NCD980602163_19830606_Warren County PCB Landfill_SERB C_Dioxin Report article - Both Incidence, Control of Dioxin Are Highly Complex-OCR

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Both Incidence, Control of Dioxin
Are Highly Complex
A by-product of many industrial processes, dioxin
presents big problem in· waste disposal; the technology is
on hand, but economic, political barriers persist
Ward Worthy
C&EN Chicago
C&EN's dioxin coverage
now turns to the practical
world of industry. How
and where exactly,,!..._
10x1nslurn UP,.? And how
canlhev·be controlled?
It's a' complicated situa-
tion, in part because of the
,yriad of dioxin structures
and reactions. So a short
review of chemistry is in
order before a look at com-
mercial reactions and dis-
posal methods.
On the dioxin molecular frame-
work-consisting of two benzene
rings connected by two oxygen
bridges-there are eight positions
where substitutions can take place. In
any or all of these eight substituent
positions, hydrogen atoms can be
replaced by other atoms or by organic
or inorganic radicals. The number of
possible com bi nations is almost
limitless.
Tht>se days, of com~e, when people
speak of dioxins, they likely are re-.
ferring to the black-sheep branch of
the family, the chlorinated dioxins
(CDDs), in which one to eight of the
substituent positions are o~upied by
chlorine atoms. The a,:rangement
allows for a total of 75 different
CDDs; most but not all of them have
either bee·n synthesized or identified
as by-products or contaminants in
other materials.
........
·:-,-:. ·-:· ... _
There are 22 isomers of tetrachlo-
rodibenzo-p-dioxin (TCDD) alone,
all of which have been synthesized.
However, the bulk of attention has
gone to what is apparently the most
toxic member of the group, 2,3,7 ,8-
TCDD. This isomer is svmmetrical
across both horizontal and vertical
axes. At room temperature, it is a
colorless crystalline solid. -It roelts"at
· 305 °C. Chemically, it is quite stable;
for example, its thermal dest~n
requires tem_Reratures of more than
"7UlPC~-It'is lio"hi ic an it in s
stro'n°gly tosoils and other particµla_te
~a e_r: 1s on y ipirJp~y ,teluble i
water and most organic liquids .
.. -Although 2,3,i,8-TCDD is the most
notorious of the dioxins, it usually
occurs mixed with other chlorinated
dioxins. Some of these also are quite
toxic.
How, then, do these compounds
arise? To oversimplify the situation,
a dioxin comes from a
dioxin precursor: this
compound must contain an
ortho-substituted benzene
ring, and one of the sub-
stituents must include an
oxygen atom attached di-
rectly to the ring. In addi-
tion, two substituents (but
not the oxygen atom itself)
must be able to react with
each other to form another
compound. The reaction is
favored by bask conditions
-ana1,y temperatures in the G
range 180 to 400 ° The JS't:'",r
presence-of a catafystsuch as ~er 7r2.-"'r
powder, promotes the re~tion.
Although7M re exist a multitude
of organic chemicals that qualify as
dioxin precursors, perhaps the most
notable of these is 2.,4,5-trichloro•
phenol (TCP). It's notable-if for no
other reason-because its geometry
is such that when two TCP molecules
condense, the likely result is
2,3,7,8-TCDD. According to several
studies, the reaction takes place in
two steps, with a diphenyl ether
serving as the intermediate.
That's one way dioxins can be
formed. However, it's not the onlv
way. Actual findings don't alway's
conform to what would be expected
from that straightforwa'!'d conden-
sation reaction. Other, more complex
mechanisms for forming CD Os have
been discovered and still others
proposed.
In fact, a case can be made-and
June e. 1963 C&eN s1
I
Dioxin Report
has been made-that many reactions
can occ;ur whenever organic and
chlorine-containing materials are
burned together, and that one of the
things that happens is the formation
of trace amounts of CDDs. There is ·
evidence to suggest that the hy-
pothesis is true, at least in principle,
at least some of the time. Whether it's
relevant to current problems of
dioxin contamination is a matter of
controversy, . with the dispute
stemming in good part from differ-
2,3,7,8-TCDO ls one compound In a family
All dibenzo-p,dioxlns have a three-ring
structure consisting of two benzene
rings connected by oxygen atoms:
And 2,3, 7,8-tetrachlorodibenzo-~ioxln
Is one of the 75 possible chlorinated
dioxins:
ing opinions as to what level of Relat$d are chlorinated dlbel'llofl.zans:
dioxins, if any, is acceptable in the
environment.
