Biology of Toxins -Spring 2009-

Presentation on theme: "Biology of Toxins -Spring 2009-"— Presentation transcript:

1 Biology of Toxins -Spring 2009-
30 years after, AGENT ORANGE still kills!!!! Ana Isela Hernandez Biology of Toxins -Spring 2009-

2 General Background Information

3 Overview of Agent Orange 30 years after, AGENT ORANGE still having severe effects on humans!!!!
Over the past few decades, a substantial body of scientific and medical research has shown that Agent Orange and other herbicides containing dioxin have a high probability of causing or contributing to a variety of health conditions suffered by veterans who served in Vietnam between January 1962 and May 1975. More than 19 million gallons of herbicides were sprayed in Vietnam between (Kang et al, 1991)

4 Overview of Agent Orange… 30 years after, AGENT ORANGE still having severe effects on humans!!!!
Agent Orange contains DIOXIN a highly toxic chemical that has been correlated to many type of cancers, male reproductive problems, miscarriages, and birth defects Dioxin effects are shown in both, American Veterans and Vietnamese population. (Kang et al, 1991)

5 Facts on Agent Orange during the War
At the beginning of the 1970s, the Herbicide Assessment Commission (HAC) sent a group of experts to Vietnam to investigate the effects of the herbicides, especially Agent Orange/dioxin, on the environment and humans. After the trip, they asked the U.S. government to stop the use of the herbicides in Vietnam because these chemicals destroyed mangrove forests and caused miscarriages and birth defects. (Kang et al, 1991)

6 Facts on Agent Orange during the War…
The culprit was the dioxin contained in Agent Orange. This conclusion conformed to the results of experiments on animals. It means that the U.S. was quite aware of the negative effects of the herbicides, Agent Orange in particular, on the environment and humans. At the beginning of 1970, 2, 4, 5-T (a key Agent Orange ingredient) was banned for use in agriculture in the U.S. because it could cause cancers, but the U.S. did not stop using it in Vietnam until 1971, and it allowed the South Vietnamese army to continue to use it until the end of the war, April 30, 1975. (Kang et al, 1991)

7 Objective

8 Objective… spinal bifida, hydrocephalus, among others
This study investigates the effects of Dioxin, a component of Agent Orange, and birth defects such as, spinal bifida, hydrocephalus, among others This study will also provide general information about other consequences such as cancer, skin damage, and immune system.

9 Why was this topic selected?
The first reason why I selected this topic was because Dioxin LD is 10^-3 mg/kg and it grab my attention when I saw this number on the handout that Professor Toolson gave us in class. Dioxin causes severe birth defects not just in Vietnamese population but also in American Veterans and even though it has passed 30 years after the war, it still harming many people.

10 Why was this topic selected?...
Finally, this topic was selected when I found out that my friend Veronica was born with spinal bifida and hydrocephalous as a consequence of Agent Orange. Veronica’s father is a Vietnam Veteran and he was exposed for a few years to Agent Orange during the war.

11 Why is it important to know…
Dioxin, does not break down easily in the environment. Instead, it bioaccumulatesm meaning that the body accumulates any dioxin to which you are exposed. Over time, continual low level exposures will "build up" until subtle adverse health effects begin to occur. skin, cancer, miscarriages, abortions, birth defects, among others. According to EPA, 90% of human exposure occurs through diet, with foods from animals being the predominant pathway.

12 Why is it important to know…
Animals are exposed primarily from dioxin emissions that settle onto soil, water and plant surfaces. Soil deposits enter the food chain by ingestion by grazing animals. People then ingest dioxin through the meat, dairy products, fish and eggs they consume.

13 Why is it important to know…
A recent study by Dr. Arnold Schecter of the State University of New York found dioxin in many food products purchased in an upstate New York supermarket. Schecter estimated that the average daily intake of dioxin is "at least 50 times greater than what EPA estimates is a virtually safe dose of dioxin.“ In addition, while dioxin and birth defects is debated, American Veterans and Vietnamese population are trying to live day by day; both population need compensation in order to obtain treatment.

