HEEDING THE `SMOG' SIGNAL ABOUT LEAD POISONING
Dzulkifli Abdul Razak

In June last year, Habitat II Summit, the second United Nations Conference on Human Settlements, also known as the City Summit was held in Istanbul. One of the major concerns expressed is to lessen the negative impact of urban environment on human health by reducing lead and particulate emissions, apart from providing the essential services to city dwellers. That lead have been single out is interesting because lately, a traffic policeman in a neighbouring country, was reported to have died apparently as a result of lead poisoning. In fact, the Summit reinforced the already strong worldwide movement to phase out leaded petrol by incorporating a proposal to this effect in its Global Plan Action.

The fact that motor vehicles are a major cause of death is almost a foregone conclusion, at least in Malaysia. Generally, Malaysians are noted as one of the world's worst drivers, and therefore in many cases are accessories to such tragedies. Before the implementation of Ops Pacak over the recent double festivities, the number of death due to road accidents has been on the raise since the past few years. Even then Ops Pacak did not quite reduce the number of accidents per se, although the number of death dropped slightly.

Lead is in the air

Death associated with motor vehicles however can occurred in many other insidious ways. Given the vibrant local economy and the increasing number of motor vehicles pouring into the road, this consideration is becoming increasingly weighted. It has been noted that large populations around major cities especially in the developing world are slowly being poisoned by obnoxious vehicle fumes. Invariably these fumes are loaded with heavy metals, especially lead. But the effect is so subtle that the dangers usually go unnoticed or not easily discernible. Moreover, the impending death is not as dramatic as compared to that of a smashed up vehicle, with blood spluttering around the twisted remains; plus, it took place out of the full view of the public and in almost all cases. Therefore the cause for concern is less overt if at all. Hence, there will never be an equivalent of Ops Pacak in the attempt to minimize death due to the polluting effects of motor vehicles. Heavy vehicles in particular will continue to quite happily belch odious smog into the air as they ply over the clean and beautiful national expressway, Ops Pacak regardless.

The belief that motor vehicle pollutants are not as dangerous is an out-moded myth that must be exploded. Although it does not cause 'instant' mortality as such but increased sufferings relating to chronic respiratory, lung and heart diseases, are vivid 'smog' signals of the gruesome things to come. It has been reported that around the world, about 830,000 people die every year through illnesses linked to exhaust fumes and industrial smog which engulf many cities of the Third World. In Latin America alone the figure stands at 115,00. The remaining are in Asia, Africa and Eastern Europe. Some of these concerns have been voiced out at the First World Congress on Air Pollution in Developing Countries held in San Jose, Costa Rica late last October.

All in all 17 billion people, mostly city-dwellers in developing countries are said to be at risk from lead poisoning warned the World Bank in recommending a worldwide phasing out of leaded petrol. Examples of countries already imposing such a ban are Australia, Brazil, Canada, Colombia, Costa Rica, Japan, Sweden, Slovakia and United States. Very few are from Asia or the African continent. In contrast, these two continents provide ample examples of cities literally being choked by high lead levels, including cities like Algeria, Cairo, Cape Town, Hong Kong, Jakarta, Jeddah, Karachi, Mexico City and Nairobi. Others like Bangkok and Manila are fast catching up.

Preliminary local studies are beginning to indicate that Kuala Lumpur is lagging not far behind. The 1994 Air Quality Report by the Malaysian Meteorological Service (MMS), for example revealed that the annual lead deposition in Petaling Jaya is 20 times greater compared to places like Tanah Rata in Cameron Highlands. The upward trend in Petaling Jaya was "a reflection of the increase in vehicle use and the rise in industrial sources against the backdrop of the country's economic growth which is concentrated in the Klang Valley." On the whole, the atmospheric lead in the west coast of Peninsular Malaysia was consistently higher than other parts of the country. Only three out of 23 MMS monitoring stations showed zero readings for atmospheric lead. They were in Labuan, Lawa Mandau and Tawau - all in Sabah.

