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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 3  |  Issue : 4  |  Page : 131-135

Genotoxic risk evaluation of cleaning workers


1 Department of Biology, Faculty of Science and Letters, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey
2 Department of Biology, Faculty of Science and Letters, Çukurova University, Adana, Turkey

Date of Submission19-Aug-2019
Date of Acceptance22-Nov-2019
Date of Web Publication26-Dec-2019

Correspondence Address:
Prof. Lale Donbak
Department of Biology, Faculty of Science and Letters, Kahramanmaras Sutcu Imam University, Kahramanmaras
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/LJMS.LJMS_48_19

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  Abstract 


Background and Aim: Cleaning agents are used in large quantities by millions of people throughout the world for disinfection and surface maintenance. Although there is a complex pattern of exposure to cleaning agents and resulting health problems among cleaners, genotoxic risks of cleaners as an occupational group are uncertain. In the present study, possible genotoxic effects of exposing to cleaning agents in peripheral lymphocytes of cleaners were investigated. Materials and Methods: In this study, possible genotoxic risks of cleaning workers were investigated by sister chromatid exchange (SCE) and chromosomal aberrations (CAs) tests. The frequencies of SCE and CA were determined in peripheral blood samples taken from 32 cleaning workers exposed to cleaning agents and 20 healthy controls as the control group. Cell kinetic parameters of mitotic index (MI) and proliferation index (PI) were also detected for determining the possible cytotoxic effects. Data analysis was perfomed using SPSS (17.0) package program. Results: A significant SCE formation was found in the peripheral blood of cleaners in comparison with the control group (P < 0.05). Similarly, the differences in the SCE values between nonsmoker cleaners and the nonsmoker control group were statistically significant (P < 0.05). However, CA value determined for cleaners did not show a statistically significant difference from that of control group (P > 0.05). The CA values were correlated with both the working period and the ages of the cleaning workers. No marked differences were detected concerning PI and MI indices between the workers and controls. Conclusion: The results of this study suggest that cleaning workers may have weak genotoxic risk due to occupational exposure.

Keywords: Chromosomal aberrations, cleaning workers, DNA damage, genotoxic risk, sister chromatid exchange


How to cite this article:
Donbak L, Kasan E, Kayraldiz A, Istifli ES. Genotoxic risk evaluation of cleaning workers. Libyan J Med Sci 2019;3:131-5

How to cite this URL:
Donbak L, Kasan E, Kayraldiz A, Istifli ES. Genotoxic risk evaluation of cleaning workers. Libyan J Med Sci [serial online] 2019 [cited 2020 Jan 22];3:131-5. Available from: http://www.ljmsonline.com/text.asp?2019/3/4/131/274101




  Introduction Top


Cleaning agents developed to facilitate dust and dirt removal are used in large quantities by millions of people throughout the world as well as cleaning workers for disinfection and surface maintenance. These agents typically consist of a mixture of many chemical substances which can be divided according to their technical function into disinfectants, detergents, alkaline agents, acids, complexing agents, and solvents, etc.[1],[2],[3] On the other hand, dust on the floors or surfaces of the living/working environment contains minerals, metals, fibers from textiles, paper and insulation material, particles from tobacco smoke, and also materials from biological sources.[4],[5] Furthermore, indoor dust may contain both frameshift and base-pair substitution mutagens, and some house dust samples composed cancer risk for preschool children.[6]

Cleaning workers are potentially at risk exposure to dust, cleaning agent constituents, and other particulate matter suspended during cleaning activities and the products of secondary pollutants by inhalation or dermal contact and pose health risks.[7],[8],[9] Studies indicated that working as a cleaner is associated with several respiratory and dermatologic diseases, musculoskeletal disorders, and other conditions due to toxic chemicals that they are exposed to during the cleaning process and the overall conditions of working place. Besides, gasses released from the mixture of cleaning agents may cause sleep disorders, memory losses, prostration, extreme fatigue, dizziness, and mental and personality behavior disorders.[10],[11],[12],[13],[14],[15] More importantly, some constituents of cleaning agents may cause DNA damages in somatic and/or germ cells and have carcinogenic effects.[2],[7],[16],[17] Reulen et al.[18] indicated a significantly higher risk of bladder cancer for housekeepers, cleaners, and laundry workers.

