Understanding Dioxins: Environmental Risks and Human Health Effects

1. DIOXINS: ARE WE ALL AT RISK? Linda. S. Birnbaum, PhD, DABT NHEERL/US EPA Research Triangle Park, NC Saginaw, MI – April 13, 2005

2. What is Environmental Risk? • The likelihood of injury, disease, or death resulting from human exposure to a potential environmental hazard • Human Health Risk Assessment • The process by which we evaluate the likelihood and nature of public health effects of environmental pollution

3. Risk Assessment: Basis for Standard Setting • Exposure Assessment • Who? What? When? Where? Why? How? • Hazard Identification • Potential for a problem • Dose/Response Assessment • Relationship between amount of exposure and observed effects • Risk Characterization • Critical evaluation of all the data and uncertainties

4. Risk Assessment RiskManagement Dose- Response Assessment Actions Hazard Identification None Issues Risk Characterization Public Information Ambient Standards Economics Control Devices DECISIONS Legal Exposure Assessment Emission Limitations Social Ban Political Engineering

5. What Are “Dioxins”? A family of structurally related chemicals which have a common mechanism of action and induce a common spectrum of biological responses

6. 2,3,7,8-Tetrachlorodibenzo-p-dioxin“The Most Toxic Man-Made Compound” • Prototype for family of structurally related compounds • Common mechanism of action • Common spectrum of biological responses • Environmentally and biologically persistent (Basis for TEQ approach)

7. 1899 – Chloracne Characterized 1929 – PCBs produced commercially 1947 – “X” Disease in cattle 1949 – Nitro, West Virginia 1957 – Chick Edema Disease; TCDD identified in TCPs 1962-1970 – Agent Orange use in Southeast Asia 1968 – “Yusho” oil disease 1971 – Times Beach; TCDD causes birth defects in mice 1973 – PBB contamination in Michigan 1976 – Seveso, Italy 1978 – Kociba rat cancer study 1979 – “Yucheng” oil dieases 1981 – Capacitor fire in Binghamton, NY 1985 – 1st US EPA health assessment of TCDD 1991 – NIOSH cancer mortality study of US workers 1999 – Belgium dioxin poisoning; Viennese poisoning Why the Interest in Dioxins???

8. “Dioxins” Polyhalogenated Dibenzo-p-dioxins and furans Never produced intentionally Unwanted byproducts of industrial and combustion processes Polyhalogenated Biphenyls, Naphthalenes, Azo/azoxybenzenes Commercially produced Major industrial chemicals Limited number of congeners have dioxin-like properties Lateral halogenation > 3 Halogens Chlorinated, brominated, and mixed chloro-bromocongeners

9. PCBs • Large Family of Chemicals • 209 Possible Congeners • Small Subset Are “Dioxins” • NEVER have PCBS without Dioxin-like PCBs • Majority Have Own, Inherent, Toxicities • Multiple, Overlapping, Structural Classes • Can Interact Additively, Synergistically, and/or Antagonistically With Dioxins and With Other PCB Congeners

10. TCDD is NEVER Found Alone • Complex Mixtures Exist both Environmentally and in Animal and Human Tissues • TCDD is only a Small Part of Total Chemical Mass • We have the Most Toxicological Information about TCDD

11. Problem: Broad Specturm of Chemicals with Unknown Toxicity but with Striking SAR • 3 Regulatory Approaches • Treat All as Equi-toxic to TCDD • Ignore all those lacking Definitive Toxicological Data • Develop a Relative Potency Ranking Scheme which utilizes Existing Data and Expert Scientific Judgment

12. Toxic Equivalency Factors (TEFs) • Developed for Risk Assessment • Interpret Complex Database Derived from Analysis of Samples Containing Mixtures of Dioxin-like Chemicals • Express Quantitatively the Toxicity of a Chemical in terms of an Equivalent concentration of TCDD (Relative Potency) • ∑([Chemical] x TEF)PCDD/PCDF/PCB=TEQ

13. Five Compounds Make up about 80+% of the Total TEQ in Human Tissues • Four of 17 Toxic PCDD/PCDF Congeners • 2,3,7,8-TCDD • 1,2,4,7,8,-PeCDD • 1,2,3,6,7,8-HxCDD • 2,3,4,7,8-PeCDF • One of the 12 Toxic PCBs • PCB 126

14. Major Past Sources of Dioxins (20th Century Problem) • Chloralkali Facilities • Chlorinated herbicide and biocide Production • Leaded Gasoline • Municipal, Medical, and Hazardous Waste Incineration • Chlorine Bleaching of Paper and Pulp Products

15. Recently Identified Sources • Open Burning of Household Waste • Uncontrolled Combustion • Forest Fires and Volcanos • Metal Refining

16. Major US Dioxin Sources 1987 1995 2004

17. Sources and Pathways to Human Exposures SOURCES TRANSPORT FOOD SUPPLY Reentrainment DEPOSITION Industrial Processes Combustion Runoff Erosion Direct Discharge

