A study was carried out on the assessment of lead in the organs and tissues of domestic chicken (Gallus gallus domesticus) in Ibadan from August to September 2015. Ten (10) chickens (layers and broilers) expressed as samples 1-10 were purchased from different retailer markets (Bodija, Ojoo and Sango) within Ibadan City. The chickens were dissected to remove the intestine, liver, kidney, blood, feathers and muscles were oven-dried at 220 degree Celsius. The pulverized organ and tissues samples were acid-digested and analyzed for the heavy metal lead (Pb) using Buck Scientific Atomic Absorption Spectrophotometer (AAS). The results showed that the highest Pb concentrations in parts per million (ppm) were recorded in the liver (2.940+0.040), intestine (3.9800+0.500), kidney(3.6600+0.6000), feather (3.5900+0.06000), and muscle (3.400+0.4000) in sample 10, while the lowest concentration was recorded in the kidney (0.150+0.0300) in sample 1 all at Bodija Market . Analysis of Variance (ANOVA) revealed significance of the Pb metal in the organs and tissues of chickens at P< 0.05. Less than half of the samples had Pb concentration that exceeded the permissible limit of 0.1ppm set by FAO/WHO.
ABSTRACT
A study was carried out on the assessment of lead in the organs and tissues of domestic chicken (Gallus gallus domesticus) in Ibadan from August to September 2015. Ten (10) chickens (layers and broilers) expressed as samples 1-10 were purchased from different retailer markets (Bodija, Ojoo and Sango) within Ibadan City. The chickens were dissected to remove the intestine, liver, kidney, blood, feathers and muscles were oven-dried at 220[0]C. The pulverized organ and tissues samples were acid-digested and analyzed for the heavy metal lead (Pb) using Buck Scientific Atomic Absorption Spectrophotometer (AAS). The results showed that the highest Pb concentrations in parts per million (ppm) were recorded in the liver (2.940+0.040), intestine (3.9800+0.500), kidney(3.6600+0.6000), feather (3.5900+0.06000), and muscle (3.400+0.4000) in sample 10, while the lowest concentration was recorded in the kidney (0.150+0.0300) in sample 1 all at Bodija Market . Analysis of Variance (ANOVA) revealed significance of the Pb metal in the organs and tissues of chickens at P< 0.05. Less than half of the samples had Pb concentration that exceeded the permissible limit of 0.1ppm set by FAO/WHO. The study shows that meat from the chicken organs and tissues in Ibadan are relatively safe for human consumption. There is need for regular biomonitoring of heavy metals in chicken meat and offal globally.
Keywords: Lead, , Bioaccumulation, Blood, Kidney, Liver, Intestine, Muscle and feather, Buck scientific atomic absorption spectrophotometer.
CHAPTER ONE
1.0 INTRODUCTION
Due to industrialization and urbanization in developing countries of West Africa, heavy metal pollution is likely to reach disturbing levels. The problem is that preparations are not being made towards the protection of the environment.
Nigeria is one of the petroleum exporting countries and use of automobiles by middle and high income groups is rather high. In fact,the growing rate of industrialization is gradually leading to contamination and deterioration of the environment, thus industrialization and heavy metal pollution are positively correlated (Walsh, 2000, Olaifa et al, 2004). The Nigerian petroleum contains >0.45 g/l lead as per the Nigerian Industrial Standards (NIS 116:1981). In Nigeria, gasoline with an average lead content of 0.66 g/L remains in use. With high automobile importation, the national consumption of petrol in the country is estimated at 20 million liters per day, with about 150 people/car/city, therefore close to 15,000 kg of lead is emitted into the environment through combustion daily. Heavy metal pollution is posing a serious problem in Nigeria, threatening animals, human health and quality of the environment (Dekofehiniti, O.O., 2012).
