Blood Pressure and Lipid Profile in Automechanics in Relation to Lead Exposure.

CONTEXT: Elevated blood pressure and alterations in lipid and lipoproteins play a major role in the development and progression of cardiovascular diseases. AIM: This study is aimed at determining the blood pressure and lipid profile in automechanics. SETTINGS AND
DESIGN: A total of 120 male subjects between 18 and 55 years of age comprised 60 automechanics and 60 age-matched occupationally unexposed control subjects in Emene, Enugu State, Nigeria. SUBJECTS AND METHODS: Four milliliters of fasting blood samples was collected from all subjects, 2 mL of blood was dispensed into K2-EDTA vacutainer tube for blood lead analysis, while the other 2 mL was dispensed into plain vacutainer tube, allowed to retract, centrifuged, and the serum used for serum lipid profile analysis. Blood pressure was measured using aneroid sphygmomanometer. STATISTICAL ANALYSIS: Statistical Package for Social Sciences (SPSS) version 21.0 was used for data analysis.
RESULTS: Automechanics had significantly higher values of systolic and diastolic blood pressures compared with the controls. Serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and triglyceride (TG) were also significantly higher in the automechanics compared with the controls (P < 0.05); serum high-density lipoprotein cholesterol (HDL-C) level, however, did not differ significantly between the two groups (P > 0.05). Blood lead level showed a significant positive correlation (P < 0.05) with systolic and diastolic blood pressures, serum TC, LDL-C, VLDL-C, and TG, with no significant correlation with serum HDL-C (P > 0.05) in the automechanics and no correlation in the controls.
CONCLUSION: The result of this study indicates that blood pressure is elevated and lipid profile altered in automechanics which suggests that these groups of workers are prone to increased risk of developing hypertension and cardiovascular disorders due to occupational exposure to lead.

INTRODUCTION

Automechanics are engaged in various automobile repairs and services including autobody and radiator repairs, welding, spray painting, and automobile battery recycling among others. Similar to other professions, these artisans also encounter certain hazards which adversely affect their health. These groups of workers are engaged in the informal sector without access to any structured occupational health programs such as pre-employment or periodic medical screening, enlightenment, or awareness campaigns to protect and promote health at workplaces and may have little or no knowledge of the health hazards inherent in their job.

These workers are exposed to various toxic chemicals including lead (Pb) and polycyclic aromatic hydrocarbons[1] which could be absorbed into the body through direct skin contact, ingestion, or inhalation.

Lead is a heavy metal which is toxic and ubiquitous in nature, and it is regarded as nonessential as it plays no role in the biological system but rather adversely affects various organs in the body in both children and adults. Regrettably, in many developing countries, Nigeria inclusive, occupational exposure to lead is absolutely unregulated and most time unmonitored,[2] which may account for increased occupational exposure to this toxic metal.

In the automechanic workshops, sources of lead include use of leaded gasoline, automobile batteries, radiators, scrap metals, exhaust fumes, and paints. As mentioned earlier, most of these workers are oblivious of the hazards they are exposed to, probably due to illiteracy or lack of awareness programs, and therefore pay little or no attention in protecting themselves from possible ingestion or inhalation of these toxic substances. Apart from not making use of personal protective equipment, they also engage in some unhealthy practices such as sucking of gasoline and washing their hands with the same, a significant source of exposure.

The adverse health effects of lead include hypertension, cardiovascular diseases, renal failure, liver damage, cancer, and so on. Lead may affect blood pressure directly or indirectly, and it has also been shown to alter lipid metabolism in both human and animal studies.[34] The alterations in lipid and lipoproteins may contribute to the development and progression of atherosclerosis and cardiovascular diseases.[5] Studies have also reported that exposure to lead induces dyslipidemia[67] thereby resulting in the accumulation of lipids in the walls of blood vessels.

Various studies have shown that lead exposure adversely affects the liver, kidney, heart, and other organs; however, lead exposure in relation to blood pressure as well as lipid and lipoproteins remains controversial. This study therefore aims to assess the blood pressure and lipid profile in automechanics in relation to lead exposure.

SUBJECTS AND METHODS

Study population and design

A total of 120 male subjects between 18 and 55 years of age comprised 60 automechanics and 60 age-matched occupationally unexposed control subjects in Emene, Enugu State, Nigeria, were recruited for the study. The details of the study were explained to each subject, and informed consent was obtained before commencement of the study.

Inclusion criteria

Male subjects between 18 and 55 years of age who gave their consent were recruited for the study.

