Se ha denunciado esta presentación.
Utilizamos tu perfil de LinkedIn y tus datos de actividad para personalizar los anuncios y mostrarte publicidad más relevante. Puedes cambiar tus preferencias de publicidad en cualquier momento.
Restoration Advisory Board
Former NAS Moffett Field

Polychlorinated Biphenyls
          (PCBs)

  Patrick Wilson, Ph.D., ...
THE DOSE MAKES THE
         POISON
     All Substances are Poisons.
There is None Which is Not a Poison.
The Right Dose Di...
PCB PHYSICAL PROPERTIES
•Colorless
•Odorless
•Low vapor pressure
•Viscous liquid or solid
•Low electrical conductivity
PCBs CHEMICAL PROPERTIES
•   Flame Retardant

•   Lipophilic (mix easily with oil or fat)

•   Very Stable
PCB Molecular Structure
          meta        ortho    ortho         meta
                 3'    2'         2          3

...
Fully-Chlorinated PCB Molecule

     Cl    Cl Cl        Cl


Cl                           Cl


     Cl    Cl   Cl      Cl
Key Concepts
Polychlorinated biphenyls (PCBs): a mixture of
compounds containing the biphenyl structure with
varying numbe...
Key Concepts
Congener: One of the 209 possible PCB molecules, each
distinguished by the number and arrangement of chlorine...
Key Concepts
Dioxins and Furans: Two families of chemicals related
by their similar physical and biological characteristic...
Why Were PCBs Banned??
•   Persistent in the environment

•   Bioaccumulation and bioconcentration
    effects

•   Found ...
Toxicities of Concern
•   Cancer
•   Non-cancer Toxicity
        Kidney
        Liver
        Skin
        Immune System
 ...
What Are the Acute Health Effects of
              PCBs?

                  Chloracne (reversible)


                  Irr...
What Are the Chronic Health Effects of
              PCBs?
EPA Risk Assessment Guidelines for
          Carcinogens
Group A - Human Carcinogens

Group B - Probable Human Carcinogen
...
POTENTIAL FOR HUMAN EXPOSURE
Superfund Sites With PCB Contamination
National PCB Fish Advisories
Bioaccumulation/Biomagnification
Mean Concentration of PCBs in Human
           Breast Milk
Serum PCB Concentrations
Serum PCB Concentrations
PCB Half Lives
How Are PCBs and Dioxins Related?


•Chemical structural similarity
   •Dioxin-like PCBs pr Coplanar PCBs (CPCBs) are simi...
PCB Congeners Toxicity
                                    Exhibit A-2
              TOXIC EQUIVALENCY FACTORS (TEFs) FOR ...
Intelligence is about making decisions
based upon imperfect knowledge and
among partially good choices.


Douglas R. Hofst...
EPA presentation to the Moffett Field Restoration Advisory Board on May 15, 2008, giving background on Poly-Chloronated Bi...
Próxima SlideShare
Cargando en…5
×

EPA presentation to the Moffett Field Restoration Advisory Board on May 15, 2008, giving background on Poly-Chloronated Biphenyls (PCBs).

4.196 visualizaciones

Publicado el

Publicado en: Salud y medicina, Tecnología
  • Sé el primero en comentar

  • Sé el primero en recomendar esto

EPA presentation to the Moffett Field Restoration Advisory Board on May 15, 2008, giving background on Poly-Chloronated Biphenyls (PCBs).

