Question 37 If the K_ow for the compound was 10^6, how many mg would have been f

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Question 37

If the K_ow for the compound was 10^6, how many mg would have been found in the water? Why are so there incredibly many different pesticides that have been tried and placed on the market? Into what type of tissue material do biaccumulating compounds partition (mostly)? Proteinaceous or lipid, and WHY? Not counting the common presence of chlorine, two chemical characteristics are typical of so-called "legacy" (aka old school) pesticides like DDE, dieldrin, etc. have led to a lot of problems. What are these two? What two molecular characteristics of octanol make it a useful surrogate for lipid material into which bioconcentration can occur? Draw the bad guy dioxin, namely 2, 3, 7, 8-tetrachlorodibenzodioxin. Include any hydrogens. Organohalogen compounds like the freons are rather stable in the environment, i e., they are persistent. However, they do not accumulate in biological tissue or soils or sediments Why not? (An example of a Freon is CCl_2F_2 which is Freon 12.) In a given environmental setting (e.g., Portland), compounds like PCBs and the flame retardant PBDEs are mostly found in the soil and sediments and in the lipid tissues of local organisms. How is it possible then that these compounds can reach places where they were never used? Like within the Arctic Circle ... in other words, what are the mechanisms involved in the movement?

Explanation / Answer

Question 37

Answer -

The main pathway for pollutants to get into the environment is through emission to the atmosphere. As the pollutants disperse into the air, facility workers and people close to the source might be exposed directly through inhalation or indirectly through consumption of food or water contaminated by deposition of the pollutants to soil and vegetation. Other people can be exposed through a different mix of environmental pathways after the pollutants travel some distance in the atmosphere; go through various chemical and physical transformations; or pass through soil, water, or food.

Polybrominated diphenyl ethers (PBDEs) are a class of recalcitrant and bioaccumulative halogenated compounds that have emerged as a major environmental pollutant. PBDEs are used as a flame-retardant and are found in consumer goods such as electrical equipment, construction materials, coatings, textiles and polyurethane foam (furniture padding). Similar in structure to polychlorinated biphenyls (PCBs), PBDEs resist degradation in the environment.

Polybrominated diphenyl ethers (PBDEs) are used in paints, plastics, foam furniture padding, textiles, rugs, curtains, televisions, building materials, airplanes and automobiles. PBDEs constitute 5% to 30% of some of these products by weight.

PBDEs are seeded into, but are not covalently bound into polymer matrices. Over time, they diffuse out of the polymer matrix and become airborne and widely dispersed. Polyurethane foam exposed to ambient outdoor conditions for 4 weeks becomes brittle, disintegrates and disperses penta-PBDE containing fragments.

They are released into the environment at industrial manufacturing sites as well as leached from common household products. The main non-point source of PBDEs is household trash (e.g., furniture, bedding, foam cushions, and electronics).

Once airborne, PBDEs are dispersed varying distances depending upon meteorological conditions, airborne particle size and extent of bromination.

The primary source of exposure to humans is believed to be consumption of contaminated fish, poultry, meat and dairy products. Occupational exposures may occur in computer and electronic warehouses, and formulation facilities. Dismantling and grinding polymer parts may increase the PBDE concentration in the air.

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