19 other industrial chemicals Flashcards
what is dioxin?
-strikes fear into the heart of regulators and the regulated!! not to mention the public
-extremely toxic (dose makes the poison)
-extremely low concentrations (DMTP)
-extremely expensive to clean up
how are we exposed to dioxin?
-humans are primarily exposed to dioxins by eating food contaminated by these chemicals
-dioxin accumulates in the fatty tissues, where they may stay for months or years
-dioxins stay in the environment for a long time because of their chemical stability
-health canada in 2019 ranged from 0.11-0.16 pg TEQ/kg bw per day
what are dioxins and furans?
PCDDs (polychlorinated dibenzo-p-dioxins)
PCDFs (polychlorinated dibenzofurans)
-members of the family of halogenated aromatic compounds
-1-8 chlorines
-75 isomers of PCDD and 135 isomers of PCDF are theoretically possible
what is TCDD?
-most toxic of all the PCDDs and PCDFs
-PCDD/Fs occur as complex mixtures but express their toxicity thru the same mechanism of action so potency of mixtures is additive
-for todays discussion we will just talk about “dioxins” as a summary term for all the chemicals and TCDD to refer to the one specific chemical
what is the LD50 of TCDD?
what is dioxin history?
-did not know that they existed before 1970
-saw effects but didn’t know the cause
-could not even measure until the late 1970s
-accurate techniques for low ppt analysis not available until the late 198s0s
-still a challenging and therefore expensive analysis
what is the approximate ranges of dioxins and furans in environmental compartments?
what happens to trout exposed to 1-10 ppt levels of TCDD during development?
what was happening with the great lakes fish eating birds?
-increased detection of deformities particularly of the beak
-deformity rates pre-hatch much higher (up to 30% of embryos) (some deformities prevent hatch)
-people eat the same fish
what are the sources of PCDDs and PCDFs?
-unwanted by-products of chemical processes (any combustion process with chlorine present)
-industrial sources associated with the production of chlorinated phenols (eg: pentachlorophenol), phenoxy herbicides (eg: 2, 4-D and 245-T)
-pulp and paper industry, metallurgical processes, chlor-alkali process
-municipal, hospital and industrial waste incinerators-fly ash, sewage sludge, automobile exhaust (largest current source?)
was dioxin used as a herbicide?
dioxin was NOT used as a herbicide
-agent orange was a herbicide mix that was contaminated with ‘high’ levels of dioxins
how much was used in vietnam?
what is the suggested half-lives of PCDDs?
how can TCDD be degrated?
-TCDD must reach soil to be ‘safe’ from environmental degradation
-forest has multiple layers of canopy
-spray methods were designed to pray the tree canopy
-in fact <5% of the spray reached the ground
-TCDD in canopy is degraded by light
what is the TCDD half-life on vegetation?
-when agent orange was spread on leaves and exposed to natural sunlight, the half-life of TCDD was less than 6 hours
-when agent orange was applied to loam soil and exposed to sunlight, degradation of TCDD was somewhat slower, presumably due to shading of lower layers by soil particles
-in deep soils, TCDD is persistent
-the requirements for photodegradation of TCDD are dissolution in/on a light-transmitting film or material, the presence of a hydrogen-donor (such as herbicide or the waxy cuticle) and UV light
where does this leave you (TCDD)?
what are the two most common perfluorinated acids?
what are a few uses of the fluorinated surfactants?
what is the properties summary of PFCs?
-PFCs are both hydrophobic and lipophobic (amphiphobic)
-environmental properties not like any other compounds so current thinking and models do not work and should not be used
-do not behave like normal persistent organics but do bioaccumulate
-wide spread dispersive uses leave potential for entry into food chains
what is the frequency of detection of PFOs?
what is the risk assessment of PFOs Mink?
what are PFCs in the north american population?