In the great majority of everyday
combustion ptocesses, the amount of
dioxins produced is likely to be very
-small-and not much can be done
about it anyway. In certain cases,
however, the combustion hypothesis
should be (and is being) looked at
from a practical standpoint: for ex-
ample, in the incineration of munic-
ipal wastes that may contain signifi-
cant amounts of polyvinyl chloride
or chlorophenol-preserved wood
products.
Dioxin precursors combine
to form dioxin In the general
reaction:
For example, 2,3, 7,8-TCDD Is the mos1
llkely result from the reaction of
· 2,4,5-trlchtorophenol:
--NaCl
CIXXONa
2 I · -NaCl
Cl Cl
.c'~xxcr
C~ Cl Regardless of how many odd ways
trace amounts of dioxins may enter
the environment, and regardless of
what they may mean, the fact re-,
mains that those dioxin-related in),:·.chlorobenzene. Reaction of 1,2,4,5-monitored very carefully for dioxin,
ddents that have become publk·,:,:~~trachlorobenzene with sodium content. However, purity is a relative
scandals-Seveso, agent orange, hy~oxide yields, mostly, the sodium term-in the chemical industry, at
Love Canal. Times Beach-can fairly salfof TCP. That salt can be used as is least-and, in general, higher purity
be traced back to the chemical in-to make derivatives, or it can be is reflected in higher cost for the
dustry. Specifically, they can be neutralized with a mineral acid to product. So, before the nature of the
traced to producers of halogenated give TCP. dioxin problem became evident, -
phenols and their derivatives. Process details va-ry. For instance, producers weren't always so careful.
Among these chlorinated organics, one of several solvents (including Consequently, there have been many
o-~hlorophenols deserve particular methanol and water) can be used for confirmed instances in which com-
attention. One of these, TCP, practi-the hydrolysis. Proper attention to merdal products-some quite widely
cally demands especially dose scru-temperature o1nd pH control can used-have been found to contain
tiny. TCP is made in large quantities. minimize the formation of dioxins _ trace levels of dioxin.
It's an intermediate in the manufac-during the hydrolysis. However, Many millions of pounds of chlo•
ture of several other widely used trace amounts of dioxins usually are rinated phenols and related com-
products, including 2.,4,5-trichloro-formed, along with other impuri-pounds are made and used each year.
phenoxyacetic acid (2,4,5.'r) and re-ties. Not surprisingly, they turn up ev-
lated herbicides. As noted, its struc-As one step in the purification erywhere. Pentachlorophenol (PCP),
ture is such that 2,3,7,8-TCDD is a process, the crude salt is washed with for example, is used in large tonnages
likely by-product of its manufacture. toluene, which removes some of the to preserve wood. PCP, TCP, and re-
TCP's the one that directly or indi-high-boiling impurities, including lated products are used as biocides
rec:tly, has caused most of the trouble dioxins. The organic and aqueous for process and cooling waters in
with dioxins. phases are allowed to separate and many industries and in a host of
Although it's not the only possible the toluene layer is sent to a still for small-volume applications.
way to do it, commercial production recycling. 'rhe product can be further Given that an ,..QfJ.hese ..mdllcts
of TCP in the U.S. was carried out by purified-for example, by vacuum may contc1:~!l-~.9.!11~ J~n l .of .d..i~in
-hydrolyzing 1,2.4,S~tetr3chloroben-distillation. --cOltlamination, there are several
2:ene, which is one of the isomers Current production of chlorinated soufc§~ whi~h clio~i~s can ~tcr
obtained b)' rechlorinating o-di-phenols and related products is the environment. Obviously, the
...... ~~ ;,.. • .,,,. f
52 June 6. 1983 C&EN
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I: . _::., ___ .,..:.. ______________________________________ _
products themselves are one source,
and this can be a matter of concern to
those who work routinely with those
products. But they probably are~'t
the most important source, from the
standpoint of imminent danger to
the public. Many dilution effects are
at work, so just traces of dioxins are
what finally get into the environ•
ment.