DNA damages, caused by mutagenic/genotoxic substances, can lead to several health diseases and complications such as cancer, tissue-related conditions infertility, aging, and multifactorial disorders and also cause hereditary defects due to the mutations in germ cells.[19],[20] Therefore, the assessment of the genotoxic effects in populations, occupationally/environmentally exposed to potential genotoxic substances, by detecting DNA damage is an important approach for preventive medicine. Several genotoxicity tests with different endpoints have been developed since 1970 and used to detect mutations in a single gene, chromosome, or genome.[21],[22] The most frequently used endpoints to assess genotoxic effects of exposure to complex mixture of chemicals on human populations are chromosomal aberrations (CAs), micronucleus, and sister chromatid exchanges (SCEs) tests detecting macrodamages of chromosomes which visible in the light microscope.[21],[23],[24]

Although there is a complex pattern of exposure to cleaning agents resulting in health problems among cleaners, genotoxic risks of cleaners as an occupational group are inadequate. Hence, in the present study, possible genotoxic effects of exposing to cleaning agents in peripheral lymphocytes of cleaners were investigated by in vitro SCEs and CA tests. Cell kinetic parameters of mitotic index (MI) and proliferation index (PI) were also detected for determining the possible cytotoxic effect of the exposure. Lymphocytes are used as a surrogate for the actual target tissues of genotoxic agents.


  Materials and Methods Top


Study population

Thirty-two male cleaning workers who were occupationally exposed to cleaning agents and dust in the workplace for varying durations of years were studied for the four different parameters (SCEs, CA, PI, and MI) and were compared to twenty nonexposed control groups. Characteristics of the exposed and the control groups are shown in [Table 1].
Table 1: The characteristics of the workers and control groups

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The exposed group

This group included 32 workers from a private cleaning company in the city of Adana (Turkey). All of the workers were men and they were in the age range of 26–42 years. Concerning smoking habits, 13 of the workers (41%) were active smokers and 19 were nonsmokers (59%). The workers have had varying duration of years (2–16 years) and were studied 40 h/week. They did not use any protective measure (gloves and/or mask) while working, so they were occupationally exposed to various cleaning chemicals and dust.

The unexposed group

It consisted of twenty men who were not exposed to any known physical or chemical agents except for smoking and were mainly working in the office. The group belonged to a similar age and socioeconomic status as that of the workers. Of the 20 workers, 8 were active smokers (40%) and 12 were nonsmokers (60%).

Prior to the cytogenetic study, questionnaires were administered to each individual. These questionnaires contained personal and demographic data, history of occupations, and exposure, including exposure to known genotoxic agents, medical history, smoking habits, recent illness, and medical treatment. The study population was formed based on the responses to the questionnaires. Persons with medical treatment including radiography and vaccination up to 3 months before venipuncture and having a family history of cancer and alcohol consumers were not included in the study. After obtaining informed consents of each individual, 5 ml venous blood samples were taken and heparinized in 1/10 ratio. Labeled blood samples were immediately transported to the genetic laboratory for the experiments.

Sister chromatid exchange and chromosomal aberration assays

Heparinized blood samples (0.2 mL) were added to the labeled culture tubes containing 2.5 mL chromosome medium. After addition of the blood, 5-Bromo-2′-deoxyuridine was added at a final concentration of 50 μg/mL and culture tubes were incubated for 72 h in 37°C. Two hours before harvesting the cultures, colchicine solution (0.06 μg/ml) was added to arrest the cell cycle at the metaphase stage. Cultures were harvested, and the slides were prepared according to the standard method[25],[26] with slight modifications suitable to the laboratory conditions. The slides were stained with 5% Giemsa for CA analysis and modified fluorescence plus Giemsa method for SCE analysis.[27]