Apart from increasing exhaust emissions coming from leaded petrol and poorly-serviced vehicles, badly-regulated factories and greater use of fossil fuels have also been identified as the main causes of pollution with high lead content. Recently, a local environmental consultant was quoted as saying that more needs to be done to stop heavy metal waste contamination. This is with respect to metal finishing industry in particular, so that the waste can be totally eliminated before effluents are discharged into streams. Such an industry - said to be one of the major sources of heavy metal contamination - are normally engaged into electroplating and coating components that produces wastes like cyanide, chromium, iron and nickel which are highly toxic and can cause harmful effects if they are allowed to pollute water sources.

Lead is also not excluded in the list of industrial toxic substances especially if it involved small and medium industries (SMIs) - the engine for growth in many developing countries like Malaysia. According to one study, when the workers are engaged in high lead-generating process, such as grid inserting and welding, mixing, assembly welding and casting there will be greater risk involved. The tendency that SMIs are normally located nearer the smaller towns and villages would also mean that the spread of such environmental pollutants containing lead would be even greater.

Are we poisoning our children?

Widespread of lead fumes and dust in the air have other serious implications too. There is one vital population often neglected when it come to discussing about lead exposure, notably children, especially of pre-schooling age. This group is more at risk when associated with lead according to a number of well-controlled studies. Children are indeed vulnerable by the very fact that they can absorb as much as 50 per cent of ingested lead compared to 8 - 10 per cent in the adult population. Moreover, children of this age group are more curious 'hand-to-mouth explorers' such that the probable ingestion of lead-containing materials are highest, coming from a variety of unsuspecting sources. Again the World Bank warned that as many as 18 million children may face permanent brain damage associated with excessive lead in the body. In addition, it is also known to result in behavioural and learning difficulties, hearing impairments, reduced attention span as well as a drop in IQ. What does this actually mean for a 'young' nation like Malaysia?

To quote an author from US CDC published in JAMA (Nov. 7, 1990): "What is society's loss from the exposure of children to lead? Simple enumeration of children with overt intoxication, encephalopathy, or death from lead exposure does not reflect the full spectrum of lead's biologic effects and damage. Among lead's most insidious effects is its poisoning of the developing nervous system as measured by a decrease in the IQs of children with even low-level lead exposure." Similar messages are in fact being reiterated again and again in the scientific literature. Even as late as last year, another study was published in British Medical Journal (312:1569-75, 1996), citing that there was a significant inverse correlation between IQ and blood level at all ages, even at higher age group of 11 to 13 years but especially between 15 months and 7 years. All these messages are succinct - we tend to lose more than what meets the eye.

In fact, the damaging effects of lead exposure exerted themselves long before even the child is born. A number of reports have related lead concentrations to reproductive abnormalities. These include miscarriages and stillbirths. Others have also established that lead compounds are abortifacients. Women working with lead have been known to have high miscarriage rates. As such women of child-bearing age is of particular interest because it has been shown that lead can affect gestation, and lead transfer through the placenta continues throughout the fetal life. This can lead to fetal lead intoxication for example following maternal exposure to lead during the 8th month of pregnancy. In many countries, therefore, the employment of women at worksites involving lead is prohibited by law.

Against the rich background of scientific findings described above, how do developing countries in general fare? It comes to no surprise that this issue has not caught the attention of many decision-makers and policy planners, unlike that of road accidents. Many have yet to fully appreciate the long-term impact relating to lead exposure, especially involving children. In fact, there is virtually a dearth of local data on this matter in our the literature. It is in this context that the study carried out by the National Poison Centre with the assistance of the Sabah Foundation mid-last year could be considered as a landmark study. The study has indicated a number of significant findings (see Study Briefs below) which gives insights as to what would be in store for the younger generation if no immediate concerted efforts are taken. It is interesting to note that another recent study conducted at end of last year found that thirty per cent of pregnant mothers in Klang Valley showed higher levels than the acceptable level of 10 microgrammes per decilitre (mcg/dL). The highest reading was 29.5, while most had a mean of about 7 mcg/dL.

