Full Project – Comparative evaluation of heavy metal loads in some selected soft drinks in Owerri, Imo state

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CHAPTER ONE

1.0 INTRODUCTION

A heavy metal is a member of a loosely –defined subset of elements that exhibit metallic properties which affects human health. it mainly includes the transition metals, some metalloids, lanthanides and actinides. Heavy metals are natural components of the earth crust which cannot be degraded or destroyed, to some extent they enter our bodies through food, drinking water, air and some heavy metals which are trace elements [e.g. selenium, zinc] are essential to maintain the metabolism of the human body. However at higher concentrations, they can lead to poisoning which could result from drinking water contaminated with lead pipes, high ambient air concentrations near emission sources, or in take through the food chain, thus being dangerous, tend to bioaccumulation. Bioaccumulation means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical concentration in the environment. Common heavy metals are;

Arsenic

Barium

Cadmium

Chromium

Lead

Mercury

Selenium and

Silver.

However, heavy metals are chemical elements with a specific gravity that is at least 5 times the specific gravity of water. The specific gravity of water is 1 at 4⁰C [39⁰F]. For instance, Arsenic has 5.7, Cadmium 8.65, Iron 7.9, Lead 11.34, Mercury 13.54 which is 5times to compare to an equal volume [amount] of water. As such, they are stable elements (meaning that they cannot be metabolized by the body) and bio-accumulative (passed up the food chain to humans).

Once liberated into the environment and taken up through food drinks and inhalation, they accumulate in body tissues faster than the body’s detoxification pathways can dispose of them, a gradual buildup of these toxins occurs. For instance, soft drinks such as wines and grape drinks in Roman Empire have been contaminated by lead-lined jugs and cooking pots leading to a “decline and fall” of the Roman Empire and the mad hatter character in Alice in wonderland was likely modeled after nineteenth-century hat makers who used mercury to stiffen hat materials and frequently became psychotic from mercury toxicity. As discussed, heavy metals occur naturally in the ecosystem with large variations in concentration, where in modern times, anthropogenic sources of heavy metals includes pollution being introduced into the ecosystem by human activities.

BENEFICIAL HEAVY METALS

In small quantities, certain heavy metals are nutritionally essential for a heavy life. Some of these are referred to as the trace elements (e.g. Iron, Copper, Manganese and Zinc). These elements, or some form of them are commonly found naturally in foodstuffs, fruits, soft drinks and vegetables and also in commercially available multivitamin products, other means include Diagnostic medical applications which include direct injection of gallium during radiological procedures, dosing with chromium in parental nutrition mixtures, and the use of lead as a radiation shield around x-ray equipment. Heavy metals are also common in industrial applications such as in the manufacture of pesticides, batteries, electroplated metals parts, textiles dyes, steel, etc.

TOXIC HEAVY METALS

Heavy metals become toxic when they are not metabolized by the body and accumulate in the soft tissues. Heavy metals may enter the human body through food, water, air or absorption through the skin when they come in contact with humans in agriculture, and in manufacturing, pharmaceutical, industrial or residential setting. Industrial exposure accounts for a common route of exposure in adults and ingestion is the common route of exposure in children which occurs normally from hand to mouth activity of small children who come in contact with contaminated soil or by eating objects that are not food (dirt or paint chips).

RELATIONSHIP OF HEAVY METALS TO LIVING ORGANISMS

Living organisms require varying amount of “heavy metals”. Irons, Cobalt, Copper, Manganese, Molybdenum and Zinc are required by humans thus excessive levels can be damaging to the to the organisms. Other heavy metals such as mercury, plutonium and lead are toxic metals that have no known vital or beneficial effects on organisms and their accumulation over time in the bodies of the animals can cause serious illness. Certain elements that are normally toxic are, for certain organisms or under certain conditions beneficial. Examples include vanadium tungsten and even cadmium.

