lecture 6 (1).pdf

Lecture Outline A. Continued: Major Classes of Pollutants (chemistry, source, effects): 1. Inorganic Lecture #6 2. Organic...

Lecture Outline A. Continued: Major Classes of Pollutants (chemistry, source, effects): 1. Inorganic Lecture #6 2. Organic B. Chemical Management Plan in Canada — Canada’s Domestic Substances List — categorization of chemicals (PBT) C. Introduction to Biotransformation 1 2 Organic Pollutants Contain carbon (C) Organic Pollutants — C atoms form stable bonds with one another -- thus numerous molecules (rings, chains, etc.) very stable — C alone (eg graphite & diamond) or C + H (hydrocarbons) have low polarity — Thus low water solubility (lipophilic/fat soluble) — Lipophilicity associated with hydrocarbon-like properties and by the presence of halogen atoms in the molecule (most often Cl, Br) — C-compounds tend to be more polar and chemically reactive if: — polar functional group ie OH, HCO, NO2 more polar = soluble — Polar molecules have electrical charge — More water soluble (hydrophilic) — Hydrophilicity is promoted when the substance carries a charge (ionic compounds) or when organic compound has a high proportion of polar groups (esp. OH, NH2, NO2) — May be naturally occurring ie hydrocarbons, pyrethroids, nicotine — Plants and animals and their toxins have co-evolved and have some detoxification mechanisms. less chance having some innate detox mechanism — Many non-naturally occurring (anthropogenic) — Detoxification mechanisms Chemical Structure of Pyrethrin: Pyrethrin I R = CH3 3 Pyrethrin II R = CO2CH3 used for insects (insecticide), naturally occuring 4  Pesticide Multiresidues in Waters of the Lower Fraser Valley, Major Organic Pollutants British Columbia, Canada. Part II. Groundwater — Polycyclic aromatic hydrocarbons (PAHs) — Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBDs) — Woudneh et al. — Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans — Journal of Environmental Quality (PCDFs) Volume 38 May–June 2009 — Personal care products — Pharmaceuticals — Plasticizers — Many pesticides: that have organic pollutants in them — Organochlorine insecticides — Organophosphorous and carbamate insecticides — Anticoagulant rodenticides — Pyrethroid insecticides — Neonicitinoid pesticides — and many more… 5 many diff organic pollutants present in our water bodes Why are so many organic Review Polar versus Non-Polar pollutants toxic? — Toxic (including lethal and/or sub-lethal effects) http://socratic.org/questions/why-are- metallic-compounds-insoluble-in-water- dissolve many metals. polar vs nonpolar chemically* has structure of lipid bilayer. many organic compounds hydrophobic, can dissolve into fat cells = bioavailable = act on targets they are lipophilic 7 http://www.sciencebuddies.org/science-fair-projects/project_ideas/BioChem_p045.shtml 8  Polarity: Often Measured by Octanol- Many Organic Pollutants are Water Partition Coefficient (Kow) — Kow = concentration of solute in octanol measuring how much chemical remain in octanol phase and in water phase/ Persistent and Toxic concentration of solute in water increasing of contaminant up the food chain focus one species, how this contaminant accumulating over time very lipophilic, hydrophonic — (Kow ) is the ratio of a chemical's concentration in octanol to its concentration in the aqueous phase of a two-phase system at equilibrium. more dissolved in octanol = higher Kow = more lipophilic — Partitioning between octanol and water in the lab is a model for the partitioning of a xenobiotic between the aqueous and lipid phase in vivo (in animal = in vivo) — higher Kow = more lipophilic — very useful parameter in predicting the fate of a chemical in a biological system. 9 10 http://sustainable-nano.com/2013/12/17/the-cautionary-tale-of-ddt-biomagnification- high Kow = in protection act, anything value >5 is considered lipophilic. bioaccumulation-and-research-motivation/ if get exposure scenario, measure concentration, its in water, what kind of factor calculate using this info? can u calculate bioaccumulation factor or only bioconcentration factor? Bioaccumulation Processes in which a chemical substance is absorbed in an organism by all routes of exposure as occurs in the natural environment (ie dietary, and ambient environmental sources such as air, water, soil) to understand this ratio: BAF = concentration in organism concentration in water (or environment organism resides in) F = factor Net uptake and loss processes: — respiratory, dietary uptake, dermal and loss by egestion, passive diffusion, metabolism, transfer to offspring, growth — Measured in field scenario measure in field, not lab cuz its hard! incorporating food chain all routes of exposure! Bioaccumulation = net uptake (diet, respiratory, dermal Bioconcentration: the process by which a chemical substance is absorbed by an absorption) – (elimination + growth dilution) organism from the ambient environment only through its respiratory and dermal specific