Abstract
Cholinesterase is one of many important enzymes needed for acetylcholine hydrolysis. This study aimed to evaluate the serum pseudo-cholinesterase (BuChE) level and its relation to biological parameters (hematological and biochemical parameters) and symptoms among occupational workers, gasoline station worker in Bangkok, Thailand. Our results revealed that the average BuChE level was in normal range, but it had strong relation to hemoglobin (Hb), hematocrit (Hct), blood urea nitrogen (BUN), creatinine (Cr) and serum glutamic pyruvic trans-aminase (SGPT) (Linear regression analysis, p < 0.05, p < 0.05, p < 0.01, p = 0.001 and p < 0.01 respectively). Although, BuChE was not related to white blood cell parameters, but it may exhibit the skin irritation (p = 0.058) of the workers as it showed significant correlation to conjunctivitis and nausea (Pearson’s correlation, p < 0.01 and p < 0.05). In conclusion, this finding may explain that BuChE was significantly related to red blood cells (RBC), liver and kidney functions.
Keywords: Serum cholinesterase, Biological parameters, Symptoms, Gasoline station workers
Introduction
Cholinesterases hydrolyze acetylcholine (a neurotransmitter) into choline and acetic acid which used in the proper functioning of the nervous systems of humans, other vertebrates, and insects. There are two types of acetylcholinesterase (AChE, EC 3.1.1.7), the Red blood cell (RBC) cholinesterase (erythrocyte cholinesterase, or acetylcholine acetylhydrolase) and the pseudo-cholinesterase (BChE or BuChE, EC 3.1.1.8) which is also known as plasma cholinesterase, serum cholinesterase, butyrylcholinesterase, or acylcholine acylhydrolase. The RBC cholinesterase found primarily in the blood and neural synapses while the pseudo-cholinesterase (BuChE) normally found in the liver [1]. The BuChE is generally used in reference to a clinical test that reflects levels of enzymes in blood which chemically interfere with the action of cholinesterase and become potent neurotoxins such as carbamate and organophosphate pesticides [2].
Human plasma is overwhelmingly with BuChE as exhibited at the ratio of BuChE to AChE of 1,000:1 [3]. The relationship between blood measures of AChE and or other factors is usually not known. Data on AChE inhibition in neural tissues are preferred. Peripheral nervous system data are rarely available in animals, and in humans neither peripheral nor central nervous system data are typically available. The level of BuChE can serve as surrogate information for projecting potential hazards, as a matter of science policy in protecting human health.
Generally, the cholinesterase is interesting neurotransmitter which related to nervous system [4, 5]. Human exposure to cholinesterase inhibiting chemicals such as organophosphate insecticides can affect cholinesterase activity in both red blood cells and in blood plasma, and can act directly, or in combination with other enzymes, on cholinesterase in the body result from inhalation, ingestion, or eye or skin contact during the manufacture, mixing, or applications of these pesticides [6]. Therefore, any information from blood cholinesterase inhibition would provide important insights into potential hazard. While, the Red blood cell (RBC) measures of acetylcholinesterase (AChE) are generally preferred over plasma measures of cholinesterase activity because data on red blood cells may provide a better representation of the inhibition of the neural target enzyme, AChE. Organophosphate pesticide (OPP), however, may use plasma cholinesterase inhibition data under certain circumstances, such as if red blood cell data are insufficient, of poor quality, or unavailable; if there is a lack of dose-dependency for the red blood cell AChE inhibition; or, if the dose responses for inhibition of BuChE more closely approximate those for AChE inhibition in the nervous system than do the dose responses for RBC (AChE) inhibition [2].
Our previous study showed that BuChE in gasoline station worker was lower than the control group which it may be affected of volatile organic compounds (VOCs) exposures [7, 8]. This study aimed to conduct the relationship between BuChE and biological parameters (hematological and biochemical parameters) and personal symptoms among gasoline station workers, in Bangkok, Thailand who had risk exposed to various volatile organic compounds (VOCs).
Materials and Methods
Study Population
A cross sectional study was conducted on 105 gasoline station workers in Pathumwan District, Bangkok, Thailand. The participant workers were provided with the consent form prior to the interview. This study was approved by Ethical Review Committee for Research Involving Human Research Subject, Health Science Group, Chulalongkorn University before the study.
