Chemosphere, Vol.17, No.9, pp 1831-1850, 1988 0045-6535/88 $3.00 + .00 Printed in Great Britain Perqamon Press plc

ASSESSING ENVIRONMENTAL CONTAMINATION FROM A PENTACHLOROPHENOL FIRE:

SCREENING SOILS FOR OCTACHLORODIBENZO-~-DIOXIN

William M. Draper* and Jane Phillips,

California Public Health Foundation,

2151 Berkeley Way, Berkeley, CA 94704

Martha Harnly

State of California Department of Health Services,

Epidemiological Studies and Surveillanc~ Section,

2151 Berkeley Way, Berkeley, CA 94704

Robert D. Stephens

State of California Department of Health Services,

Hazardous Materials Laboratory,

2151 Berkeley Way, Berkeley, CA 94704

ABSTRACT

Evaluation of environmental contamination caused by pentachlorophenol (PCP)

fires is extremely costly and time consuming because elaborate measurements

of polychlorinated dibenzodioxin and furan (PCDD/F) isomers are required.

Large geographic areas may potentially be affected greatly increasing the

number of samples required for adequate investigation. Our laboratory has

developed a rapid gas chromatography procedure for measurement of soil-bound

octachlorodibenzo-~-dioxin (OCDD), a probe for PCP combustion products.

Congener profile analyses of PCP combustion samples in our laboratory and

others have revealed that OCDD is the principal PCDD/F product and, thus, a

useful marker for these substances. For the screening procedure, composited

soil samples are sieved and Soxhlet extracted with hexane. Quantitative

analysis of OCDD in soil extracts is accomplished by capillary gas-liquid

chromatography (GLC) using on- column injection and a 63Ni electron capture

detector. Recoveries were >99% (at 20 ug/kg) and, without supplemental sample

cleanup, the method detection limit was 6 ug/kg, adequate for detection of

1831

1832

OCDD above expected background levels. OCDD levels determined by this method

agreed with those measured by gas chromatography-mass spectrometry (GC-MS).

The OCDD screening procedure was used to investigate contamination from a

recent industrial fire in northern California that consumed an estimated

4,500 kg of PCP and was predicted to impact an area of about 2,000 km 2. For

this incident a weighted, stratified sampling scheme was used to locate

sampling points in communities in the path of the plume. Environmental

sampling was stratified on ground level exposure concentration (or

deposition) contours predicted by atmospheric dispersion modeling conducted

by Systems Applications Inc. (San Rafael, CA). The number of samples

collected in each contour was determined by the predicted degree of

deposition as well as population.

The combined application of soil screening for OCDD and sampling based on

human exposure potential provides a rapid means for evaluating PCDD/F

contamination caused by PCP fires.

INTRODUCTION

Northern California PCP Fire

In the spring of 1987 a fire occurred at a wood treatment facility located

near the north-central California community of Oroville. Preliminary

estimations by the site operator indicated that about 4,500 kg of

pentachlorophenol were consumed on combustion of a wood treatment mixture

consisting of liquified butane (85% w/w), PCP (5%), isopropyl ether (5%) and

No. 2 fuel oil (5%). The fire was fueled by the contents of a single hopper

on which the emission estimates were based, although a second vapor plume was

observed rising from a silo containing technical PCP and partially engulfed in

flames.

The fire produced a dense plume of black smoke thoughout its 6.5 hour

duration indicating incomplete combustion and the formation of submicron

aerosols. Signs of dermal exposure to PCP aerosols and symptoms of PCP

poisoning were observed in over I00 residents within 2 to 3 miles of the

site. The major concern among public health officials, however, was the

potential for exposure to extremely toxic PCDD/F produced on incomplete

combustion of the pesticide.

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Contaminants in Technical PCP and PCP Pyrolysis.

Technical PCP contains numerous byproducts including tetra- and tri-

chlorophenols, hexachlorobenzene and PCDD/F (1,2). Recent European

production batches of PCP contain -i mg PCDD/F per g of technical product,

principally the hepta- and octachloro- congeners (3). Furthermore,

predioxins (polychlorinated phenoxyphenols) constitute about 3 to 6% by

weight of the commercial pesticide.

