environmental diseases due to heavy metals

pathophysiology and diseases related to heavy metal toxicity

1. ENVIRONMENTAL DISEASES DUE TO METALS. 1

2. Submitted to: Ma’am Fatima. Group #4. Group Members: - Tayyab Ayub. Ahmed Nawaz. Muhamad Zain. Jawad Ali. Amna Latif. Laiba Mir. Muhammad Huzaifa. 2

3. INTRODUCTION. Several health hazards have been associated with heavy metals for a long time. It is because of the fact that the heavy metals are very difficult to recycle and the new therapies used for treatment of many neurogenetic disorders involve the intake of heavy metals. Cigarette smoking whether active or passive is also an important source of exposure to these metals. The process of biomagnifications has given fatal diseases to many people where the pregnant women and the fetus are at maximum risk. They sometimes act as a pseudo element of the body while at certain times they interfere with the basic metabolic processes. Various measures have been taken by different countries at policy level and public level to control, prevent and treat metal toxicity occurring at various levels, such as occupational exposure, accidents and environmental factors. However, metal toxicity depends upon the amount of absorbed dose, the route of exposure and duration of exposure, i.e., acute or chronic. 3

4. This can lead to various disorders and can also result in excessive damage due to oxidative stress induced by free radical formation. One of the most negative consequences of industrialization is the proliferation of the heavy metal pollution in the air, water and land. Rising pollution, changing lifestyle, and distributed circadian cycles has led to rise in health-related disorders. There are phenotypic and genotypic factors which affects the health of an individual. The environment is the most important phenotypic effect affecting genotype also. Environmental exposure of air, water and land contaminated with heavy metals like Pb, Cd, As, Hg, Mn, Ni, Zn, Cr, Co, CU, Mo, Sb, etc., have posed serious threat to the wellbeing of humans. Heavy metals are essential only as trace elements for normal metabolic functioning but, at higher concentration, heavy metals are toxic. Once the heavy metals are consumed, they persist for indefinite time and cannot be biodegraded. They keep on accumulating and at higher concentration they form complex compounds within the cells and tissues, leading to diseases. 4

5. S. No. Nontoxic Low Toxic Moderately Toxic Highly Toxic 1. Aluminum Tin Antimony Uranium 2. Bismuth Scandium Beryllium Vanadium 3. Calcium Barium Boron Zinc 4. Iron Germanium Actinium Tungsten 5. Magnesium Gold Copper Polonium 6. Sodium Tin Mercury Silver 7. Potassium Gallium Lead Titanium 5

6. ETIOLOGY. An environment can be polluted or contaminated. Pollution differs from contamination; however, contaminants can be pollutants, and pose detrimental impact on the environment. Pollution is defined as the introduction by man, directly or indirectly, of substances or energy into the environment resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to environmental activities and impairment of quality for the use of the environment and reduction of amenities. Contamination is the presence of elevated concentration of substances in the environment above natural background level for the area and for the organism. Environmental pollution can be referred to undesirable and unwanted change in physical, chemical and biological characteristics of air, water and soil which is harmful for living organisms – both plants and animals. 6

7. 7 Air Pollution Water Pollution Soil Pollution

8. SOURCES OF HEAVY METALS. Natural Processes. Many studies have documented different natural resources of heavy metals under different and certain environmental conditions, natural emission of heavy metals occur Such emissions include volcanic eruptions, sea salt sprays, forest fires, rock weathering, biogenic sources and wind-borne soil particles. Natural weathering processes can lead to the release of metals from their endemic spheres to different environment compartments. Heavy metals can be found in the form of hydroxides oxides sulphide sulphates phosphates silicates and organic compounds The most common heavy metals are Pb, Ni, Cr, Cd, As, Hg, Zn and Cu.   8

9. 9 Anthropogenic Processes. Industries, agriculture, wastewater, mining and metallurgical processes, and runoffs lead to the release of pollutants to different environmental compartments. Anthropogenic processes of heavy metals have been noted to go beyond the natural fluxes for some metals. Metals naturally emitted in wind-blown dusts are mostly from industrial areas. Some important anthropogenic sources which significantly contribute to the heavy metal contamination in the environment include automobile exhaust which releases lead; smelting which releases arsenic, copper and zinc; insecticides which release arsenic and burning of fossil fuels which release nickel, vanadium, mercury, selenium and tin.