Food safety is a major public concern worldwide. The risk of heavy metal contamination in meat is of great concern for both food safety and human health because of the toxic nature of these metals at relatively minute concentrations (Akan et al., 2010). The poultry industry is one of the largest and fastest growing agro based industries in the world. This can be attributed to an increasing demand for poultry meat and egg product (Burel, S.A. and Valat, C., 2009). Several millions of chickens are raised annually as a source of food for both their meat and eggs. A complete and balanced diet is necessary for human health and vitality. chicken meat is a major source of protein to man and is widely consumed in Ibadan city and other parts of the world so its safety cannot be ignored. Meat of chicken is rich in many of the essential nutrients including protein (essential amino acid s), minerals (e.g., iron, zinc, selenium), vitamins (e.g., Vitamin E) and fat (essential fatty acid s such as Omega 3 fatty acid s) (Schonfeldt and Gibson, 2008).
Birds population are particularly susceptible to the effects of anthropogenic activities on the environment. Several biological and physiological processes, such as eating habits, growth, age, breeding, moulting may influence metal concentration and distribution in birds (Kim et al., 2007). The concentration of heavy metals in internal tissues of chicken has been extensively determined by several researchers (Demirbas, 1999; Mariam et al., 2004; Iwegbue et al., 2008; Uluozlu et al., 2009). According to Duruibe et al. (2007), some heavy metal ions that are known to be potentially toxic include aluminium, arsenic, cadmium and lead. Toxic elements can be harmful to birds even at low concentrations when ingested over a long period of time (Young, 2005).
In recent times, there has been considerable interest in the level of heavy metallic elements in foods because of their deleterious effect on human health (Uche, I.O., 2012). Apart from those communities exposed to high levels of pollution by industrial effluents or emissions rich in heavy metals, it is evident that, for most individuals food and diet are the most common sources of these potentially toxic heavy metals. These heavy metals in food and drinking water amount to approximately 80% for cadmium, 40% for lead and 8% for mecury (Bennet, 1984). Metal contamination in food, especially in meat have been broadly investigated (Sharif, et al, 2005; Miranda, 2005; Lawal, et al 2006; Jukna, 2006).
Lead is a well-known pervasive chemical and is known for its toxicity. The environmental sources of metallic lead is through auto exhaust, food, and water. A major source of exposure to lead comes from inhalation.The main source of human exposure to lead is through food, which is believed to account for over 60% of blood lead levels; air inhalation accounts for approximately 30% and water of 10% (John et al, 1991). Lead is a cumulative poison whose effects include damage to the brain and central nervous system but symptoms may not appear until after several years of exposure. Excessive amounts of lead may displace essential trace elements thereby causing nephropathy and liver dysfunction, anemia, nervous system dysfunction, weakness, hypertension, kidney problems, decreased fertility and increased level of miscarriages, and low birth weight and premature deliveries in man and animals.
1.1 AIM OF THE STUDY
The aim of this study was to assesss the concentration of lead(Pb) in chicken organs which is widely consumed in Ibadan City, Nigeria.
1.2 OBJECTIVE OF THE STUDY
The specific objectives of this study are enumerated below;
1. To determine concentration and distribution of lead (Pb) in different tissues of chicken including consumption organs (muscle, liver, intestine and kidney) and other tissues (blood and feather).
2. To assess the data by comparing estimation of the obtained results with Chinese, World Health Organization and other International permissible limits.
3. To assess the accumulation of lead (Pb) in chicken meat that will useful information for food safety in order to safeguard public health.
CHAPTER TWO LITERATURE REVIEW
2.0 HEAVY METAL POLLUTION
In Ibadan city, the rate of urbanization and industrialization is increasing day by day. These developments tend to produce certain changes in the environment. The major problem associated with these development is pollution. There are different types of pollution but the most hazardous type of pollution is the contamination of food. It occurs due to untreated industrial effluents, domestic wastes and use of pesticides in crops. Heavy metals are chemical elements with specific gravity that is at least five times the specific gravity of water (Haukes, S.J., 1997). Examples of heavy metals commonly found in the environment include lead, cadmium, mercury, zinc, arsenic, bismuth etc. These metals are particularly dangerous because they tend to bio-accumulate in the body tissues and organs (Babalola, O.O., Ojo, L.O., and Aderemi, M.O., 2005).