Many combustion processes afford
some possibility of reJease-or even
creation-of dioxins, with the degree
of hazard depending on what is
being burned and the conditions
under whid:l combustion takes place.
Again, concentrations typically are
very low. · .
Accidents or mistakes in manu-
facturing chlorinated organics are
another potential source of dioxins.
They can be an extremely dangerous
SQurce of heavy local contamination,
as demonstrated by the release from
the TCP reactor at Seveso. In addi-
tion, there have been numerous
other smaller, less-publicized-but
not necessarily insignificant-acci-
dents involving the making of TCP.
Aside from Seveso, the most fa-
mous cases of dioxin contamination
of the environment have resulted
from improper disposal, by certain
manufacturers or by their agents, 0£
products and process wastes con-
taining relatively high concentra-
tions of dioxins.
To return to the aforementioned
production example, crude TCP can
be purified by washing it with tolu-
ene (which is distilled and recycled,
so that the impurities accumulate in
the still bottoms). It can be further
purified by vacuum distillation
(again, the impurities collect in the
bottoms). The dioxins and other im-
purities aren't destroyed in these
operations. They're just moved
somewhere else and, in the process,
concentrated to even more danger-
ous levels.
These highly contaminated wastes
can be rendered essentially harmless
,by a.number of methods, including
incineration. That isn't what always
happened, however. Incineration is
a comparatively expensive disposal
option. In all too many instances, it
was cheaper-or so it seemed at the
time-just to put the stuff in drums
and burv it where it couldn't hurt
anybody. That would have been fine,
except that the drums inevitably
leaked and the dioxins (and other
nasty compounds) started showing
up in the water and soil around the
storage site, such as at Love Canal.
Or, as happened at Times Beach,
the producer simply turned his
wastes over to some guy with a truck,
who hauled them away, mixed the
dioxins with oil, and sprayed them
~.ver the countryside.
Once at large, dioxins spread at
varying rat~g_ru:l_to_v..arying.4~g~~
t1ffi51Ighsoii, water ruL~i.L. nd
throirgn ~iv~~It~Ll}_gs. The J!\tim.ate
fate ··of d19xms "'aepends.oA..CJ.l'.C.Um-
sl!Hfes·. Although the details vary, a
number of studies have shown that
dioxins are degraded rather qu~kly
6y su~ ..or a_xJ 'cial ultraviolet
l:ig t.""For this to happen, however,
ttre' photolytic rays must be able to
reach the dioxin molecules, and hy ..
drogen for the reaction must be
available from some organic donor.
ln the real world, such a hydrogen
donor usually is nearby-either
some other component of the waste
of which the dioxins are a part, for
example, or even the vegetation on
which the dioxins have been depos-
ited. n~u:s, .. 4t9>.c:_i~.~, spread thinly .in
t}le s~IT"F:UJ,.withiiu..f~il~~t... USU•
a)f,i.i!isappear Qt at le~t.4~m~ni,s. Jo
UJ'l"d~table, levels.·
:::._Howfrer;-o.nce dioxins _F_~rate
the soil;'J_hey are ere to st~y__fQr
quite-ff "fong !ime, according to_ a
number of-s"fudies. Some studies in-
dicate that no significant de radaf on
of dioxin~ occ rs m the soi . Other
studies sugge;t t at some egrada-
tion does take place, but it's usually
too slow to be of any comfort. In any
event, places like Seveso and Times
Beach demonstrate that dioxins, un•
disturbed, can persist in soils for
many years, unless they are washed,
blown, or otherwise carried away.
Since dioxins have s read rather
extensive y t roughout the enyi-
rolllm!n , w at can be done abouL
tnem~e omt rha,2.s,
Wnaf s ou@·be -dorie a out them?
