chapter One

Introduction and literature review

1.1 Introduction.

In today’s industrialized world, exposure to contaminants such as heavy metals such as arsenic, lead and manganese poses a high risk. These metals are also found in drinking water. Arsenic is mainly found in groundwater. Because these metals are so widely distributed in our environment, we consume more than our bodies need (Ferrer, 2003). Elevated concentrations of arsenic in the environment are attributed to industrial products and wastes, agricultural pesticides and herbicides. Manganese is an essential element, but it can be toxic through drinking water, food, occupation, etc. Exposure to these heavy metals can poison and damage the model (human body). Arsenic effects have been documented in both human and experimental ATSDR a, 2012. Kannan et al., 2001 reported. Mn exposure can also cause neurotoxicity (ATSDR b, 2007). Manganism, the result of exposure to high levels of Mn, is a well-known neurological syndrome with many symptoms similar to Parkinson’s disease (Santamaria, 2008). Manganese and arsenic also target the same organ in the body, namely the brain (ATSDR, 2007a,b,c).

Because they coexist in soil and air, toxic exposure does not occur in isolation (Kordase et al., 2010). Indeed, real-world exposure to complex mixtures is the norm rather than the exception (Scherer, 2005). In recent decades, the prevalence of neurological disorders has increased (WHO, 2006). Mn poisoning causes an irreversible condition known as ‘manganism’. It is a neurodegenerative disorder that resembles Parkinson’s disease in both symptoms and underlying cellular mechanisms (Ellingsen et al., 2008; Martinez-Finley et al., 2012). Neuropathy caused by chronic metal exposure can progress and become clinically apparent decades after the initial exposure (Gil and Pla, 2001). The onset of neurotoxic effects is mostly subtle, latent, and indistinguishable from distinct disease (Shy, 1993).

Exposure to drinking water contaminated with arsenic and lead is associated with an increased incidence of congenital heart disease (CAD). Groundwater is an important hidden natural resource

(Tularam and Krishna 2009; Lashkaripour and Ghafoori 2011). Groundwater occurs in most environments, generally requires no pretreatment, and can often be found at low cost near the point of use (MacDonald and Calow 2009). Arsenic poisoning or arsenic disease is a condition caused by

Arsenic toxicity in male and female reproductive organs was also described. We also shed light on therapeutic strategies for metal toxicity. Manganese is a probable reproductive toxicant, and exposure to manganese can adversely affect the human reproductive system. may be influenced by factors. Effects on the male reproductive system include changes in sexual behavior, changes in fertility, and problems with sperm shape and number.

Manganese also has beneficial effects on the reproductive system, such as helping the production of sex hormones and sperm. Manganese acts as a catalyst for the breakdown of fatty acids and cholesterol. Manganese has a positive effect on the male reproductive system and also improves the brain’s ability to send and receive messages. Sex hormones are produced in the pituitary gland, where significant amounts of manganese are present. For this reason, manganese is thought to support sexual health.

Studies have been conducted on the individual effects of manganese and arsenic on the male reproductive system, but this study focuses on both their individual effects and their combined effects on the reproductive system. Studies have shown that both accumulate in the brain and affect hormone production. Apart from affecting the human reproductive system, arsenic and manganese cause other side effects, including cancer.Arsenic and manganese induce oxidative damage to membranes, which can lead to cancer and apoptosis. It has been shown to lead to the production of free radicals. Meanwhile, some studies suggest that arsenic may help thin the blood and thus support cancer treatment.
However, these studies have not been confirmed. The effects of arsenic and manganese can be assessed in male induced rats using assays such as H2O2, lipid peroxidation, GSH, GST and SOD. Environmental pollution with these heavy metals is certainly a cause for concern, and according to WHO, they have adverse effects on the human body. Unexpected sources of water, such as groundwater, indicate a lack of awareness among individuals.

1.2 Literature review

All foreign substances that enter the body are called xenobiotics. These substances can pass through one of the following pathways:

2.The excretion to the outside of the body is intact

3. Spontaneous self-reaction

Four. undergo metabolism.

Most xenobiotics go through her 3rd pathway, but if the body is overexposed to a compound it can trigger its own response and go through her 2nd pathway above . Arsenic and manganese are foreign substances that enter the body in different ways.

1.2.1 Arsenic

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic is found in many minerals, mainly associated with sulfur and metals, and can also be found as pure elemental crystals. Arsenic is a semimetal. It can exist in various allotropes, but only the gray form has significant industrial use. Certain bacteria can utilize arsenic compounds as respiratory tract metabolites. Trace amounts of arsenic are an essential dietary element for many other species, including rats, hamsters, goats, chickens, and possibly humans.However, when levels are higher than necessary, arsenic poisoning occurs in multicellular organisms. .

Arsenic contamination of groundwater is a problem that affects millions of people worldwide (Mameli et al., 2001). Arsenic and its compounds, especially trioxide, are used in the production of pesticides, treated wood products, herbicides and pesticides. However, these applications are declining. Arsenic occurs naturally on earth in low concentrations. it comes to the ground

Despite its notoriety as a deadly poison, arsenic is an essential trace element for some animals, and perhaps humans as well, but requires an intake of as little as 0.01 mg per day. Most arsenic is associated with sulfur in minerals such as arsenopyrite (AsFeS), realgar, orpiment, and enargite. It is a by-product of refining the ores of other metals such as copper and lead, so it is not mined as is. Very high exposures to inorganic arsenic can cause female infertility and miscarriage, skin disorders, reduced resistance to infection, heart problems, and brain damage in both men and women (Dhatrak and Nandi, 2009). ; Mejı´a et al., 1997) ).

