DDT - a quick finishing comment

As you would now be aware, DDT appears to have many long term environmental effects particularly the problems of biomagnification and bioaccumulation.  When levels get to a certain point, it then begins to have noticeable effects on animals, such as eggshell thickness in birds etc.  I should also point out that if enough DDT or other toxic substance accumulates in your body, it will eventually kill you.  Combined effects of biomagnification and bioaccumulation meant that the effects of DDT were first noticeable in fish eating birds.  The reason for this because the food chain can have 4-5 links which enhances the biomagnification effect for the top predator.

In addition, the effects of DDT and similar pesticides may affect nervous system development in young children. Evidence for this was shown comparing 2 groups of children with varying degrees of exposure.  The high exposure kids had reduced coordination, memory and fine motor skills.

Potentially more alarming is the estrogenic (feminising) effect that DDT and its breakdown products have.  It could well be affecting fertility of many male animals, including humans and, may be linked to other defects involved in the formation of male reproductive systems.

DDT is also non specific, that is it will kill target species, but also species that just have the misfortune to be around.  This includes potential pollinators.  As a result farmers have looked beyond pesticides when they can, and are trying differing strategies.  This is the basis of our next module.