Slide Types of toxicants

Lecture TYPES OF TOXICANTS INORGANIC • METALS • METALLOIDS • NON-METALS • RADIOACTIVE ISOTOPES ORGANIC • ALIPHATIC COMPOUNDS • AROMATIC COMPOUNDS • COMPLEX PESTICIDES • ORGANOMETALLIC COMPOUNDS Lecture TOXIC NON-METALS & METALLOIDS Halogens (F2, Cl2, Br2, I2) - very reactive and therefore highly toxic - reaction products usually toxic - when covalently bond, typically increases toxicity and persistence of organic compounds - in ionic form, Cl, I (and F) are essential nutrients; Br-, I- and F- are toxic at relatively low levels - Common uses: disinfectant (in water Cl2 forms hypochlorous acid, a.k.a bleach; betadine = I- plus I2 in water); in cleaner (HCl); chemical synthesis (everything organic with halogen bound to it: pesticides, PVC) - inorganic Cl and Br compounds are made by some sea weeds for disinfection purposes Lecture 3 Phosphorus (P4) - yellow form very reactive and therefore highly toxic - red form found in matches - essential nutrient (mostly in the form of phosphate: PO43-); key element in DNA, RNA, ATP - Phosphine (PH3) is common insecticide and rodenticide - covalently bond to organic compounds: pesticides, fire retardants Sulfur (Sx) - in various forms used as fungicide, since antiquity - S containing compounds have typical smell - essential nutrient (S containing amino acids) - common uses: gun powder, sulphuric acid, preservative (sulfite in wine suppresses yeasts) Lecture Arsenic (As) - in various forms used as pesticide, since antiquity - famous poison: killed Napoleon - used as wood preservative, pesticide and in metal alloys - sometimes present in natural environments at relatively high levels - some ores have high As content; smelting releases this As Selenium (Se) - essential micronutrient but toxic at low levels (mind your supplements!) - mimics S in biochemical reactions, hence its toxicity - used in semi-conductors, pigments Fertilizers (PO43-, NO3-, NH4+, urea) - At low levels, not directly toxic (except ammonia to some extent) - alter species composition, especially in sensitive habitats - may cause algal bloom and deprive environment of oxygen - may cause toxic organism to grow explosively (red tide, cyanobacteria) Lecture TOXIC METALS Tin (Sn) - in inorganic form relatively little toxic - in organic form used as fungicide (cyhexatin) and antifouling agent TBT (tributyltin) TBT is extremely toxic, especially for molluscs - common uses: coating of iron to prevent oxidation, pots and flatware (all these uses mostly obsolete) Mercury (Hg) - fluid at room temperature (quick silver) - easily forms covalent bonds with organic compounds, which are extremely toxic (cf Minamata disease) - complex behavior in environment (speciation, cycling) - common uses: thermometers; amalgams (dentistry, gold mining), batteries, paints, fungicides Lecture Lecture Lecture Lead (Pb) - most widely distributed toxic element, mostly because of its use in the past (lead based paint, tetraethyl lead in gasoline, lead arsenate as insecticide, solder, piping – now all obsolete in the West) - still used in batteries, lead crystal, ceramics, ammunition and as weights (fisheries, wheel balancing) and released during smelting of ores - Pb2+ causes anemia and neurological dysfunction Copper (Cu) - in ionic form (Cu+, Cu2+), used as pesticide, since antiquity - essential micronutrient - complex speciation, bioavailability depends on pH, salinity and humic acid concentration - common uses: electronics, plumbing, antifouling, wood preservative Lecture Cadmium (Cd) - closely associated with zinc (a micronutrient), which it (as Cd2+) mimics biochemically, hence its toxicity (also