Article in Toxicology and Industrial Health (2006), 22: 381-393 by Hassan I Afridi, Tasneem G Kazi, Mohammad K Jamali, Gul H Kazi, Mohammad B Arain, Nusrat Jalbani, Ghulam Q Shar and Raja A Sarfaraz of Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro , Pakistan.
Abstract
The determination of toxic metals in the biological samples of human beings is an important clinical screening procedure. This study aimed to assess the possible influence of environmental exposure on production workers (PW) and quality control workers (QCW) of a steel mill, all male subjects aged 25-55 years. In this investigation, the concentrations of Pb, Cd, Ni and Cr were determined in biological samples (blood, urine and scalp hair samples) from these steel mill workers in relation to controlled unexposed healthy subjects of the same age group. After pre-treatment with nitric acid-hydrogen peroxide, the samples were digested via a microwave oven, and for comparison purposes, the same samples were digested by the conventional wet acid digestion method. The samples digested were subjected to graphite furnace atomic absorption spectrometry (GFAAS). To assess the reliability of these methods, critical factors, such as detection limit(s), calibration range(s), accuracy and precision, were studied. Quality control for these procedures was established with certified sample of human hair, urine and whole blood. The results indicate that the level of lead, cadmium and nickel in scalp hair, blood and urine samples were significantly higher in both groups of exposed workers (QW and PW) than those of the controls. The possible connection of these elements with the etiology of disease is discussed. The results also show the need for immediate improvements in workplace ventilation and industrial hygiene practices.
Extracts
Introduction
Human biomonitoring for toxic metals continues to receive considerable attention as the effort to reduce the uncertainty in health risk assessment increases. The primary goal of biomonitoring studies is to evaluate human exposure by comparing the measured concentrations of toxic elements with those of control groups or with literature-based ‘background’ values. Thus, in the assessment of health risk, the knowledge of reference values (RVs) in human tissues and fluids provides a meaningful insight into the extent of the exposure, and is of fundamental importance in environmental pollution control. A number of heavy metals as well as dust fumes and gases are found in these working environments. The exposure may have both acute and long term effects.
Cadmium, lead and nickel are toxic metals with a long history of detrimental effects. Exposure to these toxic metals is common in industry, where the metals are used in a wide range of manufacturing processes. The presence of heavy metals, such as Pb and Cd, replaces Ca and Zn, respectively, by competition with binding sites in biological systems. It is also known that these toxic metals and their compounds can be toxic if their concentrations exceed certain limits (Smith-Sivertsen et al., 1997). ...
Cadmium exposure has been associated with many physiological disorders, such as hypertension, and many studies show that hair levels of Cd in hypertensive patients are higher than controls (Engvall et al., 1985). The Cd concentration in urine (U-Cd) is mainly influenced by the body burden, being proportional to the kidney concentration. The urine level of cadmium is also a good measure of body stores (Lauwerys et al., 1994). Cigarette smokers and people living in contaminated areas have higher level of Cd in blood and urine, but smokers have more than twice as high concentration as non-smokers. Blood-Cd generally reflects current exposure, but partly also lifetime body burden (Waalkes et al., 1992; Jarup et al., 1998).
Although the role of Cr and Ni as essential trace elements in humans is no longer debated, the interest in these metals is mainly dictated by their noxious potential as industrial and environmental pollutants. Individual Ni exposure, in turn, seems also to be associated with the level of urbanisation. This may be traced back to Ni content in automobile exhausts and bitumen, the main component of asphalt. Nickel occurs also in road dust; Ni containing particles may thus easily make their way into the respiratory tract. Nickel accumulates with age and smoking, perhaps explaining why tissue levels are highest in patients who died of cardiovascular disease. Nickel’s ability to cause contact dermatitis, and its observed perturbation of immunoglobulin levels was investigated that elevated levels of nickel in hair may serve as an indicator of possible immune dysfunction, as well as a potentially useful marker of cardiovascular problems (Vienna et al., 1995).