Health safety is very important aspect of food quality. Hazardous substances enter the food chain and are the main sources of contamination for humans. Heavy metals are most dangerous contaminants. Heavy metal poisoning results from contamination of drinking water (e.g. lead pipes) or intake through food chain. Heavy metals are dangerous because they tend to accumulate inside living organisms ( Ramya, S., Rajeswari, S., 2009). These contaminants pollute air, rivers, canals and underground water resources. The most dangerous heavy metals contaminants are lead, cadmium, and mercury and entrance of these toxic metals to human body results in various harmful diseases.The main source of heavy metal exposure to the human body is food and one of the important food item is Chicken meat. Poultry meat is considered as a source of animal protein with high biological amino acids, many vitamins and minerals which are required for human nutrition beside its relative low price compared with red meat (Institute of Medicine, 2001). It contains fats, protein and other important minerals which should be clean and safe from lead ( Pb). Contamination with heavy metals is a serious threat because of their toxicity and bioaccumulation in the food chain (Demirezen and Uruc, 2006). Heavy metals, in general are not biodegradable, having long biological half-lives and having the potential for accumulation in the different body organs leading to unwanted side effects (Jarup, L., 2003).
2.1 DOMESTIC CHICKEN (GALLUS GALLUS DOMESTICUS)
As one of the most common and widespread domestic animals, with a population of more than 19 billion in 2011. There are more chickens in the world than any other species of bird or domestic animal. Humans keep chickens primarily as a source of food, consuming both their meat and their eggs. Chickens are omnivores. Chickens may live for five to ten years, depending on the breed.
2.1.1 SCIENTIFIC CLASSIFICATION
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Galliformes
Family: Phasianidae
Genus: Gallus
Species: G.gallus
Subspecies: G.g. domesticus
Trinomial name; Gallus gallus domesticus ( Linnaeus, 1758)
2.2 PROPERTIES OF LEAD
Lead is a rare metal in the Earth's crust and its deposits are scattered throughout the world. It is one of the oldest occupational toxins and evidence of lead poisoning can be traced to the Roman times. Lead production started at least 5000 years ago and outbreaks of lead poisoning occurred from this time (Gidlow, 2004). Lead, however, is concentrated in the mantle and can be found in appreciable quantities in specific locations. The largest producers of lead in 2004 were China, Australia, the United States, Peru and Mexico (U.S. Geological Survey 2007).
Lead is a naturally occurring element known for its softness, malleability and corrosion resistance. Lead exists in four valence states (0, +1, +2, and +4). In the environment lead usually occurs in the +2 and +4 states. Organic lead compounds are almost in the +4 oxidation state. Lead has four stable and naturally occurring isotopes [204]Pb, [206]Pb [207]Pb and [208]Pb. Stable lead isotopes have been used to discriminate among potential sources of lead contamination and lead exposure in wild birds (Church et al. 2006). Common lead compounds include lead acetate, lead arsenate, lead carbonate (cerussite), lead chloride, lead chromate, lead nitrate, lead oxide, lead dioxide, lead phosphate, lead silicate, lead sulfate (anglesite), lead sulfide (galena), tetraethyl lead, lead thiocyanate, and lead thiosulfate. Lead is a poisonous metal, which exist in both organic (Tetraethyl lead) and inorganic (lead acetate, lead chloride) forms in the environment (Shalan et al., 2005).
Table 1: Chemical properties of Lead
Abbildung in dieser Leseprobe nicht enthalten
Source: www.ecy.wa.gov/biblio/0907008.html
The most common ore is galena (lead sulphide-87% lead). Lead is obtained from the ore by smelting to produce lead oxide, which is reduced to lead bullion then refined to remove other metallic impurities (IPCS, 2010). It has been used in medicines, paintings, pipes, ammunition and in more recent times in alloys for welding storage materials for chemical reagents (Garaza et al., 2006). A variety of forms of lead are used industrially, the most common being lead oxide (PbO) and red lead oxide (lead tetraoxide; Pb3O4). Lead oxides are used in the plates of electric batteries and accumulators and in other substances (Stellman and Osinsky, 2007). Also, it is used in glassware and ceramics as well as stabilizer in plastics. About 10% is converted into alkyl-lead compounds and used as antiknock additives in gasoline, although this use is in decline as more and more countries move to limit the concentration of such additives in gasoline (Massaro, 2008).
