1. Environmental Health Debate
DDT Savior or Poison?
Environmental Health Debate

2. The Debate Back story: Questions:
The only company that makes DDT is now bankrupt.
Production to cease in January, 2009.
Debate rages about environmental/human health impact vs disease vector control.
Questions:
Should the World Bank step in an save the company so DDT production can continue?
You, the audience, are the World Bank and must decide whether to save DDT production or allow it to cease.

3. What do you think?
For continued DDT use?
Against continued DDT use?

4. Debate Format
A series of prepared questions will be asked and the groups will respond to each question.
You, the audience will have the chance to ask questions and ultimately decide the fate of DDT in our future.

5. DDT Background History Dichloro-Diphenyl-Trichloroethane
First discovered in 1874
Used as an insecticide in WWII
Sprayed, applied to clothes, used as soap
Used to control malaria, typhoid fever and others
1948 Nobel Prize in Medicine (Paul Hermann Muller)
Agricultural use began after WWII
Silent Spring published in 1962 (Rachel Carson)
Banned for most purposes in US in 1972
Stockholm Convention banned agricultural use of DDT worldwide (ratified 2001, effective 2004)

6. DDT Background Chemistry - Synthesis Mechanism Insect Resistance
Chloral + Chlorobenzene (+ Sulfuric Acid)
Mechanism
Na channels of insects
Locks in open state
Insect Resistance
T929 and T932
Cyt-p450

7. Alternatives to DDT Integrated Vector Management
Utilization of multiple approaches to control vector expansion and transmission of disease
Integrated Disease Control
Early disease detection
Prompt treatment of disease

8. Integrated Vector Management
Physical barriers
Protective clothing, mosquito nets or bed nets, screens on doors and windows
Vector habitat management
Draining and elimination of breeding sites (wetlands) to decrease vector numbers
Filling depressions or planting to dry out areas with high water table.
Vegetation management
changing water levels or flooding schedules in irrigated agriculture such as rice cultivation.
alternating rice cultivation with dry land crops
Introduction of natural enemies
“Larvivorous” organisms into natural wetlands and bodies of water to eat larvae of mosquitoes or other vectors.
Mosquitofish
African Tilapia
Guppies
 perturb biodiversity with overgrowth
eradicated malaria in southeastern US in 50’s, Israel/Palestine in 60’s, Italy before WWII

9. Integrated Vector Management
Using baits to divert vector from humans
Research in Mwea Kenya – village with highest livestock population had the lowest prevalence of malaria, although mosquito counts were highest.
Substitution with less toxic pesticides
Pyrethroids (permethrin, deltamethrin) - synthetic chemicals similar to natural chemical pyrethrins produced by flowers of pyrethrums
Keep sodium channels of in neuronal membranes of insects, interfering with nerve excitation  insect paralysis.
Deposit in fat cells, CNS and PNS.
Shorter half life – deltamethrin up to 2 years – thus lower bioaccumulation
Some as inexpensive as DDT to use
Not as toxic to humans as carbamates and organophosphates
Toxic to invertebrates (aquatic species and arthropods); dispose of contaminated material by burial or pit latrines in which pyrethroids degrade quickly
Decrease volume of pesticides used and reduce bioaccumulation.
Impregnate bait targets or bed nets with pyrethroids vs. indoor house spraying.
eradicated malaria in southeastern US in 50’s, Israel/Palestine in 60’s, Italy before WWII

10. Overall Goals Combined integrated vector and disease management
Affordable methods – minimize use of pesticides lower costs.
Education – health awareness and disease identification, as well as training in process implementation.
Community involvement – important in implementing and sustaining programs
eradicated malaria in southeastern US in 50’s, Israel/Palestine in 60’s, Italy before WWII

11. Countries Controlling Malaria with Alternative Approaches
Kheda District, Gujarat, India - achieved lower cost-per-person protected compared to conventional house spraying with DDT
eliminating mosquito breeding habitat
using guppies to remove mosquito larvae in permanent and semi-permanent water bodies.
aggressive disease surveillance
Mwea, Kenya
water management in rice growing community
using cattle as bait
introducing bacteria into stagnant water to kill mosquito larvae
mosquito nets
The Philippines – reduction in number of malaria cases per 100,000 populationn form 97 to 55 ( )
bed nets impregnated with pyrethroids
stream clearing or seeding with tilapia both for malaria mosquito control and source of income.
Bagamoyo District, Tanzania ( ) – children of communities with bednets treated with pyrethroids had 60% fewer episodes of malaria-related fevers and 50% less malaria infections anemia, and treatments for malaria, and grew more than unprotected children.
eradicated malaria in southeastern US in 50’s, Israel/Palestine in 60’s, Italy before WWII

12. Insecticide
Class
Recommended dosage of active ingredient (g/m2)[2]
Duration of effective action (months)
Estimated cost per house per 6 months (US$)[3]
WHO toxicity rating[4]
DDT
Organochlorine
1–2
>6
1.6 II
Fenitrothion
Organophosphate 2
3–6
14.8
Malathion
2–3
8.2
III
Pirimiphos-methyl
Propoxur
Carbamate
18.8
Bendiocarb
0.1–0.4
2–6
13.8
Alpha-cypermethrin
Pyrethroid
0.02–0.03
4–6
Cyfluthrin
0.02–0.05
Deltamethrin
0.02–0.025
Etofenprox
0.1–0.3 U
Lambda-cyhalothrin
8.6
Bifenthrin
0.025–0.05
1. ^ a b Indoor Residual Spraying: Use of Indoor Residual Spraying for Scaling Up Global Malaria Control and Elimination. World Health Organization, 2006.
2. ^ Sadasivaiah, Shobha; Tozan, Yesim & Breman, Joel G. (2007), "Dichlorodiphenyltrichloroethane (DDT) for Indoor Residual Spraying in Africa: How Can It Be Used for Malaria Control?", Am. J. Trop. Med. Hyg. 77(Suppl 6): 249–263, <
3. ^ "Excluding operational costs and freight and other external costs"
4. ^ Ia = Extremely Hazardous; Ib = Highly Hazardous; II = Moderately Hazardous; III = Slightly Hazardous; U = Unlikely To Be Hazardous. Source: World Health Organization, The WHO Recommended Classification of Pesticides by Hazard, 2005.

14. DDT Environmental Impact
Biopersistant
Half life of up to 15 years
Other, more toxic, insecticides break down much faster
Persistent breakdown products
85% of tested milk in 2005 had detectable DDE
Egg shell thickness may still be 10% thinner in raptors than before DDT used
Stored in body fat
Biomagnification

15. Fish eating birds (25ppm)
DDT Biomagnification
Fish eating birds (25ppm)
Large Fish (2ppm)
Small Fish (0.5ppm)
Zooplankton (0.04ppm)
Water ( ppm)

16. DDT Environmental Impact
DDT impairs calcium absorption and results in weak egg shells

17. DDT Environmental Impact
Killed parasitic wasps
Killed anopheles mosquitos
Accumulated in Borneo geckos

18. DDT Movie

19. DDT Adverse Health Effects
Psychiatric
Asthma
Diabetes
Hepatocellular carcinoma
Cholangial carcinoma
Pancreatic adenocarcinoma
Non-Hodgkin Lymphoma
Testicular seminoma
Breast cancer
Disruption of normal semen production, menses and lactation
Fetal neurotoxicity
Congenital hypothyroidism
Early pregnancy loss
“Do No Harm”

20. Your Turn
For continued DDT use?
Against continued DDT use?