HEAVY METAL POLLUTION

Heavy metal pollution can arise from many sources. But most commonly source arises from the purification of metals. Example; the smelting of copper and the preparation of nuclear fuels. Electroplating is the primary source of chromium and cadmium through precipitation of their compounds or by ion exchange into soils and mud. Heavy metals can localize and lay dormant. Unlike organic compounds(pollutants), heavy metals do not decay and thus pose a different kind of challenge for remediation. Currently, plants or micro organisms are tentatively used to remove some heavy metals such as mercury. Plants which exhibit hyper accumulation can be used to remove heavy metals by concentrating them in their bio-matter.

One of the largest problems associated with the persistence of heavy metals is the potential for Bioaccumulation and Biomagnifications causing heavier exposure for some organisms that is present in the environment alone where coastal fish(such as the smooth toadfish) and seabirds(such as Atlantic puffin) are monitored for the presence of such contaminants/pollutants.

DIFFERENT TYPES OF HEAVY METALS
- ARSENIC

This is a chemical element with symbol As_,atomic number 33. it occurs naturally in many minerals usually in conjunction with sulphur and metals. Aside from occurring naturally in the environment, arsenic can be released in larger quantities through volcanic activities, erosion of rocks, forest fires and human activity. Arsenic is also found in paints, dyes, drugs, soaps, semiconductors, pesticides, cigarette, table salts, seafood and fertilizers, and also industrial practices such as copper or lead smelting, mining and coal burning.

HEALTH EFFECTS

Arsenic can cause cancer of the skin, lungs, liver and bladder.
Acute arsenic poisoning causes symptoms such as convulsion, drowsiness and headaches.
Arsenic ingested in very high level can cause coma and death.
Low level exposure can cause nausea, vomiting, decrease in red and white blood cell productions and damage to blood vessels.

CADMIUM

Cadmium is a chemical element with symbol CD. It is very similar to Zinc, thus accumulates in the body by replacing Zinc, an essential mineral in the liver and kidney.

HEALTH EFFECTS

Toxic levels of cadmium causes anemia, loss of appetite, high blood pressure, joint soreness, scaly skin, weakening of system and causing kidney disease.

LEAD

Lead is one of the most toxic metals known and as a result of human activities such as fossil fuel burning, mining and manufacturing, lead compounds are found in all parts of our environments, they are just like calcium. So pregnant women, children and other people who are deficient in calcium absorb lead more easily.

HEALTH EFFECTS

Lead poisoning causes arthritis, chronic fatigue, juvenile delinquency, learning disabilities, and liver failure.

CHROMIUM

Chromium is found in rocks, animals, plants and soil which are either liquid, solid, or gas mainly used in metal alloys such as steel, electroplating, paints pigments, cements, paper and rubber.

HEALTH EFFECTS

High level of chromium can cause irritation to the living of nose and thus, breathing problems such as cough, asthma, and wheezing.
Chromium causes skin ulcers, damage to liver, kidney circulatory and nerve tissues.

SELENIUM

This is a chemical element with symbol Se. it rarely occur in elemental state in nature or as pure ore compounds but found impurely in metal sulphur. It is used in glassmaking and in DC power surge protectors.

HEALTH EFFECTS

Oral exposure causes selenosis such as hair loss, nail brittleness and neurological abnormalities.
Also exposures to high levels can result in respiratory tract irritation, bronchitis and stomach pains.
- MERCURY

Mercury is one of the toxic substances we are exposed to on fairly regular basis. It is found in fungicides, pesticides, carbonated drinks (juices), dental fillings, contaminated sea foods, thermometers and host of products such as cosmetics, inks, tattoo inks, latex medications, paints plastics, solvents and wood preservative. When inhaled or absorbed by the skin, it passes through the blood-brain barrier and is attracted to and absorbed by nerve endings. This neurotoxin lodges inside neuron cell disrupting cellular communication.

HEALTH EFFECTS

Exposure to high level can permanently damage the brain, kidney, and also causes autoimmune disorders.
Also mercury causes arthritis, blindness, candidacies, depression, dizziness, fatigue, hair loss muscle weakness and menstrual disorder.

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