Toxicology One Major Technique That

Toxicology One major technique that is used for malaria control is that of Indoor residual spraying (IRS). Currently there are twelve insecticides that are recommended for IRS use. One of these recommended insecticides is DDT. The production and use of DDT is strictly prohibited by an international agreement known as the Stockholm Convention on Persistent Organic Pollut-ants. This prohibition by the Convention is to protect both human health and the environment from persistent organic pollutants.

DDT has been identified as one of twelve chemicals that as a persistent organic pollutant, the Convention restricts. "DDT has a spatial repellency and an irritant effect on malaria vectors that strongly limit human-vector contact. Vector mosquitoes that are not directly killed by DDT are repelled and obliged to feed and rest outdoors, which con-tributes to effective disease-transmission control" (The Use of DDT in Malaria Vector Control, 2007).

The Convention has provided an exemption for the production and public health use of DDT for indoor application to vector-borne diseases, such as malaria. The reasoning is because there is an absence of an equally effective and efficient alternative. WHO has in the past actively sup-ported the promotion of chemical safety and along with the United Na-tions Environment Program has committed to idea of reducing and eventually eliminating the use of DDT (The Use of DDT in Malaria Vector Control, 2007).

The risks that use of DDT poses upon the health and well being of humans are re-evaluated by WHO on a regular basis. In order to re-evaluate the position that WHO has in regards to the use of DDT for malaria control, information regarding exposure rates and the effects that these exposures have on humans would need to be looked at. It would also be necessary to look at what is being done to limit the exposure rates during and after the application process.

Another factor to look at would be that of any alternatives that may be available for use and their effectiveness. All of this data would be looked at in relation to how toxic DDT really is. There are four phases of the disposition that can be looked at in order to asses the toxicity of DDT.

These phases are: Absorption of chemicals into the body- this looks at what rate chemicals are absorbed into the body Distribution of chemicals within the body- this looks at how chemicals are distributed within the body Metabolism of chemicals within the body- this looks at the rate at which chemicals are metabolized by the body Excretion of chemicals from the body- this looks at the rate at which the body gets rid of any chemicals that are present (Disposition of Chemical Compounds, n.d.).

When looking at DDT in association with these four phases it appears to have a low acute toxicity. However, because it is a very stable chemical, it tends to ac-cumulate in the environment through food chains and in tissues of exposed organisms, including people living in houses that have been treated with it. This has raised concerns about their being possible long-term toxicity issues surrounding DDT (The Use of DDT in Malaria Vector Control, 2007).

Discussions and studies on the health consequences of DDT use have focused around reducing infant illness and death from vector control. "In laboratory experiments, effects of DDT include hepatic and central nervous system toxicity, estrogenic and antiandrogenic effects, and possible carcinogenicity" (Chen and Rogan, 2003). Some evidence has suggested that DDT exposure increases the risk of preterm delivery and shortens the length of lactation.

If this evidence holds true then these conditions could increase the rate of infant deaths and thus void any benefits on mortality rates from a reduction in malaria. In a study conducted by the National Institute of Environmental Health Studies, it was found that the association between DDT exposure and infant illness and death were causal and the effects were very small compared to the conceivable benefits from vector control (Chen and Rogan, 2003).

When doing re-evaluations of DDT, the World Health Organization works hard to gain a scientific con-sensus on the appropriate methodology to use in order to assess the risks from DDT exposures in IRS applications. WHO also takes into account both the potential exposures to the people that live in a home along with the operators who are applying the chemicals.

Another factor that is looked at is the amount of chemical that is released into the environment and the effects that they have (The Use of DDT in Malaria Vector Control, 2007). It is projected that DDT will continue to be used in malaria control until an equally cost-effective alternative is developed. A premature shift to less effective or more costly alternatives to DDT, without a strengthening of the capacity (human, technical, financial) of Member States will not only be.