Forensic Medicine & Applied Toxicology-5

Information about Forensic Medicine & Applied Toxicology-5

Published on August 7, 2014

Author: willismochieng



Forensic Classification of Poisons (4,5): Forensic Classification of Poisons (4,5) Dr. Willis Ochieng Toxicologist 07/08/2014 1 Classification of Poisons-4 Irritant Poisons:   Irritating when in contact with tissues. The outcome of exposure is variable. Common manifestations of acute poisoning are cramps, diarrhoea, vomiting, gastric pain, jaundice, paralysis, peripheral neuritis, salivation and urine retention . Chronic exposure may manifest as weight loss, hair loss and anaemia. A group of poisons which best fits this class are heavy metals and their compounds. Heavy metals exist in different speciation giving rise to different chemical reactivity. In general, they are relatively chemically inactive and have a long environmental biological half life. Onset of symptoms may arise usually after several hours and in serious toxic exposure, death may occur within 24 hours but more commonly after several days. Because of their charge and a long life span , contact with the cell membranes often confers irritant properties the characteristic symptomatology . Predilectional sites for these poisons are kidney, urine, intestinal contents, bone, hair and nails. The commonly detected poisons in this class are arsenic, iron, lead, lithium, mercury, gold aluminiun and thallium . Aluminium is now suspected of predisposing human to certain types of mental disorders. Most of these metals are usually detected as a component of agro-chemicals, therapeutic and industrial chemicals. Classification of Poisons-4 Irritant Poisons 07/08/2014 2 Classification of Poisons-4 Arsenic Poisoning-1 : Exposure is via- Drinking water Contaminated soil Food Inorganic arsenic is methylated in humans as well as animals and micro-organisms. There are considerable differences between species and individuals Arsenic rate of excretion increases with the methylation efficiency. There are large inter-individual variations in the methylation of arsenic. Children have a lower degree of methylation of arsenic than adults hence more susceptible to poisoning There are indications of a lower degree of arsenic methylation in men than in women, especially during pregnancy. Classification of Poisons-4 Arsenic Poisoning-1 07/08/2014 3 Classification of Poisons-4 Arsenic Poisoning-2: Only inorganic As is toxic in human. It is important to consider speciation as regards toxicity Acute poisoning is characterised by-- Burning in mouth Gastro-enteritis presenting with nausea Abdomen pain Regurgitation Vomiting and diarrhoea Chronic poisoning is characterised with-- Loss of appetite Occasional vomiting Jaundice Loss of weight Anaemia Other signs of chronic poisoning are skin eruptions-eczema, keratosis of plantars and soles, brittle nails, hair loss, melanesia with patches of leukaplakia , peripheral neuritis and cathexia . The poison is permanently stored in the nails and hair Autopsy findings are- Usually and not always, highly inflamed upper small intestine and stomach mucus membrane presenting with a velvety appearance , red and oedema of the stomach There may be bleedings from erosions The liver may show patchy fatty degenerative change or necrosis with jaundice The heart muscle and kidney parenchyma may show similar fatty change Peripheral neural degenerative changes may also be present Classification of Poisons-4 Arsenic Poisoning-2 07/08/2014 4 Classification of Poisons-4 Lead Poisoning-1: Lead is a highly toxic metal, the main source of which is contamination from combustion of leaded petrol The neurotoxicity of low-level long-term exposure has a special relevance in children Low-level lead exposure causes deficits in the neurobehavioral-cognitive performance evidenced in childhood through adolescence Neurosensory processing may be affected by lead , with consequent decrease in auditory sensitivity and visuomotor performance Lead disrupts the main structural components of the blood-brain barrier by -- Primary injury to astrocytes Secondary damage to the endothelial microvasculature Within the brain, lead-induced damage occurs preferentially in— Prefrontal cerebral cortex Hippocampus Cerebellum In general, lead acts as a chemical stressor and causes breakdown of the homeostatic cellular mechanisms This is expressed in both the anatomical site and the neurotransmitter systems which are crucial in modulating emotional response, memory and learning Classification of Poisons-4 Lead Poisoning-1 07/08/2014 5 Classification of Poisons-4 Lead Poisoning-2: Lead exposure leads to inhibition of delta- aminolevulinic acid dehydratase activity (ALA-D) an enzyme important in the biosynthesis of haeme whose inhibition may lead to haemo / neurotoxic