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Overview of Dioxin Biomonitoring Data in
the 2005 CDC National Exposure Report
July 21, 2005
Introduction
With its Third National Report on Human
Exposure to Environmental Chemicals, released July 21,
2005, the U.S. Centers for Disease Control and Prevention
(CDC) provides a glimpse of the levels of 148 chemicals in
a representative sample of the U.S. population. This short
interpretive document focuses exclusively on one group of
those chemicals-dioxins1
. Blood levels of dioxins were measured in the U.S. population
as part of the National Health and Nutrition Survey (NHANES)
in 1999-2000 and in 2001-2002, and were reported in the CDC's
second and third national exposure reports in 2003 and 2005,
respectively.
CDC's Third National Report confirms that dioxin levels
in human tissues are very low. CDC affirms the new data support
the observation that human blood levels of dioxins have decreased
by more than eighty percent since the 1980s. Findings also
show that there are generational differences in dioxin levels.
Is there an increase in dioxin blood levels measured
between the 2003 and 2005 reports? No. Dioxin levels in
humans have been decreasing since the early 1970s and scientific
models project continued declines in all age groups. The appearance
of an increase between the last two CDC reports is due to
the following:
- Additional dioxin/furan compounds were
analyzed for in the 2005 report compared to the 2003 report2.
- Missing data in the 2003 and 2005 reports
were treated in calculations3
as "zero" levels of dioxins. An "artificially" low average
dioxin level resulted because there was more missing data
in the 2003 report than the 2005 report.
- The volume of individual blood samples available for dioxin
analysis in the 2003 report was too small to detect low
levels of dioxins. (This was corrected in sampling for the
2005 report.)
| Dioxin Levels: Historically
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.And Looking Ahead |
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Figure 1
(See Appendix 1
for data sources and notes for Figures 1 and 2.)
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Figure 2
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Scientific models show levels of dioxins are declining
in all age groups.
Since the 1970s, levels of environmental dioxins have decreased
significantly. Dioxins accumulate in human tissue and are
slowly eliminated at a rate determined by the amount of dioxin
in the body. Scientists tell us that levels of dioxins in
human blood are related to a person's birth year: children
today have lower levels of dioxins in their blood than their
parents and grandparents did when they were children. Moreover,
with today's lower exposures, babies born today will likely
never reach the levels of dioxins of their grandparents.
How low can they go?
Humans will always be exposed to some low level of dioxins
because there are natural sources of these compounds from
which we cannot escape. For example, dioxins are formed in
forest fires and volcanoes.
Low body levels of dioxins are the result of low average
intake of dioxins.
The main source of human exposure to dioxins is the diet.
The U.S. Environmental Protection Agency (EPA) and U.S. Food
and Drug Administration (FDA) have estimated daily intake
levels of dioxins, and these intake amounts fall well below
safe intake guidelines set by the U.S., Europe, Canada, Japan
and the World Health Organization.
Figure 3: The Current
Daily Dioxin Intake of the
Average American is Below Government Guidelines4
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Daily Intake in pg-TEQ/kg/day
WHO, World Health Organization; JECFA,
Joint FAO/WHO Expert Committee on Food Additives; ESCSF,
European Commission Scientific Committee on Food; ATSDR,
Agency for Toxic Substances Disease Registry; TEQ, Toxic
Equivalency; pg-TEQ/kg/day, picogram-TEQ per killogram
per day.
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EPA data show a significant decline in emissions of dioxins.
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(See Appendix
1 for data sources and
notes for Figure 4.) |
Dioxins have never been manufactured for commercial purposes.
They are formed in trace amounts in a variety of combustion
environments, both natural (e.g., forest fires and volcanoes)
and those controlled by man (e.g., energy generation, chemical
manufacturing, backyard trash burning, vehicle fuel combustion
and various types of waste incineration). Government regulators,
industry and environmentalists have worked hard to reduce
emissions of dioxins to the environment. These pollution control
efforts resulted in estimated declines in emissions from EPA-quantified
sources of 92 percent between 1987 and 2004.
Where do dioxins come from today?
The pie chart below illustrates the estimated contributions
of dioxin sources in 2004. The CDC states in its 2005 National
Exposure report, "Releases from industrial sources have decreased
approximately 80% since the 1980s. Today, the largest release
of these chemicals (dioxins) occurs as a result of the open
burning of household trash and municipal trash, landfill fires,
and agricultural and forest fires."
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(See Appendix
1 for data sources and notes for Figure 5.) |
For More Information:
Appendix 1: Data Sources and Notes for Figures
Figure 1
Data for 1965, 1985 and 1995 are modeled average dioxin-TEQ
for ages 20 to 70 (Lorber, 2002).
