Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Chemical toxicology


Published on

In this you can learn about Chemical Toxicology like toxic chemical in environment in water in enzymes.You can learn about uses of pesticides in environment and many more....THANK YOU

Published in: Science
  • Be the first to comment

Chemical toxicology

  1. 1. CAREER POINT UNIVERISTY MAJOR ASSIGNEMNT CHEMISTRY Anugyaa Shrivastava K12986 Ashish Kumar Jha K12593 Sanjay Singh Chaudhary K12336
  2. 2. Chemical Toxicology….. TOXIC CHEMICALS IN THE ENVIRONMENT Of the numerous chemicals present in the atmosphere, only some are toxic. The toxic chemicals are released mostly from chemical activities. They get into human food chain and once they get in there, they often lead to fatal consequences. An effort will be made here to study the mode of action of these chemical in chemical toxicology. The list of these chemicals is very long and even now, one is not sure whether a particular chemical is toxic or not, since non-toxicity has not been adequately established. Any division of these basis can be misleading. Many of these listed as environmental hazards are often essential ingredients for animal growth, viz. Al, Ba, B, Co, Cu, Cr, etc. Sonwatz drew a concentration line, to show the demarkation: 1. Essential in trace level for sustenance of life process, 2. Toxic in higher levels, causing adverse effects, and 3. Deficient in lower levels causing metabolic disorder. Thus, even well-known toxic elements as Pb, Cu, Cd are required in trace quantities for animal growth. The well- known inert Al, causes brain disorder. Toxic chemicals can be classified according to their environmental effect. The US Environmental protective
  3. 3. agency has listed 24 extremely hazardous chemicals found in the atmosphere. Acetonitrile, As, Asbestos, Benzene, Be, Ca, Chlorinated solvents are some of them. TOXIC ELEMENTS IN WATER Toxic Elements in Waste Water and Normal Water Elements Sources Effect Arsenic Byproducts of mining, pesticides, chemical waste Toxic, possibly carcinogenic Boron Coal, detergent industries and industrial waste Toxic to some plants Beryllium Coal, nuclear power and space industries Possibly carcinogenic Copper Metal plating, industrial and domestic waste Toxic to animals + algae at moderate levels Floride Natural geological sources, industrial waste Bone damage at about 5 ms/1 Lead Industry, mining coal and gasoline Anemia, wild life destruction Cadmium Industrial discharge, mining waste, metal plating and water pipes Replaces Zn biochemicall, High blood pressure, damage and destruction to testicular cells
  4. 4. Mercury Industrial, activities + coal industry Highly toxic in all forms Molybdenum Natural resources + Industrial waste Possibly toxic to animals Selenium Natural sources Toxic at higher levels Zinc Industrial waste metal plating Toxic to plants at higher level *K. Schwartz, Chemical Toxicology of metals (Elsevier, 1977) cited in G.S. Fell, Metals in Environment Chem, Britain, 1980. PESTICIDES IN WATER Drainage of agricultural land does leave a large number of pesticides belonging primarily to two major groups. Chlorinated hydrocarbons and the more biodegradable organic phosphates.
  5. 5. IMPACT OF TOXIC CHEMICALS ON ENZYMES Toxic chemicals attack the active sites of enzymes, and thus inhibit enzymes functioning. Divalent Cd2+ , Pb2+ and Hg2+ are effective enzyme inhibitors, they have affinities for containing liquid SCH3 and SH, which are part of the enzyme structure. These enzymes known as metalloenzymes contains metals in their structures and thus inhibit the functioning of the enzyme. One metal ion is replaced by another metal of similar size. Thus, Zn2+ in some metalloenzymes is replaced by Cd2+ leading to Cd2+ toxicity. The biochemical effects of some typical toxic substances are discussed below. BIOCHEMICAL EFFECTS OF ARSENIC This metal commonly occurs in all herbicides, fungicides and insecticides. Triopositive As3+ is most toxic, and it attacks SH groups of an enzyme thereby inhibiting enzyme action.
  6. 6. This adversely affect the generation of cellular energy in the citric and cycle, which is based on the inactivation of pyruvate dehydrogenase by complexation with As(III) preventing the generation of ATP. P and As have a chemical similarities, therefore, As interferes with some of the biochemical ATP (adenosine triphosphate). An important step in ATP regeneration is the enzymatic synthesis of AQ single compound
  8. 8. High concentration of As (III) compounds coagulates proteins and attaches s bonds maintainingthe secondary and tertiary structures of proteins. The general antidotes for As poisoning are devices having----SH groups are capable of bounding to As (III). Arseno-3 phosphoglecerate In nature Cd occurs in association with Zn minerals. Growing plants require Zn and they up and concentrate Cd. BIOCHEMICAL EFFECTS OF LEAD Lead is relatively abundantin nature and the major source of lead is in the combustion gases of petrol and gasoline. Lead is added primarily as lead tetraethyl and tetramethyl. Pb(C2H5)4, Pb(CH3)4 along with scavengers 1,2 dichloro methane CH2 Pb(CH3)4 and 1,2 dichloro ethane, Pb(C2H5)4. This causes an enrichment in street dust amongst other things. The major biochemical effect of lead is interference with heme synthesis which leads to haematological damage. Pb inhibits several key enzymes. An important phase of heme synthesis is conversion of delta aminolevunic acid to porphobiugen.
