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Chapter: Modern Medical Toxicology: Chemical Poisons: Heavy Metals

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Lead - Chemical Poisons: Forensic Issues

Metallic lead has been part of the human environment for over 5000 years, and is today detectable in practically all phases of the inert environment and in all biological systems worldwide.

Autopsy Features

·      Pale skin, conjunctivae, and mucosa (anaemia).

·      Emaciation.

·      Burtonian line.

·      Lead lines on x-ray.

·              Pathological lesions or changes are sometimes found in kidneys, liver, male gonads, nervous system, blood vessels.

Forensic Issues

·              Metallic lead has been part of the human environment for over 5000 years, and is today detectable in practically all phases of the inert environment and in all biological systems worldwide. Because of its malleability and low melting point, it was one of the first metals smelted and used by early human societies. Hippocrates is credited with the earliest description of chronic lead poisoning when he associated persistent abdominal colic in a man, with his occupation of extracting metals (around 370 BC). The ancient Romans were however the first to experience the metal’s adverse effects on a massive scale mainly because of chronic poisoning through lead acetate which was used to sweeten wine in those days. Chemical analyses of the bones of Roman rulers have demonstrated high lead content and the madness of some of the Roman aristocracy (Nero, Caligula), may actually have been the result of lead poisoning.

·              Today chronic lead poisoning is said to be the most important environmental health problem, particularly among young children. Children are especially susceptible to lead poisoning because of their increased absorption of lead from the GIT when compared with the adult. The child with pica is in enhanced danger because of the tendency in such a case to lick lead-based paints off walls, furniture, toys, pencils, etc. Sadly, a child’s environment (particularly in countries such as India) is full of lead. Exposure can occur through paint, petrol, soil, food, water, and even air. Millions of children are probably affected annually leading to permanent neurological sequelae. The increasing antisocial behaviour of street urchinsand slum dwelling children in congested and polluted cities may also be the offshoot of chronic lead poisoning, since studies have demonstrated a high incidence of plumbism in juvenile boys with delinquent behaviour. In addition, the alarming rise in recent years of learning disabilities, lowered IQ, and memory problems of children may be related to the effects of plumbism.

·              Strategies to minimise, and if possible totally eliminate lead poisoning were evolved in the last two decades in Western countries such as the USA, and have met with significant success. Actually the first law in this regard was passed in Australia banning the use of lead in house paint. In 1971, the USA enacted a similar law. But the most important legislation passed was in 1980 when leaded petrol was banned in many of these countries.

·              In India, the first National Emission Standards for lead were issued in February 1990, but the stipulated permissible limit of 0.56 gm/L was still much higher than the recom-mended limit of 0.013 gm/L prevailing in the Western countries. Today petrol has finally made its entry into the entire country, and the situation is expected to improve in the coming years.

·              Another important step taken in the West to minimise the  paints, while such paints are still freely available in India. incidence of plumbism was to ban lead-based household paints, while such paints are still freely available in India. It has been proved that even occasional nibbling of pencils or toys painted with lead containing compounds, or licking of wall paint can lead to significant lead intoxication. In the USA, the Consumer Product Safety Commission stipulated that the maximum permissible level of lead in household paints should not exceed 0.06% and recommended to house owners that painted surfaces containing in excess of 0.7 mg/cm2 of surface lead be stripped and repainted (lead abatement). However, industrial paints for cars, machinery, bridges, highway stripes, etc., still contain 10 to 20% lead even in USA, while in India this may be upto 40%.

·              Though today lead pipes are hardly used for supplying drinking water in most parts of India, the latter even now constitutes an important source of lead poisoning. Contamination can occur through atmospheric lead or industrial wastes, or from the soldered joints in the water distribution system.

·              Lead intake through various food stuffs and beverages has been discussed in the preceding sections. The most sizeable chunk of plumbism occurs from occu- pational exposure among workers exposed to lead such as miners, plumbers, battery makers, plastic manufacturers, garage workers, etc..

·              Apart from all the conventional sources of lead exposure mentioned, novel situations are reported from time to time: ingestion of indigenous pharmaceuticals (especially Ayurvedic preparations) containing lead, home-made acidic beverages and fruit juices stored in ceramic ware, infant formula milk reconstituted with lead containing water, illicit alcohol (especially whiskey) distilled in lead soldered stills, and lead contaminated flour originating from negligently maintained mills.

·              As would be evident from the foregoing, lead poisoning is almost always accidental or inadvertent in nature. Instances of suicide or homicide with lead-based compounds are extremely rare.

 


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