effects, especially in new-borns who have high level of neurogenesis Biochemical index of toxicity is– Blood ALAD activity level at around 100 units is an indication of excessive body lead Elevation of a significant urine microalbumin in people chronically exposed may suggest renal glomerular damage Plasma creatinine , blood urea nitrogen (BUN) and uric acid are often raised in cases involving heavy lead exposures Control of lead poisoning is best done by— Strict adherence to personal hygiene Public health education Statutory intervention Control by dietary calcium supplement has been done to competitively decrease gastrointestinal lead absorption thereby reducing the risk for lead poisoning. Best done by- Daily drinking of milk . Addition of dietary calcium Addition of Vitamin C Use of ascorbic acid shows a marked reduction in blood and liver lead concentration Classification of Poisons-4 Lead Poisoning-2 07/08/2014 6 Classification of Poisons-4 Lead Poisoning-3: Symptoms of Acute Poisoning -- Similar to arsenic except that constipation is marked Stool is blackened and offensive There may be kidney damage Renal failure Lead palsy   Symptoms of Chronic Poisoning   Anaemia with punctate basophilia Colic pain, constipation, blue line on gums Vorist drop with paralysis and muscle atrophy Inhibits regular developmen t if exposure has started prenatally Skeletal muscle is a common target hence the myotoxic effects Tremors of hands, encephalopathy with convulsions, confusion, tremors of eye, tongue, fingers, incoordination , loss of vision, scelerosis of kidneys and hypertension Classification of Poisons-4 Lead Poisoning-3 07/08/2014 7 Classification of Poisons-4 Mercury Poisoning-1 : Is methylated by bacteria in aquatic environments to methylmercury . It is then concentrated by the food chain Elemental mercury is not as toxic as organic mercury, however, its exposure may induce severe axonal sensorimotor polyneuropathy in humans with neurological deficits which may persist in severe cases Chronic poisoning was discovered for the first time as a strange neurological disease in Japan in people living around the Minamata Bay Its neuropathology consists of nervous system lesions. Affects the calcarine cortex by the destruction of nerves In the peripheral nerves, sensory nerves are more affected than motor nerves The uptake of food-related organic mercury is six times higher than the uptake of mercury from amalgam. F ood-related mercury is significantly more toxic Classification of Poisons-4 Mercury Poisoning-1 07/08/2014 8 Classification of Poisons-4 Mercury Poisoning-2: Methyl mercury readily crosses the placenta and the blood-brain barrier and is neurotoxic Prenatal poisoning with high dose methyl mercury causes mental retardation and cerebral palsy Occupational exposure to mercuric compounds and use in suicide is of forensic significance Mercuric chloride is commonly used as a suicidal agent Ingestion of mercuric chloride causes the development of haematemesis , melena and acute renal failure Chronic exposure to mercury is demonstrated by elemental X-Ray analysis of lipofuscin deposits Classification of Poisons-4 Mercury Poisoning-2 07/08/2014 9 Classification of Poisons-4 Gold Poisoning: A precious metal most mined and responsible for many mining accidents Is now used as a delivery vehicle for gene therapy in modern medicine Its administration to humans is both deliberate and inadvertent It is universally recognised as the most inert of metals, yet it can be sensitising Until recently, gold allergy was considered to be extremely rare. It is employed clinically to suppress immune system It can engender toxicities that stem from immunostimulation Toxicity of gold, unlike that of most pharmaceuticals, is, in general, not predictably related to the levels it attains within bodily tissues Classification of Poisons-4 Gold Poisoning 07/08/2014 10 Classification of Poisons-4 Aluminium Poisoning: Is ubiquitous and is found in many foods including drinking water. Acute exposure is not uncommon as a compound For example, aluminium phosphide is widely used as a fumigant to protect stored grain from pests and rodents Chronic exposure remains a controversial possible cause of some forms of Alzheimer's disease . Aluminium causes disorders mainly in motor coordination Neurotoxicity may lead to progressive dementia and Alzheimer's disease Use of drinking water with a high aluminium concentration, with pH about or less than 7.0, and with low fluoride concentration, is associated with the increased relative risk of Alzheimer's disease Morphological and biochemical characteristics of neurofibrillary tangles which occur in the brain after aluminium exposure may be aetiological in Alzheimer's disease Alzheimer’s disease is characterised by a catastrophic loss of