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Applause music hello students. I am ashish bertier assistant professor at the government institute of of forensic science nagpur today i bring you an interesting and learning episode in bsc science. On an important unit.
That is introduction to forensic toxicology in which we will discuss many important aspects of forensic toxicology its history and development classification. Various techniques used etc. In brief lets start our episode.
While taking a look at what we are going to learn today module. 1 introduction to forensic. Toxicology module 2 history and development of forensic toxicology module 3 classification of forensic toxicology module 4 significance of forensic toxicology module.
5. Techniques used in forensic toxicology module. 6.
Dose response relationship and finally module. 7. That would be the conclusion.
Okay so now let us begin with module 1 introduction to forensic toxicology. The word toxicology is derived from the greek word toxic on which was used as a poisonous substance in arrowheads hence. It would literally translate into the study of poisons that is toxicology toxicology is the branch of medical science.
That deals with the study of poisons with reference to their source character fatal effect lethal dose analysis of poisons and the remedial measures. A poison is defined as the substance. Which when administered.
Inhaled or swallowed is capable of producing ill health disease injury or death. When absorbed. Appropriate dosages can differentiate poison.
And also the remedial measures. All chemicals can produce injury or death. Under certain conditions.
Hence. A poison can be defined as a substance that is capable of producing detrimental or deleterious effects on a living organism as a result. There may be a change in the structure of the substance or functional processes.
Which may produce injury or even. Death. Poison is a quantitative concept almost any substance being harmful at some doses.
But at the same time being without harmful effect. I had some lower dose between these two limit. There is a range of possible effects from certain long term chronic toxicity to immediately thala t vinyl chloride may be taken as an example.
It is a potent hepatotoxic and at high doses. A carcinogen with a long latent period at lower doses and apparently without effect at very small doses clinical drugs are even more poignant examples because although therapeutic and highly beneficial at some doses. They are not without deleterious side effects and may be lethal at higher doses example.
Is aspirin. Which is considered as a relatively safe drug. Had recommended doses and is taken by millions of people worldwide at the same time chronic use can cause deleterious effects on the.
Gastric mucosa and it is fatal at a dose of about. 02 to 05. Gram per.
Kg. Approximately 15 percent of reported accidental deaths from poisoning. In children.
Result from ingestion of salicylates. Particularly aspirin. The importance of dose is well illustrated by metals that are essential in the diet.
But are toxic at higher doses. The toxicologist especially a trained expert to examine the role of such substances and their adverse effects. The variety of potential adverse effects and the diversity of chemicals present in our environment contribute to make toxicology a very broad field of science.
Therefore. Toxicologists are usually specialists to handle various areas of toxicology. The professional activities of toxicologists fall into four main categories that is forensic industrial clinical and environmental toxicology forensic toxicology emerged as the hybrid of analytical chemistry and toxic principal effects forensic toxicologist are also primarily concerned with the medical legal aspects of the harmful effects of chemicals on humans and animals.
The expertise of forensic toxicologist is primarily utilized in establishing the cause of death. And elucidating its circumstances in post mortem investigations. The work of forensic toxicologist is therefore considered as highly complicated as small quantities of poisons and their metabolites are to be isolated purified and quantified from high complex matrices forensic toxicology is a branch of forensic medicine dealing with medical and legal aspects of harmful effects of chemicals on living beings especially humans but it may also include some animals animals of importance like protected and endangered species of animals and birds equally module to historical development of toxicology or forensic toxicology.
Much of the early history of toxicology has been lost and in much that has survived toxicology is of almost incidental importance in many scripts dealing primarily with medicine. Some however deal more specifically with toxic actions or with the use of poisons for judicial execution suicide or political assassination regardless of the scarcity of the early records and given the need of people to avoid toxic animals and plants toxicology must rank as one of the oldest practical sciences. The egyptian papyrus eberts dating from about 1500 bc must rank as the earliest surviving pharmacopoeia and the surviving medical works of hippocrates aristotle and theophrastus published during the period 400 to 250 bc.
All include some mention of poisons the earliest surviving attempt to classify plants according to their toxic and therapeutic effect is that of cordis a greek employed by the roman emperor nero about ad 50 there appear to have been few advances in either medicine or toxicology between the time of galan that is ad 131 to 200 and paracelsus that is from 1493 to 1541. It was the latter who despite frequent confusion between fact and mysticism laid the groundwork for the later development of modern toxicology by recognizing the importance of the dose response relationship his famous statement all substances are poisons. There is none that is not a poison.