Data Collection
The face-to-face interview was conducted to all participants during their work shifts. The questions included general characteristics such as age, body mass index (BMI), work duration, cigarette smoking, alcohol drinking and on their symptoms of headache, dizziness, fatigue, sore throat, skin irritation, conjunctivitis, nausea and depression which could be occurred during working.
The biological analysis of hematological and biochemical parameters was also performed by collecting 4 ml blood samples by vacuum tube. The hematological tests included red blood cell parameters [hemoglobin (Hb), hematocrit (Hct), mean corpuscular volume or mean cell volume (MCV), abnormal red blood cells (RBC), abnormal hemoglobin], white blood cell parameters [white blood cell count (WBC), neutrophils (N), lymphocytes (L), monocytes (Mo), eosinophils (Eo), basophils (Ba), platelets (Plts)], biochemical tests including kidney function [blood urine nitrogen (BUN), creatinine (Cr)] and liver function [serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT) and alkaline phosphatase (ALP)] and serum pseudo-cholinesterase (BuChE). All the tests were performed at Department of Microscopy, Faculty of Allied Health Sciences, Chulalongkorn University.
Statistical Analysis
The statistical analyses were performed by using the SPSS 17.0 for Windows Program. The descriptive statistical analysis was used of mean, median, standard deviation (SD), minimum (Min), maximum (Max) and percentage (%) for the characteristics and biological parameters of gasoline workers. Pearson’s correlation was calculated for symptom correlations between headache, dizziness, fatigue, sore throat, skin irritation, conjunctivitis, nausea and depression. While the linear regression was used to describe the association between BuChE and most of blood parameters, while the logistic regression was used to explain the association between BuChE and abnormal RBC, between BuChE and abnormal Hb and between BuChE and symptoms among gasoline station workers.
Results
Characteristic of Workers
Of all participants of 105 gasoline station workers, 76.2 % were men and 23.8 % were women. Their average age, BMI and work duration were 29.9 years, 23.3 kg/m2 and 5.3 years respectively (Table 1). Among them, 34.3 % were cigarette smokers and 60.0 % drink alcohol.
Table 1.
Characteristic of gasoline station workers
| Parameter | Mean or % N = 105 |
SD | Min–Max |
|---|---|---|---|
| Age (years) | 29.9 | 9.3 | 15.0–59.0 |
| BMI (kg/m2) | 23.2 | 4.9 | 16.3–41.2 |
| Work duration (years) | 5.3 | 6.4 | 0.5–36.0 |
| Sex | |||
| Men n (%) | 80 (76.2) | – | – |
| Women n (%) | 25 (23.8) | – | – |
| Cigarette smoking n (%) | 36 (34.3) | – | – |
| Alcohol drinking n (%) | 63 (60.0) | – | – |
Blood Biological Parameters
Analysis of their hematological and biochemical parameters revealed that there were in normal range as well as BuChE which was 9,222.0 U/L (Table 2).
Table 2.
Blood biological parameters among gasoline station workers
| Parameter | Referencea | Mean or % N = 105 |
SD | Min–Max |
|---|---|---|---|---|
| Red blood cells | ||||
| Hb (gm%) | 13.0–17.0 | 14.1 | 1.8 | 6.1–17.3 |
| Hct (%) | 39.0–51.0 | 41.8 | 4.5 | 22.0–49.0 |
| MCV (ft) | 80.0–98.0 | 81.9 | 8.9 | 57.2–98.7 |
| Abnormal RBC (%) | 27.6 | – | – | – |
| Abnormal Hb (%) | 44.8 | – | – | – |
| White blood cells | ||||
| Total WBC (X109/L) | 5.0–10.0 | 7.83 | 1.62 | 4.7–13.1 |
| N (%) | 40.0–75.0 | 52.9 | 10.5 | 1.0–78.0 |
| L (%) | 20.0–45.0 | 34.0 | 7.7 | 1.0–54.0 |
| Mo (%) | 2.0–10.0 | 5.7 | 1.6 | 1.0–10.0 |
| Eo (%) | 1.0–6.0 | 6.0 | 5.4 | 0.0–26.0 |