10. MORPHOLOGY. Heavy Metals & Immune System. One of the important aspects related to the immune system is that exposure to heavy metals can suppress the immune system and increase production of toxic products in the body. Heavy metals are stable, xenobiotic and are non-biodegradable, once taken they persist in the body, tissues and cells. Exposure to the toxic environment is done by inhalation of air contaminated with metal dusts, fumes and small particle generated by combustions, intake of contaminated food, eating at contaminated site, eating without washing hands. On intake, the heavy metals become integral part of some body parts like bones. Kidney, liver, brain and accumulate with many years half-life. There are some proteins which play an important role in their detoxification. Metallothionein (MT) a cysteine rich protein, MW ranging from 500-14000 Da, exist in ten closely related expressed proteins form in human body. 10

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12. PATHOPHYSIOLOGY. The pathophysiology of the heavy metal toxidromes remains relatively constant. For the most part, heavy metals bind to oxygen, nitrogen, and sulfhydryl groups in proteins, resulting in alterations of enzymatic activity. Increased synthesis of metal binding proteins in response to elevated levels of a number of metals is the body's primary defense against poisoning. For example, the metalloproteins are induced by many metals. These molecules are rich in thiol ligands, which allow high-affinity binding with cadmium, copper, silver, and zinc among other elements. Other proteins involved in both heavy metal transport and excretion through the formation of ligands are ferritin, transferrin, albumin, and hemoglobin. 12

13. Although ligand formation is the basis for much of the transport of heavy metals throughout the body, some metals may compete with ionized species such as calcium and zinc to move through membrane channels in the free ionic form. For example, lead follows calcium pathways in the body, hence its deposition in bone and gingivae. Thallium is taken up into cells like potassium because of their similar ionic radii. Nearly all organ systems are involved in heavy metal toxicity; however, the most commonly involved organ systems include the CNS, PNS, GI, hematopoietic, renal, and cardiovascular (CV). To a lesser extent, lead toxicity involves the musculoskeletal and reproductive systems. The organ systems affected and the severity of the toxicity vary with the particular heavy metal involved, the chronicity and extent of the exposure, and the age of the individual 13

14. Parkinson’s Disease. Parkinson’s Disease (PD) is a progressive neurodegenerative disorder. The disease is related to destruction of neurons in the Substantia Nigra Pars Compacta ( SNpc ) of the basal ganglia. The combination of high concentration of iron and the neurotransmitter, dopamine contributes to the selective vulnerability of the SNpc . Dopamine can auto-oxidize to produce free radicals particularly in the presence of iron and other heavy metals. There is a geographic association between PD mortality and the industrial use of heavy metals and their exposure like iron, zinc, copper, mercury, magnesium, and manganese. Studies have suggested that a disturbance of the plasmatic rate of Cu could be a marker of PD or at least, a risk factor for the development of this disease. 14

15. Although zinc participates to the reduction of oxidative stress and the antioxidant role of the selenium, their implication in the onset of PD is not clearly established. Zhao et al., generated a model to predict PD patients based on the plasma concentrations of trace elements (Se, Fe, Zn and Cu), which achieved an accuracy of 80.97±1.34% using 10-fold cross-validation. It was found that plasma Se and Fe concentrations were significantly increased whereas Cu and Zn concentrations decreased in PD patients as compared with controls. Meta-analysis studies were done to evaluate whether circulating Zn levels in the serum, plasma, and Cerebrospinal Fluid (CSF) are altered in PD which suggested that reduced Zn levels in the serum and plasma are associated with an increased risk for PD. 15

16. Multiple Sclerosis. Multiple Sclerosis (MS) is a complex disease with an etiology that is hypothesized to involve both environmental and genetic factors. The cellular accumulation of lead and mercury has been associated with the development of auto antibodies against neuronal cytoskeletal proteins, neurofilaments, and myelin basic protein in humans and animals. Overexposure to lead and mercury ions is known to be neurotoxic, particularly to motor Neurons. Low-to-moderate levels of lead exposure can cause functional alterations in T-lymphocytes and macrophages that lead to increased hypersensitivity and can alter cytokine production, which increases risk of inflammation-associated tissue damage. Studies have shown that the mercury exposure in genetically susceptible animals, even at low doses accelerates autoimmune disease and leads to disruption in cytokine production. These studies support an etiologic role of metals in autoimmune disease and suggest the importance of interactions between gene and environment, or between environmental factors in understanding metal toxicity. 16

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18. Asthma. Asthma is one of the most common chronic health conditions, affects an estimated 334 million individuals worldwide. Several metals have been reported to be associated with childhood asthma. The elevated urinary levels of metals such as Cr, Cu, As, Se, Sr, Mo, Cd, Sn, Sb, W and U were significantly associated with the prevalence of asthma. High levels of chromium entered by breathing, cause irritation to the nasal cavity, asthma and cough. A study suggested that the low concentration of cobalt is relatively less toxic compared with many other metals but toxic effect in higher concentrations affect mainly the lungs, leading to asthma, pneumonia and wheezing. 18

19. CONCLUSION. Overexposure to heavy metal such as lead, arsenic, mercury, cadmium, chromium is serious public health problems that harmfully affect human health including cardiovascular diseases, developmental abnormalities, neurologic and neurobehavioral disorders, diabetes, hearing loss, hematologic and immunologic disorders, and various types of cancer. The use of implants in dentals, skin surgeries and grafts in bone formation also contribute in exposure to heavy metal toxicity. Effective laws, strategy is necessary to control the heavy metals pollution. The detection of the areas where there are higher levels of heavy metals is necessary to fulfill the task. Failure to control the exposure of these heavy metals will result in severe complications not only in human health but also in the future environment, plant health and well-being of all organisms. 19