14 Why is it important to know…
3-6% of Vietnam veterans’ children are born with some kind of birth defect Dioxin and its effects has been a controversial issue because there is not enough evidence, therefore, more studies need to be performed in order to clear out the major effects of Dioxin not just in the human body but in the ecology perspective (plant and animals) Dioxin it is a topic relevant to many medical fields such as immunology, genetics, neurology, and ecology.

15 What to expect? This presentation will provide information about Dioxin It will also provide information about studies relevant to Dioxin and birth defects Videos are also provided to have a better visual and emotional context. (People experiences: American and Vietnamese position) Interview with Veronica Guardian Summary Future studies

16 Introduction

17 What is Agent Orange? Patches", The Air Force C-123 that took the most ground fire of any aircraft flying herbicide missions in Vietnam (U.S. Air force Photo) Agent Orange is the name used to describe a particular type of herbicide blend used for military purposes in Vietnam from 1965 to 1971. The purpose of the herbicide was to kill unwanted plants and removed leaves from trees which otherwise provided cover for the enemy. (USA Department of Veterans Affairs, 2009)

18 Agent Orange… The name “Agent Orange” came from the orange stripe on the 55-gallon drums in which it was stored. Orange was a reddish-brown to tan colored liquid. Agent Orange was created by mixing equal quantities of two agricultural herbicides commonly used to kill weeds: 2,4-D and 2,4,5-T Present in the 2,4,5-T as an impurity was 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a dioxin contaminant that is highly toxic. (USA Department of Veterans Affairs, 2009)

19 Summary of Chemicals Used
A high amount of Agent orange was sprayed during the Vietnam war in South Vietnam. CHEMICAL AGENT TOTAL GALLONS PROCURED BY DOD USED PERCENT OF  REMAINING Green 8,208 0.04% Pink 122,792 0.6% Purple 145,000 0.7% Blue 2,166,656 11.2% White 5,600,000 5,239,853 27.0% 360,147 Orange 13,927,985 11,712,860 60.4% 2,215,125 TOTAL: 21,970,641 19,395,369 2,575,272

20 Introduction… Dioxin Compound

21 Dioxin: 2,3,7,8-Tetrachlorodibenzo-p-dioxin
Dioxin was the primary toxic component of Agent Orange. Dioxins and furans are some of the most toxic chemicals known to science Dioxin is a general term that describes a group of hundreds of chemicals that are highly persistent in the environment. The most toxic chemical in the class is 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD). The highest environmental concentrations of dioxin are usually found in soil and sediment, with much lower levels found in air and water. U.S. Environmental Protection Agency 1994 (Landers et al.,1991)

22 Dioxin Production Dioxin does not occur naturally, nor is it intentionally manufactured by an industry. Dioxins are formed during combustion processes: waste incineration Fires involving chlorinated benzenes forest fires, backyard trash burning, As well as during some industrial processes pulp bleaching herbicide manufacturing. Wood preservatives made from trichlorophenols Combustion of wood in the presence of chlorine (National Academy of Sciences , 2009)

23 Dioxin Chemical Composition
These principles explain the formation of the very toxic families of PCBs, furans and dioxins The molecule is perfectly symmetrical . The presence of chlorine on the outside of the ring, makes dioxins extremely stable compounds. They do not break down as easily as enzymes do The human body tends to store dioxin in adipose (fatty) tissue. Three benzene rings that bind themselves together (Landers et al.,1991)

24 Dioxin Mechanism Dioxin can alter key biochemical and cellular functions by interacting with a Ah cellular receptor This mechanism affects the hormonal system and the way the cell grow and develop Ah receptors move some molecules to cells' interior. Ah receptors match the shape of 2,3,7,8 TCDD very closely. Other dioxins and furans have many of the same effects as 2,3,7,8 TCDD, but are less deadly because they are less symmetrical and do not fit the Ah receptor as well (Landers et al.,1991)

25 Dioxin Mechanism… When Ah receptor binds to 2,3,7,8-TCDD it forms a strong unit with the receptor and this unit is known as the receptor-dioxin complex Once the dioxin-receptor complex is formed, it moves to the DNA in the cell where it has two main effects: 1) It activates genes which produce P450 enzymes 2) It activates genes which produce substances that regulate the growth and division of cells. In this way dioxin is behaving like a hormone. (Landers et al.,1991)