  1. 1. Restoration Advisory Board Former NAS Moffett Field Polychlorinated Biphenyls (PCBs) Patrick Wilson, Ph.D., M.P.H. Senior Regional Toxicologist U.S. EPA
  2. 2. THE DOSE MAKES THE POISON All Substances are Poisons. There is None Which is Not a Poison. The Right Dose Differentiates a Poison and a Remedy Paracelsus (1493-1541)
  3. 3. PCB PHYSICAL PROPERTIES •Colorless •Odorless •Low vapor pressure •Viscous liquid or solid •Low electrical conductivity
  4. 4. PCBs CHEMICAL PROPERTIES • Flame Retardant • Lipophilic (mix easily with oil or fat) • Very Stable
  5. 5. PCB Molecular Structure meta ortho ortho meta 3' 2' 2 3 para 4' 4 para 5' 6' 6 5 meta ortho ortho meta Structure of Polychlorinated Biphenyl (PCB) Molecule
  6. 6. Fully-Chlorinated PCB Molecule Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl
  7. 7. Key Concepts Polychlorinated biphenyls (PCBs): a mixture of compounds containing the biphenyl structure with varying numbers (i.e., one to ten) and arrangements of chlorine atoms attached. Aroclor: One of nine commercial PCB mixtures, with varying levels of chlorination, formerly produced in the United States. The percent of chlorine content varies across the different Aroclors, depending on their intended uses. Generally, samples of pure Aroclor exhibit a distinct pattern of congener concentrations, but transformations during routine use and/or weathering can alter these patterns.
  8. 8. Key Concepts Congener: One of the 209 possible PCB molecules, each distinguished by the number and arrangement of chlorine atoms. Commercially-produced PCB mixtures collectively include about 175 congeners, some at concentrations so low they are not detectable in environmental samples. One hundred and ten of the 209 congeners typically constitute 98 percent of PCB mass measured in samples. Dioxin-Like Congener: One of 12 PCB congeners that exhibits toxicity similar to that of dioxin as the result of structural similarity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). The 12 dioxin-like PCB congeners are: 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169 and 189.
  9. 9. Key Concepts Dioxins and Furans: Two families of chemicals related by their similar physical and biological characteristics. Several hundred different compounds exist among the chlorinated dibenzo-p-dioxins (CDDs) and the chlorinated dibenzofurans (CDFs). The term “dioxin” is often used to refer to the most toxic dioxin compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). CDDs and CDFs are products of combustion created by anthropogenic activities and natural processes. Weathering: Physical, biological, or chemical processes that can alter the chlorination pattern of a PCB molecule, and thereby change the congener composition of environmental mixtures of PCBs.
  10. 10. Why Were PCBs Banned?? • Persistent in the environment • Bioaccumulation and bioconcentration effects • Found in virtually all human fat tissue Humans 2300 ng/g (ppb) Human Breast Milk 1200 ng/g (ppb)
  11. 11. Toxicities of Concern • Cancer • Non-cancer Toxicity Kidney Liver Skin Immune System Nervous System DevelopmentalReproductive System
  12. 12. What Are the Acute Health Effects of PCBs? Chloracne (reversible) Irritation of eyes, face & skin
  13. 13. What Are the Chronic Health Effects of PCBs?
  14. 14. EPA Risk Assessment Guidelines for Carcinogens Group A - Human Carcinogens Group B - Probable Human Carcinogen Group C - Possible Human Carcinogen Group D - Not Classifiable Group E - Negative Evidence
  15. 15. POTENTIAL FOR HUMAN EXPOSURE
  16. 16. Superfund Sites With PCB Contamination
  17. 17. National PCB Fish Advisories
  18. 18. Bioaccumulation/Biomagnification
  19. 19. Mean Concentration of PCBs in Human Breast Milk
  20. 20. Serum PCB Concentrations
  21. 21. Serum PCB Concentrations
  22. 22. PCB Half Lives
  23. 23. How Are PCBs and Dioxins Related? •Chemical structural similarity •Dioxin-like PCBs pr Coplanar PCBs (CPCBs) are similar dioxins •Preliminary test data indicate correlation between chemical structure and toxicity •Products of Incomplete Combustion (PICs) of PCBs •Dioxins •Dioxin-like chlorinated polycyclic aromatic hydrocarbons (PAHs) •Presence of dioxins or dioxin-like chlorinated PAHs results in risk regardless of route of formation
  24. 24. PCB Congeners Toxicity Exhibit A-2 TOXIC EQUIVALENCY FACTORS (TEFs) FOR THE DIOXIN -LIKE PCBS Humans/ 1 2 2 Congener Mammals Fish Birds 77 0.0001 0.0001 0.05 81 0.0003 0.0005 0.1 105 0.00003 <0.000005 0.0001 114 0.00003 <0.000005 0.0001 118 0.00003 <0.000005 0.00001 123 0.00003 <0.000005 0.00001 126 0.1 0.005 0.1 156 0.00003 <0.000005 0.0001 157 0.00003 <0.000005 0.0001 167 0.00003 <0.000005 0.00001 169 0.03 0.00005 0.001 189 0.00003 <0.000005 0.00001 1 . WHO TEFs for humans and mammals were updated in 2005 (Van den Berg, et al., 2006) 2 WHO TEFs for fish and birds were published most r cently in Van den Berg, et al. (1998). e
  25. 25. Intelligence is about making decisions based upon imperfect knowledge and among partially good choices. Douglas R. Hofstadter Pulitzer Prize Winner

×