Pyrolysis or low temperature combustion (e.g., <900°C) of PCP greatly

increases the PCDD/F content (4 - 8). PCDD/F formation has been observed on

incineration of a variety of chlorinated phenols, chlorophenol-containing

wood preserving formulations, treatment residues and treated wood (7). The

heating of PCP is believed to form chlorinated dioxins by dimerization and

dechlorination reactions, and cyclization of predioxin contaminants (9)

(Figure i.). As indicated in Figure 1 pyrolysis of PCP preferentially

increases the OCDD content (8,10).

The chemical composition of the combustion products at the California fire

was examined at the Hazardous Materials Laboratory by isomer- specific

analyses of soil, vegetation, surface wipes, and bulk samples from the burn

area at the wood treatment plant. Of these samples one charred PCP sample

collected beneath the butane hopper cone provided an indication of the

composition of the combusted material. This product was greatly enriched in

tetra- through octa- isomers (Table I.) as indicated by the congener data.

The production of these compounds would be expected in the 700 - 800°C

temperatures developed in the butane fire.

The charred material analyzed and (presumably combustion aerosols emitted)

were substantially more toxic than PCP. The technical material was estimated

to contain 2.9 parts-per-million (ppm) TCDD equivalents while the pyrolyzed

product contained 321 ppm TCDD equivalents.

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Cl CI.,~Cl

Cl'~,,,r~ OH Cl

A

Cl OH Cl Cl

>

Cl Cl Cl~ 0 ~Cl

Cl 0 Cl Cl CI

Cl CI Cl~ 0 ~Cl

Cl 0 Cl Cl Cl Cl c, o c,

Cl 0 Cl Cl

Figure 1. Pyrolysis reaction leading to the formation of PCDD in technical PCP.

1835

Table I.

Sample a .

Trace Chemical Composition of Technical PCP and a PCP Combustion

PCDD/F Concentration (ma/kq) Abundance

Congener Technical PCP b Fire Sample TEF c Factor d

CI4-PCDD <0.i 260 1.0 0.045

CI4-PCDF <0.I 44 1.0 0.026

CI5-PCDD <0.i 2,200 1.0 0.071

CI5-PCDF <0.i 142 1.0 0.071

CI6-PCDD 2.5 4,100 0.03 0.30

CI6-PCDF <0.3 292 0.03 0.25

CI7-PCDD 175 5,800 0.03 0.5

CI7-PCDF 19 i,i00 0.03 0.5

CI8-PCDD 500 13,000 0 1.0

CI8-PCDF 25 - 0 1.0

a For comparison the PCDD/F values are normalized to PCP content which was

91 wt % for the technical material and 0.19 wt % for the combusted sample.

b Ref. 4.

c State of California toxicity equivalency factor based solely on

carcinogenicity in the mouse and rat.

d The abundance factor assumes an equal isomer distribution and represents

that fraction of PCDD/F with the 2,3,7,8- chlorine substitution pattern.

Emergency Response by Health Authorities.

Immediately after the fire, emergency responses by health authorities

included: i) temporary evacuation of the sparcely populated areas just south

of the site; 2) voluntary medical examinations in the community; 3)

biological monitoring of PCP in blood and urine; 4) environmental monitoring

consisting of PCP and isomer-specific dioxin measurements at the burn site

(noted above) and surrounding communities; and 5) atmospheric dispersion

modeling of the plume.

Within a week the initial health and environmental investigations provided

substantial evidence that the fire did not represent an imminent and

substantial health hazard to the community. The highest level of TCDD

equivalents in community soil was 70 parts-per-trillion (ppt) and OCDD did

not exceed 15 parts-per-billion (ppb). These findings allowed relaxation of

1836

emergency measures and commencement of cleanup in the burn area. There were,

however, lingering concerns that toxic substances released from the fire had

contaminated the community and continued to represent a threat to public

health. Theoretically, the fine combustion aerosols produced in the fire

would not be expected to undergo rapid deposition due to their low

sedimentation velocity, but no experimental data were available to support

this view.

Objectives of this Study

The objective of this work was to define the distribution of PCP combustion

products over an extended area. Atmospheric dispersion modeling was used to

predict areas of maximum ground-level impact and, in combination with census

data, the sampling intensity. OCDD was selected as a marker for PCDD/F

because of its: i) abundance in pyrolyzed PCP; 2) similarity in environmental

fate and mobility to the more toxic PCDD/F; and 3) speed and low cost of

analysis. The methods developed for this study may prove generally useful in

evaluating future contamination from PCP fires or those of other chlorinated

aromatic compounds.