The subtlety and pervasive nature of lead exposure could be gauged from the number of sources readily available in own daily surrounding. It ranges from soil to paints, lead glazed ceramics to toys, from furniture to canned foods with exposed lead solder and, from antique pewters to metallic objects and equipment. In this regard, one is reminded of the case of 'toxic' colour pencils that took the nation by surprise in 1995. In fact, a team from Bristol University and the Thomas Coram Research Institute has found that blood lead levels were significantly higher in families with household pets compared with families that had none. The researchers believe the answer is that pets bring in lead-laden dust from outside and are then stoked by the children.

Lead can also be found in cosmetics and medicinal products - in particular traditional medicines. The latter is a worldwide phenomenon and several reports exist implicating lead-containing Asian traditional medicines. In this respect, Malaysia is no exception. Of late, tests on traditional medicines conducted by the National Pharmaceutical Control Bureau between the period of 1993 to 1995, indicated that of the overall data analysis of samples (n=2702) carried out, 11.6 per cent failed to comply with the limit test for lead, that is not more than 10 parts per million. Thus, the programme to register all traditional medicinal products marketed in this country is indeed a step in the right direction.

Leading the way

In summary, there is no doubt then that lead poisoning is a long-standing problem. In countries like Malaysia it is an issue that remains to be addressed in the larger context of protecting childhood health. In fact, most industrialized countries have recognized this problem to be one of the most prevalent childhood health issue. Yet it is also regarded as one that is most preventable. Indeed this one case in point where the wisdom 'prevention is better the cure' should be put to practice as a viable strategy. The obstacle is no longer due to the lack of technology or expertise, since ways of dealing with the problem are already well-documented; rather it is a question of political will and the ability to effectively enforce and upgrade the existing laws. It may be worthwhile to recount the experience almost a decade ago when the government introduced legislation to reduce lead content in petrol to a level of 0.15 gm/ml in 1986. This was followed by the introduction of unleaded petrol soon after. As a result it was reported that there was a brief downward trend in atmospheric lead in urban centres in the country.

At present however in Malaysia lacks a comprehensive coordinated approach to deal with the problem of environmental lead, lead exposure and lead poisoning in one go. For example, there is still a lot of room for public and professional education on the hazards of lead, and the measures that can be taken to prevent lead poisoning or to minimize exposure and lead absorption at various levels of the society. An overall national strategy - namely of screening, treating, educating, researching - to eradicate lead poisoning among children in particular is timely as we can no longer afford to underestimate the hidden cost to our society of this pervasive poison.

If the present scientific evidences about the delirious effects of lead are to be taken seriously, then the benefits that could be accrued from such a national strategy are indeed invaluable. In short, by eliminating lead as much as possible from the lives of our children, we are at once taking remedial steps to proactively reduce a significant proportion of school failures, delinquent behaviour and ultimately impaired productivity in adulthood, apart from lead-related diseases, which would otherwise continue to put tremendous strain on our society. As one concerned physician puts it: "Our challenge today is to design creative and forward thinking solutions to keep lead and other hazards from whittling away at our most valuable resources…our children." And for all these to happen, a greater commitment from all parties - professionals, government, industries and the public - is needed to confront this looming public health problem - a message ceaselessly brought to our attention by the ever darkening `smog' signal.

PRN CONSULT

SPECIAL FEATURE ARTICLE
Review of Lead Toxicity -- Part I
Razak Hj Lajis, MSc.

Introduction

Malaysia is moving towards achieving her vision as an industrialised nation. Inevitably, among other things, it will depend on an educated pool of citizen and productive skilled workforce. However there have been studies to suggest that low lead concentration in children could account for a significant proportion of school failures, delinquent behaviour and ultimately impaired productivity in the adulthood. Collectively this may translated to be a sore-point in our journey towards Vision 2020. PRN Consult takes a closer look at this potential problem in a two-part series.