18. How do Dioxins Move in the Environment • If emitted into air, undergo atmospheric transport and deposition on land or water • If emitted into water, bind to sediment • Recycle in environment • Bioaccumulate up the food chain • Resistance to physical, chemical, and biological degradation

19. How are People Exposed? • Dioxins are omnipresent • Majority of exposure (>95%) is via microcontamination of food • Meat, fish, dairy • Sensitive Subpopulations with High Exposure • Subsistence Fishers and Hunters • Nursing Infants • Occupational Workers • Oral, dermal, and inhalation exposures

20. Soil ingestion Vegetable fat Soil dermal contact Other meats Poultry Freshwaterfish and shellfish 6% Pork 5% 19% Marine fish and shellfish Beef 7% 14% 1% Inhalation 4% 16% Eggs 21% Milk Dairy U.S. Adult Average Daily Intake of CDDs/CDFs/ Dioxin - Like PCBs 65 pg TEQDFP-WHO98/day

21. How You are Exposed Makes Little Difference • Dioxins are well absorbed from the GI tract and lungs • Skin absorption is limited and slow • Dioxins primarily lodge in the liver and fat • Dioxins are primarily eliminated after metabolism, which is VERY slow

22. Why do the Body Burdens Increase Over Time? • Persistence • Resistance to Biological, Chemical, and Physical Degradation • Long Half-Lives in Animals and People • More Body Fat-Longer Half-Life • Half-Life is Dose-Dependent • Bioaccumulation • Due to Persistence in Animal tissues Higher Trophic Organisms have Higher Concentrations • Older Organisms have Higher Body Burdens than Young

23. Experimental exposure Background Human exposure Occupational exposure Half-Life Varies with Body Burden and Body Composition (Emond et al., 2004)

24. Background Serum Levels in the United States 1995 - 1997 (CDC, 2000)

25. Dioxin/PCB Exposure Trends • Environmental Levels • Peaked in late ’60s/early ’70s – decline since confirmed by sediment data • Decline also supported by Emissions Inventory – shows significant decrease from ’87 to ‘;95 (~80%) • Human tissue data suggest mid-90s levels approximately half of 1980 • 55  25 ppt TEQ lipid (~5ng/kg ww) • Decrease continues • Success of Regulatory Agenda

26. Dioxin TEQ Levels (PCDDs/PCDFs) in U.S. Residents Have Fallen from 1960s (Lorber, 2002)

27. Mean and Range of TEQs By Age Group 12-19 20-39 40-59 60+ Age Group (years) (Needham, 2005)

28. Wildlife and Domestic Animals Great Lakes fish, birds, mammals Baltic seals, Dolphins Developmental/reproductive effects Immunological effects Effects observed at environmental levels Cows, Horses, Sheep, Chickens Effects observed during poisoning episodes Laboratory Animals Fish Amphibians Turtles Birds Rats Mice Guinea Pigs Hamsters Rabbits Dogs Non-human primates Adverse Effects

29. BIOCHEMICAL Induction of Drug Metabolizing Genes Cyp1A1/2, 1B1; GST; UDPGT; ALDH… Induction of Proliferation Genes Induction of Cytokines TNF, IL-6, IL-1β Induction of Oxidative Stress Induction of Growth factors/receptors TGFs, EGFR… Modulation of Hormones/Receptors TOXIC LethalityWasting Gonadal/Lymphoid Atrophy Hyperplasia/Metaplasia Endocrine Disruption Carcinogenicity Repro/Developmental toxicity Functional Devpt. Toxicity Dermal Toxicity Immunotoxicity Neurotoxicity Hepatic Toxicity Cardiovascular Toxicity Bone/Teeth Toxicity Effects of Dioxins

30. Multiple Effects Multiple Tissues Both Sexes Multiple Species Throughout Vertebrata Molecular/ Biochemical Metabolic/ Cellular Tissue/Organ Growth/ Differentiation Wasting/Death Effects of Dioxins

31. Dioxin Effects Require the “Ah Receptor” • Highly conserved protein • throughout Vertebrates • Related Proteins in Invertebrates • Member of Growing Family of Key Regulatory Proteins • Development, Aging, Hypoxia, Daily Rhythms • Necessary, but Not Sufficient, for All of the Effects of Dioxins

32. Mechanism of Action AIP,.. TCDD, ... hsp90 Other Proteins AhR hsp90 Arnt HIFa, Sim,... Transport Mechanism Rb, RelA,… AIP,.. hsp90 O O O O Cl Cl Cl Cl Cl Cl Cl Cl phosphorylation/ dephosphorylation Cl Cl Cl Cl Cl Cl Cl Cl O O O O hsp90 chromatin Co-activators Co-repressors Differentiation and Proliferation AhR BTFs Arnt BTFs DRE TATA Changes in protein levels (e.g., CYPIA1, IL-1, ...) Altered gene expression mRNA

33. Nearly All Vertebrate Animals Examined Respond to DioxinsWhat about People? • People have the Ah Receptor and the other members of its signaling complex. • Human cells and organs in culture respond to Dioxins. • Biochemical Responses have been Measured in Exposed People. • Subtle effects have been detected in the General Population. • Adverse Effects have been seen in highly exposed populations. • THE REAL QUESTION IS NOT CAN PEOPLE RESPOND TO DIOXINS, BUT AT WHAT DOSES THEY RESPOND!