":A"Jl-SWers fo ~tnel'irs uestfon .-e
f~ycl~;:'...!'-ns~·~_!'S to e second
ques 1on are much less C ear, an
SUOJi cf -fi)-honestdiTferenceso[ opinion":----·-·-··~·---· ·
"""lti the case of extremely low dioxin
1~~1~.W -P.AttLl?.~!... !tillion __Qr
.lo~!!.-::the answer to both questions
Making 2,4,5-trlchlorophenol
can lead to dioxin contamination
1 ,2,4,S-Tetrachlorobenzene
.---sodium hydroxide
Na-TCP In water
Hydrochloric
acid
Air emisslonsa
Alc:ohol
recycle
Toluene
Wastes• (still bottoms)
ConV&rslon• ----.(optional)
Wastewater•
Air emissions•
Wastes•
(stll! bottoms)
a .Potential aourcee of environmental dlcixln cootamlna\lon.
8ollrc.: Adoptod from EPA. "Croxrna"
is probablfE nothing, except to stem
th e high-eveJM?J.!rc~,_1Q._pte¥ertt anyrnoreo the ~aks, e~issiont .P.nd
in'I prop ff <ii$po!~l ___ ope!~!~~ns _. that
w~re the original source of mos of
the low-lever onfamiriaH on.
"i t e case of the more highly
contaminated dioxin dumps, there
are a number of things that could be
done, all of them quite a bit of trou-
ble. Although something should be
done to clean up these worst cases,
there is much disagreement as to
what. In the "in-between" cases, the
cost-benefit analyses get even blur-
rier, and there i:. even less agree-
ment.
June 6. 1983 C&EN U
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IU r . .L r
Dioxin Report
,-------------------------------=-========~-------,
GC, MS useful techniques in the analysis of dioxin t,o; MS analysis. The presence and
1 amount of specific isomers like mndard is a(kjed to help determine how 2,3, 7 ,8-TCDD then can be determined How does one determine whether and to
what extent something is contaminated
by dioxins? The easy answer is that It's
usually done with gas chromatography
and mass spectrometry. Bvt there's a lot
more to It than that. Normally, dioxins
are present. If at all. at levels ranging
from parts per million down to the van-
ishing point. They coexist with many
other compounds, and many of these
are present In much larger amounts and
capable of Interfering with . the anal-
.: ysls.
·· Since it's Impossible to run a sack of
dirt or a Coho salmon through even the
most user-friendly GC/MS setup, sample
preparation is an extremely important
part of the process. The first step Is to
transfer the dlox_lns (and other chlori-
nated organics) from the sample matrix
to an organic liquid, by a series of ex-
tractions. An isotopically labeled internal
UV light degrades dioxins
to less toxic products
much sample Is lost in later steps, and from the ratios of r-tatn""t{ey mass
to assist in Quantltation. 1 fragl!)en . __
The organic extract is cleaned up with ,With sueh technlques-:anacfepending
another series of washings with aqueous the nature of the sample. it's possible I base and acid wh.rtlons and distilled to detect and quantify dioxins down to \
water. Then the organic extract under-low parts-per.trillion levels with rea· ,
goes a sequence of prellrnlnary liqui sonable confidence. In the case of a
chromatographic separations, using "simple" sample like water, one ean go
variety of columns and eluents. All t e even lower. down to the parts-per--qua-
fractlons from these separations e drillion level, by ta~ing a very large
recombined and concentrated or sample and concentrating the dioxins
GC/MS analysis. into a much smaller volume by solvent
Usually, the sample first goes lhro h extraction. In the case of more complex
a GC/lowyresolutlon MS system fo samples, like soils, this approach is
preliminary screening. This can show probably beyond the capabilities Of to-
that TCDDs, for example, are present, ·s analytlcat laboratories.
but It Isn't sensitive enough to distinguish ·s is terr· , time-con-
among the various Isomers. If TCDD or sumlng, and expensive. A lot or work is
other dioxins of interest are revealed by going on to find simpler alternatives,
this prelimlnary analysis, the sample especially for th9 preliminary screening
then goes to a second GC/hlgh-resolu-steps.