Finally, inorganic arsenic can damage DNA. The lethal dose of arsenic oxide is generally considered to be 100 mg. Organic arsenic does not cause cancer or damage DNA. However, exposure to high doses can cause certain human health effects, including: B. Nerve injury and abdominal pain.

1.2.2 Arsenic physical and chemical properties.

Arsenic occurs naturally as a monoisotopic element composed of one stable isotope, As. As of 2003, at least 33 radioisotopes ranging in atomic mass from 60 to 92 have also been synthesized. The most stable of these is 33As with a half-life of 80.30 days. All other isotopes have half-lives of less than one day (Gokcen, N.A., 1989).

Figure 1.1:
Crystal structure of arsenic

When heated in air, arsenic oxidizes to arsenic trioxide. The smoke from this reaction has an odor reminiscent of garlic. This odor can be detected by hammering arsenic minerals such as arsenopyrite. Arsenic (and some arsenic compounds) sublimates upon heating at atmospheric pressure, converting directly to the gaseous state at 887 K (614 °C), bypassing the liquid state. The triple point is 3.63 MPa and 1,090 K (820 °C). Arsenic gives arsenic acid in concentrated nitric acid, arsenic in dilute nitric acid, arsenic trioxide in concentrated sulfuric acid, and the ability to convert electrical current into laser light. The arsenic gas AsH3 has become an important dopant gas in the microchip industry, but is highly toxic and requires strict guidelines regarding its use (Norman, Nicholas C 1998). Arsenic compounds are somewhat similar to the phosphorus compounds that occupy the same group (column) of the periodic table. However, arsenic is rarely observed in the pentavalent state. The most common oxidation states of arsenic are:
Arsenic -3. B. Intermetallics like alloys, +3 for arsenites, +5 for arsenates and most organic arsenides. Arsenic also readily binds to itself, as seen in the square As3-4 ions of the mineral skutterudite [14]. In the +3 oxidation state, arsenic is usually pyramidal due to lone pair effects.
Arsenic forms the colorless and odorless crystalline oxides As2O3 (“white arsenic”) and As2O5. They are hygroscopic and readily dissolve in water to form acidic solutions. Arsenic (V) acid is a weak acid. That salt is called arsenate and is responsible for arsenic contamination of groundwater, a problem that affects many people. Paris is one of the synthetic arsenic acids

Atomic number


Atomic mass

74.9216 g.mol -1

Electronegativity according to Pauling



5.7 at 14°C

Melting point

814 °C (36 atm)

Boiling point

615 °C (sublimation)

Vanderwaals radius

0.139 nm

Ionic radius

0.222 nm (-2) 0,047 nm (+5) 0,058 (+3)



Electronic shell

[ Ar ] 3d10 4s2 4p3

Energy of first ionization

947 kJ.mol -1

Energy of second ionization

1798 kJ.mol -1

Energy of third ionization

2736 kJ.mol -1

Standard potential

– 0.3 V (As3+/ As )


Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as a free element in nature; it is often found in combination with iron, and in many minerals. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.Proposed to be an element by Carl Wilhelm Scheele in 1774, manganese was discovered by Johan Gottlieb Gahn, a Swedish chemist, by heating the mineral pyrolusite (MnO2) in the presence of charcoal later that year. Today, most manganese is still obtained from pyrolusite, although it is usually burned in a furnace with powdered aluminum or is treated with sulfuric acid (H2SO4) to form manganese sulfate (MnSO4), which is then electrolyzed. Manganese phosphating is used as a treatment for rust and corrosion prevention on steel. Manganese ions have different colors depending on their oxidation states, and are used industrially as pigments. Alkali and alkaline earth metal permanganates are strong oxidizing agents. Manganese dioxide is used as a cathode material (electron acceptor) in zinc-carbon and alkaline batteries (Lide, David R. et al., 2004.).

In biology, manganese (II) ions act as cofactors for various enzymes with many functions. Manganese enzymes are particularly important in the detoxification of superoxide free radicals in organisms that must process elemental oxygen.Manganese also functions in the oxygen-generating complex of photosynthetic plants. This element, which is a trace element necessary for all known organisms, is a neurotoxin. Larger doses are apparently much more effective than inhalation and can lead to a mammalian poisoning syndrome with partially irreversible neurological damage (ATSDR b, et al 2007).

1.2.4 Physical and chemical properties of manganese

Manganese is a pinkish-gray, chemically active element. It is a hard and very brittle metal. Insoluble but easily oxidized. Manganese is reactive in its pure state, burning as a powder in oxygen, reacting with water (it rusts like iron), and dissolving in dilute acids. Manganese is one of the most abundant metals in soil, existing as oxides and hydroxides and cycling through various oxidation states. Manganese occurs mainly as pyrolusite (MnO2) and to a minor extent as rhodochrosite (MnCO3). More than 25 million tons are mined each year, which he equates to 5 million tons of metal, with reserves estimated at over 3 billion tons. The main mining regions for manganese ore are South Africa, Russia, Ukraine, Georgia, Gabon and Australia. Manganese is an essential element for all species. Some organisms such as diatoms, mollusks, and sponges accumulate manganese. It is normally around 1 ppm, but can be present in tissues up to 5 ppm in fish and up to 3 ppm in mammals (Rancke-Madsen, E., 1975).

Manganese metal and its common ion are paramagnetic. Manganese slowly discolors in air and “rusts” like iron in water with dissolved oxygen. Naturally occurring manganese consists of one stable isotope, Mn. Eighteen radioisotopes have been characterized, the most stable being Mn with a half-life of 3.7 million years, Mn with a half-life of 312.3 days, and Mn with a half-life of 5.591 days. All remaining radioisotopes have half-lives of less than 3 hours, and most of these have half-lives of less than 1 minute.

atomic number

twenty five

atomic mass

54.9380 gram-mole -1

electronegativity by polling


density at 20℃


Leave a Comment