| Ba (%) | 0.0–1.0 | 0.4 | 0.5 | 0.0–1.0 |
| Platelets (%) | 150.0–400.0 | 256.6 | 6.6 | 121.0–527.0 |
| Blood chemistry | ||||
| BUN (mg%) | 6.0–20.0 | 11.8 | 3.2 | 6.0–20.0 |
| Cr (mg%) | 0.5–1.5 | 1.0 | 0.2 | 0.5–1.8 |
| SGOT (U/L) | 0.0–40.0 | 26.0 | 18.8 | 1.0–150.0 |
| SGPT (U/L) | 0.0–40.0 | 30.9 | 25.6 | 2.0–165 |
| ALP (U/L) | 26.0–117.0 | 71.8 | 38.0 | 26.0–298.0 |
| BuChE (U/L) | 4,260.0–12,920.0 | 9,222.4 | 2,323.6 | 4,656.0–16,154.0 |
aFaculty of Allied Health Sciences, Chulalongkorn University
Correlation of Symptoms Among Gasoline Station Workers
The personal symptoms of headache, dizziness, fatigue and skin irritate were recorded as 35.2, 27.6, 20.0 and 11.4 % respectively (Table 3). Pearson’s correlation of those symptoms showed that headache significantly correlated to dizziness (p < 0.001), fatigue (p < 0.001), sore throat (p < 0.01), conjunctivitis (p < 0.05) and nausea (p < 0.05), respectively. While fatigue was correlated to conjunctivitis (p < 0.01) and skin irritate (p < 0.0.05), whereas, skin irritate was correlated to conjunctivitis (p < 0.01) and nausea (p < 0.05).
Table 3.
Prevalence and correlation of symptoms among gasoline station workers
| Symptom | N (%) | Correlation (p value) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Headache | Dizziness | Fatigue | Sore throat |
Skin irritate |
Conjunc- tivitis |
Nausea | Depression | ||
| Headache | 37 (35.2) | 1 | 0.358** (0.000) |
0.396** (0.000) |
0.236** (0.008) |
0.162 (0.072) |
0.178* (0.047) |
0.212* (0.017) |
0.147 (0.101) |
| Dizziness | 29 (27.6) | 1 | 0.308** (0.001) |
0.08 (0.372) |
−0.066 0.472 |
0.104 (0.253) |
0.131 (0.151) |
0.147 (0.101) |
|
| Fatigue | 21 (20.0) | 1 | 0.167 (0.063) |
0.178* (0.047) |
0.257** (0.004) |
0.121 (0.177) |
0.156 (0.083) |
||
| Sore throat |
9 (8.6) | 1 | 0.026 (0.770) |
0.006 (0.943) |
0.125 (0.165) |
-0.100 (0.265) |
|||
| Skin irritate |
12 (11.4) | 1 | 0.264** (0.003) |
0.095* (0.044) |
0.064 (0.481) |
||||
| Conjunc- tivitis |
8 (7.6) | 1 | 0.180 (0.44) |
0.032 (0.724) |
|||||
| Nausea | 6 (5.7) | 1 | 0.043 (0.631) |
||||||
| Depression | 9 (8.6) | 1 | |||||||
* Correlation is significant at the 0.05 level (2-tail)
** Correlation is significant at the 0.01 level (2-tail)
Association of Serum Pseudo-cholinesterase and Characteristics, Biological Parameters of Workers
The BuChE was significantly related to BMI (Linear regression, p < 0.05) and sex (Logistic regression, p < 0.05) (Table 4). While the BuChE was associated with Hb and Hct (Linear regression, p < 0.05 and p < 0.05) (Table 5) as well as associated with blood chemistry of kidney function of BUN (p < 0.01), Cr (p = 0.001) and liver function of SGPT (p < 0.01) (Table 6). In addition, BuChE was closely associated with skin irritation (p = 0.058) (Table 7).
Table 4.
Association between serum pseudo-cholinesterase and characteristics of gasoline station workers
| Parameter | Mean | Median | Linear regression model results | ||
|---|---|---|---|---|---|
| Standardized coefficient | 95 % CI | p value | |||
| Serum BuChE (U/L) | 9220.4 | 8612.0 | – | – | – |
| Age (years) | 29.9 | 29.0 | −0.105 | 49.944–564.370 | 0.387 |
| BMI (kg/m2) | 23.2 | 22.1 | 0.257 | 27.044–216.146 | 0.012 |
| Work duration (years) | 5.3 | 3.0 | −0.023 | −91.832–75.552 | 0.847 |
| Logistic regression model results | |||||
|---|---|---|---|---|---|
| Exponential coefficient | 95 % CI | p value | |||
| Sex | – | – | 1.000 | 0.999–1.000 | 0.011 |
| Cigarette smoking | – | – | 0.010 | −958.716–1053.593 | 0.926 |
| Alcohol drinking | – | – | 0.157 | −211.507–1697.162 | 0.126 |
Independent variable: Serum ChE (U/L)
Table 5.