Occupational exposure to chromium occurs from chromate and stainless-steel production, chromeplating, and working in tanning industries; occupational exposure can be two orders of magnitude higher than exposure to the general population (Agency for Toxic Substances and Disease Registry, 1998). The trivalent Cr is the more common form. However, the hexavalent form, such as chromate compound, is of great industrial importance. The major source of Cr is from chromites ore. Metallurgical grade chromite is usually converted into one of several types of ferrochromium or other Cr alloy containing Co or Ni. Ferrochrome is used in the production of stainless steel. Over review of Cr exposures and health effect have been reviewed (WHO, 1998).
Scalp hair and urine samples are easily sampled and provide a useful indicator of exposure to toxic and heavy metals for several diseases. Blood analysis is also important to monitor the immediate effects of environmental exposure.
Hair has the potential of being an excellent biomonitor due to its historical representation of intake over prior weeks to years, depending on its unique features, hair can also be utilised for investigating the exposure of individuals or populations to toxins and pollutants, such as heavy metals (Bencko, 1995; Martin et al., 2005). Its popularity lies in the fact that it can be collected easily and non-traumatically and can be stored easily. Most trace elements have higher concentration in hair than other body compartment, which helps in the analytic process (IAEA Review, 1994). Profiling for toxic metals has been used to identify the origins of exposure to mercury (Toribara, 2001) or monitoring medical treatments (Nicolis et al., 2000). Many studies have shown a correlation between heavy metals concentration in hair and blood (Chlopicka, 1998). Significant elevations of toxic element levels are also observed in human hair, particularly cadmium, lead, and nickel (Chattopadhyay et al., 1990; Wolfsperger et al., 1994).
The standard clinical procedure for the measurement of toxic elements in biological samples is very simple and is based on the use of highly sensitive GFAAS instrumentation. Several analytical techniques have been commonly used for heavy metals in blood measurement. The recommended method is graphite furnace atomic absorption spectrometry (GFAAS) (Parsons et al., 1993; Mido et al., 1995; Zhang et al., 1997).
The biological monitoring of toxic metals in biological samples has become a matter of wide interest owing to the toxicity of these metals and their influence in controlling the course of biological processes. Karachi is the most important metropolitan city of Pakistan, having many big industrial areas, and it is also the most affected by air pollution and industrial wastes (most of the pollutants being heavy metals), which are detrimental to human health. The aim of this study was to investigate the concentration of cadmium, chromium, lead and nickel in the biological samples (scalp hair, blood and urine) of long-term exposed steel production (PW) and quality control (QCW) workers to evaluate the degree of their exposure in these working environments. The obtained results have been compared with those of same age groups, healthy persons not exposed to industrial environmental pollution. The tissue concentrations related to a number of other variables, eg, age, employment time, health and habits (smoking or chewing tobacco) have been studied. These data can provide guiding references to occupational diseases and pollution control. ...
Results and discussion
Heavy metals of considerable toxicological importance pose a challenge for authorities in the public health and industrial hygiene sectors. A number of heavy metals, as well as dust, fumes and gases, are found in these working environments. The exposure may have both acute and long term health effects (Mikac-Devic et al., 1977).
Heavy metal toxicity generally results in gastrointestinal irritation, renal toxicity and multi-organ toxicity. Gastrointestinal irritation is the most common complaint, and may manifest as nausea, vomiting, diarrhea and abdominal pain. Renal toxicity is the second most common adverse event, and may be caused by acute and subacute exposure to heavy metals. On the other hand, interstitial nephritis is more likely cause by chronic exposure to heavy metals. Multi-organ toxicity may affect the skin and central nervous system as well (Adeloju et al., 1985). ...
Conclusions
We have established the analytical procedure to determine lead, chromium, cadmium, and nickel in biological samples (blood, urine and scalp hair) by a technique that is not only easier to follow and less expensive to run, but also more rapid and accurate than other techniques, thus providing a useful tool to screen large number of individuals that are at a risk of exposure to these and perhaps other metals.
The results show that in steel production, the workers assigned to the production and QC areas are indeed exposed to these metals, presenting significantly elevated levels in all three biological samples when compared to normal controls. The significantly high level of all these metals under consideration was observed with respect to duration of exposure. This suggests the need for immediate improvement of workplace ventilation and industrial hygiene practices.
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