neuron s Free radicals (oxidative toxins) are implicated in the destruction of cells by lipid peroxidation of cell membranes. Aluminium and a fragment of beta amyloid exacerbate free-radical damage , while melatonin reduced this effect In Alzheimer’s disease, excessive quantities of aluminium are taken up into the brain, where it exacerbates iron-induced lipid peroxidation in the lysosomes . In response, the normal synthetic pathway of amyloid protein is altered to produce beta fragments which attenuate its toxicity. In the process of sequestering aluminium and iron, immature plaques are formed in the brain . Microglia are activated, in an attempt to destroy the plaques by secreting reactive oxygen species such as hydrogen peroxide. At this point in the disease process, lipid peroxidation causes a catastrophic loss of brain cells Melatonin , together with other free radical scavengers in the brain, reduces the free-radical damage caused by aluminium and beta amyloid fragment, except in the latter stages of the disease process Since melatonin is produced by the pineal gland only in the dark, the excess of electric light in developed countries may help explain why Alzheimer’s disease is more prevalent in these countries than in rural Africa Classification of Poisons-4 Aluminium Poisoning 07/08/2014 11 Forensic Classification of Poisons-4 Investigation of Pesticide Poisoning : General principal features are vomiting and convulsions. Identification of the sub-class of the suspect pesticide will provide a more accurate symptomatology Chlorinated hydrocarbons produce dizziness, headache, muscular weakness, and tremors Chlorinated phenoxyacetates produce burning sensation and low blood pressure Organophosphates produce contracted pupils, salivation, sweating, dyspnoea, anoxia and cyanosis Phenols and cresols may present with fever (main symptom), thirst, sweating, anoxia, haematuria and jaundice Onset of symptoms following exposure is generally slow and ranges between one and six hours but may occur within minutes if the suspect product contained a petroleum solvent or is inhaled Scene of poisoning- Incidents occurring in the following places should be suspected of poisoning- Farms and horticultural nurseries Food processing factories Domestic premises Additional evidence - Stained clothing, vomit, drink, stomach contents must be collected for scrutiny and analysis Colour s[- Pesticides often contain colours which may provide clues Forensic Classification of Poisons-4 Investigation of Pesticide Poisoning 07/08/2014 12 Classification of Poisons-4 Pesticide Human Poisonings : Chronically , pesticides may be producing undetected ill effects on health Children are the victims of a high % of accidental acute fatal poisonings Common poisoning among adults is by occupation exposing agricultural workers, manufacturers of pesticides etc Route of exposure— Dermal exposure route is common among workers handling pesticides Oral ingestion is the most frequent route of exposure in cases of non-occupational poisonings Inhalation route is common involving vapour generating devices and other aerosols Compounds that have a high potency as inhibitors of carboxylesterases relative to their anticholinesterase potency are likely to potentiate other organophosphate insecticides or alter toxicity of other drugs and chemicals containing carboxyl esters or amide linkages Some pesticides induce or inhibit microsomal liver enzymes The effect that microsomal enzyme induction or inhibition will have on the toxicity, and action of a particular drug or chemical, will depend upon the degree to which the enzyme activity is changed Classification of Poisons-4 Pesticide Human Poisonings 07/08/2014 13 Classification of Poisons-4 Paraquat Poisoning : No report yet of homicidal poisoning due to oral administration of paraquat in Kenya. There are however a number of cases involving suicidal ingestion of this pesticide Serious exposure to the herbicide paraquat usually results in death, either due to-- Gastrointestinal caustic lesions, shock or acute respiratory distress syndrome Death is due to progressive development of pulmonary fibrosis associated with refractory hypoxemia Treatment is consisted of early digestive decontamination and haemodialysis, followed by antioxidant therapy Includes administration of deferoxamine (100 mg/kg in 24 h) and a continuous infusion of acetylcysteine (300 mg/kg/d during for as long as it is necessary ). Early administration of an antioxidant therapy, including deferoxamine and acetylcysteine could be usefully associated with measures that may prevent digestive absorption or enhance elimination to limit systemic toxicity in potentially fatal paraquat poisoning.   