Exclusion criteria

Subjects with any history of diabetes, hypertension, cardiovascular disorder, or on antihypertensive or lipid-lowering drugs were excluded from the study.

Ethical consideration

Ethical approval for this study was obtained from Nnamdi Azikiwe University Teaching Hospital Research Ethics Committee (NAUTHREC).

Blood pressure measurement

The systolic and diastolic blood pressures of the subjects were measured using the ausculatory method with aneroid sphygmomanometer as described by Pickering et al.[8] The blood pressure measurements of the subjects were taken twice, and the average was recorded as the subject's blood pressure.

Blood sample collection

Four milliliters of fasting blood samples was collected from all subjects, 2 mL of blood was dispensed into K2-EDTA vacutainer tube for blood lead analysis, and the other 2 mL was dispensed into plain vacutainer tube, allowed to retract, spun at 3000 revolutions per minute for 5 min, and the serum was used for serum lipid profile assay.

Biochemical analyses

Blood lead (BPb) level was measured using Varian AA240 Atomic Absorption Spectrophotometer according to the method described by the American Public Health Association.[9] Serum total cholesterol (TC) was determined by enzymatic colorimetric method as described by Grove.[10] Serum triglyceride (TG) was estimated by enzymatic colorimetric reaction according to the method described by Fossati and Recipe;[11] low-density lipoprotein cholesterol (LDL-C), and very low-density lipoprotein cholesterol (VLDL-C) were calculated based on Friedewald's formula.[12]

Statistical analysis

Statistical Package for Social Sciences (SPSS) version 20.0 was used for statistical analysis. The variables are expressed as mean ± standard deviation. Independent Student's t-test was used to calculate the difference between two independent variables, and Pearson's correlation coefficient was used to assess the level of association between two variables. The level of significance was considered at P < 0.05.

RESULTS

In Table 1, both the systolic and diastolic blood pressures were significantly (P < 0.05) higher in the automechanics compared with the controls.

Table 1

Systolic and diastolic blood pressures in automechanic and control groups

Parameters	Automechanics	Control	P
SBP (mmHg)	123.83±10.91	118.50±9.62	0.005*
DBP (mmHg)	81.92±8.19	77.92±6.97	0.005*

SBP: Systolic blood pressure, DBP: Diastolic blood pressure. *Significant

In Table 2, data indicate a significantly (P < 0.05) higher blood lead level in the automechanics compared with the controls. Serum levels of TC, LDL-C, VLDL-C, and TG were also significantly (P < 0.05) higher in the automechanics compared with the controls. However, serum high-density lipoprotein cholesterol (HDL-C) level did not differ significantly (P > 0.05) between the two groups.

Table 2

Blood lead level and lipid profile in automechanic and control groups

Parameters	Automechanics	Control	P
Pb (µg/dL)	48.40±20.06	13.73±4.81	0.0001*
TC (mmol/L)	5.06±0.87	4.30±0.63	0.0001*
HDL-C (mmol/L)	1.19±0.08	1.20±0.09	0.309
LDL-C (mmol/l)	3.43±0.77	2.73±0.55	0.0001*
VLDL-C (mmol/L)	0.44±0.15	0.37±0.08	0.007*
TG (mmol/L)	0.96±0.34	0.83±0.17	0.010*

TC: Total cholesterol, HDL-C: High-density lipoprotein cholesterol, LDL-C: Low-density lipoprotein cholesterol, VLDL-C: Very low-density lipoprotein cholesterol, TG: Triglyceride, Pb: Lead. *Significant

In Table 3, blood lead showed a significant positive correlation with SBP, DBP, serum TC, LDL-C, VLDL-C, and TG (P < 0.05), with no significant correlation with serum HDL-C (P > 0.05) in the automechanics and no correlation in the controls (P > 0.05).

Table 3

Correlation of blood lead and blood pressure and lipid profile in automechanic and control groups

Parameters	Automechanics		Control
	Lead (r)	P	Lead (r)	P
SBP (mmHg)	0.651	0.0001*	0.109	0.405
DBP (mmHg)	0.576	0.0001*	0.064	0.628
TC (mmol/L)	0.622	0.0001*	0.121	0.357
HDL-C (mmol/L)	0.057	0.667	0.012	0.926
LDL-C (mmol/L)	0.606	0.0001*	0.143	0.275
VLDL-C (mmol/L)	0.456	0.0001*	−0.043	0.746
TG (mmol/L)	0.459	0.0001*	−0.061	0.645