a carcinogenic) - forms complexes with ligands, especially S containing - common uses and sources: by product of zinc mining, nickel-cadmium batteries, plastic stabilizers, pigment, vulcanized rubber Chromium (Cr) - essential micronutrient, occuring predominantly as Cr(III) and Cr(VI) - hexavalent form is especially toxic (carcinogenic, kidney necrosis) - toxicant in ‘Erin Brokovitz’ movie - used in chrome plating, tanning, pigments, wood preservation Nickel (Ni) - common element in earth crust - Nickel compounds (Ni2+) are very toxic and carcinogenic; in elemental form, it causes contact dermatitis in sensitized individuals - used in alloys to prevent corrosion (stainless steel, coins), ni-cd batteries Lecture 10 Aluminum (Al) - after iron, most common metal in earth crust - free Al3+ is toxic, but sufficiently high concentrations only occur at low pH (acid main drainage, acid rain mobilizing free Al3+ in soils) - widely used in elemental form in construction, sheet metal Lecture 15 SIMPLE HALOGINATED ALIPHATIC HYDROCARBONS - some have extensive industrial application - in the past, uncontrolled dumping of those has led to wide spread contamination Cl Cl C Cl HC Cl Cl Chloroform obsolete anesthetic carcinogenic Major source: chlorination of drinking water Cl Cl trichloroethylene (and tetrachloroethylene) industrial cleaning solvent persistent in soils wide spread contamination liver and kidney damage H C Cl CH CH C H Cl Monomers of PVC CH H Lecture 16 ALIPHATIC ORGANOCHLORINE INSECTICIDES - low water solubility - highly lipophilic (high bioaccumulation potential) - very persistent (once seen as an advantage) - highly toxic for mammals - old fashioned insecticides still found in the environment Cl Cl Cl Cl Cl 1,2,3,4,5,6-hexachloro-cyclohexane Lindane Cl Cl Cl Cl Cl Cl Cl Cl Chlordane (Aldrin, Dieldrin and Endrin are somewhat similar) Cl - other common examples: toxaphene and kepone Lecture 17 AROMATIC HYDROCARBONS Naphtalene Benzene Fluorene Pyrene Anthracene - low polarity, lipophilic, accumulate in sediments - polycyclic aromatic hydrocarbons (PAH) have or more fused rings - acute toxicity, carcinogenic - major source: petroleum, incomplete combustion of organic material Lecture 18 AROMATIC INDUSTRIAL BASE CHEMICALS - production of plastics and other polymers - formed during burning of biomass - volatile OH Phenol CH3 Toluene CH3 CH3 m-xylene disinfectant industrial solvents weak acid (glue, paint thinner) HC CH2 Styrene Lecture 19 NOT ALL AROMATICS ARE (VERY) BAD - aromatics are aromatic - many natural tastes and scents are simple aromatics derived from phenol, i.e., rosemary, geranium, lavender and O CH3 O CH3 HO CH Anisol Vanillin O - many have antiseptic (i.e., toxic) qualities - key aromatic in biodegradation OH O C CH2 Benzoic acid Lecture 20 HALOGINATED AROMATICS - mostly low water solubility - highly lipophilic (high bioaccumulation potential) - very persistent (used to be a big plus) - many are very toxic - many are banned (in US) or use is severely restricted but are still major environmental contaminants Cl Cl Cl Cl Hexachlorobenzene, unwanted by-product of Cl chlorinated solvent and pesticide manufacture, is persistent, lipophilic, has high soil adsorption coefficient and high dispersion potential Cl Detectable in most body fat samples Causes damage to skin, liver and immune system Lecture 21 BIPHENYLS Biphenyl Cl Cl Cl Cl Cl 2,3,3',5,5'-pentachloro-biphenyl, a polychlorinated biphenyl (PCB) There are 209 different PCBs (congeners) Once used as dielectic fluids, lubricants, plasticizers, heat transformation fluids PBBs have bromine; once used as fire retardants Lecture 22 DDT - insecticide with ‘low’ toxicity for mammals - once the magic bullet against malaria, now infamous - banned in US since 1972 - insect develop resistance, hence higher application loads - DDD and DDE major degradation products found in environment p,p' DDT (dichloro-diphenyl-trichloroethane) Cl Cl CH Cl C Cl Cl p,p' DDD p,p' DDE Cl Cl Cl Cl Cl C CH C Cl C Cl H H Lecture 23 POLYCHLORINATED PHENOLS - major sources: bleaching of wood pulp, wood preservatives - water soluble acids, reactive, form dioxins OH OH Cl Cl Cl OH Cl Cl Cl Cl Cl Cl Cl Lecture 24 10 DIOXINS (PCDD) AND DIBENZOFURANS (PCDF) - formed as unwanted by-product of chemical synthesis, notably during the synthesis of the herbicides 2,4,5-T and 2,4-D, and in solutions containing polychlorinated phenols - produced during combustion of organochlorine compounds, especially PCBs - highly persistent in the environment, accumulate in sediments and body fat Cl Cl HO Cl Cl O Cl Cl Cl Cl O Cl + Cl OH 2,4,5-trichlorophenol (TCP) Cl Cl 2,3,7,8-tetrachlorodibenzo-p-dioxin Cl Cl O 2,3,7,8-tetrachloro-dibenzofuran Lecture 25 11 ORGANOPHOSPHORUS AND CARBAMATE INSECTICIDES - neurotoxins (inhibitors of acetylcholinesterase) - most toxic for invertebrates - low environmental persistence; acute toxicity is main concern H3C Alkyl-O O or S CH2 O P Alkyl-O O-R CH3 H3C Organophosphorus insecticides Parathion, Chlorpyrifos CH2 O CH N P O CH3 S N Diazinon CH3 O O Carbamate insecticides Primicarb, Carbofuran C O CH3 O N R CH3 or H Carbaryl C NH CH3 Lecture 26 12 PYRETHROID INSECTICIDES - synthetic analogs of natural pyrethrins (Chrysanthemum) - esters of chrysantemic acid and an organic base - rapid biodegradation (short term toxicity) - low water solubility, adsorption to particulate matter - low mammalian toxicity but toxic for fish, invertebrates OH H3C HC C O CH3 C CH CH C H3C CH3 Chrysanthemic acid Lecture 27 13 AROMATIC HERBICIDES a SYNTHETIC ANALOGS OF INDOLE ACETIC ACID - plant hormones stimulating growth: 2,4-D; 2,4,5-T, MCPA, CMPP - uncontrolled growth leads to death of plants - more toxic to dicotyl than monocotyl plants; hence used in cereal crops and grass - mostly readily biodegradable - as defoliant used in Vietnam (Agent Orange) - can be contaminated with dioxins (ring is chlorophenol) CH3 or Cl Cl Synthetic analogs of indole acetic acid O OH CH H3C C O Lecture 28 B PIRIDINE HERBICIDES - contain piridine ring (also in DNA, RNA) - water soluble (contamination of aquifiers) - charged, readily bind to negative soil particles - uncontrolled growth leads to death of plants CH2 CH2 + + N N + + H3C N N CH3 Paraquat Diquat c TRIAZINES - heterocyclic compounds with N’s in ring - high water solubility, biodegradable - higher toxicity for dicotyls Cl N CH2 H3C NH N N Atrazine NH CH H3C CH3 Lecture 29 14 ORGANOMETALLIC TOXICANTS - organic component gives these toxicants high bioaccumulation potential CH3 H2C H3C Pb CH2 CH3 CH3 H2C CH2 CH2 H3C CH2 H2C H3C Tetraethyllead anti-knock additive H3C Hg Methylmercury bacteria methylate Hg in sediments CH2 CH2 Sn CH2 CH2 CH2 CH2 CH3 Cl Tributyltin extremely toxic for invertebrates H3C AsH2 Methylarsine made by fungi from arsenic compounds garlic odor in old hotel rooms [...]