Microscopic analysis of the slides was performed using the immersion lens (10 × 100). Chromosomal abnormalities were scored from 100 well-spread metaphases per donor for various structural aberrations. Polyploid cells were also recorded. The cells containing any kind of chromosomal aberrations were also recorded as abnormal cell (AC) to calculate the frequency of AC. For determining the number of SCEs, a total of fifty cells under second metaphases was analyzed for each donor. In addition, the MI was determined by scoring 3000 cells/donor from CA slides.[28] A total of 100 cells from each donor were scored for the determination of the PI from SCE slides.[29]

Statistical analysis

The mean and standard deviation were calculated for each biomarker. The significance of differences between workers and control groups for CA, SCE, MI, and PI values was analyzed by nonparametric Mann–Whitney U-test. The correlation between the cytogenetic markers and independent parameters (age and duration of a year) was evaluated using Spearman's rho test. The data were analyzed using SPSS (17.0) statistical software package (SPSS Inc., Illionis, ABD). P≤ 5% was referred to as statistically significant.


  Results Top


The mean frequencies of SCEs and PI for the exposed and control groups are presented in [Table 2]. A significant increase in the frequency of SCEs was observed in cleaning workers as compared to the control group. When the groups were subdivided according to smoking habit, data comparison demonstrated that there was a significant increase in the level of SCE in nonsmoker workers than in the corresponding control group (P < 0.05). On the other hand, the SCE level of smoker workers was not statistically different from that of the smoker control group (P > 0.05). As shown in [Table 2], no statistically significant differences were detected concerning PI value between the workers and the control group (P > 0.05).
Table 2: The frequency of sister chromatid exchanges/cell and proliferation index in cleaning workers and controls

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The mean values of CA, AC, and MI for the workers and corresponding control groups are summarized in [Table 3], together with the frequencies and types of CAs. Seven types of abnormalities including chromatid and chromosome breaks, dicentric chromosome, sister union, chromatid exchange, fragment, and polyploidy were observed in the exposed group with the frequencies of 2.68%, 1.09%, 0.43%, 0.03%, 0.56%, 1.12%, and 1.06%, respectively. The chromatid and chromosome breaks were the most common abnormalities observed in both of the groups.
Table 3: The types of chromosomal aberrations and frequency of aberrant cells, chromosomal abnormalities/cell and mitotic index in workers and control subjects

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The CA/cell ratio of cleaning workers was higher than that of the control group, as shown in [Table 3]. Similarly, the mean frequency of ACs was also higher in the exposed group when compared to the control. However, this elevation in the incidence of the CA and AC was not significant (P > 0.05). There were no significant differences between the workers and control groups with respect to the mean frequencies of MI (P > 0.05).

Data were also analyzed according to the duration of years to cleaning agents and ages of the workers and control group to evaluate the effect of years of exposure and age on the level of cytogenetic markers [Table 4]. According to the correlation analysis, there was no relationship between the SCE frequencies and years of exposure (P > 0.05) in workers, but a significant correlation was found between CA level and years of exposure (P > 0.01). In contrast to the cleaning workers (P > 0.05), there was a significant correlation between the SCE incidence and age of the controls (P < 0.01).
Table 4: Spearman's rho correlation between cytogenetic markers and independent variables>

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  Discussion Top


Majority of people are occupationally exposed to various chemical substances as well as environmental factors and their lifestyles (alcohol consumption and tobacco usage). As an occupational group, cleaning workers use miscellaneous cleaning products for the cleaning process and thus are occupationally exposed to these chemicals. Among these chemicals, ammonia, hydrogen peroxide, isopropyl alcohol, ethyl alcohol, sulfuric acid, sodium hydroxide, hydrochloric acid, acetic acid, trichloroethylene, perchloroethylene, and formaldehyde are the most commonly exposed ones and have the highest toxicant effect. Hydrogen peroxide, perchloroethylene, and formaldehyde have been also reported to have gonotoxic effects.[30],[31],[32]

Numerous studies have been published regarding the adverse health effects of working as a cleaner. An association between the working as a cleaner and musculoskeletal disorders, respiratory and dermatologic diseases, and other conditions have been reported due to exposure to toxic chemicals and the conditions of the workplace.[11],[12],[13],[14],[15] On the other hand, Bello et al.,[33] reported that the air exposure in the bath continues after the cleaning process has been completed and under the controlled environmental conditions, the organic volatile compounds have remained in the ambient air for about 20 min after finishing the cleaning.