26 Dioxin Toxicity … The toxicity of dioxin compounds depends on the strength of the binding to the Ah receptor (Silbergeld & Gasiewicz, 1989). The response of DNA to the altered receptor also varies and is hereditary; with differences in susceptibility to TCDD also existing between strains (Byard, 1987). Sub-lethal effects are seen at far lower doses, In mice, a dose which is 4000 times less than a fatal dose will significantly alter the ability of mice to produce cell-killing T-lymphocytes (Silbergeld & Gasiewicz, 1989).

27 Dioxin Toxicity … The TCDD dose that produces rapid death varies a great deal between species: Hamster is least susceptible, with a fatal dose of 5 mg /kg bodyweight while a dose 100 times smaller than this will kill a rat (Silbergeld & Gasiewicz, 1989). Immune system effects are similar for various animals. TCDD induced changes in the thymus and liver occur at the same dose levels in the hamster as in otherwise more sensitive species (Silbergeld & Gasiewicz, 1989). The rat and the hamster are also very similar where birth defects are concerned. In both animals, a maternal dose of 1.5 ug/kg bodyweight produced different, but equally serious, effects in the fetuses, causing digestive tract bleeding in the rat and kidney abnormalities in the hamster (Olson, 1990).

28 Exposure Pathways Lungs Skin Gastrointestinal (mouth)

29 Dioxin and the Environment

30 Dioxin and the Environment
Plants Animals Resources

31 Where are dioxins found?
In the environment, dioxins accumulate in soils, sediments and waste disposal sites. They are not present in water because of their insolubility. Agent Orange herbicides might remain in the soil, there is concern that these residues might inhibit the growth of crops and other plants Dioxins enter the food chain when animals eat contaminated plants and sediments. The dioxins are then absorbed into the animal fat and increase in concentration as they migrate up the food chain. This is referred to as bio-accumulation. U.S. Environmental Protection Agency 1994

32 How do dioxins enter the environment?
It is estimated that over 96 % of dioxins present in the environment have originated from air emissions. They are then deposited onto soil, plant and water surfaces. When released into the air, some dioxins may be transported long distances, even around the world. Fish and other aquatic organisms can then ingest and further transport and deposit them. U.S. Environmental Protection Agency 1994

33 How do dioxins affect the environment?
Dioxins are very toxic to certain animals particularly in the early stages of development. Studies have shown dioxins to have a range of adverse effects on a wide number of animals, including reproductive or developmental effects such as weakened immune responses and behavior changes in offspring. In laboratory animals, dioxin has been shown to cause cancer, birth defects and genetic damage. U.S. Environmental Protection Agency 1994

34 U.S. Environmental Protection Agency 1994

35 Trying to Reduce Dioxin
Dow’s efforts to reduce dioxin emissions date back to the early 1980s, and the company has been publicly reporting emissions of dioxins since   To date, we have spent more than $400 million on improvements to our processes and treatment technologies to reduce both the generation and emission of dioxins.  Since 1995, our emissions to air and water have been reduced 85 percent. (Birnbaum, 1993)

36 Dioxin and Its Effects

37 Dioxin causes a wide range of effects:
Potent cancer causing agent b. Damages the immune system, leading to increase susceptibility to infectious diseases c. Reproductive and developmental effects d. Miscarriages and birth deformity e. Nervous System Disorders f. Skin damage

38 General Information of Birth Defects

39 Birth Defects Major structural birth defects are common problems, affecting 3% or more of all babies. Birth defects are the leading cause of infant mortality, accounting for 20% of all deaths during infancy. If babies with birth defects survive, they usually require extensive and expensive surgical and medical care; in addition, many have lifelong disability. There are many different types of birth defects. One of the more serious and common specific kinds of defect is spina bifida caused by teratogenic exposure, that causes mutation, such as dioxin (Mitchell et al, 2004)