... due to radioactivity depends on - type of emission, - energy content of emitted particle - rate of disintegration Please note: - radiation does not lead to contamination - a short half life implies a lot of radiation (and potential damage) in a short time; waste management is easy - a long half life implies relatively little radiation over an extended period of time; waste management is problematic... thyroid gland, medical uses - Radioactive isotopes of essential elements, mostly short half life, used in biochemical studies - 60 Co, medium half life, radiotherapy of cancer - Cs, Sr, I isotopes of major concern produced during nuclear explosion - U and Pu isotopes, fuel of nuclear reactors and bombs U extremely toxic in its own right Lecture 3 13 ORGANIC TOXICANTS 1 ALIPHATIC HYDROCARBONS CH3 CH3 H3C... sources: bleaching of wood pulp, wood preservatives - water soluble acids, reactive, form dioxins OH OH Cl Cl Cl OH Cl Cl Cl Cl Cl Cl Cl Lecture 3 24 10 DIOXINS (PCDD) AND DIBENZOFURANS (PCDF) - formed as unwanted by-product of chemical synthesis, notably during the synthesis of the herbicides 2,4,5-T and 2,4-D, and in solutions containing polychlorinated phenols - produced during combustion of organochlorine... in the past, uncontrolled dumping of those has led to wide spread contamination Cl Cl C Cl HC Cl Cl Chloroform obsolete anesthetic carcinogenic Major source: chlorination of drinking water Cl Cl trichloroethylene (and tetrachloroethylene) industrial cleaning solvent persistent in soils wide spread contamination liver and kidney damage H C Cl CH CH C H Cl Monomers of PVC CH H Lecture 3 16 3 ALIPHATIC... aromatic hydrocarbons (PAH) have 2 or more fused rings - acute toxicity, carcinogenic - major source: petroleum, incomplete combustion of organic material Lecture 3 18 5 AROMATIC INDUSTRIAL BASE CHEMICALS - production of plastics and other polymers - formed during burning of biomass - volatile OH Phenol CH3 Toluene CH3 CH3 m-xylene disinfectant industrial solvents weak acid (glue, paint thinner) HC CH2... 2,3,7,8-tetrachloro-dibenzofuran Lecture 3 25 11 ORGANOPHOSPHORUS AND CARBAMATE INSECTICIDES - neurotoxins (inhibitors of acetylcholinesterase) - most toxic for invertebrates - low environmental persistence; acute toxicity is main concern H3C Alkyl-O O or S CH2 O P Alkyl-O O-R CH3 H3C Organophosphorus insecticides Parathion, Chlorpyrifos CH2 O CH N P O CH3 S N Diazinon CH3 O O Carbamate insecticides Primicarb, Carbofuran... - synthetic analogs of natural pyrethrins (Chrysanthemum) - esters of chrysantemic acid and an organic base - rapid biodegradation (short term toxicity) - low water solubility, adsorption to particulate matter - low mammalian toxicity but toxic for fish, invertebrates OH H3C HC C O CH3 C CH CH C H3C CH3 Chrysanthemic acid Lecture 3 27 13 AROMATIC HERBICIDES a SYNTHETIC ANALOGS OF INDOLE ACETIC ACID... soluble (contamination of aquifiers) - charged, readily bind to negative soil particles - uncontrolled growth leads to death of plants CH2 CH2 + + N N + + H3C N N CH3 Paraquat Diquat c TRIAZINES - heterocyclic compounds with 3 N’s in ring - high water solubility, biodegradable - higher toxicity for dicotyls Cl N CH2 H3C NH N N Atrazine NH CH H3C CH3 Lecture 3 29 14 ORGANOMETALLIC TOXICANTS - organic component... growth: 2,4-D; 2,4,5-T, MCPA, CMPP - uncontrolled growth leads to death of plants - more toxic to dicotyl than monocotyl plants; hence used in cereal crops and grass - mostly readily biodegradable - as defoliant used in Vietnam (Agent Orange) - can be contaminated with dioxins (ring is chlorophenol) CH3 or Cl Cl Synthetic analogs of indole acetic acid O OH CH H3C C O Lecture 3 28 B PIRIDINE HERBICIDES... (used to be a big plus) - many are very toxic - many are banned (in US) or use is severely restricted but are still major environmental contaminants Cl Cl Cl Cl Hexachlorobenzene, unwanted by-product of Cl chlorinated solvent and pesticide manufacture, is persistent, lipophilic, has high soil adsorption coefficient and high dispersion potential Cl Detectable in most body fat samples Causes damage to