Pesticides and Organic Chemicals Related Material

Pesticides and Organic Chemicals Overview

  • Course: PH203
  • Instructor: Professor Richard Peltier
  • This week's focus: Pesticides and Persistent Organic Pollutants (POPs) from the Friis book.
  • Upcoming assessments: Quiz and RAT (Remote Assessment Tool) due Thursday.
  • Gradings: Exams will be scaled by 3.0%. Adjustments may not yet reflect in Canvas.

Introduction to Hazardous Chemicals

  • Hazardous chemicals play a significant role in modern society.
    • Examples include paints, weed killers, and other chemicals important for aesthetic and agricultural purposes.

List of Notable Chemicals

  • Some hazardous substances highlighted for their risks:
    • Arsenic, Lead, Mercury, Vinyl Chloride, DDT
    • Other chemicals include:
    • Benzene
    • Cadmium
    • Chloroform
    • Polychlorinated Biphenyls (PCBs) and their various forms (Aroclors 1242, 1254, 1260)

The Dirty Dozen of POPs

  • Notable persistent organic pollutants (POPs):
    • Aldrin, Chlordane, DDT, Dieldrin
    • Dioxins, Furans, etc.
  • Impact example: Canadian Inuit communities' diet contributes to heavy burdens of POPs found in breastmilk.

Types of Pesticides

  • Insecticide:

    • Specific compounds used to kill or prevent insect growth (e.g., Malathion).
    • Common products: Malathion (55% active ingredient).

  • Herbicide:

    • Chemicals designed to control or destroy unwanted plants, extensively used in agriculture.
    • Can be selective (e.g., Atrazine) or non-selective (e.g., Glyphosate - associated with Monsanto’s Roundup).
    • Roundup Ready® crops are engineered to be immune to glyphosates.

Specific Herbicides

  • The non-selective herbicide, Glyphosate, is a significant player in modern agriculture, manufactured by Bayer.
  • Used extensively, e.g.,
    • 73.5 million pounds of Atrazine applied in 2013; linked to surface and groundwater contamination.

Environmental and Health Impact Studies

  • Atrazine Studies:
    • Research involving Xenopus frogs found hermaphroditism due to low concentrations (0.1 µg/L) of Atrazine, significantly higher than current EPA standards (3 µg/L).
  • Trichloroethylene (TCE):
    • Uppdate from EPA in January 2023 indicated unreasonable risks associated with the use of TCE.

Chemical Groups and Health Effects

  • Chemical groups include:
    • Organophosphate Insecticides (e.g., Diazinon).
    • Carbamate Pesticides (e.g., Sevin, Aldicarb).
  • Negative effects of exposure include:
    • Neurological conditions and endocrine disruption.

DDT and its Controversies

  • DDT was widely used from the 1940s until its prohibition in 1972 in the U.S. due to its ecological and potential human health impacts.
  • Arguments for and against DDT include:
    • Low toxicity in acute human exposure versus reproductive disruption and accumulation in ecosystem.
    • Historical efficacy in controlling malaria risks.
  • Half-life estimated at 10 years; still detected in various organisms.

Dioxins and Their Sources

  • Over 419 dioxin compounds exist, notorious for their environmental stability and toxicity.
  • Sources include:
    • Forest fires, industrial burning, and certain herbicides (e.g., during the Vietnam War).

Persistent Organic Pollutants and Clean-up Efforts

  • Historical pollution characterized by the presence of substances like PCBs in the Hudson River; current cleanup efforts are underway.
  • Example of GE plants discharging significant PCB amounts, leading to bans on fishing.

Economic Impact of Endocrine Disrupting Chemicals

  • Estimated annual cost of health effects due to EDCs: $340 billion, impacting various health conditions (e.g., obesity, male reproductive issues).

Recap and Further Reading

  • Pesticides and POPs remain critical subjects of environmental studies. Understanding their impacts on health and ecosystems is paramount for future policy and practice.
  • Additional study recommended from the New Yorker article "A Valuable Reputation" and ongoing research from the EPA.