Why lead?

There are more than forty substances that are classified as metal and lead is one of them. Lead being the most universal heavy metal is practically detectable almost in all environmental conditions and biologic systems. It is one of the principal constituents of the earth's crust, ranking sixteenth in the order of abundance. In term of toxicity, lead toxicity has plagued man since early civilization. Lead was found in almost all of the early utensils, storage containers and vessels used for cooking. A theory has been put forward that such extensive used of lead pipes in the water supply system in the past has led to the eventual downfall of the Roman Empire. These people, as the theory put it, could have consumed enough lead from this water to cause toxic and often fatal poisonings. Lead has also been implicated for the decline of numerous other civilizations who used lead-lined containers to store or transport their drinking water.

Lead is present in the soil, water, food, air and numerous industrial products. Unfortunately however, lead exposure and its dispensation into the atmosphere are principally due to industrial processes and human activities rather than natural causes. Human activities such as mining, manufacturing and the burning of fossil fuels contribute greatly to lead disposition in the environment. Eventually lead that is released to the air from industry or burning of fuels and waste will settle down and stick to soil particles. It does not move from soil to underground water or drinking water unless the water is acidic or "soft". The lead content of soil varies depending upon the surroundings.

Lead is also present in a wide variety of foodstuffs. In general, processed foods contain greater quantities than most unprocessed food; garden vegetables contain the least. Lead can enter into the food chain by way of the soil and be unsuspectingly ingested. Plants may take up lead through the leaf respiratory system. It can absorb soluble lead through their roots and transport it above ground. Vegetable farms and fruit orchard located in heavily contaminated areas have been shown to produce products with high lead content. Thus it is not surprising that lead can be found in the bodies of men and animals throughout the world. It has been detected in human liver, kidney, lung and skeleton.

Since lead serves no useful physiological functions, its accumulation is often known to be potentially toxic to several organ systems. Majority of lead poisoning cases occur from the absorption of inorganic lead and require an extended period to achieve levels sufficient to cause symptoms. To date, more is known about lead toxicity than about any other metal.

What is the fate of lead in the body?

Lead is generally distributed among three main compartments namely in the blood, soft tissues and bones or skeleton. Lead is tightly bound in the skeleton forming 60 - 90 percent of the total body burden. About 95 percent of lead in the blood is bound to erythrocytes.

Lead is a well-known bone seeker. When introduced into the body by ingestion or inhalation, the lead pigments are separated and the body is fooled into accepting them as normal, healthy elements like calcium and iron. The lead pigment then changes form and becomes a part of the body chemistry, inhibiting the ability of various organs to perform their normal function. In increasing order, lead can also be found liver, muscle, skin, dense connective tissue and hair. The total amount of lead stored in the body is often referred as "body burden".

Lead manifest its toxicity primarily by binding to sulhydryl groups of protein molecules This cause inactivation or inhibition of several vital enzyme systems. Lead inteferes with heme synthesis by preventing the conversion of delta-aminolevulinic acid (-ALA) to porphobilinogen and incorporation of iron into protoporphyrin IX to form heme. This action is made possible by inhibiting the enzymes -aminolevulinic acid dehydratase and ferrochelatase, respectively.

This causes an increase in urinary coprophyrin and -ALA excretion and a decrease in heme synthesis.

Normal daily dietary intake of lead has been estimated to vary from as little as 0.01mg (10mcg) to as high as 1mg (1000mcg). Average dietary intake of lead is said to increase from merely 20mcg/day during early infancy to between 60-80 mcg/day by the age of 5 or 6. This estimated concentration is derived from various types of sources such as foods, drinks as well as by inhalation.