40 Dioxin and Birth Defects

41 Vietnam Case Over the last 30 years, since the end of the  Vietnam War, serious birth defects have been  common in Vietnam.  Scientists believe the dioxin  in Agent Orange is causing the birth defects children are now third generation of victims

42 Vietnam case… Herbicides were sprayed from aircraft, watercraft, trucks, and backpack sprayers. The herbicide flowed into rivers and streams when it rained, and was on the ground and vegetation when troops moved through an area.  More than 3000 villages with at least 2.1 million people were sprayed directly with herbicides Vietnamese demand compensation Many Vietnamese victims who also suffer greatly have received nothing from the United States since the end of the war (Tuong et al., 2006)

43 Facts: Dioxin and Birth Defects
Since studies of Vietnam veterans exposed to herbicides in Vietnam have found much higher levels of dioxin in their bodies than the average person, these effects also should be detectable in their children (Schecter et al., 1996) In 1996, the National Academy of Sciences found “limited/suggestive” evidence of an association between Agent Orange exposure and spina bifida, a neural tube defect, in the children of Vietnam veterans (Pier, 1993) In 2000, Dr. H.K. Kang of the Environmental Epidemiology Service of the Veterans Health Administration published a study that found that the risk of moderate-to-severe birth defects was significantly associated with the mother’s military service in Vietnam (Ngo et al., 2006)

44 Facts: Dioxin and Birth Defects
The Air Force Ranch Hand study of Vietnam showed that there is an increase in spina bifida in the children of Ranch Hand veterans with high dioxin levels (Mitchell et al, 2004) Although dioxins are not believed to be directly genetically toxic, they can bind to certain genetic receptors in a manner that can promote conditions favorable to gene mutations (Landers et. al., 1991)

45 Type of Birth Defects Spina bifida Oral clefts Cardiovascular defects
Hip dislocations Malformations of the urinary tract Neuroblastoma Hydrocephalus (Donovan et al., 1997)

46 An example of Birth Defect relevant to Dioxin effects

47 Spina Bifida Spina bifida results from failure of fusion of the caudal neural tube. It is characterized by an improper formation of the vertebral column and spinal cord The causes of this disorder are heterogeneous and include chromosome abnormalities, single gene disorders, and teratogenic exposures such as Dioxin. However, the cause is not known in most cases (Mitchell et al, 2004)

48 Veronica Guardian’s Interview
Veronica Guardian was born with spina bifida and hydrocephalus Her birth defects are not as severe as other victims (especially Vietnamese victims) She has taken her deformities in a positive way. She continuously expresses infections, therefore, after every single surgery doctors need to monitored her very carefully Click on the blue screen to watch video It needs to be on “Slide Show” Duration 9:52 min

49 Dioxin and Birth Defects
Mechanism that has been proposed for TCDD, that could help explain the birth defects. TCDD by binding to the Ah receptor for too long, may produce a signal at the wrong time during organ formation. As a result, cells may become specialized too late, thus causing malformation (Silbergeld & Gasiewicz, 1989). Although dioxins have been shown to act exclusively through the Ah receptor, knowledge is not complete, and it is possible that there are further undiscovered mechanisms, such as action through another receptor. w=123&prev=/images%3Fq%3Ddioxin%2Band%2Bbirth%2Bdefects 3-year-old Xuan Minh, believed to have genetic defects from Agent Orange (Landers et al.,1991)

50 “Optional” Related videos
Agent Orange – Vietnam 22:34 min The shadow of agent orange (Michael Ryan -American Vietnam stories) 4:40 min Agent Orange. American Chemical and Biological Warfare 3:04 min Agent Orange devastates generations of Vietnamese 5:06 min

51 Results of Research Studies

52 New York Times: Study Finds Dioxin Caused No Increase In Defects at Birth
An accident in 1976 in Italy that exposed the largest population ever to the chemical byproduct dioxin caused no increase in birth defects, scientists have reported. The Journal of the American Medical Association, researchers at Rome's Catholic University and the Italian Birth Defects Monitoring Program said children born in the contaminated area after the accident appeared not to have been abnormally affected. The findings are consistent with those of several other studies on humans that have failed to find evidence that exposure to dioxin causes birth defects. The scientists suggested that if there was any increased risk of birth defects associated with exposure to dioxin it was ''unlikely to be large, or might be limited to very rare and specific birth defects.''