Solubility of lead in water varies which include lead sulphide and lead oxides being poorly soluble and the nitrate, chlorate and chloride salts are reasonably soluble in cold water. Lead also forms salt with such organic acids as lactic and acetic acids and stable organic compounds such as tetraethyl lead and tetramethyl lead (IPCS, 2010).
Lead is not bio-degradable and only accumulates where it is deposited. Due to this reason lead levels have increased enormously from the ancient times (Flegal and Smith, 1995). The magnitude of increase has resulted in adverse health effects (Budd et al., 1988). Lead has no biological function in both man and animals.
Lead’s toxicity was recognized and recorded as early as 2000 BC and the widespread use of lead has been a cause of endemic chronic plumbism in several societies throughout history. There is no such thing as normal or safe levels of lead for its toxicity to humans (George, 1999). Lead which is a soft, grey-blue heavy metal is a common cause of poisoning in domestic animals throughout the world (Khan et al., 2008).
2.3 SOURCES OF LEAD EXPOSURE
Naturally, lead can enter the environment either through natural processes or human activities. It is found naturally in some rocks as well as through soil weathering, water transport and volcanic action. Soil naturally high in lead are eroded by flowing water releasing lead-containing particles into the environment. These particles can be transported far from their source and may accumulate at specific locations. Volcanic action also leads to the distribution of lead-containing ash during an eruption and the release of lead containing magma which increases the presence of lead in surrounding soil.
Plants grown for consumption either at the household or commercial level can be a source of lead exposure if contaminated water, soil or airborne dust remains on the plant at the time of ingestion (ATSDR, 2007). One continuing source of concern is the historical use of lead pipes in domestic water distribution systems. Because of its cost and malleability, lead pipes were used historically to transport drinking water. Lead can erode from these pipes which provide a continuing source of lead contamination. Lead oxides and other lead-containing compounds form on the outer layer of the pipes. Because these compounds are relatively insoluble in water, the amount of lead released is limited. Problems have occurred when chemicals are added to water distribution systems which adversely affect the solubility of lead compounds and have the effect of removing this protective layer. Lead levels in some water systems have increased dramatically and concern has been raised about the possible impacts of increased lead concentrations upon the end users. Washington, D.C. exhibited elevated lead levels from 2000-2004, part of which EPA attributed to a change from traditional chlorine additives to chloramines (U.S. Environmental Protection Agency 2007).
The widespread occurrence of lead in the environment is as a result of human activity such as mining, smelting, refining, manufacturing processes and informal recycling of lead; use of leaded petrol (gasoline); production of lead-acid batteries and paints; jewellery making, soldering, ceramics and leaded glass manufacture in informal and cottage (home-based) industries; electronic waste and use in water pipes and solder. Human exposure to lead occurs from numerous sources including air, food, dust, soil and water, i.e inhalation and ingestion( Herman, D.S., 2007). The presence of lead in the environment is partially due to natural processes and anthropogenic sources, but is mostly the result of industrial wastes. Although atmospheric lead originates from a number of industrial sources, leaded gasoline appears to be a principal source of general environmental lead pollution. The consumption of polluted food is the main source of Lead (Pb) in animals which is important for assessing their risks to human health. Avian species such as birds and ducks are susceptible to bioaccumulation of lead mainly through the consumption of contaminated food ( Burger .J, and Gochfeldm. 2000); (Jeffrey M.L., 2003).
