Deleterious effects of exposure to constituents of cement dust on organ system in humans have been described. Molecules of primary importance in cement dust in terms of content and potential health effects basically include 60–67% calcium oxide, 17–25 silicon oxide (SiO2), and 3–5% aluminium (Al) oxide, with some amount of iron oxide, chromium (Cr), potassium, sodium, sulphur, and magnesium oxide [
Studies on effects of cement dust exposure on lung and liver functions in occupationally exposed individuals in Nigeria have been documented [
This study was conducted at the United Cement Company (UNICEM) at Mfamosing, Akamkpa local government area, Cross River State, Nigeria. The Mfamosing limestone deposit serves as the major source of raw materials used by UNICEM for the production of ordinary Portland cement (OPC). Since July 2009, the Mfamosing cement plant produces approximately 2.5 million metric tons of cement per annum and currently employs about 350 permanent workers. The factory has four major departments: Production (Crusher, Raw Mill, Kiln, Cement Mill, and Packing Section), Engineering and Maintenance (Mechanical and Electrical Section), Mining, and Administration (Cashier, Administrative Officer, Security, and Marketing Section). The site is close to 200 m west to Mbebui village at coordinates 05.04493°N, 008.298995°E, 500 m south to Abifan community at coordinates 05.07591°N, 008.52192°E, and 200 m east to Mfamosing community and 100 m east to main quarry site at coordinates 05.06993°N, 008.53908°E [
Two hundred and ten male subjects aged 18–60 years who fulfilled the inclusion criteria were randomly selected for this study. This study population comprised fifty regular cement factory workers, sixty residents of the communities surrounding the UNICEM factory, and one hundred apparently healthy individuals residing in Calabar metropolis 45 km away from the factory, not exposed to cement dust, who served as control subjects. Informed consent was obtained from them and ethical approval was obtained from The Center of Clinical Governance, Research and Training, Ministry of Health, Cross River State. This study was carried out in accordance with the Ethical Principles for Medical Research Involving Human Subjects as outlined in the Helsinki Declaration in 1975 (revised in 2000). Test subjects of the study were selected from the production section of the cement factory. This comprises permanent employees of the factory who are occupationally exposed to cement dust daily for not less than 2 years in the course of their work. Host community resident subjects were also individuals that had been resident in the communities proximal to the cement factory for not less than 2 years, while control subjects were individuals who had never been occupationally exposed to cement dust and are resident in Calabar metropolis.
Participants were notified several days before the commencement of the study and were given appropriate instructions. The physical characteristics of the subjects included weight and height measured with the use of weighing scale and stadiometer, respectively. Systolic and diastolic blood pressure were taken using sphygmomanometer. All subjects of the study were interviewed to establish their level of literacy and were assisted in filling the questionnaire to minimize errors. Sociodemographic data were collected by an interviewer-administered structured questionnaire aiming to determine age, educational levels, socioeconomic status, years of exposure as deduced from date of employment, site or position at the workplace, and use and nonuse of safety gadgets such as dust masks. Information on general health and history of past disease(s) and habits such as smoking, consumption of alcoholic beverages, and addictions were collected according to the British Medical Research Council questionnaire (BMRC, 1960). Individuals with a history of cigarette smoking, tobacco sniffing or chewing, liver disease or pulmonary disorders, chronic organ or systemic illness, and long term medication were excluded from the study.
Blood samples were collected from midmorning to noon for both subjects and controls. Seven milliliters of blood was collected by venipuncture under aseptic conditions into a dry, clean plain sample container. The blood was allowed to clot and was centrifuged at 3,500 revolutions per minute for 5 minutes. After centrifuging, the serum was separated with the aid of a Pasture pipette and dispensed into dry chemically clean serum container, after which the samples were analysed immediately or stored at −20°C for subsequent analysis.
Consider
Alanine aminotransferase catalyzes the transfer of amino group from L-alanine to
Consider
Serum bilirubin is present in two forms: conjugated which is mostly with glucuronic acid and unconjugated which is known as free bilirubin. Both react with diazotized sulphanilic acid to give a rose-purple azobilirubin. Conjugated bilirubin reacts in aqueous solution (direct reaction) whereas the unconjugated bilirubin requires an accelerator or solubilizer such as benzoate urea as in this method or alcohol which is used in other methods (indirect reaction).