'!'he basic disposal options for
dioxms are th e .. CfQr otli~
zardous wastes: to contain tb.enu:>r :2 --~~~ roy_ t~in:~:~9]£ear ~t
containm~ m J.~re..._Ja,n.d.£.ill
(witnallthat that irnpliesr.i-ndudi,n.g
"iffipervio-~jt.,. in~r.s .-and_et-er-mi l
C: .: ... monif~rmg of leachate -and, -su-r-
\ r6unding groundwaters i tis-
Perhaps the largest dioxin de-
struction operation to date involved
the incineration of more than 2 mil-
lion gal of agent orange left over
from defoliation activities in South-
east Asia. That operation took place
in 1977, in mid-Pacific Ocean, aboard
the seagoing incinerator MIT Vul-
canus, which at that time was owned
by a Dutch . company. Chemical
Waste Management, the current
owner of the ship, notes that more
trial burns of dioxin wastes are set to
take place soon in the Gulf of
Mexico.
54 June 6. 1983 C&EN
fa~tory means ~!.~~!th_ di in w~tes.----
~utse curity, like purity, is a rela-
tive term. Dioxins, at least some of
them, aren't considered just hazard·
ous wastes. They're considered ex•
tremely hazardous wastes. Thus,
there's growing sentiment not to
settle for containment of dioxins, no
matter how good the containment
system, but to demand their outright
destruction. Meanwhile, of course,
much of the world's dioxin wastes is
resting in dumps, some many years
old, that bear little resemblance to a
modern, secure landfill.
The barriers to destruction of these
dioxm cach es are mainlv economic
-attd pof1tica , rat er t antech~
lO'gitlrt:" Altnougnai'ox1n . ~rTIKem-
l~llf sta6Ie, ~ certain! can be
d'estroyea, with hi g e lc1ency,by
t-he,sam-e·high---::t-eff\~U't1re (1001rto
,l-SQO..!.G)-inci-nerati~ s usia~o
dl?s-t-r0y~-ottrer1l1izafd u(_2tg~ic
~----;•• -~--•~•-·""N--•
Mete t burning," however, isn't a
satisfactory method for disposing of
dioxins. If temperatures aren't high
enough, there'.~ a good possibility not
only'of fa_il_ing_ t<t destroy all the
di..91iins. already present, but also,of
actually forming new dioxins from
precursor compounds contained in
the wastes.
· Although test data are scanty, it's
reasonable to assume that some of the
"advanced" incineration processes
now under development, including
molten salt combustion and micro-
wave plasma destruction, might be
suitable for destruction of dioxin·
containing wastes.
Several chemical means of dioxin
destruction also have been proposed
and. to some extent, tested. These
l'i'--H!t<: l,IUHL..! I T I U r-• l t:l
·------------------------------
Dioxin Reporl
Successful dioxin cleanup
operation ls complex, costly
One of the better-documented dio;w;in
cleanup operations demonstrates that
dioxin hazards can be dealt with re-
sponslbly and effectively. It also points
up the tremendous complexity and ex~
pense of such an undertaking.
In 1969, Syntax Agribusiness bought
a chemical plant at Verona, Mo., for the
manufacture of animal feed additives.
The previous owner had leased part of
the plant and property to another firm f0<
the manufacture of trlchlorophenol and
further conversion to hexachlorophene.
After hexachlorophene essentially was
banned in 1972, that firm went out of
business and abandoned the Verona
plant.
In 1974. the Syntax plant manager
discovered that a steel tank on the
property-never used by Syntex and
presumed to be empty-actually con-
tained about 4600 gal of dark sludge.
Analysis showed the sludge to contain
.,._356 ppm of dioxins, about 7 kg.
Although $yntex perhaps could have
denied legal responsibility for the sit•
uatlon, the company felt that it was in its
own best interests. as well as the pub--
llc's, to dispose of the dioxins in a safe
and acceptable manner. ,.
The first step was to protect the tank.
A concrete dike, big enough to hold all
the tank's contents, was built under the··
tank. A building was erected over It and
a fence was pvt around It. That was only
the beginning of what would turn out to
be a six-year project.