Concentrations of lead in tissue of chickens can be used to evaluate chronic or acute exposure, as chicken are fed a wide variety of feed stocks ( Sileo and Beyer, 2003). The metal accumulation in chickens through contaminated diets have been investigated in a few studies to assess the potential human risk from poultry consumption ( Hoffman, 2004). The levels of heavy metals in chicken products and its various parts such as kidneys, liver and meat of the chicken samples have been reported in the literature ( Onianwa et al., 2000). However, this pioneering study was based only on cadmium and nickel in Nigeria foods.
2.3.1 GLOBAL LEAD CYCLE
The Global Lead Cycle consists of two components namely; the natural global cycle which existed prior to man’s mining and use of lead and the lead cycle initiated by man. The two cycles have numerous similarities. One major difference however is that the natural cycle involves a small percentage of the total lead cycle currently in use. Approximately 99% of the lead currently being cycled is due to man-made inputs.
Abbildung in dieser Leseprobe nicht enthalten
Figure 1: Lead cycle sustenance
Source: www.ecy.wa.gov/biblio/0907008.html
2.4 ABSORPTION OF LEAD
Lead enters the body through ingestion and inhalation. Lead is then absorbed, distributed throughout the body and excreted (Lead, 2001).The rate of lead absorption into the body depends on the chemical and physical properties of the form of lead and the physiological characteristics of the exposed person such as age, gender, size of lead-containing particles entering the body and nutritional status (Lead, 2001).
Once lead is absorbed into the body, it travels in the blood to soft tissues, then organs and is later stored in bones and teeth after several weeks. Lead that is not distributed in the body’s organs or stored in the bones is excreted through urine, with the half-life of lead in blood being around 30 days. Thus, the kidney is the principal route for lead excretion (ATSDR 2007). The absorption of inhaled air is influenced by particle size and solubility. Pb consumed by chickens is accumulated in bones, feathers, intestines, muscles, liver, kidney, blood and eggs. Bone Pb levels are by far the uppermost, followed by kidney and liver. The primary site of the accumulation of the lead metal is the liver and the kidney (Demirezen et al., 2006).
2.5 TOXICITY OF LEAD EXPOSURE
Absorbed lead is conjugated in the liver and passed to the kidney where a small quantity is excreted in urine and the rest accumulates in various body organs. This affects many biological activities at the molecular, cellular and intercellular levels, which may result in morphological alterations that can remain even after lead level has fallen (Sidhu and Nehru, 2004; Taib et al., 2004; Flora et al., 2006; Ibrahim et al., 2012).
Autopsy studies of lead exposed animals indicated that liver tissue is the largest repository (33%) of lead among soft tissues followed by kidney cortex and medulla. Environmental exposures to lead have caused nephrotoxicity in humans and animals (Diamond, 2005). Biomakers of kidney functions have been reported to be impaired by lead in humans and animals (Gurer-Orhan et al., 2004; Weaver et al., 2005; Ahmed et al., 2008;). In the brain exposure of animals to lead causes cerebellar edema, cerebral satellitosis and encephalomalacia (El-Neweshy and El-Sayed, 2011). Impairments in cortex, hypothalamus and cerebellum were also reported. Lead toxicity in humans can be seen from the recent report of high number of child mortality in Nigeri due to their behavioral patterns such as characteristic mouthing of object (Juberg, D.R., 2001). Research using animal models have shown that lead toxicity could be associated with oxidative stress through the generation of reactive oxygen species and can be mitigated by some antioxidants substances of animal origin and extracts of plants.
2.5.1 HEALTH EFFECTS OF LEAD
Lead is a highly toxic heavy metal that affects many parts of the body and can cause many types of health problems to both humans and animals. The health effects of lead on humans have been known for thousands of years. It affects the central and peripheral nervous systems, cardiovascular system, kidney, blood, gastrointestinal system, immune system, and reproductive system. The Environmental Protection Agency classifies lead as a probable human carcinogen, but the non-cancer effects tend to be a much greater concern at the lower humans exposure levels typically seen in most people.