Classification of Poisons-4 Paraquat Poisoning 07/08/2014 14 Classification of Poisons-4 Organophosphate Poisoning: OP poisonings cause substantial morbidity and mortality world-wide OPs are commonly used in suicides and homicides Current treatment of acute OP poisoning includes a combined administration of a cholinesterase reactivator ( oxime ), a muscarinic receptor antagonist (atropine) and an anticonvulsant (diazepam ) This treatment is not adequate since it does not prevent neuronal brain damage and incapacitation Accumulation of ACh in the synaptic cleft is considered to be responsible for the symptoms that ultimately lead to death Prevention or suppression of excessive accumulation of Ach is a generic approach to antagonise OP-poisoning Adenosine receptor agonists could be promising candidates for the treatment of acute OP poisoning In addition to acute effects, OPs may exhibit a delayed toxic response which is often fatal OP induced delayed polyneuropathy is a sensory-motor distal axonopathy which usually occurs after ingestion of large doses of certain organophosphate Classification of Poisons-4 Organophosphate Poisoning 07/08/2014 15 Forensic Classification of Poisons-5 Investigation of Corrosives: Generally, corrosives irritate the gastrointestinal tract . Common presentation may include the following manifestations-- Burning sensation in the mouth and throat, difficulty in swallowing Burns of lips and adjacent skin, vomiting, thirst, choking Dysponoea , aneumonitis , collapse or death Systemic presentations vary with the type of substance involved Cyanosis produced by formation of methaemoglobin is produced with oxidising agents Other symptoms and signs may be stained skin and mucosa as caused by permanganate, oxalate, iodine, and bleaching agents Onset of symptoms usually occurs within one hour followed by death within several hours post-exposure Common corrosives include- Nitrate, chlorate, fluoride, and fluoroacetate in agricultural communities Nitrite, oxalate, and sulphite in industrial areas Domestic sites should point towards drain and lavatory cleaners (hypochlorite), weed killers (chlorate) and insect powders (fluoride) Forensic Classification of Poisons-5 Investigation of Corrosives 07/08/2014 16 Classification of Poisons-5 Corrosives-1 : The majority of these substances are considered safe with very low incidence of fatality world-wide They affect mainly infants and young children commonly exploring their environment by placing objects in their mouth The risk group in this class of poisons is children under the age of six years with the mean age of three years More boys are affected than girls (ratio about 2:1) The use of these substances is more common in towns than in rural areas which also corresponds with the number of patients affected Most ingestions appear to be accidental They have been used as weapons by criminals, causing serious burns to skin of the victims Classification of Poisons-5 Corrosives-1 07/08/2014 17 Classification of Poisons-5 Corrosives-2: Ingestion of these substances may present with oesophageal burns with first-degree, second-degree and third-degree depending on the strength and quantity Analysis indicates that the alkaline products are ingested more frequently than acid products The most common product ingested is bleach in most cases . The most dangerous substances are dishwasher liquids and powders There are cases of deliberate adult ingestion of clothes washing liquid The offending component is the phosphate which is responsible for the dramatic metabolic upset leading to death Highly concentrated solutions of sulphuric acid are available to unclog drains . A substantial number of both accidental and intentional cutaneous burns caused by these agents is reported The acid can produce full-thickness cutaneous burns Proper use of these agents and keeping them away from children may reduce accidental contact Their abuse as agents of assault remains a source of significant morbidity Classification of Poisons-5 Corrosives-2 07/08/2014 18 Classification of Poisons-5 Corrosives-3: Death due to ingestion of these substances may be epitomised by the presence of stains on the lips, cheeks, chin and neck Corrosion may extend down the mouth, throat, glottis and into the stomach and may reach the small bowel Serious irritation of the air passages may occur with the fuming mineral acids Alkalis may cause a slimy corrosive change with copious excesses of mucus and much puffy swelling of the tissues Perforation of the oesophagus or stomach is most common with sulphuric, hydrofluoric and hydrochloric acids The phenomenon of perimortal fixation is a useful indication for the pathologist to direct the suspicion to oral poisoning by corrosive chemicals Classification of Poisons-5 Corrosives-3 07/08/2014 19 The End: The End 07/08/2014 20

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