53 Results Ngo, A.D., Taylor, R., Roberts, C.L, Nguyen, T.V. Association between Agent Orange and birth defects: systematic review and meta-analysis. Journal of Epidemiology (5): Meta-analysis (a review of the combined data from many studies from ) of Agent Orange and birth defects Results: The summary relative risk (RR) of birth defects associated with exposure to Agent Orange was 1.95 [95% confidence interval (95% CI) 1.59–2.39], with substantial heterogeneity across studies Their review indicated that parental exposure to Agent Orange was associated with an increased risk in birth defects. The association increased with greater degrees of exposure rated on intensity and duration of exposure. Although other researchers have pointed out weaknesses in the studies of birth defects from Vietnam, the birth defect association with Agent Orange exposure was statistically significant even when the Vietnamese studies were excluded.

54 Results Tuong, N.V. et al. Study on variation of some biological factors such as genetics Immunology, biochemistry, hematology in patients with high Risk of exposure to dioxin. Organohalogen Compounds Vol 68 (2006) Analyzed gene of 5 generations which are prehistoric expose to dioxin and whose dioxin in blood have been found in exposed subjects during war, changed in Gene P53, gene Cyp aA1 and gene AhR, particularly changes in amino acids related to specific cancers have been seen. Ability of respond to making good antibody in group with higher risk of expose to dioxin (HRE) is significantly lower than the control group and group with lower risk of expose to dioxin. There is difference in Enzyme activity for preventing oxidation among groups. Frequency of disorder in lymphocytes form is found in HRE.

55 Results Rowland, R.E., Edwards, L.A., Podd, J.V. Elevated sister chromatid exchange frequencies inNew Zealand Vietnam Veterans. Cytogenet Genome Res 116: (2007) Genetic damage in New Zealand Vietnam War veterans was investigated. Results from the sister chromatid exchange (higher frequency of genetic damage) show a highly significant difference between the experimental group and control. The authors suggested that New Zealand Vietnam veterans had been exposed to a harmful substance that could cause genetic damage. Although the authors recommended caution in interpreting specific health outcomes, they concluded that genetic damage to any degree has the potential to result in adverse health effects. The greatest concern about genetic damage is that it can be passed on to future generations.

56 Results Schecter, A., McGee,H., Stanley J.S., Boggess, K., Rauf, P. B. Dioxins and dioxin-like chemicals in blood and semen of American Vietnam veterans from the state of Michigan. Am J Ind Med Dec;30(6):647-54 Important new research on birth defects in the children of Vietnam veterans was presented at the 2006 meeting of the Society for Epidemiological Research in Boston. Three researchers conducted a study of neural tube defects (anencephaly, encephalocele, spina bifida) in the offspring of Vietnam veterans. They found that paternal blood levels of TCDD were significantly associated with neural tube defects in their children and that a particular paternal genotype (genetic predisposition) could enhance this association.

57 Results Schecter, A., Constable, J.D. Commentary: Agent Orange and birth defects in Vietnam. International Journal of Epidemiology (5): Meta-analyses: Researchers revised every single study that was and was not published. They conclude that, with the exception of spina bifida and anencephaly, the published peer-reviewed literature does not convincingly support an association between herbicide or dioxin exposure and birth defects in humans. Researchers expressed that there is no doubt that during and after the war, many Vietnamese absorbed this very toxic material. They also keep in mind that dioxin probably resulted in significant health effects in Vietnam. However, they are not convinced that Vietnamese investigations linking congenital malformations to dioxin are, as yet, more than suggestive.

58 Results Donovan, J.W. Case-Control Study of Congenital Anomalies and Vietnam Service (Birth Defects Study) 1997 A Australian investigation involved examination of the hospital and laboratory records of infants born with birth defects in three populous areas of Australia between the years 1966 and 1979. In all, 34 hospitals and 4 laboratories cooperated fully with the investigating team. Whenever the birth of an infant with a defect was found, it was matched to a healthy control infant born in the same hospital, to a mother of similar age, and as close as possible in time to the birth of the child with the defect.