The effects of lead and exposure pathways for other living things are similar to those in humans. Like humans, birds particularly Gallus gallus domesticus take in lead by inhalation, ingestion, exposure of the fetus, and, to a lesser extent, absorption through the skin. As with humans, chicks are the most sensitive to the effects of lead. They show damage to their nervous system even if there are no obvious signs of lead poisoning. The main sources of lead in chicken meat arise from contamination of poultry feeds, drinking water and processing (Mariam and Nagre, 2004). Health effects of lead to chickens include feed refusal, loss of weight, low digestibility, organ failure and death while in higher animals it include, kidney and liver damage, anemia, alteration of central nervous system and cancer (Hassan, A.R., 1998).
2.5.2 EFFECT OF LEAD IN THE KIDNEY
Poultry kidney is considered to be one of the sources of mineral nutritents in human diet when consumed. The kidney is the major organ of drug excretion and is also one of the organs of primary target during lead toxicity. It manifests as proximal tubular damage, glomerular sclerosis, and interstitial fibrosis. Signs include proteinuria, impaired transport of glucose and organic anions, and lowered glomerular filtration rate( Diamond, 2005). However, renal insufficiency is found in acute lead toxicity and is accompanied by abdominal pain (lead colic), cognitive defects, peripheral neuropathy etc. Goyer and Ryne (1973) reported that the proximal tubules of the nephron are lead sensitive.The renal proximal tubules are rich in mitochondria and swelling of mitochondria can be observed at a relatively low lead concentrations.
2.5.3 EFFECT OF LEAD IN THE LIVER
Poultry liver is considered to be one of the most important sources of mineral nutrients in humans' diet, but due to its specific structure, it tends to bind chemical contaminants such as heavy metals and pesticides. However, the liver is a major organ involved in metabolic processes, is considered to be one of the most eloquent witness of any disturbance in the body, as it is subjected to different types of etiologic attacks whether infectious, toxic, metabolic, nutritional and traumatic (Doneley, 2004).
2.5.4 EFFECT OF LEAD IN THE GASTROINTESTINAL SYSTEM
Gastrointestinal lead absorption and retention is the major pathway of lead intake that vary depending on the chemical environment of the gastro-lumen, age and iron stores. One of the earliest clinical signs of lead poisoning can be nonspecific, gastrointestinal effects.
2.5.5 EFFECT OF LEAD ON THE RED BLOOD CELLS
The haemopoietic system is very sensitive to the effects of lead, and subclinical effects on a number of enzymes involved with haem biosynthesis have been seen at very low lead levels. At higher levels, lead-induced anaemia may result, owing to a combination of reduced erythrocyte survival (due to haemolysis) and reduced haemoglobin formation (Massaro, 1997). After absorption lead enters the blood where 97% is taking up by the red blood cells and half-life dead of lead in the red blood cells is 2 – 3 weeks ( Timbrell John A, 2000) due to its deposition in bones and teeth.
2.5.6 EFFECT ON THE REPRODUCTIVE SYSTEM
The effects of lead on reproduction are well established for both men and women, with reports dating to the 19th century. At one stage, lead was even used to induce abortions (Hall and Cantab, 1905). Although the majority of human studies have been based on small numbers of subjects, there is nevertheless general agreement that women, especially those exposed to lead during pregnancy, report higher rates of miscarriages, stillbirths and preterm deliveries. The effects of lead on sperm include decreasing sperm count and an increasing number of abnormal sperm (Lin et al.,1996).
2.5.7 EFFECT OF LEAD ON THE NERVOUS SYSTEM
In humans, lead causes damage to a variety of organs, particularly the central nervous system (Massaro, 1997). Low lead concentrations enhance the release of neurotransmitter from presynaptic endings (Cooper et al., 1984). Lead has been shown to stimulate the release of dopamine, acetylcholine, and gammaaminobutyric acid (GABA) (Minnema et al., 1988). Some of these effects may be due to the ability of lead to alter calcium entry into nerve cell or by an increase in the intracellular calcium levels. Lead may enter cells through calcium channels. Calcium may also competitively inhibit lead uptake in non-excitatory cells such as the adrenal medulla and cannot be discounted as the potential mechanism in nerve cells. Calcium channel blockers likewise may inhibit lead uptake in the same cells (Simons and Pocock, 1987.) Lead is known to substitute for calcium as a second messenger and can bind to calmodulin. In fact, calmodulin has a greater affinity for lead than for calcium. If lead acts as calcium in the activation of this kinase, this may explain the ability of lead to result in neurotransmitter release (Massaro, 1997). Theoretically, these effects are reversible if lead is removed from the synapse.