Only about 10 percent of the ingested lead is absorbed. In young children, the absorption can be as high as 50 percent. A small portion of the absorbed lead is excreted via the bile into the alimentary tract and passes out in the feces with the unabsorbed portion. Thus, the amount of lead ingested with the food can be roughly estimated by the fecal excretion of lead. The remainder of the absorbed lead is excreted in the urine. Therefore, the daily intake of lead is equal to the daily output under normal conditions. However, the fact remains that lead accumulates in the body with age in a variety of human tissues especially the bones. When the intake of lead is increased, urinary and fecal excretion increase, blood levels are elevated and storage is enhanced. Through inhalation, 30 to 50 percent is retained by the lung and is readily absorbed.

What are sources of lead

As a natural constituent of the earth's crust, lead may be found in drinking water, soil and vegetation. Its low melting point, malleability and high density as well as its ability to form alloys, have made lead useful for various purposes. In general, lead was added to paint because it helped the paint to dry more quickly and gave it a glossy and harder finishing. Lead combined with chromate and molybate to form paint pigments. Paint pigments contain lead - white lead (lead carbonate) and red lead (lead oxide). Its silicate is used in ceramics and in tireproofing fabrics. Lead arsenate has been used as an insecticide. Organic lead especially alkyllead compounds have been used in gasoline as "anti-knock" additives. The combustion of gasolines containing tetraethyllead and tetramethyllead contribute large quantities of organic lead daily.

Another source of lead is improperly soldered cans particularly those containing acidic food-stuffs. Food should not be directly heated in such can as heating increases the dissolution of lead. Domestic burning of lead-painted wood and newspaper also cause additional hazard to environment. Industrial uses such as manufacture of batteries, cables and ceramics also present potential sources of lead exposure. In a related study done locally, it was found that workers in batteries factory have a remarkably high lead levels in their blood. Such findings are parallel to overseas experiences.

Eating or drinking anything contained in lead-glazed or lead-soldered containers can also contribute to lead poisoning. Other sources of lead include juice or food contained in an improperly fired ceramic dish coated with lead-based glaze, painted furniture and colour-tinted newspaper. Lead can also contaminate water flowing through old lead-pipes, slowly poisoning those who drink it.

Summary of sources of lead disposition in the environment

• lead-contaminated soil and paint chips
• dust particles containing lead in the air, water and food.
• water that has been excessively boiled or stored in lead based kettles or containers.
• storage of fruits especially acidic fruits (fruit and vegetable juices), in leaded container.
• exhaust from motor vehicles using leaded gasoline
• lead based cosmetics.
• contaminated illicitly distilled alcohols.
• medicinal sources especially herbal or folk remedies, health foods
• metal smelters and lead-recycling facilities
• improper burning of lead-painted wood, newspaper and old battery casings.
• leaded glass and home-glazed pottery.

What lead can do to your body?

Acute lead poisoning in adult is rare but may result from massive inhalation or ingestion of large quantities of lead fumes or finely lead powder. Distribution of lead through the body is relatively slow which may account for the observation that lead poisoning is not an acute event. The usual source of lead poisoning among adults is contamination in the workplace. The symptoms include sweet metallic taste, salivation, vomitting, intestinal colic, lowered body temperature and cardiovascular collapse. Most cases of symptomatic lead poisoning appear when blood lead level (BLL) is greater than 70 mcg/dL. In children the level is very much lower. Many clinical and epidemiologic studies conducted in the United States, Germany and the United Kingdom have clearly indicated that BLL below 50 mcg/dL can cause neuro-psychologic deficit in asymptomatic children. It may also be produced in children with BLL below 35 mcg/dL. At 30 mcg/dL, a level previously thought to be safe, it is known to induce loss of neurologic and intellectual function even in asymptomatic children.

In children, the toxic effects of lead are evident across a broad range of exposures. The long-term consequences to environmental lead sources can be serious. Most lead poisoning is slow in onset and result from gradual acumulation of lead from sources of low solubility. Symptoms of lead poisoning at all ages are not specific and often go unrecognized. In toddler, anorexia is the earliest symptom. Other emerging problem may include occasional vomiting, irritability and unwillingness to play. More serious signs include persistent vomiting, peripheral nerve weakness, convulsion and coma. Generally, chronic lead intoxication usually is manifested by CNS toxicity. In adults, the symptoms are primarily gastrointestinal.