EXPERIMENTAL SECTION

Quantitative Analysis for OCDD in Soil

Korfmacher and coworkers (11,12) described an analytical procedure for

determination of OCDD and CIT-PCDD in dust and surface wipe samples from

building interiors contaminated by PCB-transformer fires. The present soil

method is similar except that the cleanup steps involving partition of the

extracts with acid and base, and high pressure liquid chromatography on an

active carbon column were unnecessary for the soil matrix.

Chemicals. OCDD was obtained from Cambridge Isotope Laboratories (Woburn,

MA). Solvents were commercially-available, pesticide grade and other

chemicals were reagent grade.

Soil Extraction. Soil composites were mixed thoroughly by agitation and

passed through a #18 sieve (i.0 mm openings). The total sample weight and

fines weight were recorded. A portion of the fine soil fraction (i0.0 +/-

0.I g) was added to a paper Soxhlet thimble with a wad of glass wool to

retain the sample. The Soxhlet receiver was charged with 200 mL of hexane

1837

and glass beads and samples were extracted for three hours after the first

cycling. Extracts were cooled and reduced just-to-dryness on a rotary flash

evaporator and the residue dissolved in isooctane. The isooctane was dried

by passing the solution through a sodium sulfate column prepared in a Pasteur

pipet. The final sample volume was adjusted to 5.0 mL giving 2.0 g soil

equivalent/mL of solvent.

Quantitation of OCDD. A Hewlett-Packard 5890A gas chromatograph (Avondale,

PA) fitted with a 63Ni electron capture (EC) detector and a J & W Scientific

capillary on-column injector (Rancho Cordova, CA) was used for quantitative

analysis. A Spectra-Physics Model No. 4290 recording integrator (San Jose,

CA) was used to measure peak areas. The instrument operating conditions were

as follows: range, 3; attenuation, I; digitizer attenuation, 4; detector

temp., 325°C; detector purge gas, 60 mL/min argon-methane (90:10, v/v) ; column

head pressure; 9.0 psi; carrier gas flow, 1.8 mL He/min; injector purge flow,

12 mL/min. The GLC column was a 30 m X 0.32 mm ID fused silica capillary with

a chemically-bonded 0.25 um SPB-5 silicone phase (equivalent to SE-54)

(Supelco, Bellefonte, PA). The column originally had an efficiency of -2,500

effective plates/m and a 97% coating efficiency, but had been used extensively

and was previously cleaned by rinsing with pentane and methylene chloride.

Purged splitless injection with inlet temperatures between 175 and 250 °C

(purge off time, 1 min; initial column temp., 80°C for 2 min; temp. programmed

at 40°C/min to 280°C; OCDD tR, -35 min) was evaluated in preliminary studies

and found to be inadequate due to poor peak shape and reproducibility.

Two uL injections were used routinely. The oven temperature was isothermal

at 285°C resulting in a retention time of about ii minutes for OCDD.

External calibration was by peak area relative to a 40 pg/uL standard in

isooctane -- for determination of detector linearity standards between 1 and

400 pg/uL were used. OCDD was identified by retention time (tR) with an

acceptance criterion of +/- 0.i min.

Method Detection Limit Study

A soil sample from the Oroville area was mixed and sieved as described above.

Ten g samples were placed in Soxhlet thimbles and spiked at 20 ug/kg by

addition of 200 uL of a 1.0 ng OCDD/uL isooctane solution. Replicate analyses

of spiked (n = 7) and unspiked soil were used to determine method precision

and accuracy.

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Atmospheric Dispersion Modelinq

The dispersion of gaseous and fine aerosol emissions was modeled by Systems

Applications Inc. (San Rafael, CA) with the objective of reconstructing

ground-level pollutant concentrations (13). This information was needed to

identify potentially exposed populations and quide further environmental

sampling. A U. S. Environmental Protection Agency (EPA) model, INPUFF of the

UNAMAP VI model package, was used. This model predicts the plume rise and

path from inputed meteorology data (e.g., surface temperature, temperature

aloft, wind speed and direction, atmospheric stability, mixing height) and

data on the characteristics of the fire (e.g., flare dimensions, heat

produced). Other forms of evidence including videotape footage, photographs

and eyewitness accounts were examined for corroboration. The EPA model was

used because it allowed the inputed factors to vary by time of day and had

regulatory recognizance.