TC: Total cholesterol, HDL-C: High-density lipoprotein cholesterol, LDL-C: Low-density lipoprotein cholesterol, VLDL-C: Very low-density lipoprotein cholesterol, TG: Triglyceride, SBP: Systolic blood pressure, DBP: Diastolic blood pressure. *Significant

DISCUSSION

Lead is a toxic metal which is ubiquitous in nature and plays a major role in the development and progression of atherosclerosis and cardiovascular diseases. Our study observed higher values of both systolic and diastolic blood pressures in the automechanics which may be associated with the nephrotoxic effect of lead which indirectly affects blood pressure. The subsequent alterations in tubular function could lead to salt retention and volume overload, eventually resulting in elevated blood pressure.[13] On the other hand, lead may in addition cause a direct effect on vascular smooth muscles or central/peripheral nervous system.[14] In addition, lead may alter the renin angiotensin system through the activation of angiotensin converting enzyme,[15] or as a result of lead-induced oxidative stress which enhances the production of reactive oxygen species, thus limiting the availability of nitric oxide,[16] and consequently enhancing vascular contraction and endothelial dysfunction.[17] These findings support earlier studies which reported that lead exposure is a significant risk factor for the development of hypertension.[1819] Contrary to these findings, Ajani et al.[20] observed no differences in the systolic and diastolic blood pressures in automobile mechanics and the control population.

This study further observed a direct relationship between the blood metal levels and blood pressure (systolic and diastolic), and these correspond with the reports of Kasperczyk et al.,[21] Alghasham et al.,[22] and Lee et al.,[23] who also reported a direct relationship between blood lead levels and blood pressures. However, An et al.[24] in their study on workers of smelting industry reported a positive relationship between blood lead and blood pressure which could be as a result of the low blood lead levels (<7 μg/dL) recorded in these workers.

Blood lead measurement has been used as a reliable marker of recent exposure to this toxic metal,[25] and the elevated blood lead level in the automechanics observed in this study indicates that these groups of workers are more exposed to these metals than the general population because they come in contact with these metals in their daily activities at their various workshops. These findings correspond with those of Ahmad et al.[26] and Alli[27] who also reported similar increase in blood lead levels in subjects occupationally exposed to this toxic metal.

In addition to the increased blood lead level observed in the occupationally exposed, the study also observed that the blood lead level in the occupationally unexposed subjects was higher than the World Health Organization–permissible range of <10 μg/dL of lead in adults.[28] The increase in the blood lead level observed in the nonoccupationally exposed subjects could be from other environmental contamination and exposures[29] including inhalation of exhaust fumes or contaminated dust particles or inadvertent ingestion of contaminated foods or drinks which is a possible indication of the extent of lead pollution in Nigeria. This is of serious concern as many Nigerians may be exposed to lead from the environment irrespective of their occupations. Similarly, Orisakwe[30] and Galadima and Garba[31] also reported a high blood lead level in nonoccupationally exposed subjects. These findings support the fact that lead is a generally recognized occupational and environmental pollutant.[32]

This study also observed significant elevations in the serum levels of TC, LDL-C, VLDL-C, and TG with no significant change in HDL-C level in the automechanics, and this may be attributed to the adverse effect of lead on lipid metabolism[33] possibly by altering normal lipid and lipoprotein fractions through lipid peroxidation.[34] It may also be attributed to the upregulation of plasma cholesterol and TG concentrations by this toxic metal,[7] and these alterations in cholesterol metabolism increase the risk of cardiovascular diseases in subjects exposed to this metal.[6] Toxic metals probably enhance the activity of 3-hydoxy-3-methylglutaryl coenzyme A (HMG CoA) reductase which is the rate-limiting enzyme in cholesterol biosynthesis thereby enhancing cholesterol synthesis. Other researchers had earlier reported cases of dyslipidemia in both humans and animals exposed to lead.[67] Studies on exposure to lead have demonstrated similar increase in TC, LDL-C, and TG levels as well as decreased HDL-C level in animal[3435] Human studies also reported a similar increase in TC, LDL-C, and VLDL-C levels,[36] elevated TG level (Ajani et al., 2011), and normal levels of HDL-C.[6] Adejumo et al.,[37] however, observed a low serum HDL-C level in automobile mechanics and spray painters.

This study further observed a direct relationship between blood lead and TC, LDL-C, VLDL-C, and TG, with no significant association with HDL-C in the automechanics. Sharmar et al.[36] also observed a similar association between blood lead and TC and LDL-C. The results of this study indicate that blood pressure is elevated and lipid profile altered in automechanics which suggest that these groups of workers are prone to increased risk of developing hypertension and cardiovascular disorders due to occupational exposure to lead.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.