The right dose differentiates. A poison and a remedy concisely summarizes that concept there are some important developments during the 18th century probably. The best known is the publication of ramas amis diseases of workers in 1700 which led to his recognition as the father of occupational medicine.
Mathieu orfila. A spaniard working at the university of paris in the early 19th century is generally regarded as the father of modern toxicology. He clearly identified toxicology as a separate science and in 1815.
Published. The first book devoted exclusively to toxicology workers of the late 19th century. Who produced theses on toxicology include christian cobert and levine.
The recognition of the site of action of cure. A by claude bernard began. The modern study of mechanisms of toxic action.
Since then advances have been numerous too numerous to list in detail. They have increased our knowledge of the chemistry of poisons. The treatment of poisoning.
The analysis of toxicants and toxicity modes of toxic action and detoxication processes as well as specific molecular events in the poisoning process. It is clear. However that since the 1960s toxicology has entered a phase of rapid development and has changed from a science.
That was largely descriptive to one in which the importance of mechanisms of toxic action. Is generally recognized since the 1970s with increased emphasis on the use of techniques of molecular biology. The pace of change has increased even further and significant advances has been made in many areas including chemical carcinogenesis and zero biotic metabolism.
Among many others recent studies. However are mostly focused on the development of new methods for the detection of poisons and different matrices and the in vitro studies concerning the effects of various chemicals module. 3 classification of toxicology forensic.
Toxicology or toxicology per. Se may be divided into many sub disciplines. Let us have a look on what they are biochemical and molecular toxicology.
Considered events at the biochemical and molecular levels. Including enzymes that metabolize xenobiotics generation of the intermediates interaction of xenobiotics or their metabolites with macromolecules gene expression in metabolism and modes of action and signaling pathway in toxic action. It sounds a bit difficult.
But it is behavioral toxicology deals with the effects of toxicants on animal and human behavior. It includes the studies of the effects of alcohol and drugs on human performance and behavior. The medical legal consequences of drug and alcohol use this may include investigations of impaired driving vehicular assault and homicide drug facilitated crimes including sexual assault and aircraft motor vehicle and maritime collision investigations.
Forensic toxicologist perform analysis of drugs and alcohol in biological samples typically blood and urine. But increasingly in other matrices as well such as oral fluid and here for the purposes of determining their timing. Extent and impairment resulting from different patterns of drug and alcohol use next is nutritional toxicology.
It deals with the effects of diet on the expression of toxicity and the mechanisms of these effects next is analytical toxicology. It is a branch of analytical chemistry. That is mainly concerned with the identification and assay of toxic chemicals and their metabolites in biological and environmental materials.
Next is toxicological pathology is the branch of pathology that deals with the effects of toxic agents manifested as changes in sub cellular cellular tissue or organ morphology next branches bio mathematics and statistics that relates to many areas of toxicology. They deal with the data analysis. The determination of significance and the formulation of risk estimates and predictive models next branch is applied toxicology that includes the various aspects of toxicology as they apply in the field or the development of new methodology or new selective toxicants for early application in the field setting next branch is environmental toxicology.
It is concerned with the movement of toxicants and their metabolites and degradation products in the environmental and food chains and with the f of such contaminants on individuals and specially populations. Because of the large number of industrial chemicals and possibilities for exposure as well as the mosaic of overlapping laws that govern such exposures. This area of applied toxicology is well developed next branch is industrial toxicology.
It is a specific area of environmental toxicology that deals with the work environment and constitutes a significant part of industrial hygiene next is aquatic toxicology. It is the study of the effects of manufactured chemicals and other interpol genic and natural materials and activities on aquatic organisms at various levels of organization from subcellular through individual organisms to communities and ecosystems. Next is doping control governing bodies of most competitive and intramural sports.
Have derived rules regarding performance enhancing drug use to protect the health and welfare of the emeter and professional athletes to maintain a fair and even competitive standard and avoid forgetting fraud. This applies to both human and animal sports lets begin the module for that is significance of forensic toxicology forensic toxicology is a highly specialized area of forensic science which requires expertise in analytical chemistry. Pharmacology biochemistry.
And forensic investigation skills. The practicing forensic toxicologist is concerned not only with the isolation and identification of drugs and the other poisons from tissues. But also with the interpretation of his findings for the medical examiner coroner or other legal authority since it is the legal obligation of the medical examiner to certify that the cause and mode of death confirmed to medical and scientific facts in all cases of sudden and unexplained death complete.
