Ur,:ted States
Env.ronmentai Protection
Agency
Of^ce of
Public Affairs'A-i 07)
Washington DC 20460
&EPA Dioxin Tier 4
October :9
905R84116
Answers to Commonly Asked Questions
i.
Background
The National Oioxin Study is a
multi-media study mandated by
Congress to examine the potential
sources and risks due to dioxin in the
environment. The study is organized into
seven tiers or categories ranging from
sites where known dioxin containing
chemicals have been manufactured (Tiers
1 and 2) to sites with no known
manmade contamination (Tier 7). A
comprehensive explanation of the
National Dioxin Study is covered in the
EPA Dioxin Facts, July 1984.
Q
What is the Tier 4 study?
A Tier 4 of the National Dioxin Study
is a subpart of the EPA National Study
which focuses on the potential emissions
of dioxins from combustion sources. The
study will attempt to assess the
probability of dioxin emissions that may
be formed in the actual combustion
process generated from boilers,
incinerators and other sources. The study
will also quantify such emissions and
their concentrations, assess any health
and environmental risks involved and
develop the basis, if necessary, for any
regulatory or control effort
Q
What is included in 'dioxins'?
r\ Dioxin is often used to refer to any
or all of 75 chlorinated isomers of the
organic compound, dioxin. Frequently,
2,3.7,8-Tetrachlorodibenzo-p-dioxin
(2,3,7,8-TCDD) is the isomer associated
with the term as it is considered one of
the most toxic compounds known. The
Tier 4 study will also provide results for
2,3,7,8-TCDD and certain groups
(homologues) of isomers which may also
have health implications.
\JL What types of combustion sources
wilt b* tested and when?
A The following combustion sources
are expected to be tested for the
potential emission of 2,3,7,8-TCDD in the
fall of 1984 through the summer of 1985:
• Sewage Sludge Incinerators
• Black Liquor Boilers
• PGP Sludge Incinerators
• Carbon Regeneration (industrial)
• Charcoal Manufacturing
• Wire Reclamation
• Wood Stoves
• Wood Boilers (firing PCP treated wood)
I
• Mobile Sources
• Small Spreader-stoker Coal Boiler
• Chlorinated Organic Waste Incinerators
• Lime-Cement Kilns Co-Fired with
Chlorinated Organic Wastes
• Commercial Boilers Firing Fuels
Contaminated With Chlorinated Organic
Wastes
• Forest Fires
• Apartment House Flue-fed Incinerators
• Agricultural Burning
• Landfill Flares
Residential Oil Burners Burning Waste
Oil
Q
What are the potential hazards
from combustion sources to the public?
A Though 2,3.7,8-TCDD and other
dioxin isomers are toxic compounds an
are known to exist in emissions from
some combustion sources. At this time,
available data does not indicate that
there is an unreasonable risk to public
health. For example, municipal
incinerators have been identified as one
of the largest combustion sources of
dioxins, but they have not been found tc
emit sufficient quantities or
concentrations to be of unreasonable ris
to public health. However, since it has
been hypothesized that many
combustion sources have a potential to
emit dioxins, the Tier 4 testing is aimed
at collecting actual emissions data so
that these hypotheses ann be confirmed
or disproven.
Q
When will the testing results be
known?
A After all the identified sources are
tested, the samples will be analyzed at
EPA and contract laboratories. The final
data are expected to be available and
summarized in a report scheduled for tru
end of 1985.
Q. What will EPA do if dioxins are
found?
A A risk assessment will be made to
determine the likelihood of harm to
public health. If risks are significant.
follow-up regulatory and control
measures may be warranted. The data
collected from Tier 4 will provide
information to determine whether dioxir
should be listed as a hazardous air
pollutant.
Municipal Solid Waste Incinerators
Industrial Boilers Co-Firing Wastes
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