59 Results Donovan, J.W. Case-Control Study of Congenital Anomalies and Vietnam Service (Birth Defects Study) 1997 The fathers of both cases (for this study, a case is a baby with a birth defect) and controls (for this study, a control is a baby without a birth defect) were identified in 8,517 instances and those identified were compared with a list of every man who served in the Australian Army between 1962 and 1972, the period of Australian involvement in Vietnam. The important finding of the study is that 127 of the fathers of children with birth defects were Vietnam veterans and 123 veterans were among the fathers of healthy children. Researcher found that 9.2% of fathers of babies with birth defects had served in Vietnam, compared to 9.5% of fathers of babies born without defects. This indicates that there is no evidence that Army service in Vietnam increased the risk of fathering a child with a birth defect.

60 Results Dragin, N., Dalton, T.P., Miller, M.L., Shertzer, H.G., Nebert, D.W. For Dioxin-induced birth defects, mouse or human CYPA2 in maternal liver protects whereas mouse CYP1A1 and CYP1B1 are inconsequential. BioChem. J. 2006; 28 (27) : Birth defects in mice are mediated by Ah receptor. Cyp1a2 and Cyp1b1 genes are up-regulated by the Ah receptor Researchers compared Cyp1a1 (-/-), Cyp1a2 (-/-), Cyp1b1 (-/-) knock-out in mice with Cyp1 (+/+) Results: Incidence of cleft palate and hydronephrosis was not significant among genes except Cyp1a2 (-/-) Cyp1a2 (-/-) exhibited a increase sensitivity to birth defects and it can be lethal Results indicated that maternal mouse hepatic CYP1A2 by sequestering dioxin, protects the embryo from toxicity and birth defects. In humans, CYP1A2 trans gene provides same protection. In contrast, neither CYP1A1 nor CYPB1 appears to play a role in dioxin mediated teratogenesis.

61 Results Lawson, C.C., Schnorr, T.M., Whelan, E.A., Deddens, J.A., Dankovic, D.A., et al. Paternal Occupational Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin and Birth Outcomes of Offspring: Birth Weight, Preterm Delivery, and Birth Defects. Environ Health Perspect October; 112(14): 1403–1408 Researcher studied pregnancy outcomes among wives of male chemical workers who were highly exposed to chemicals contaminated with TCDD and among wives of no exposed neighborhood referents by estimating serum TCDD concentration at the time of conception using a pharmacokinetic model Results: Six major CNS defects were reported: one case of spina bifida, two anencephalus cases, two hydrocephalus cases, and one case of multiple congenital anomalies. Conclusion: data were too limited to present statistical analysis of reported birth defects and paternal TCDD exposure, although descriptive information on birth defects did not suggest any relationship to TCDD.

62 Discussion

63 Discussion… Dioxin is a highly toxic chemical, and as Professor Toolson mentioned in class, everything is toxic, all depends in the amount or concentration. Therefore, even though there is controversy between dioxin and birth defects, I truly believe that there is a chance that people who are exposed to this chemical are able to develop adverse effects and it can go through generations as any other genetic or hereditary disorder/impairment. Chemicals work in the body using different mechanism, even though more research need to be done, Dioxin mechanism can definitively affect cell leading to abnormal development and abnormal organogenesis.

64 Discussion… Many studies have been done in animals and they shown severe effects, therefore, even though we as human have different metabolism and different toxicity level, we need to take these results into consideration. Researchers try to ignore these values because of lack of data from human specimen. Moreover, these results are from animal, therefore researcher believe that human can respond differently to chemicals. Don’t we supposed to take this results into consideration?

65 Discussion… On the other hand, many studies do not support this idea, but the number of people, American Veterans especially Vietnamese population, who have shown birth defects as a consequence of “Dioxin” is large, therefore, there is something going on among people that has been exposed to this chemical. As mentioned before, Dioxin can accumulate, cancers develop over time, therefore it is difficult to express that cancers cannot develop because of the chemical as many studies have described. Are people with birth defects show high levels of dioxin or is it because of a mutation or cell division issues? It will be interesting to investigate more about it.

