1. BIOACCUMULATION

2. The problem begins with us…
Humans have been introducing synthetic (man-made) chemicals into the environment.
PCBs are used widely in products such as paints, plastics. They interfere with the immune function of an organism and make them more susceptible for disease.
Examples:
PCBs (polychlorinated biphenyls) widely used in paints, plastics, lubricants up to 1977
Pesticides
Engine products
Household cleaning agents
DDT (an insecticide for mosquitos) now banned in many countries
Heavy metals such as mercury, cadmium, lead etc.

3. Persistent organic pollutants' (POPs)
Some of these toxins are persistent…
Persistent organic pollutants' (POPs)
Take a long time to break down!
Half-life (PCBs) = years
Half-life (DDT) = 15 years

4. Bioaccumulation = the accumulation of a contaminant or toxin in or on an organism from all sources (e.g., food, water, air).
Why does this happen though?
This occurs if compounds are taken up and stored faster than they are broken down (POPs).
Or if they are non-biodegradable.

5. Biomagnification = the increase in concentration of toxin as it passes through successive levels of the food web

6. DDT DDT was first used in WWII to protect against diseases
such as typhus and malaria.
It is cheap and effective as
an insecticide – so it began to
be manufactured for home
use.
Before it was banned in 1972
by the EPA for use in
agriculture, 1,350,000,000
pounds of DDT had been
made in North America.

11. How does DDT get to organisms?
Is able to get into the waterways by runoff from pesticides, runoff from fertilizers, seepage and dispersal and sedimentation from land clearance and erosion
Effects of DDT:
Causes reproductive disorders
Weakens the shells of eggs (eggs break or do not hatch)
Can also cause nervous system/ immune system disorders in animals
DDT is still used in places such as Zimbabwe and Ethiopia to control mosquities and the tsetse fly. These two insects cause serious diseases such as malaria and sleeping sickness.

13. The effects of Bioaccumulation:
Reproductive failure
Birth defects
Immune system disorders (cancers and weakness to disease)
Behaviour and learning disorders
Death

14. Prac #8: A little goes a long way