Modeling revealed that the plume initially moved south from the site, away

from population centers. The plume rose 50 to 60 m due to the intense heat

generated and emissions penetrated the inversion layer minimizing impacts at

ground level. As the fire progressed both the meteorologic conditions, and

the characteristics of the fire changed. The wind direction shifted from a

northerly to a southerly direction and both the wind speed and the mixing

height increased. The height of the flare diminished as both the fuel

consumed and heat generated declined. During the late stages of the fire the

plume did not climb as high into the atmosphere and was carried north toward

more highly populated areas.

Modeling predicted that the gaseous and fine particle emissions were

dispersed over a large geographic area providing a sizable dilution factor.

Maximum impacts normalized over the 6.5 hour fire were predicted along two

paths, one to the southwest (SW) and the second to the north (N). Within

each path, modeling predicted areas of maximum concentration and isopleths

of lesser concentration surrounding each maximum. Predicted deposition

within the isopleths was unitized relative to the maxima because of the lack

of reliable data on PCP consumed and the composition of emissions. This

provided information on relative impacts to surrounding communities, but no

predictions as to air or soil concentrations.

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Stratified Sampling Based on Plume Modeling and Census Data

Thirty sites were sampled during the initial survey. The number of sampling

sites within each isopleth was decided by weighting on the modeled relative

ground-level exposure and on population within each isopleth. To estimate the

population the 1980 U. S. census enumeration district centroids in each

maximum and isopleth were summed, and the proportion of the total population

in the two plume paths was calculated. The proportion was then multiplied by

the exposure intensity to produce a combined deposition and population

weighting factor. The fraction of the total samples collected in each maximum

and isopleth was then equal to the relative weight of the combined weighting

factor for the isopleth or maximum.

The specific sample locations within each maximum and isopleth were

determined by systematic sampling. A fine grid (over 2,000 cells) was

superimposed over each geographic isopleth and maximum. Grid cells with

streams, lakes, and other bodies of water were deleted. The number of grid

cells in each isopleth was divided by the total number of alloted samples in

each isopleth to equal n and a sample location was then selected at every nth

cell.

Soil Sampling

At the designated sampling site a grid was layed out to identify four points

at the corners of a 4 foot square where a i0 X i0 cm area was marked with a

template. The surrounding soil was cleared away and approximately 2 cm of the

elevated plateau were collected. The four samples were combined in a glass

sample container with a Teflon-lined closure giving a composite of -700 g.

0CDD Measurements by GC-MS

The PCP combustion sample was analyzed for PCDD/F using EPA method 8280 with

sample extraction modifications developed by C. Rappe and coworkers. The

sample was Soxhlet extracted with toluene for over 8 hours followed by

extract cleanup on silica/sulfuric acid, potassium silicate, alumina and

carbon columns. Final extracts (i0 to i00 uL) were analyzed bY GC/MS using

electron impact ionization and multiple ion detection. Recoveries of

isotopically-labeled internal standards were consistently above 50%. To

confirm OCDD in soil extracts the original extract was diluted, spiked by

1840

addition of labeled internal standards, and then analyzed directly for tetra-

through octa- PCDD/F.

RESULTS

Analysis of OCDD in soil

When using an on column capillary injector OCDD exhibited a sharp

chromatographic peak and excellent reproducibility and linearity. The

practical instrument detection limit was -5 X 10 -12 g. Soil samples

subjected to the analytical procedure were free of interfering signals and

were only distinguishable from solvent injections by their broader solvent

peak and minor shoulder peaks. Soil extracts fortified with OCDD at 2 ug/kg

of soil (Figure 2.) gave a distinct chromatographic signal quantified as 1.9

ug/kg (RSD = 11%, n = 5).

To determine the method detection limit (MDL) seven soil samples were spiked

at 20 ug/kg and then carried through the entire analysis procedure. The mean

and standard deviation of these measurements were 20 +/- 2.1 ug/kg

corresponding to an MDL of about 6 ug/kg. With 2 uL manual sample injections

the expected precision was about 10% RSD indicating that the MDL may actually

be lower than estimated here.

Soil OCDD Distribution in the Community

The majority of the soil samples taken were coarse sand with the fine

fraction accounting for between 7 and 71% of the sample weight (Table II.).

OCDD was not detected anywhere in the southwest path of the plume where

surface soil from i0 sites was analyzed (Figure 3.). OCDD also was not

detected in three "background" sites in the Palermo area east of the wood

treatment plant. To the north of the fire OCDD was detected at 4 of the 20

sites tested and measured levels were 6.5, 34, 59 and 240 ug/kg. OCDD was

not detected in 16 of 20 of the sites located to the north of the fire.

