lecture 7 Persistent Organic Pollutants

Plastic & chemical pollution

Properties

Usually hydrophobic and lipophilic, bioaccumulate in fatty tissues of living organisms, toxic to both humans and wildlife, typically halogenated which are less reactive

Grasshopping

Repeated process of volatilization and deposition, pollutants evaporate with warm air and return to earth with rain and snow in the colder areas of the globe

Stockholm conventions

Decision criteria for POPs, environmental half-life greater than 2 months, bio-accumulation factor(BCF) greater than 5,000, an atmospheric half-life exceeding 2 days, proven toxicity

PCDDs/dioxins

dibenzo-p-dioxin, two benzene rings and one ring connecting them with two oxygens and some oxygen groups

PCDFs/furans

Similar to dioxins but less toxic and have a oxygen less in the middle ring

Sources dioxins and furans

Combustiaon, pesticide production, chlorine bleching paper pulp, leaded fuel, smelting, volcanic eruptions and forest fires

TCDD

agent orange herbicide, most toxic dioxin, leads to birth defects

Toxicity PCDDs and PCDFs

Bind with AhR receptor in cell→forms complexs with other proteins and enters the cell→messes with genes

PCB’s

Are dioxin-like, no middle ring and thus no oxygen group there, manufatured between 1930 and 1980, great insolator, often contain actual dioxins as impurities

DL vs. non-DL PCBs

If the Cl group is on the inner parts of the ring they are less dioxin like because the Cl group in the middle cause the molecule to twist→less toxic

Exposure to dioxin-like compounds

fire and volcanic activity, marl clay in potato selection, poisoning, disasters, illegal activities

Functional substitution approach

1. evaluate if the compound is necessary

2. if yes, search for a safer chemical or alter product/production

   Substitution: chemical function (replace with other chemical with same function), end-use function (use of chemical in product), function as service (is the service provided really necessary)