Toxicological analysis are essential to complete investigation in drug induced and drug related. Deaths. Some evidences of the foreign chemical or its specific toxic effect.
Must be found in the body of the deceased or no positive proof. Exists of their role in the terminal episode. The tissue concentration together with an estimate of the total amount of drug remaining in the stomach at the time of death.
Not only offer information regarding the degree of toxicity x. But often proved helpful to the medical examiner in his determination of intent. That is accidental or suicidal in post murder.
Investigation suspected drug overdoses are clear situations. Where toxicology is required to establish if an excessive intake of the drug occurred. And if so whether this contributed to death conversely toxicology can eliminate the possibility of a drug overdose.
If concentrations are not capable of causing death. Given all the other factors. This means that toxicology testing can produce a positive result.
Even in cases where drug use is not mentioned in the police circumstances. This is not surprising given the wide availability of potentially toxic substances both legal and illegal in addition concentrations of substances change after death making any interpretation difficult in many cases poisons will be detected by the toxicological laboratory. But are not necessarily a cause of death rather their presence may be relevant in the circumstances of death in death cases.
Where natural disease is partially to blame drugs that indicate an underlying disease are often undetected such as drugs that have been used to treat a condition or pain. Sometimes these drugs are regarded as contributing to the cause of death regardless. How the individual died toxicological testing can determine whether levels of toxic substances.
May have contributed to this death. In conclusion. The knowledge of forensic toxicology can aid the coroner or medical examiner in his search for the cause and manner of death.
By his technical capacity to find evidence showing the role that the ubiquitous drugs of our society. Play in unexplained deaths module. 5.
Techniques used in forensic toxicology. Various techniques are used in forensic toxicology for a range of purposes. Including extraction of the active constituent that is poison in matrices of interest.
Stripping or purification of active constituent thus separated rapid screening and identification quantification qualification etc. We shall deal with many important techniques in detail during later lectures right now we will just have a brief description of a few of them like solid extraction solvent extraction is a common technique in forensic toxicology related to biological matrices. Solvent.
Extraction method. Has now been upgraded and made automatic that is accelerated solvent extraction in case of solid non biological matrices continuous extraction by a sox light may be employed that is continuous extraction. A system of two immiscible liquid is required for the separation of material by solvent extraction.
The active constituent should be unevenly soluble in the system. Thereby facilitating extraction of the constituent from one phase to the other the efficiency of extraction is determined by a distribution coefficient d b. Is the total weight of solute in grams in the organic phase divided by the total weight of solute in grams in the aqueous phase next technique is distillation the process involves heating a sample of liquid to convert it into vapor.
Which is then allowed to flow in another location. Where it is cooled condensing it back into a liquid various modifications of the basic distillation processes are used for specific purposes. Like steam distillation fractional distillation.
Distillation. Under reduced pressure sweep. Co distillation.
Etc. Next technique is micro diffusion. It is a convenient and popular method.
That facilitates toxicants in blood urine and gastric s. Spirits to be isolated detected and determined. This is done by conway micro diffusion dish next processes dialysis.
It involves separation of a crystalloid from a colloid by filtering through a semi permeable membrane. This separation method may be employed for the separation of toxic cations and anions in a colloidal solution. Or dispersion or colloidal matrices specially biological material.
The separation process may be accelerated by applying electromagnetic field that is by electro dialysis next process is sublimation. This is similar to distillation except the sample is a solid to begin with and is converted directly into vapor and then back into solid sublimation applicable to isolate a toxicant in solid matrices like naphthalene anthracene with sublimes next method is digestion or chemical treatment. Sometimes activist.
Students or toxicants are separated on treatment with acid or alkali or digestion on a water bath or muffle furnace like biological matrices are digested on a water bath for one or above or digested in muffle furnace with acid alkali or chemicals to isolate inorganic metals. Volatile inorganic poisons like phosphine arsine and hydrogen sulfide are isolated from their salts on treatment with dilute acids. Next technique is microwave.
Digestion. Matrices are digested with acids or alkalis. In microwave oven to facilitate isolation of inorganic poison in organic matrices under a specific analytical condition of operation like operation of oven at a specific microwave for some time the interaction of microwave with the matrices results in the production of heat with rise of temperature for which digestion occurs next method is absorption.
It is a slow process compared to adsorption at the surface involving diffusion of one substance into the interior of absorbent material toxic gases and volatiles in oil are entrapped and enriched by the process using a tube containing divers. Absorbing materials specific for a particular toxicant and online detection and determination is facilitated next technique is immunoassays. These methods have recently been introduced.