Although cleaners are exposed to cleaning agents and dust in a complex manner, genotoxic risks of cleaners as an occupational group are uncertain. Tucker et al.[34] have studied the genotoxic effects of perchloroethylene exposition in dry-cleaning workers. Peripheral blood samples taken from 18 dry-cleaning workers did not show statistically significant differences from those of 18 laundry personnel who were not exposed to perchloroethylene, as a control group, regarding the chromosome translocation. However, it was detected that there is an important correlation between perchloroethylene level and cell frequency containing acentric fragment.

In the present study, possible genotoxic risk of 32 cleaning workers, employment of a private cleaning company in Adana, was investigated by SCE and CA tests using peripheral lymphocytes due to the lack of knowledge concerning the genotoxic riks of cleaning workers. They were divided into two groups according to the smoking habit: 13 of whom were smokers and 19 of whom were nonsmoker. According to the data, a significant increase in SCE level was observed in cleaning workers as to the control group (P < 0.05). Concerning the smoking habit, there was also a marked elevation in the level of SCE in nonsmoker workers than in the corresponding control group (P < 0.05). SCEs originate from breakage of two sister chromatids, following an exchange of the fragments, rejoin with one another, during DNA replication in S phase of mitosis. Its frequency is considered a reliable marker of pathological cell situations, as well as a genetic indicator for potential genotoxic/mutagenic compounds. The formation of SCE is elevated by mutagenic agents that form DNA adducts or that interfere with DNA replication.[35],[36]

In this study, the CA/cell ratio and also the mean frequency of ACs of cleaning workers were higher than that of the control group; however, these elevations were not statistically significant (P > 0.05). Chromosome aberrations are one of the important biological consequences of exposure to physical factors and genotoxic chemicals. Studies have shown a linkage between the frequency of chromosomal abnormalities and cancer formation. Majority of chromosomal abnormalities are caused by the inability to repair damaged chromosomes, improper repair, or abnormalities that occur in the migration of chromosomes to the poles during cell division.[37]

Several biomonitoring studies indicated a positive correlation between the levels of cytogenetic markers and years of exposure or ages of the individuals. In this study, no relationship between the SCE level and years of exposure was observed in workers (P > 0.05), but a significant correlation was found between CA level and years of exposure (P > 0.01). There was a significant correlation between the SCE incidence and age of the control subjects (P < 0.01), on the contrary to workers.

Determination of the possible cytotoxicity is particularly important when the results are used to assess the risk of substances to which humans may be exposed. MI gives the percentage of cells in the mitotic phase of the cell cycle and is used for the analysis of induced cellular toxicity in in vitro CA preparations. The decrease in MI indicates the inhibition of cell cycle progression and/or loss of proliferative capacity.[38],[39] PI is the total number of divisions divided by the number of cells that went into division and analyzed from the SCE preparations. In this study, when the cytotoxic risk of cleaning workers was examined, there were no significant differences between the workers and control groups with respect to the mean frequencies of MI and PI indices (P > 0.05).


  Conclusion Top


The results of this study indicated that occupationally exposure to cleaning chemicals and dust significantly induced the SCE formation in cleaning workers, and cleaners may pose a weak genotoxic risk. The significant rise observed in SCE formation may be due to the complex exposure pattern to chemical substances in combination with dust exposition rather than a single substance. Air-conditioning system must be optimized and the workers must wear masks and gloves during cleaning process to prevent exposure by inhalation and dermal contact.

Acknowledgment

We would like to thank the Research Fund of Kahramanmaras Sutcu Imam University for supporting the study (Grant No. 2012/2-11M).



Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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