  9. 9. The overall effect is the disruption of the synthesis of haemoglobin and allied respiratory pigments like cytochromes, which require heme. Pb also does not permit utilization of O2 and glucose. The Ag interference can be detected at lead levels in the blood of about 0.3 ppm. At higher level of Pb in the blood, symptoms of anemia appear due to haemoglobin deficiency Pb level (0.5-0.8) ppm are dysfunction of kidney and finally, brain damage. Due to chemical analogy of Pb2+ and Ca2+ , bones act as respositories of Pb in the body. Lead poisoning can be cured by treatment with chelating agent which binds Pb2+ . REMEDIAL MEASURES 1. Chlor-alkali plants must stop using Hg electrodes, and switch-over to new technology. 2. All mercurial pesticides banned or restricted to a limited selected areas. BIOCHEMICAL EFFECTS OF CARBON MONOXIDE The global atmosphere contains about 530 million tonnes of CO with an average residence of 36 to 100 days. It attacks haemoglobin and forms carboxy haemoglobin (COHb)
  10. 10. O2Hb + CO  COHb + O2 (Hb = haemoglobin) The initial effect of CO poisoning is loss of awareness and judgement. BIOCHEMICAL EFFECTS OF PESTICIDES The biochemistry of pesticides is of considering significance, and constitue the major mechanism by which pesticides in the environment are degraded and detoxified. Amongst the pesticides, the biological action of DDT on the environment has been most extensively studied. DDT is fairly stable persists in the environment while the organophosphate and carbomates degrade quite rapidly in the environment. The latter reacts with O2 H2O, undergoing decomposition in a few days in the environment producing compounds which are non-toxic. The mechanism of action of these insecticides is that they inhibit the vital enzyme, acetylcholine sterase as per the scheme below.
  11. 11. Acetylcholine neurotransmitter which triggers nerve cells insecticide the nerve cells called synapse contains the enzyme chloniesterarte, which decomposes acetylcholine and prevents the nerve cells from firing in steps (1) and (2). In the first step, the enzyme acts upon acetylcholine preventing it from acetyl enzyme and one of the products, chlorine. In the next, the actual enzyme is decomposed by H2O to form CH3COOH regenerating the enzyme. An organophosphateinsecticidecan mimic acetylcholine and induce the formation of a phosphonyl enzyme, the rate of the reaction is determined by the rate of displacement of X group from P by the enzyme. In step(2), breakdown of this
  12. 12. intermediate is much slower than that of that actual enzyme in A (2). DDT IN FOOD CHAIN As mentioned above, DDT is a persistent chemical. Once introduced into the environment, it keeps circulating for many years. It is interesting to note the manner in which DDT accumulates in the food chains. Plankton in river/sea water contains about 0.04 ppm DDT. The clams that consume planktonconcentrate it ten times, i.e., they contain about 0.4 ppm DDT. From clams, to fish which feed on this clams, to fish eating birds, the DDT level builds up from 0.4 to 2.1 and up to 75.5 ppm.
  13. 13. DDT which was first introducing during World War II, is widely used in agriculture. It was later banned because of its long-term effects on health. DDT does not act on human system in the same way as on insects. The potential long- term effects of DDT being stored in the human body compelled the environmental protection agency to ban DDT particularly in areas where it is still endemic. It is a well-known fact that birds having higher levels of DDT is threatened with extinction, as the eggshells become too thin and fragile due to interferences with hormones which control calcium deposition. METHYL ISOCYNATE (MIC) Methyl isocynate CH3NCO (MIC) is the raw material for the production of carbomate pesticide. MIC is a volatile liquid (bpt 43-45°C), extremely hygroscopic and is, therefore, stored in moisture-free refrigenration tanks. It is synthesized by its reaction of phosgene with primary amine. The intermediate product is decomposed by heating with time. CH3NH3Cl + CoCl2  CH3NHCOCl + 2HCl 2CH3NHCOCl + CaO  CH3NCO + CaCl2 + Ca(OH)2 (MIC) MIC is always associated with unreacted phosgene, CoCl2 to the event of 2%. The threshold limiting value of MIC is 0.02 ppm and for CoCl2 is 0.1 ppm. It can be fatal for most vicims.
  14. 14. REFERENCES A.K. De, Environment Chemistry, Wiley Eastern Limited. B.L. Valle and D.D. Ulmen, Biochemical Effects of Lead, Cadmium and Mercury. R. White Stevens, Pesticides in Environment,Marcel Dekkar Inc. New York (1971). J. Weber, ”The pesticides scoreboard”. Environ. Sc. Tech. 12:520 (1971). C.A. Edwords, Pesticides in Environment, 2nd ed., CRC Press, Cleveland (1973).