It is based on antibody antigen reaction. Which is very sensitive and specific a label antigen or antibody is employed for the purpose like a radioisotope. Other methods are based on the use of diverse traces in different ways like an enzyme or erythrocyte.
A bacteriophage. A fluorescent group and a stable free radical. The commonly used types of enzyme immunoassay.
Are homogeneous enzyme immunoassay or enzyme multiplied. He you know si. That is emi tea.
Another type in which the antigen or antibody is linked to a solid state carrier is known as enzyme linked immunosorbent assay also known as eliza. The above two techniques are simple rapid and do not require pretreatment of biological sample next technique is chromatography chromatography involves the separation of substances based on the relative affinity for two phases that is stationary and mobile phase substances. Which have higher affinity for the mobile phases are moved or carried along with it and are thus separated from those with higher affinities for the stationary phase thus.
The toxicants in molecular mixtures may be separated conveniently under different chromatographic methods and operating conditions in a particular chromatography. There are different controlling parameters like nature of toxicant mobile and stationary phase and temperature the different types of chromatographic techniques are column chromatography paper chromatography thin layer chromatography high performance. Thin layer chromatography high performance liquid.
Chromatography ion. In chromatography gas. Chromatography.
Etc. Other techniques of importance apart from the above. Mentioned techniques.
There are some others that are of prime importance in forensic toxicology like uv. Visible. Spectroscopy ir spectroscopy atomic absorption spectroscopy neutron activation analysis x ray diffraction nuclear magnetic resonance etc module 6 those response relationships as mentioned previously toxicity is a relative event that depends not only on the toxic properties of the chemical and the dose administered.
But also on individual and interspecific variation in the metabolic processing of the chemical. The first recognition of the relationship between the dose of a compound and the response elicited has been attributed to paris. Ellis.
It is noteworthy that his statement includes not only that all substances can be toxic at some doses. But that the right dose differentiates. A poison from a remedy.
A concept that is the basis for pharmaceutical therapy for many chemicals and effects. There will be a dose which no effect or response is observed. This is known as the threshold dose.
This concept is of significance. Because it implies that a no observed effect level n. Oe l.
Can be determined and that this value can be used to determine the safe intake for food additives and contaminants. Such as pesticides. Although.
This is generally accepted for most types of chemicals and toxic effects for chemical carcinogens acting by a gnote oxygen ism. The shape of the curve is controversial and for regulatory purposes. Their effect is assumed to be a no threshold phenomenon discussed below are some important definitions.
Which are required to understand the concept of those response relationships. The first is lc50 the concentration of a toxin or toxicant needed to produce death or lethality in the 50 of the treated population is known as lc50 of that particular chemical next is ec 50. The dose needed to produce an effect in 50 of a population of test animals to which it is administered by any of a variety of methods.
Available is known as ec 50 ld50. The amount or dose of a chemical. Which produces death of 50 of a population of test animals to which it is administered is known as ld50.
Conclusion forensic toxicology has benefited from advances in broader areas of science and technology. However the demand for toxicological examinations has continued to grow outpacing the ability of nations forensic crime laboratories to process them this solicitation aims to increase the amount of research development refinement and improvement of analytical techniques used by crime laboratories to gather data on complex chemical substances. And their metabolites.
It also seeks research into alternative matrices that crime laboratories can use to test for controlled substances. Applicants to this solicitation. Must demonstrate an appreciation of and general familiarity with forensic technologies as they relate to the research.
Topic. Forensic. Toxicology is a good example of a multidisciplinary science.
Combining various aspects of analytical chemistry. Physiology pharmacology and toxicology forensic. Toxicologist are first and foremost trained in analytical chemistry.
Because they need to extract and identified drugs and toxins and body fluids and tissues from living and deceased persons forensic toxicologist are also expected to provide expert testimony in code cases especially interpretation of the analytical results in relation to signs and symptoms of intoxication. Or. Whether a fatal poisoning has occurred or not continuous development in analytical chemistry.
Including computerization and highly sensitive and specific methods has meant that drugs and their metabolites can be measured in body fluids in an unequivocal way hyphenated techniques such as computer. Aided gas chromatography combined with mass spectrometry that is gcms. And more recently liquid chromatography and mass spectroscopy that is lc ms.
Have revolutionized the work done at the forensic toxicological laboratories thats it for now with this i conclude this lecture. I hope you guys have enjoyed it thank you music applause music. .
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