CHEMISTRY OF LEAD AND IT’S TOXICITY EFFECT IN THE HUMAN BODY
TABLE OF CONTENTS
Contents
Cover page
Title page
Certification
Dedication
Acknowledgements
Table of content
CHAPTER ONE: INTRODUCTION
1.1 Origin and Occurrence
1.2 History of Lead
CHAPTER TWO: CHEMISTRY AND USES OF LEAD
2.1 Chemistry of Lead
2.1.1 Physical Properties
2.1.2 Chemical Properties
2.2 Uses and Application of Lead
CHAPTER THREE: EXPOSURE AND TOXICITY EFFECT OF LEAD IN HUMANS
3.1 Exposure Sources of Lead in Humans
3.1.1 Ingestion
3.1.2 Inhalation
3.1.3 Dermal Contact
3.2 Toxicity Effect of Lead
CHAPTER FOUR: SUMMARY AND RECOMMENDATION
4.1 Summary
4.2 Recommendation
CHAPTER ONE: INTRODUCTION
1.1 Origin and Occurrence
Lead is an element known to occur in space and on earth
In space, lead’s per-particle abundance in the solar system is 0.121 parts per billion (Lodders, 2003). However the amount of lead in the universe is slowly increasing as most heavier atoms (all of water are unstable) gradually decay to lead (Roederer et al., 2009). Thus, since its formation 4.5 billion years ago, the abundance of lead in the solar system has increased by about 0.75% and despite its relatively high atomic number, lead is more prevalent than most other elements with atomic number greater than 40. Record have shown that primordial lead which comprises the isotopes lead 206, lead 207 and lead 208 was mostly created as a result of receptive neutron capture processes occurring in stars and the two main modes of capture are the s-process and r-process. In the s-process (s is for “slow”), captures are separated by years or decades, allowing less stable nuclei to undergo beta decay. In the r- process (r is for rapid), captures happen faster than nuclei can decay. This occurs in environments with a high neutron density, such as a supernova or the merger of two neutron stars. The r- process does not form as much lead as the s- process.
On earth, lead is classified as a chacophile under the Goldschmidt classification, since it is generally found combined with sulfur (Langmuir and Broecker, 2012). It rarely occurs in its native, metallic are relatively light and over the course of the Earth’s history, have remained in the crust instead of sinking deeper into the Earth’s interior. This accounts for lead’s relatively high crustal abundance of 14ppm and hence the 38th most abundant element in the crust (Emsley, 2011). The main lead bearing mineral on earth galena (Pbs), which is mostly found in zinc ores. Most other lead minerals are related to galena in some way. For instance boulagerite, Pbs Sb4S11 is a mixed sulfide derived from galena; anglesite, PbS04 is a product of galena oxidation while cerussite or white lead ore, PbCO3 is a decomposition product of galena (Davidson et al., 2014).
1.2 History of Lead
metallic lead beads dating back, to 7000-650000 BCE have been found in Asia Minor and may represent the first example of metal smelting. At that time lead had few applications due to its softness and dull appearance (Rich, 1994). The major reason for the spread of lead production was its association with silver, which may be obtained by burning a common lead mineral called by galena. The ancient Egyptians were the first to use lead minerals in cosmetics an application that spread to Ancient Greece and beyond. Furthermore, the Egyptians used lead for sinkers in fishing nets, glazes, glasses, enamels and for ornaments. Various civilization of construction material. Lead was also used in the Ancient Chines royal court as a stimulant, the fertile crescent used lead as a writing material, as coins and as a writing material, as coins and , as currency and as a contraceptive. The indus valley civilization and the Mesoamericans used it for making amulets and the eastern and southern African peoples used in wire drawing (Yu and Yu, 2004; Bisson and Vogel, 2000).
Rome’s territorial expansion in Europe and across the Mediterranean, and its development of mining led to it becoming the greatest producer of lead during the classical era, with an estimated annual output peaking at 80,000 tonnes. Like their predecessors, product of silver smelting 9Hong et al., 1994). Lead mining was formed to in central Europe, Britain, the Balkans, Greece, Anatolia and Hispania, production (Hong et al., 1994).
Lead mining in Western Europe declined after the fall of the Western Roman Empire, with Arabian Iberia being the only region having a significant output. Thereafter the largest production of lead occurred in south and East Asia, especially China and India, where lead mining grew rapidly. In Europe, lead production began to increase in again used for roofing and piping and starting in the 13th century, lead was used to create stained glass (Rich, 1994). Despite being more expensive than iron, lead also become the chief material for making bullets for firearms. This is because it was less damaging to iron gun barrels had a higher density and its lower melting point made the production of bullet easier since they could be made using a wood fire (Ramage, 1980). In the New World, lead production was recorded soon after the arrival of European settlers the earliest record dates to 1621 in the English colony of Virgirna, fourteen years after its foundations and in Australia, the first mine opened by colonist on the continent was a lead mine, in 1841. In Africa, lead mining and smelting were known in the Benue Trough and the lower Congo Basin, where and as a currency by 17th century well before the scramble for Africa (Bisson and Vogel, 2000).
In the second half of the 18th century, Britain and later continental Europe and United States, experienced the industrial revolution. This was the first time during which lead production rates exceeded those of Rome (Hong et al., 1994). Britain was the leading producer, losing this status by the mid-19th century with the depletion of its mines and the development of lead mining in Germany, Spain and the United State. By 1900, the United States was the leader in global lead production and other non-European nations Canada, Mexico and Australia had begun significant production (Rich, 1994). A great share of the demand for lead came from plumbing and painting as lead paints were time, more working class people were exposed to the metal and lead poisoning cases escalated. This led to research into the effects of lead intake consequently was proven to be more dangerous in its fume form than as a solid mental. As the effect of chronic ingestion of lead, including mental disorders were also studied in 19th century (River et al., 2012).
Further evidence of the threat that lead posed to humans was discovered in the late 1970s, the United State and Western European Countries introduced legislation to reduce lead in air pollution.
