of mercury in epidemiological studies. This study also reinforces the need for effective preventive programs in fluorescent lamp industry workplaces, especially in developing countries with the most unhygienic, ill-ventilated conditions.
The authors are grateful to all the workers and the participants who generously agreed to participate and the administrator of the factory, who facilitated the access to the study group.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]