Association between serum pseudo-cholinesterase and blood parameters among gasoline workers
| Parameter | Mean | Median | Linear regression model resultsa | |||
|---|---|---|---|---|---|---|
| Standardized coefficient | 95 % CI | p value | ||||
| BuChE (U/L) | 9220.4 | 8612.0 | – | – | – | |
| Red blood cells | ||||||
| Hb (gm%) | 14.1 | 14.2 | 0.228 | 0.000–0.000 | 0.022 | |
| Hct (%) | 41.8 | 42.0 | 0.204 | 0.000–0.001 | 0.037 | |
| MCV (ft) | 81.9 | 83.1 | 0.034 | 0.000–0.001 | 0.754 | |
| Logistic regression model resultsb | ||||||
|---|---|---|---|---|---|---|
| Exponential coefficient | 95 % CI | p value | ||||
| Abnormal RBC (%) | – | – | 1.000 | 1.000–1.000 | 0.327 | |
| Abnormal Hb (%) | – | – | 1.000 | 1.000–1.000 | 0.925 | |
| Linear regression model resultsa | ||||||
|---|---|---|---|---|---|---|
| Standardized coefficient | 95 % CI | p value | ||||
| White Blood cells | ||||||
| Total WBC (X109/L) | 7.8 | 7.5 | 0.132 | 0.000–0.000 | 0.209 | |
| N (%) | 52.9 | 54.0 | 0.186 | 0.000–0.002 | 0.081 | |
| L (%) | 34.0 | 34.0 | −0.134 | −0.001–0.000 | 0.209 | |
| Mo (%) | 5.7 | 5.0 | −0.045 | 0.000–0.000 | 0.676 | |
| Eo (%) | 6.0 | 5.0 | −0.071 | 0.000–0.000 | 0.515 | |
| Ba (%) | 0.4 | 0.0 | 0.005 | 0.000–0.000 | 0.961 | |
| Plt (%) | 256.6 | 241.0 | 0.020 | −0.005–0.006 | 0.846 | |
Independent variable: Serum ChE (U/L)
a,bAdjust for age, BMI, work duration, sex, cigarette smoking and alcohol drinking
Table 6.
Association between serum pseudo-cholinesterase and biochemical parameters among gasoline workers
| Parameter | Mean | Median | Linear regression model resultsa | ||
|---|---|---|---|---|---|
| Standardized coefficient | 95 % CI | p value | |||
| BuChE (U/L) | 9220.4 | 8612.0 | – | – | – |
| BUN | 11.8 | 12.0 | 3.854E−04 | 0.000–0.001 | 0.005 |
| Cr | 1.0 | 0.9 | 2.624E−04 | 0.000–0.000 | 0.001 |
| SGOT | 26.0 | 21.0 | −4.50E−04 | −0.002–0.001 | 0.589 |
| SGPT | 30.9 | 24.0 | 2.809E−03 | 0.001–0.005 | 0.008 |
| ALP | 71.8 | 64.0 | 2.277E−03 | −0.001–0.005 | 0.132 |
Independent variable: Serum ChE (U/L)
aAdjust for age, BMI, work duration, sex, cigarette smoking and alcohol drinking
Table 7.