An extract of the physiological sample is deproteinized and the filtrate is treated as lanthanum. This is aspirated in AAS which measures the absorbance of trace metals at various wavelengths corresponding to its bandwidth. The absorbance is proportional to the concentration of trace element in the sample.
The PEFR test is done with a peak expiratory flow meter: Spiroflow by Spirometrics, USA (originally described by Wright and McKerrow [
Data analysis was done using the statistical package for social sciences (SPSS version 20.0). Student’s
Mean age, anthropometric indices (weight, height, and body mass index), systolic and diastolic blood pressure, some liver function tests (ALT, AST, TB, and CB), peak expiratory flow (PEFR), and serum elements levels (Fe, Zn, Pb, As, Cd, Cr, Se, Mn, and Cu) in cement workers, residents near the cement factory, and controls were shown in Table
Mean age, anthropometric indices (weight, height, and BMI), systolic BP, diastolic BP, some liver function tests, peak expiratory flow rate, and serum elements levels in cement workers, residents near cement factory, and controls.
Parameter | Cement workers |
Residents |
Controls |
|
|
---|---|---|---|---|---|
Age (years) | 39.98 ± 5.56 | 38.32 ± 4.03 | 37.67 ± 5.32 | 0.453 | 0.636 |
Weight (kg) | 61.04 ± 13.53 | 62.04 ± 12.55 | 61.90 ± 13.35 | 0.204 | 0.816 |
Height (meters) | 1.67 ± 0.10 | 1.68 ± 0.09 | 1.72 ± 0.06 | 0.055 | 0.747 |
BMI (kg/m2) | 23.35 ± 2.56 | 23.95 ± 2.32 | 23.10 ± 2.11 | 2.574 | 0.079 |
Sys. BP (mmHg) | 128.80 ± 8.80 | 127.80 ± 8.83 | 128.80 ± 7.86 | 0.166 | 0.847 |
Diast. BP (mmHg) | 84.20 ± 13.10 | 82.33 ± 10.14 | 82.50 ± 10.76 | 0.476 | 0.622 |
ALT (IU) | 29.78 ± 2.58 | 11.25 ± 0.96 | 8.72 ± 0.41 | 76.53 | 0.000 |
AST (IU) | 37.00 ± 2.61 | 17.41 ± 1.70 | 9.46 ± 0.64 | 84.29 | 0.000 |
TB ( |
18.26 ± 0.91 | 18.18 ± 0.81 | 13.82 ± 0.62 | 12.80 | 0.000 |
CB ( |
7.57 ± 0.58 | 7.33 ± 0.52 | 5.84 ± 0.27 | 5.66 | 0.004 |
PEFR (L/min) | 324.96 ± 10.40 | 340.25 ± 10.38 | 400.17 ± 9.10 | 16.97 | 0.000 |
Fe ( |
102.08 ± 1.78 | 96.13 ± 1.43 | 150.99 ± 1.35 | 447.99 | 0.000 |
Zn ( |
80.94 ± 2.01 | 78.25 ± 1.86 | 106.52 ± 0.70 | 147.64 | 0.000 |
Pb ( |
15.93 ± 0.42 | 20.09 ± 0.64 | 10.33 ± 0.60 | 70.32 | 0.000 |
As ( |
0.011 ± 0.002 | 0.011 ± 0.005 | 0.003 ± 0.002 | 183.45 | 0.000 |
Cd ( |
0.042 ± 0.008 | 1.950 ± 0.212 | 0.022 ± 0.001 | 102.20 | 0.000 |
Cr ( |
0.033 ± 0.003 | 1.60 ± 0.125 | 0.012 ± 0.000 | 200.39 | 0.000 |
Se ( |
0.022 ± 0.004 | 1.75 ± 0.127 | 0.044 ± 0.015 | 217.479 | 0.000 |
Mn ( |
2.970 ± 0.074 | 3.346 ± 0.062 | 2.579 ± 0.038 | 56.101 | 0.000 |
Cu ( |
216.64 ± 6.93 | 234.62 ± 7.16 | 173.06 ± 3.662 | 37.83 | 0.000 |
Table
Comparison of some liver function tests and peak expiratory flow in cement workers, residents near cement factory, and controls using post hoc analysis.