The signs and symptoms of chronic lead poisoning, include

• hematologic

The appearance of basophilic stippling is indicative of lead poisoning although it can also occur in a variety of blood dyscrasias. Basophilic stippling occurs as part of the metabolic disturbances of heme synthesis which occurs with lead poisoning. Another consistent finding in lead poisoning is the appearance of -ALA in urine. This results from an inhibition by lead of the enzyme ALA dehydratase which converts -ALA to porphobilinogen. Some evidence has been presented that a raised urinary -ALA level gives an ealier sign of lead exposure than a raised coproporphyrin level. The presence of raised coproporphyrin level is another important chemical clue to the effects of lead on the hemopoietic system. Again it could be misleading as coproporphyrinuria occurs in a large variety of other diseases and poisonings.

Lead also interferes with the incorporation of iron into protoporphyrin to form heme. The anemia associated with lead poisoning is of the hypochromic, normocytic type and is seldom severe. The anemia is a result of a decrease in the lifespan of the red blood cell as well as interference with hemoglobin synthesis.

• neurologic

The central nervous manifestation of lead poisoning are known as lead encephalopathy. These symptoms occur rarely in adults but after only very high doses of lead. In children, they are of more importance. The early symptoms include clumsiness, lethagy, headache, insomnia, restlessness, irritability and ataxia. Later confusion, delirium, convulsions and coma may develop.

• gastrointestinal

Stimulation of the smooth muscle of the gastrointestinal tract by lead constitutes an important early sign of lead exposure. Early symptoms are mild and undescriptive. However, as lead intoxication progresses, anorexia and constipation (adult) or diarrhea (children) appears. There is an increase in the frequency and intensity of intestinal spasms leading to more severe abdominal pain commonly referred to as lead colic. Appetite loss leads to a loss of body weight. They occur sporadically and often without warning. The victim's abdominal muscles become rigid and the pain can be severe.

• neuromuscular and others

The action of lead on neuromuscular system will result in a condition referred as lead palsy. Lead causes de-myelination of the median nerve which innervates the extensor muscles of the hand to produce a "wrist drop" phenomenon. A thin line of lead sulfide deposit along the gingival margin is another characteristic of chronic lead poisoning. This blue-black line is called a "Burtonia" line. However a similar discoloration of the gums may be caused by chronic accumulation of other metals such as silver, iron and mercury.

Lead also produces a toxic effect on the kidney by causing damage to the proximal tubules. This results in impaired tubular reabsorption of glucose, phosphate, amino acids, bicarbonate and uric acid. Lead also causes irreversible nephritis characterized by progressive interstitial fibrosis, sclerosis of the renal blood vessels and gromerular atrophy.

Some clinical signs and symptoms of lead intoxication

STUDY BRIEFS
LEAD EXPOSURE OF PRE-SCHOOL CHILDREN FROM THE WEST COAST OF SABAH

The study is aimed as investigating the implications arising from lead poisoning among pre-school children. The objective of the study are to:

• identify the level of lead poisoning in pre-school children from the West Coast of Sabah
• identify the high exposure risk kindergartens
• identify the population of children affected by lead poisoning

Activities and Results

For this purpose thirteen (13) kindergartens from six (6) districts from the West Coast of Sabah were randomly selected for inclusion involving four hundred and thirty-five (435) children. Blood samples were obtained and analysed by atomatic absorption spectroscopy (graphite oven - Perkin Elmer SIMAA 6000) with Zeeman effect line correction. Each sample was run in triplicate and the average was used as the final reading. Whenever a reading for the lead concentration exceeded 10 mcg/dL, the analysis was repeated.