66 Discussion… If currently studies offer evidence that birth defects such as spina bifida, cleft lip or palate are associated with dioxin-contaminated herbicide exposure in Vietnam. Therefore, researcher need to use new technology that has been developed over time or find new procedures in order to obtain more accurate results. It will be a good idea to try to replicate this studies and compare the results

67 Discussion… Studies have shown that there is inadequate or insufficient evidence to determine whether an association exists between exposure to herbicides and all other birth defects. Implications of most studies: Use meta-analyses, small population lack on statistical analyses many of the patients are recruited by interviews instead of medical records People were exposed to different concentrations of dioxin Different time of exposure. Exposure to other herbicides

68 Discussion… Although dioxins are not believed to be directly genetically toxic, they can bind to certain genetic receptors in a manner that can promote conditions favorable to gene mutations A research study has described that changed in Gene P53, gene Cyp aA1 and gene AhR, are related to specific cancers. Therefore, more studies in genetics and embryology must to be performed

69 Discussion… If Dioxin can bind perfectly to Ah receptor, then it becomes stable because of the presence of chloride, then it makes it difficult to breakdown. In animals genes, according to Dragin et al (2006): CYP1A1 nor CYPB1 appears to play a role in dioxin mediated teratogenesis maternal mouse hepatic CYP1A2 by sequestering dioxin, protects the embryo from toxicity and birth defects What about human? I believe that the genotype of the affected fetus may not be a determinant of teratogenic risk; rather, instead, the maternal genotype appears to be more important. In addition, mother should show probably a lower CYPA2 activity that would affect the fetus

70 Discussion… In addition, Dioxin is able to affect the immune system.
I have understood that low levels of dioxin directly reduces the number of B cells and the number of T cells Pregnant victims exposed to dioxin are susceptible to many infections, probably immunological problems can be involved in offspring birth defects. According to researchers, lymphocyte cells of newborns exposed to higher concentrations of these chemicals during prenatal development secreted fewer cytokines. Could this be involved within the mother during pregnancy and affect organogenesis within the fetus?

71 Summary

72 Summary… More than 11.2 million gallons sprayed after 1965 were dioxin-contaminated Agent Orange during the Vietnam war to destroyed the forest in order to see the enemy. Agent Orange contains Dioxin which is highly toxic not just for the environment (plants and animals) but also for humans. Dioxin, a man-made chemical, can cause male reproduction problems, neurological impairments, miscarriages, developmental abnormalities (birth defects), cancers, among others.

73 Summary… Dioxin appears to act like a persistent synthetic hormone that interferes with important physiological signaling systems that can lead to altered cell development, differentiation, and regulation. Dioxin undergoes a mechanism which involves Ah receptors which move molecules to cells' interior affecting the hormonal system and the way the cell grow and develop. Dioxin and its adverse effects had been under research for many years The association between parental exposure to Agent Orange or dioxin and birth defects is controversial, due to inconsistent findings in the literature but available data are inadequate to assess this possibility critically.

74 Summary… Studies have shown that American Veterans and Vietnamese population showed a higher risk to birth defects. Studies offer evidence that birth defects such as spina bifida, cleft lip or palate are associated with dioxin-contaminated herbicide exposure in Vietnam. Scientists reported that Vietnam veterans’ risk of fathering an infant with one or more major malformations was increased at a statistically significant level. There is evidence on genetic damage that can be passed through generations.