34. Unfortunate Poisoning Episodes • PCBs/PCDFs • Japan (“Yusho”) • Taiwan (“Yucheng”) • PBBs/PBNs • Michigan • TCDD • Seveso, Italy • Vienna, Austria • Ukraine • Clear Evidence of Adverse Health Effects

35. Viktor Yushchenko(Before and After)

36. Cardiovascular Disease Diabetes Cancer Porphyria Endometriosis Decreased Testosterone Chloracne Biochemical Enzyme Induction Receptor Changes Developmental Thyroid Status Immune Status Neurobehavior Cognition Dentition Reproductive Effects Altered Sex Ratio Delayed Breast Devpt Dioxins’ Effects in People

37. Chloracne Classic Toxic Effect • “Hallmark of Dioxin Toxicity” • High-Dose Response • Genetic Polymorphism • Occurs in People, Monkeys, Cows, Rabbits, and Mice • Associated with multiple problems with skin, teeth, hair and nails following prenatal exposure

38. HEALTH EFFECTS IN “HIGHLY” EXPOSED POPULATIONS • Exposures Are Not As High As We Once Thought:10-100X Background (“Ambient”) • Occupational Populations • Chloracne, Cancer, Heart Disease, Diabetes, ... • Poisoning Episodes • Chloracne. Cancer, Heart Disease, Diabetes, Reproductive, Developmental, Hormonal and Immune Effects

39. Peak Dioxin Body Burden Levels in Background Populations and Epidemiological Cohorts

40. EFFECTS SEEN IN ADULTS AT BACKGROUND EXPOSURES • Type II Diabetes • Decreased Glucose Tolerance • Hyperinsulinemia • Mechanistic Plausibility • Endometriosis • Hormone Disruption and Immune Suppression • Animal Models • Cancer????

41. All Cancer ED01 and Slope Factor Calculations from Published Studies

42. HEALTH OUTCOMES IN PRENATALLY-EXPOSED CHILDREN • Studies in the US (Michigan, North Carolina, Lake Oswego); Japan; the Netherlands; Sweden; Finland • Low Birthweight • Cognitive and Behavioral Impairment • Immune System Effects • Hormonal Changes (Thyroid Effects) • Altered Dentition

43. Dioxin Effects of Greatest Concern • Developmental Alterations Occurring at “High End” of Background Population • Decreased neuro-optimality and IQ • Altered Behavior • Altered Immune System • Altered Hormone Systems • Altered Growth

44. Are Health Effects Occurring in the General Population? • What Effects? • Are they Adverse? • Who are most Susceptible? • Can we Predict the Future?

45. What You See Depends on How and Where you Look! • Subclinical Effects Can have Population Impacts • Think of the “LEAD” Example • “Second Generation” Effects • Exposed Mothers Can Result in Developmental Neurological, Reproductive and Immune Effects in Children • Exposed Fathers Can Result in Fewer Boys

46. Benefits of Nursing Outweigh the Risks! • Majority, if not all, of the effects are associated with in utero exposure. • Nursing infants do better than those who are bottle-fed (Given the same level of prenatal exposure). • Nursing leads to greater infantile exposure, but this does not have long term effects on the adult body burden.

47. Key to Epidemiology Studies on Dioxins • Multiple chemicals • EVERYONE has Some Exposure • Approach to Consider • Distribution of Populations • Altered Sensitivity/Susceptibility

48. Body Burdens Associated with Effects in Animals

49. Dose/Response Relationships • Biochemical Effects Occur in Animals Within Range of General Population Body Burdens • Within 10X of Current Body Burdens • Endometriosis and Immune Suppression in Adults • Developmental Problems – learning, immune, reproductive, teeth • Within 100X of Body Burdens • Porphyrin Accumulation • Cancer

50. Integrating Exposure and Effects M-O-E = exposure of interest low effect level Avg. Daily Intake = 1-2 pg TEQ/kg/day WHO TDI (1998) = 1-4 pg TEQ/kg/day Cancer (A&H) Altered Glucose Tolerance,Insulin Metabolism, Diabetes * Dev.Eff. (Dutch, Japanese, Finnish, German Studies) Low Dose Animal Effects1 Average Body Burden --------------------------------------- 10-2 10-1 100 101 102 103 104 Body Burden (ng/kg) A = Animal H = Human 1 enzyme induction, cellular effects, viral susceptibility, oxidative damage, developmental effects, endometriosis