Three (3) important conclusions were drawn from the results obtained:

1. The estimation of the level of lead exposure suggested that as many as 6.9% of the blood samples analysed from the children contained lead in excess of 10 mcg/dL compared with 20.7% between 5-9.99 mcg/dL and 72.4% between 0-4.99 mcg/dL.
2. Based on a concentration of 10 mcg/dL, three (3) districts namely Ranau, Kota Belud and Tuaran can be classed as high exposure regions and the percentage of children exposed to lead in these three areas are much higher compared to the other districts. The kindergartens involved in these areas have been identified. The highest concentration of lead detected in these districts was 18.8 mcg/dL.

Population of children at high risk suggested that age is a factor in lead exposure. Children of age six (6) years showed relatively higher levels of lead as compared to the younger population. It is evident lead absorption was continous over time. There was no gender difference observed.

Proposals

Although in general the level of lead poisoning among pre-school can be considered as not critical, there were however nearly 7% of the children in the study group who required serious attention. They require continuous monitoring.

It is proposed that a follow-up action be taken especially for the one hundred and twenty (120) children who have lead concentrations in excess of 5 mcg/dL. It is also proposed that a long term action plan be undertaken to reduce the instances of lead exposure in the West Coast of Sabah in particular, and in the whole of Sabah in general. 

Unexpected cases of lead poisoning

CASE I

In Mexico, a 6 month-old boy was admitted to a hospital. He was suffering from abdominal distention, pallor, superficial breathing and nasal flarring. He has mucus diarrhoea for a month prior to the admission. He was found to be on a medication in the form of an orange-coloured powder prescribed by a local health practitioner. The powder was later identified as lead tetra-oxide (97.4%).

CASE II

A 10 week-old infant was admitted to a hospital in Canada because of a sudden onset of seizure. The infant appearred healthy otherwise and was only fed breast milk and commercial infant formula. It was later confirmed that she had an extremely high blood lead level. Further investigations showed that the water used to prepare the infant formula had been thoroughly boiled in a special container which showed a distinct spot of lead solder.

CASE III

A 42-year old woman was admitted to hospital after complaining of severe myalgia, arthralgia and abdominal and back pain. These systems had been present for over two years and were associated with symptoms of anemia. On examination, she was pale and tired. A blood determination revealed a coarse basophilic stippling, hypochromic macrocytic cells. A bone marrow aspirate indicated moderate basophilic stippling. The blood lead concentration was found to be 131.58 mcg/dL. After the diagnosis were made, the rest of the family with whom the patient had lived in were screened. It was found that a number of the family member experiencing signs and symptoms of chronic lead poisoning. Despite an extensive investigation of the family`s workplace, home environment and diet, it has not been possible to identify the source of the lead poisoning. The most likely possibilities include the storage of home-made wine in lead-containing vessels and the use of poorly glazed pottery in cooking.

CASE IV

During a routine pre-employment examination, a 46-year-old microwave technician was found to have a blood lead level (BLL) of 50 mcg/dL. The worker complained of numbness of his fingers and palms, tinnitus and a possible decrease in his ability to perform basic mathematical calculations. A comprehensive occupational and environmental history was carried out. A repeat BLL test still revealed no apparent source of his lead exposure. He reported no history of exposure to lead from soldering or welding. He has no activities or hobbies associated with exposure to lead or lead products. He also denied taking illicitly distilled alcohol or wine. The house which he lived-in was lead-free. Blood lead testing of family members did not show any signifant increased in lead levels.

However, during a follow-up clinic visit, he mentioned that for the past 20 years, he had habitually chewed on the plastic insulation that he stripped off from the ends of electrical wires. Samples were taken and analyzed. It was later identified that the coloured coatings of the wire contained between 10mg to 39mg of lead per gram of coating. He was instructed to discontinue his dangerous habit. (Plastic coatings have been associated with lead exposure in the burning of lead-containing plastics, the production of plastics and the manufacture and use of stabiliser and pigments in the plastic industry. Lead salts such as lead oxides, chromate, phthalate, sulfate or carbonate have been used as stabilisers).