Parameter | Groups | Mean diff. |
|
|
---|---|---|---|---|
Cem. workers | Controls | |||
|
|
|||
ALT (IU) | 29.78 ± 2.57 | 8.72 ± 0.41 | 21.06 ± 1.75 | 0.000 |
AST (IU) | 37.00 ± 2.61 | 9.46 ± 0.64 | 27.540 ± 2.12 | 0.000 |
TB ( |
18.26 ± 0.91 | 13.82 ± 0.62 | 4.44 ± 1.09 | 0.000 |
CB ( |
7.57 ± 0.58 | 5.84 ± 0.27 | 1.73 ± 0.60 | 0.004 |
PEFR (L/min) | 324.96 ± 10.40 | 400.17 ± 9.10 | −75.21 ± 14.58 | 0.000 |
|
||||
Residents | Controls | |||
|
|
|||
|
||||
ALT (IU) | 11.25 ± 0.96 | 8.72 ± 0.41 | 2.53 ± 0.55 | 0.000 |
AST (IU) | 17.41 ± 1.70 | 9.46 ± 0.64 | 7.95.90 ± 2.00 | 0.000 |
TB ( |
18.18 ± 0.81 | 13.82 ± 0.62 | 4.36 ± 0.18 | 0.000 |
CB ( |
7.33 ± 0.52 | 5.84 ± 0.27 | 1.49 ± 0.26 | 0.004 |
PEFR (L/min) | 340.25 ± 10.38 | 400.17 ± 9.10 | −59.92 ± 0.13 | 0.000 |
|
||||
Cem. workers | Residents | |||
|
|
|||
|
||||
ALT (IU) | 29.78 ± 2.58 | 11.25 ± 0.96 | 18.53 ± 1.94 | 0.000 |
AST (IU) | 37.00 ± 2.61 | 17.41 ± 1.70 | 19.58 ± 2.35 | 0.000 |
TB ( |
18.264 ± 0.91 | 18.18 ± 0.81 | .081 ± 1.204 | 0.947 |
CB ( |
7.57 ± 0.58 | 7.33 ± 0.52 | .24 ± 0.67 | 0.723 |
PEFR (L/min) | 324.96 ± 10.40 | 340.25 ± 10.38 | −15.29 ± 16.12 | 0.344 |
Comparison of serum elements levels in cement workers, residents near the cement factory, and controls using post hoc analysis was shown in Table
Comparison of serum elements level in cement workers, residents near cement factory, and controls using post hoc analysis.
Parameter | Groups | Mean diff. |
|
|
---|---|---|---|---|
Cem. workers | Controls | |||
|
|
|||
Fe ( |
102.08 ± 1.78 | 150.99 ± 1.35 | −48.92 ± 2.19 | 0.000 |
Zn ( |
80.95 ± 2.01 | 106.52 ± 0.70 | −25.58 ± 1.97 | 0.000 |
Pb ( |
15.93 ± 0.42 | 10.33 ± 0.60 | 5.60 ± 0.89 | 0.000 |
As ( |
0.011 ± 0.002 | 0.003 ± 0.002 | 0.008 ± 0.001 | 0.000 |
Cd ( |
0.042 ± 0.008 | 0.022 ± 0.001 | 0.035 ± 0.005 | 0.000 |
Cr ( |
0.033 ± 0.013 | 0.012 ± 0.000 | 0.021 ± 0.002 | 0.000 |
Se ( |
0.023 ± 0.004 | 0.044 ± 0.015 | −0.010 ± 0.002 | 0.000 |
Mn ( |
2.97 ± 0.074 | 2.58 ± 0.038 | 0.39 ± 0.078 | 0.000 |
Cu ( |
216.65 ± 6.93 | 173.07 ± 3.66 | 43.58 ± 7.917 | 0.000 |
|
||||
Residents | Controls | |||
|
|
|||
|
||||
Fe ( |
96.13 ± 1.429 | 150.99 ± 1.35 | −54.86 ± 0.08 | 0.000 |
Zn ( |
78.25 ± 1.863 | 106.52 ± 0.70 | −28.28 ± 1.16 | 0.000 |
Pb ( |
20.091 ± 0.643 | 10.33 ± 0.60 | 9.76 ± 0.04 | 0.000 |
As ( |
0.011 ± 0.005 | 0.003 ± 0.002 | 0.007 ± 0.003 | 0.000 |
Cd ( |
1.95 ± 0.21 | 0.022 ± 0.001 | 1.93 ± 0.143 | 0.000 |
Cr ( |
1.60 ± 0.13 | 0.012 ± 0.000 | 1.60 ± 0.08 | 0.000 |
Se ( |
1.75 ± 0.13 | 0.044 ± 0.015 | 1.71 ± 0.09 | 0.000 |
Mn ( |
3.35 ± 0.06 | 2.58 ± 0.038 | 0.77 ± 0.07 | 0.000 |
Cu ( |
234.62 ± 7.17 | 173.07 ± 3.66 | 61.56 ± 0.50 | 0.000 |
|
||||
Cem. workers | Residents | |||
|
|
|||
|
||||
Fe ( |
102.08 ± 1.78 | 96.13 ± 1.43 | 5.945 ± 2.422 | 0.015 |
Zn ( |
80.95 ± 2.007 | 78.25 ± 1.86 | 2.69 ± 2.19 | 0.219 |
Pb ( |
15.93 ± 0.42 | 20.09 ± 0.64 | −4.16 ± 0.98 | 0.000 |
As ( |
0.011 ± 0.002 | 0.011 ± 0.005 | .0002 ± 0.0005 | 0.693 |
Cd ( |
0.042 ± 0.008 | 1.95 ± 0.212 | −1.91 ± 0.168 | 0.000 |
