Environmental Health Debate DDT Savior or Poison? Environmental Health Debate

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.

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

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.

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)

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

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

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

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

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

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 (1993-1996) bed nets impregnated with pyrethroids stream clearing or seeding with tilapia both for malaria mosquito control and source of income. Bagamoyo District, Tanzania (1990-1995) – 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

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, <http://www.ajtmh.org/cgi/content/full/77/6_Suppl/249> 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.

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

Fish eating birds (25ppm) DDT Biomagnification Fish eating birds (25ppm) Large Fish (2ppm) Small Fish (0.5ppm) Zooplankton (0.04ppm) Water (00000.3ppm)

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

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

DDT Movie http://www.youtube.com/v/Ew9TbquPheM

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”

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