DDT and its impact on environment

Q. Why is it in News?

A. India has recently supplied 20.60 MT of DDT to South Africa for its Malaria control program.

Q. What is DDT and what are its usage? 

 A.  Dichloro-diphenyl-trichloroethane commonly known as DDT is a colorless, tasteless, and almost odorless crystalline chemical compound. It was developed in 1940s as first modern synthetic insecticide. It was initially used with great effect to combat malaria, typhus, and other insect-borne human diseases among both military and civilian populations.

Q. Why is it controversial?

• DDT is a persistent organic pollutant that is readily adsorbed to soils and sediments, which can act both as sinks and as long-term sources of exposure affecting organisms.
• Routes of loss and degradation include runoff, volatilization, photolysis and aerobic and anaerobic biodegradation.
• Due to hydrophobic properties, in aquatic ecosystems DDT is absorbed by aquatic organisms and thus bio-accumulates in the food web.

Q. What is Bio-accumulation and Bio -magnification and how do they both differ? 

A. Bioaccumulation and biomagnification are two different processes that often occur in tandem with one another. Bioaccumulation is the process by which toxins enter the food web by building up in individual organisms. Biomagnification is the process by which toxins are passed from one trophic level to the next (and thereby increase in concentration) within a food web

Q. What are various Threats of DDT? 

• The bioaccumulation of DDT has caused eggshell thinning and population declines in multiple North American and European bird of prey species.
• DDT is an endocrine disruptor. It is considered likely to be a human carcinogen.

Q. Why is it in use despite ban?

A worldwide ban on agricultural use of DDT was formalized under the Stockholm Convention on Persistent Organic Pollutants.

But its limited and still-controversial use in disease vector control continues, because of its effectiveness in reducing malarial infections, balanced by environmental and other health concerns.

Q. What is Stockholm Convention on POPs?

Stockholm Convention is an international environmental treaty, signed in 2001 and effective from May 2004 that aims to eliminate or restrict the production and use of persistent organic pollutants (POPs).

In 1995, the United Nations Environment Programme (UNEP) called for global action to be taken on POPs. POPs are defined by the UNEP as chemical substances that persist in the environment, bio-accumulate through the food web, and pose a risk of causing adverse effects to human health and the environment.