The easiest way to get rid of the
dioxins would have been to incinerate
them. However, there were no suitable
Incinerators In Missouri. Efforts to In-
·--i
Syntex photolysis pr~ urtll
cinerate the wastes elsewhere were
thwarted because Syntex was prohibited
from shipping them across state llnes.
So Syntex started exploring the possi-
bilities of on-site destruction.
In 1978 Syntex engaged IT Envlro-
. science to undertake a"!hhte-pffffe
pl'ogram: technology review to deter-
mine the best method, laboratory de-
velopment and refinement of the chosen
process, and finally the actual detoxifi-
cation. A committee of experts was
fonned to provide independent evalua-
tion and guidance. The Environmental
Protection Agency also was Intimately
Involved, along with other agencies.
Building a suitable incinerator on-site
for a one-time operation would have
been prohibitively expensive.JI Eolli•
rosclence came up with three other
candidate processes: ciital9'iS wet ox-.. "rea1i6n,pnofocne'!Wt'5i uc ,on:-ana
C emic~,f tre§!.1tt . fi . e,.t~ive
'evAAi'atTon, · 'P otolytic metru,d)was
chosen. main on-a s o safety,
since it operated at ambient pressures.
This approach required that the dioxins
first be separated from the wastes by
hexane extraction.
A period of refinement and scaleup
followed. leading eventually to a full-size
extraction and photolysis unit that in-
cluded a bank of 10-kW industrial ultra-
violet lamps. All this time. of course,
much analytlcal chemistry was being
conducted, along with contingency
planning, Industrial hygiene, legal ac-
tivities, and liaison.
Finally, In May 1980, EPA approved
the ~~ Pho~ol lc._destruction was camed out batchwlse, over a period of
"ievera1-we'eks:with adesfruc on erfl-c~-ncrory]l. ~::, .. 4 ,_
either Syntex nor IT Envlroscience
will reveal what the total operation cost.
According to a 1980 article in Waste
A9e, the installed equipment cost Syn.
tex about _$500,000. But with all of
Syntex's other expenses, that was
probably Just the tip of the iceberg.
include zonol sis, chlorinolysis, ins was extracted from 4600 gal of peated extractions with various or-
£_a~~!iS .. ~~t.R~t ,ahQ.n, .and :yari~ TCP wastes and then degraded to ganic solvents, including hexane.
catafytii;. . .sk~hlw:'.lni!J.L9!l..,,P;'.?Cesses. relatively nontoxic compounds by Supercritical fluid extraction oi the
Ffowever, none have been applied· exposure to ultraviolet light. dioxins also has been proposed, and
full-scale. Biological methods may as ·n.gS.l.lP the uestion of it might work.
prove useful, especially for eco-~~!.~erlt'.~-.P.~lt.~ to tre,t.t · · -Where millions of tons of materials
nomical ~reatment of la_rge amounts -5~.~E'~e!~g.mate.tials.in..hulls, Q,LJQ ~ are cont~minated by a few kilogr~ms
of very lightly contaminated mate-~~ ~ncentrate the dioxins of dioxins, as at Seveso, it might
rials. So far, however, test results --~ef.o;:_e_ the,i_,re destr~d. s wifh-prove easier and more economical to
have been equivocal. many ot erdioxin questions, the extract the dioxins and destroy them
,..In fact, aside from inc~p eration, the answer isn't ob~~io_!:ls. B th ap-separately rather than to incinerate ~ ~1;12:toxin -~~~.!ruc~i~~effi2_,ct to Ee ·pm~i5~Jl~~--e~~.':1~_<!:. the whole mess. Either way, the lo-~A .. emi: ?Y.e . ~'3F! _a_!!!,s~ .. J.?Y aiffll?J -o·iox ins can be efficiently and gistics strain the imagination. Even~
..... s_-:.l:~~z:d.sTsca~.has_.!~!:!' Fi'£_ s1s. fairly selectively removed from, for tually, experience likely will provide
In tnat operation, some "/ kg o diox-example, contaminated s0ils by re-the best ~olutions. □
56 June 6. 1983 C&EN