2.5.8 EFFECT OF LEAD IN THE BRAIN
Repeated lead exposure of moderate to high levels can cause encephalopathy which is a progressive degeneration of certain parts of the brain. Early symptoms of encephalopathy include dullness, irritability, poor attention span, headache, muscular tremor, loss of memory and hallucinations. More severe symptoms occur at very high exposures and include delirium, lack of coordination, convulsions, paralysis, coma and death (Lead, 2001). The encephalopathy induced by lead toxicity is most likely due to a compromise in blood brain barrier. Brain oedema occurs in the interstitial area and appears due to compromised blood vessel integrity. The brain capillaries and blood vessels have endothelial cells that contain tight junctions and act as a seal or barrier that excludes many plasma proteins and organic molecules and impedes Na+ and K+ exchange (Bradbury, 1984). Elevated lead levels disrupt these vessels, and plasma proteins such as albumin enter the interstitial spaces, as do some ions. This increases osmotic pressure, thereby making water to accumulate in response. The lack of lymphatic structures within the central nervous system means that the fluid flows into the cerebrospinal fluid. This oedema causes an increase in intracranial pressure and restricts blood flow to the brain, resulting in ischemia (Goldstein et al., 1974).
2.5.9 EFFECTS ON THE CARDIOVASCULAR SYSTEM
This is another effect that is seen at low blood lead levels. Elevated blood pressure has been associated with an increased risk of cardiovascular and cerebrovascular disease. The association between the blood lead level and blood pressure is strongest for increases in systolic blood pressure in adult males. Schwartz (1995) showed that decreases in blood lead from 10 μg/dl to 5 μg/dl were associated with a decrease of 1.25mmHg in systolic blood pressure; other studies found decreases of 2 mmHg for reductions in blood lead from 20 μg/dl to 15 μg/dl, and from 15 μg/dl to 10 μg/dl (Schwartz, 1988; Pirkle et al., 1985).
2.6 OTHER EFFECTS OF LEAD
The effects of lead in other organisms are similar to those in humans. Human activities have spread lead throughout the environment in the air, land and soil. Most animals have higher levels of lead than in pre-industrialized times and a threshold at which there is no effect has not been found (Pain, 1996). Animals that do not die directly from acute lead exposure may face sub-lethal effects of chronic lead exposure, which contribute to their inability to survive in the wild( Eisler, 1998).
Plants take up lead from the soil and water. An increase in active calcium metabolism, such as during egg laying, affects lead metabolism. Birds that are actively egg laying have higher levels of lead than either non-laying females or males (Pain, 1996). Diet has a similar affect on lead absorption by wildlife as it does in humans. There are some sources of lead exposure that are especially important for animal populations. There are risks to:
1. Waterfowl from ingesting lead shot. Predators and scavengers that eat game wounded by hunters.
2. Wildlife that forage near roads.
3. Aquatic life near industrial or legacy sources of lead.
4. Crops and invertebrates living in lead-contaminated soil.
5. Domestic livestock and zoo animals near industrial sources and/or in enclosures with lead paint.
In plants , lead is not essential and excessive amounts can cause growth inhibition, as well as reduced germination rates, photosynthesis, mitosis and water absorption. Crop plants may have reduced yield. Population level damage to plants from lead is rare, but atmospheric lead may have contributed to the decline of the European spruce forests (Eisler 1988).
[...]
- Quote paper
- Emmanuel Tyokumbur (Author), 2015, Evaluation of Lead in the Organs and Tissues of Domestic Chicken (Gallus gallus domesticus). Food Safety, Munich, GRIN Verlag, https://www.hausarbeiten.de/document/1363592