Cr ( |
0.033 ± 0.013 | 1.60 ± 0.125 | −1.57 ± 0.10 | 0.000 |
Se ( |
0.023 ± 0.004 | 1.75 ± 0.127 | −1.73 ± 0.103 | 0.000 |
Mn ( |
2.97 ± 0.074 | 3.35 ± 0.062 | −.38 ± 0.09 | 0.000 |
Cu ( |
216.65 ± 6.93 | 234.62 ± 7.17 | −17.97 ± 8.75 | 0.041 |
Figure
Correlation plot of duration of exposure to cement dust against peak expiratory flow rate in cement workers.
The lung and liver function and some serum elements levels in occupationally exposed cement workers and residents near cement factories were studied. Decreased peak expiratory flow rate (PEFR) was observed in cement workers and residents living near cement factory when compared to unexposed controls. Similar findings have also been reported in cement workers in other developing countries [
Prolonged duration of exposure to cement dust was associated with decreased peak expiratory flow. Similar observations have been reported by other studies [
Increased levels of serum alanine aminotransferase, aspartate aminotransferase, and total and conjugated bilirubin were observed in cement workers compared to controls. The higher levels of aminotransferase observed in the cement workers are still within normal range for the liver enzyme in circulation and hence are not indicative of liver impairment. The liver has a high functional reserve capacity and only shows dysfunction when about 50% of the hepatocytes are affected. However, this increase may be an indication of potential for future development of hepatotoxic complications in occupationally exposed individuals. Our findings are in agreement with reports from other studies [
Increased serum lead, arsenic, cadmium, chromium, selenium, manganese, and copper levels and lower iron and zinc levels were observed in cement workers and residents living near cement factory when compared to unexposed controls. Increased levels of chromium, copper, manganese, and selenium have also been demonstrated in cement factory workers and had been attributed to their exposure to cement dust [
Cement workers had higher levels of ALT, AST, and Fe and lower levels of Pb, Cd, Cr, Se, Mn, and Cu compared to residents of communities near the cement factory. The observation of higher serum levels of ALT, AST, and Fe and lower Cu seen has been discussed above. Contrary to our findings, no significant difference was reported in serum blood lead levels of cement workers and residents of neighboring community in a cement factory [
The findings of this study have shown that occupational exposure to cement dust may be associated with changes in the homeostasis of some essential and toxic elements resulting in higher levels of Pb, As, Cd, Cr, Se, Mn, and Cu and lower levels of Fe and Zn which may be implicated in impaired peak expiratory flow rate with potentials for future development of hepatotoxicity. These observations emphasize the need for adequate safety and precautionary measures among cement factory workers.
The authors declare that there is no conflict of interests regarding the publication of this paper.