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contaminant/pollutant

chemicals occur where they wouldn’t naturally, or at higher concentrations than they would naturally

three categories

• toxins

• toxicants

• naturally occurring chemicals

toxin

naturally produced harmful chemicals, usually made by plants or animals (poison, venom)

toxicant

synthetic or manmade chemicals

aka xenobiotic chemicals

naturally occurring abiotic chemicals

mercury, selenium, polycyclic aromatic hydrocarbons

toxic

chemicals that cause an adverse effect in biota depending on exposure

toxicity

the adverse effects of chemical exposure

toxicology

• the study of adverse effects of chemicals for biota

• began w early humans

• biomedical, pharmacology, pesticide emphasis

• setting standards and regulations

• focused on human health and physiology

ecotoxicology

• formalized in the 1970s

• focus on NONhumans

• many scales, molecular → whole biosphere

• accounts for more complex exposure pathways

environmental toxicology

• began w rachel carson’s silent spring

• focusing on the effects of xenobiotics on flora and fauna

• focused on huma health effects associuated w chemicals

  • pesticide exposure

  • air, water quality

  • air pollution, smoking

  • cancers

• researchers often in public health and medical programs

industrial revolution

• began large scale use of coal, petroleum, synthetic chemicals

• large scale pesticide apps to agricultural fields

• industrial waste disposal

• byproducts had negative impacts on water, soil

early research on environmental contaminants

• attention to the formal effects of radiation

• introduction of food chain concentration and biomagnification

• development of the ecosystem concept, flow of energy and materials through organisms in their environment

when and why was the EPA founded?

• 1970

• in response to silent spring

• broad focus on regulating pollution

• many acts around this time

  • clean eair act

  • clean water act

  • resource conservation and recovery act

  • toxic substances control act

main issue with many regulations

they don’t consider the effects on ecosystem processes or context-dependence

early ecotoxicology experiments

lab based using model species of fish and amphibians

types of ecotoxicology research

• monitoring

• experimental

• foresic

• exposure-effects assessments

• risk asssessments

in labs, vivaria, mesocosms, field sites

pesticide

any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating pests

insectivides, fungicides, herbcides, rodenticides

large scale develpment began in 1930s

Otmar Zeidler

first synthesized DDT

Paul Hermal Muller

discovered insecticidal properties of DDT

DDT

• dichloro-diphenyl-trichloroethane

• organochlorine

• colorless, crystalline solid

• virtually insoluble in water but highly soluble in fats and organic solvents

• eliminated via breastmilk

isomer

compounds w the same chemical formula but different molecular arrangement of atoms, resulting in distinct chemical properties

inital DDT uses

• malaria

• typhus

• body lice

• bubonic plague

mechanism

the underlying moleculat events that lead from initial exposure to a chemical to the ultimate manifestation of toxic injury

more detailed and complicated

mode of action

the key events and basic processes that lead to functional or structural toxic effects

less detailed, more general

LogKow

predicts contaminant behavior of food webs

< 3 = relatively non bioaccumulative

> 3 = likely to bioaccumulate

> 5 = likely to bioaccumulate and biomagnify

stockholm convention

chemical cannot be used if the half life of the chemical in water is more than 2 months, or more than 6 months in sediment or soil

acute toxicity

adverse effects of a chemical that occur a short period of time after exposure

chronic toxicity

adverse effects of exposure to a chemical that manifest over a long period of time following exposure

neonicotinoids

• systemic insecticides that are synthetic modifications of nicotine; target the nicotinic receptor

• the most widely used class of agricultural insecticides in the world

systemic insecticide

absirbed by plant and designed to distribute throughout the plant; toxic when insect eats plant

msot effective on piercing sucking insects like aphids, leafhoppers, whiteflies

non systemic insecticides

toxic w direct contact, not taken up by plant

issues w neonics

• global pollinator decline

• causes reduction in food consumption, mass, fat, and probabiloty od departure in migratory songbirds (WCSP)

toxicokinetics

describes the changes of the concentrations of contaminant in the organism over time

• uptake into tissue

• distribution among tissues

• metabolic conversions into metabolites

• excretion