uptake of chemical from ambient enviro only!! imagine chemical in water, uptake be oral through gills, surfaces, i.e. chemical exposure in the diet is not included. but chemical also in water, so dermal exposure, but excluding diet. BCF = concentration in organism Bioconcentration = uptake from ambient environment only concentration in water(or ambient env) cant do in field, cuz they eat (no diet) - (elimination + growth) 11 Measured in lab tests just look at that one exposure scnario 12  CEPA Criteria for CEPA Criteria for Bioaccumulation/Bioconcentration Environmental Persistence how to determine persistence Parameter Value we consider that chemical Medium Half-Life Bioaccumulation Factor BAF ≥ 5000 bioacumulative Air ≥ 2 days if 50% not degrade in 2 days = persistent Bioconcentration Factor BCF ≥ 5000 Octanol-Water Partition log Kow ≥ 5 consider it bioaccumulate Water ≥ 6 months Sediment ≥ 1 year can just be octanol-water partition. A substance is considered bioaccumulative when the Soil ≥ 6 months criterion is met for any one parameter A substance is considered persistent when the criterion is BAF is better than BCF is better than Kow. met for any one medium even if its just soil, then its persistent and of concern! http://laws-lois.justice.gc.ca/eng/regulations/SOR-2000-107/page-1.html#h-3 13 ex. ddt is persistent and bioaccumulative and is toxic 14 CEPA criteria for inherently Canada’s Chemical toxic -> main act that deals with chemicals, and how we manage them properly old list Management Plan — Proposed criteria for non-human organisms: — CEPA 1999 required Ministers of the Environment and — Aquatic acute effects of < 1 mg/L substance considered toxic Health to categorize the DSL to identify substances that may: — Above 1 mg/L professional judgment considering — Present to individuals in Canada, the greatest potential for other factors (eg molecular weight, metabolism…) exposure; or — Log Kow>5 (often considered) — Are persistent (P) or bioaccumulative and inherently toxic to humans or non-human organisms as determined by laboratory or other studies priotize which chemicals require depth screening assessment Categorization was a prioritization process that involved the systematic identification of substances that should be subject to a screening assessment (completed in 2006) — There are new substances added to the DSL but these have already undergone assessment, and therefore not 15 subject to the categorization process 16  Introduction to 2 Phases of Xenobiotic DSL: 23K existing substances used, imported or manufactured in CA for commercial purposes (1984-1986) List Biotransformation Reactions -> assessing the risks xenobiotic does detoxifies All xenobiotics may be metabolized -> can be metabolized Phase I by phase I and/or phase II metabolism Oxidation chp 12 - p. 285 - 290 Reduction ex. ddt once taken up, can be converted to DDE Hydrolysis must understand which metabolites are produced. Phase II metabolism (SLRA) Conjugation 4300 chemicals identified and needing SLRA / 19000 no SLRA (didnt required) -SLRA done for 3621/4300 chemicals Synthesis something is added to it, --456 found to be harmful to envt and/or human health New substances all like enzymes ass gluthonine to a chemical -implemented 90 risk management actions undergo SLRA; ~400 to 500 / year -> makes xenobiotic more water soluble!! excreted through urine new substances that come in from companies, now must all go through SLRA!! ~350 no further action implemented Elimination so we identified a number of chemicals that were concerning after chemical assess, added to priority substance list. Or regulatory control 17 18 similar think of liver, as major detox organ. figure in chapter 6, figure 6.2 Determining individual organism effects of xenobiotics requires info on: What Is Biotransformation? 1. fate and transformation provide defintions on exam in organism 2. interaction of xenobiotic with site of action — Biotransformation: 3. impact on whole organism’s health — the sum of the chemical reactions that occur within the body to alter the structure of a xenobiotic/endogenous compound — Occurs in many tissues and organs — intestine, lung, kidneys, skin, "liver" — Carried out by various enzyme systems — same enzymes are used to metabolize endogenous substances and xenobiotics think about parent xenobiotic, understand which metabolites are produced 19 20  What Is the Function of Integration of 2 Phases of Xenobiotic Biotransformation? Biotransformation Reactions and be eliminated Xenobiotic -------> Phase I —Conversion of xenobiotics into more hydrophilic less toxic enter, and be eliminated forms: with xenobiotics, trying to decreaee Xenobiotic — decrease intracellular concentration via excretion polar l l —However, toxicity can be affected in two possible ways: Product A l l Phase II < — Conversion into a less toxic form - detoxification s — Conversion into a more toxic form - bioactivation Product A Product B very polar Product C Elimination 21 22