Data for 1996-2001 are measured average TEQs from individuals
age 15 to over 60 from LA, MO, NC, and NY (588 people) and
includes 4 PCBs (Patterson et. al., 2004).
Data for 1999-2000 are from CDC (2003) for people aged 20
and over.
Data for 2001-2002 are from CDC (2005) for people aged 20
and over.
Range for governmental exposure guidelines is 8 - 32 ppt,
which includes dioxins and PCBs with TEFs.
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Figure 2
Chlorine Chemistry Division of the American Chemistry Council
modeled the future body levels (from 2002 to 2020) starting
with the mid-point measurement for the average dioxin ppt-TEQ
for each reported age group (20 years and older) reported
in the Third National Exposure Report (2005).
Chlorine Chemistry Division of the American Chemistry Council
based projections for the 15 year old age group on the 2001-2002
pooled blood samples (Needham, 2005).
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Figure 4
Data for 1987 and 1995 are from the "US Environmental Protection
Agency Inventory of Sources of Dioxin-Like Compounds in the
United States-1987 and 1995" http://cfpub.epa.gov/ncea/cfm/dioxindb.cfm?ActType=default.
Year 2000 data are from the "External Review Draft: The Inventory
of Sources and Environmental Releases of Dioxin-Like Compounds
in the United States: The Year 2000 Update," EPA (March, 2005).
http://www.epa.gov/NCEA/pdfs/dioxin/2k-update/pdfs/Dioxin_Frontmatter.pdf
The 2002/4 data are based on EPA projections assuming full
compliance with regulatory levels by this period and the closure
of a copper smelter (personal communication, Dwain Winters,
US EPA, 9-9-02).
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Figure 5
*With the exception of forest fire data, dioxin
emissions source data are based on EPA projections for 2002/4,
assuming full compliance with regulatory levels and the closure
of a copper smelter (personal communication, Dwain Winters,
US EPA, 9-9-02).
#The dioxin contribution from forest fires was
calculated using National Interagency Fire Center acreage
burned in year 2004 wildland fires; an emission factor of
20 ng-TEQ/kg biomass burned [Gullett and Touati (2003)]; and
a biomass consumption rate of 9.43 metric tons/acre in areas
consumed by wildfires from Ward et al. (1976), as cited in
the EPA Draft Dioxin Reassessment (September, 2000).
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End Notes
1"Dioxins" refers to 7 dioxins
and 10 furan chemical compounds. There are 210 known chlorinated
dioxins and furans, but only 17 of interest. [return
to top]
2Of the 17 dioxin compounds
of interest, 15 were measured for the 2003 report, but all
17 were measured for the 2005 report. [return
to top]
3Calculations were performed
by the Chlorine Chemistry Division of the American Chemistry
Council. [return to top]
4Government guidelines are set
to be protective of individuals over a lifetime. [return
to top]
References:
CDC (2005). Third National Report on Human Exposure to Environmental
Chemicals, Atlanta, GA., NCEH Pub. No. 05-0570. July 2005.
See http://www.cdc.gov/exposurereport/
CDC (2003). Second National Report on Human Exposure to Environmental
Chemicals, Atlanta, GA., NCEH Pub. No. 02-0716. Revised March
2003. See http://www.cdc.gov/exposurereport/
Gullett, B.K. and Touati, A. (2003). PCDD/F emissions from
forest fire simulations, Atmospheric Environment 37,
p. 803-13.
Lorber, M. (2002). A pharmacokinetic model for estimating
exposure of Americans to dioxin-like compounds in the past,
present, and future. Science of the Total Environment. 288.
81-95.
Needham, L.L. (2005). Exposure Levels as Determined by Serum
Levels from Control Data Sets and National Health and Nutrition
Examination Survey (slides show preliminary data), presentation
to the National Academy of Sciences, Expert Panel on Review
EPA's Exposure and Human Health Reassessment of TCDD and Related
Compounds, Project BEST-K-03-08-A. February 2, 2005. Slides
are available by contacting NAS staff. http://www4.nas.edu/cp.nsf/Projects+_by+_PIN/BEST-K-03-08-A?OpenDocument.
Patterson, D.G., Canady, R., Wong, L-Y., Lee, R., Turner,
W., Caudill, S., Needham, L., Henderson, A. (2004). Age specific
dioxin TEQ reference range. Organohalogen Compounds
66, 2878-2883.
Ward et al., 1976 An update on particulate emissions from
forest fires. Presented at: 69th Annual Meeting of the Air
Pollution Control Association, Portland, OR June 27-July 1,
1976] as cited in the EPA Draft Dioxin Reassessment, September,
2000.
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Dioxin TRI Data - Cl2 Sector