75 Summary… Considering the fact that approximately 2.6 million veterans served in Vietnam and the fact that 3-6 percent of all children are born with some kind of defect, scientists expect to see many children with abnormalities among the offspring of Vietnam veterans. Unfortunately, in many instances scientists cannot explain what caused these birth defects. There is limited/suggestive evidence between exposure to the herbicides, therefore many other studies need to be performed. More studies need to be performed using other procedures that will help us to answer the questions that have developed over time

76 Future Studies

77 Future Studies… There is needed for continued rigorously controlled research to definitively answer questions. It is necessary to do more research on Genetic and Molecular Aspects of 2,3,7,8-Tetra-Chlorodibenzo-P-Dioxin Action. A more deeply investigation on how does Dioxin affects cell division and chromosomes Prenatal exposure to endocrine exposures Disrupt of hormone activity altering hormones and reproductive tissue

78 Future Studies… I believe it is necessary to investigate the effects on different genes such as p53, cytochrome 450, Ach receptor mutations Use different procedures besides meta-analyses Larger population Long term consequences Materials and Methods Same amount of concentration Different amounts of concentration Same time of exposure Use new technology Genetics Embryology More animal research

79 Future Studies… Serum TCDD concentration is high in patients with birth defects? Serum TCDD concentration is high in pregnant mothers whose husband is veteran? Is CYP1 metabolism is required for mediating TCDD? Is there an increase of Ah receptor or ligand that could affec birth defect or genetics? TCDD affects cell growth and reproduction, how? By increasing the Ah ligand or receptor? By apoptosis? Damage genes Protein synthesis Signal transduction?

80 References Birnbaum, L. Great Lakes Water Quality Board 102nd Meeting, Chicago, Illinois, July 15, 1993, pg. 4 Donovan, J.W. Case-Control Study of Congenital Anomalies and Vietnam Service (Birth Defects Study). Epidemiology, 1997. Dragin, N., Dalton, T.P., Miller, M.L., Shertzer, H.G., Nebert, D.W. For Dioxin-induced birth defects, mouse or human CYPA2 in maternal liver protects whereas mouse CYP1A1 and CYP1B1 are inconsequential. BioChem. J. 2006; 28 (27) : New York Times News. Study Finds Dioxin Caused No Increase In Defects at Birth Kang, H.K., Watanabe, K.K., Breen, J., Remmers, J., Conomos, M.G., Stanley, J., Flicker, M. Dioxins and dibenzofurans in adipose tissue of US Vietnam veterans and controls. Am J Public Health March; 81(3): 344–349. Landers , P.L., Bunce, N.J. The Ah receptor and the mechanism of dioxin toxicity. Biochem J ; 276( 2): 273–287 Lawson, C.C., Schnorr, T.M., Whelan, E.A., Deddens, J.A., Dankovic, D.A., et al. Paternal Occupational Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin and Birth Outcomes of Offspring: Birth Weight, Preterm Delivery, and Birth Defects. Environ Health Perspect October; 112(14): 1403–1408 Mitchell, L. Melchione, J., pasquariello, P.S. Spina bifida. The Lancet (9448): Ngo, A.D., Taylor, R., Roberts, C.L, Nguyen, T.V. Association between Agent Orange and birth defects: systematic review and meta-analysis. Journal of Epidemiology (5): Pier Alberto Bertazzi et al. Cancer Incidence in a Population Accidentally Exposed to 2,3,7,8-Tetrachlorodibenzo-PARA-dioxin," Epidemiology Vol. 4 (September, 1993), pgs Rowland, RE., Edwards, LA., Podd, JV. Elevated sister chromatid exchange frequencies in New Zealand Vietnam War veterans. (2007) Cytogenet Genome Res 116:248–251 Schecter A, McGee H, Stanley JS, Boggess K, Brandt-Rauf P. Dioxins and dioxin-like chemicals in blood and semen of American Vietnam veterans from the state of Michigan. Am J Ind Med Dec;30(6): Schecter, A., Constable, J.D. Commentary: Agent Orange and birth defects in Vietnam. International Journal of Epidemiology (5): Tuong, N.V. et al. Study on variation of some biological factors such as genetics, Immunology, biochemistry, hematology in patients with high Risk of exposure to dioxin. Organohalogen Compounds Vol 68 (2006) U.S. Environmental Protection Agency, HEALTH ASSESSMENT DOCUMENT FOR 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) AND RELATED COMPOUNDS. Vol. 3, 1994 Veronica Guardian Video Los Lunas, NM. April 27, 2009 Woods, L. Understanding the immune system . NIH Publication 1988, (88): 529