Association between serum pseudo-cholinesterase and symptoms among gasoline workers
| Parameter | Percentage | Number | Logistic regression model resultsa | ||
|---|---|---|---|---|---|
| Exponential coefficient | 95 % CI | p value | |||
| Headache | 35.2 | 37 | 1.000 | 1.000–1.000 | 0.083 |
| Dizziness | 27.6 | 29 | 1.000 | 1.000–1.000 | 0.885 |
| Fatigue | 20.0 | 21 | 1.000 | 1.000–1.000 | 0.871 |
| Sore throat | 8.6 | 9 | 1.000 | 1.000–1.000 | 0.704 |
| Skin irritate | 11.4 | 12 | 1.000 | 0.999–1.000 | 0.058 |
| Conjunctivitis | 7.6 | 8 | 1.000 | 1.000–1.001 | 0.493 |
| Nausea | 5.7 | 6 | 1.000 | 1.000–1.001 | 0.298 |
| Depression | 8.6 | 9 | 1.000 | 1.000–1.000 | 0.253 |
Independent variable: Serum ChE (U/L)
aAdjust for age, BMI, work duration, sex, cigarette smoking and alcohol drinking
Discussion
Results from our study showed that mean of all biological parameters of gasoline station workers were in normal ranges. However, the maximum levels of some parameters were higher than normal but the median values were nearly the means. Most personal symptoms had trended to decrease from the previous study by Tunsaringkarn [9]. There were inter-correlations between the personal symptoms such as headache which was strongly correlated to dizziness, fatigue, sore throat, conjunctivitis and nausea while nausea was correlated to skin irritation.
The BuChE was related to some general characteristics such as BMI and sex. The BuChE of men (9557.0 U/L) was significant higher than women (8143.0 U/L) workers (Independent sample t-test, p < 0.01) which supported previous studies [10–12]. There was no significant correlation, in either men or women, with alcohol intake or smoking. However, the BuChE was significantly related to hemoglobin (p < 0.05) and hematocrit (p < 0.05) but not related to the mean corpuscular volume/mean cell volume (MCV), morphology and hemoglobin typing of red blood cells or any parameters of white blood cells.
The BuChE was nearly significantly related to skin irritation (p = 0.058) which concurred with the reports by the Environmental Protection Agency (EPA) on the key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in BuChE levels, nausea, emesis, epistaxis, fatigue, dizziness [13, 14].
The BuChE measures were associated with blood chemistry of kidney function of BUN and liver function of SGPT. As reported by Brash et al. [15] and Miller [16], they found that the pseudo-cholinesterase levels may be reduced in patients with advanced liver disease. The decrease must be greater than 75 % before significant prolongation of neuromuscular blockade occurs with succinylcholine. Absence of the pseudo-cholinesterase enzyme leads to a medical condition known as pseudo-cholinesterase deficiency but elevation of plasma pseudo-cholinesterase was observed in 90.5 % cases of acute myocardial infarction [17]. Venkata et al. [18] found that pseudo-cholinesterase concentration decreased correspondingly and specifically with more functional liver cell damage. Other studies [19, 20] found that plasma cholinesterase had relationship with triglycerides, HDL-C, and LDL-C. More recent reports [10, 11, 21, 22] extended the association to wide range of variables with the metabolic syndrome including body mass index, apolipoprotein concentrations, insulin, liver enzymes, and blood pressure. Moreover, Nyblom et al. [23] reported that the SGOT/SGPT ratio can be used as an indicator of cirrhosis in alcoholic liver disease, hepatitis C and supported that the high ratio (>1.1) actually reflects cirrhotic changes in the liver. The SGOT to SGPT ratio in our study was 0.84 which may be exhibited mild chronic liver disease. Serum cholinesterase is useful both as a liver function test and in the diagnosis of jaundice provided consideration is given to the other factors which affect the level of activity of the enzyme [24].
Even though, all blood parameters were in normal ranges at present study but it should be recommended that the monitoring of BuChE, Hb, Hct, BUN, Cr, SGOT and SGPT should be continued for a longer period of time in order to observe the biological changes of chronic diseases in occupational workers who directly expose to the VOC, such as the gasoline station workers.The BuChE may be considered as a potential biomarker of adverse health effects of red blood cell, kidney and liver function and skin irritation from VOC exposure.
In conclusions, the pseudo-cholinesterase (BuChE) level was related to red blood cells (RBC), liver and kidney functions parameters and it may be related to skin irritation of gasoline workers.
Acknowledgments
This study was solely supported by the Surveillance Center on Health and Public Health Problem Surveillance Center on Health and Public Health Problem under Centenary Academic Development Project, Chulalongkorn University, the College of Public Health Sciences, Chulalongkorn University and National Research Council of Thailand (NRCT). The authors thank Dr. Kriangkrai Lerdthusnee for his advice and reviewing this paper.
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