OCDD was confirmed in the high concentration extract by GC/MS analysis using

an isotopically-labeled internal OCDD standard. By this procedure the OCDD

content was estimated at 290 ug/kg.

1841

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0 I-- U u l I,,- W

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• ¢ - I

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Figure 2. Electron capture chromatogram for 80 pg of OCDD (a) ; soil extract spiked with 2.0 ug/kg of OCDD (b); method detection limit soil sample containing 20 ug/kg of OCDD (c); and OCDD signal in sample "N- 4" corresponding to 240 ug OCDD/kg soil (d). N-4 was diluted 1:9.

1842

Table II. OCDD Concentrations in Oroville Community Soil Samples a.

OCDD Concentration Collector Fine Fraction Cuq/ka. DDb} Sample # Weight (wt %) Original Replicates

B-I 36 ND B-2 27 ND B-3 45 ND N-I 59 ND N-2 66 ND N-2 DUP 70 ND N-3 71 ND N-4 59 240 250, 290 N-5 51 ND ND N-5 DUP 61 ND N-6 32 ND ND N-6 DUP 29 6.5 N-7 52 ND N-7 DUP 53 ND N-8 37 ND N-9 23 ND N-10 52 ii 15, 19, 90 N-II 39 ND N-12 41 ND N-13 44 ND N-14 63 ND ND N-15 19 ND N-16 42 51 50, 77 N-17 31 ND ND, ND, ND N-17 DUP 21 ND N-18 44 ND N-19 42 ND N-19 DUP 23 ND N-20 43 ND S-I 13 ND SW-I 55 ND SW-2 23 ND SW-3 7.2 ND SW-4 32 ND SW-5 15 ND SW-6 58 ND SW-7 24 ND SW-8 8.3 ND SW-9 18 ND

Field blank 1 - ND Field blank 2 - ND Field blank 3 - ND

a Fine fraction is that material passing through a #18 sieve; B = background sample, N = north plume path, SW = southwest plume path, ND = not detected, DUP = duplicate, MDL = method detection limit. The MDL was 6 ug/kg. b OCDD concentration confirmed by GC/MS analysis as 290 ug/kg.

1843

Figure 3. Distribution of OCDD in surface soil in the vicinity of the wood

treatment plant fire. The height of the histogram bar indicates OCDD

concentration.

240 PPB

N O R T H P L U M E

/

/ / / , / • 0

PENTA CHLOROPHENOL FIRE

0

S O U T H W E S T P L U M E 0 PALERMO

GRIDLEY

"HONCUT

O S C A L E 1 0 M I L E S

1844

DISCUSSION

Rationale for selectinq OCDD as a marker

A marker or surrogate for PCDD/F must satisfy certain requirements among

which ease of analysis is of obvious importance. Many of the technical

challenges associated with PCDD/F analysis do not plague OCDD measurement.

Extensive sample cleanup is required in PCDD/F analysis due to a variety of

interferences including chlorinated- biphenyls, diphenyl ethers,

phenoxyphenols, and other compounds, some of which are much more abundant in

the environment than the dioxins. Due to its high molecular weight, OCDD

elutes late in a relatively clean portion of the gas chromatogram after

pesticides and most PCBs on non polar columns (ll).

OCDD is perchlorinated and therefore the difficulties in distinguishing the

75 PCDD and 135 PCDF isomers are avoided. Finally, because of its high

abundance in PeP combustion samples, analysis at the ppb level is adequate

whereas multicomponent dioxin analyses demand detectabilities in the low ppt

range. As a result requirements for instrumentation, highly trained

laboratory personnel, turn around times and laboratory costs are minimized.

The occurrence of the marker should correlate with the compounds of interest,

in this case the toxic chlorinated congeners. The correlation is less

critical if the marker is used in screening as opposed to a true surrogate for

purposes of human health risk assessment, or establishing cleanup levels.

Thompson and coworkers have successfully used OCDD as a reliable surrogate for

PCDD/F produced on incineration of PCB, but only after a thorough

investigation of the relationship between OCDD and PCDD/F concentrations

(12,14).

Our objective in screening was to extend analytical resources and maximize

the yield of useful data. The occurrence of a high number of elevated OCDD

values, or a consistent pattern of OCDD contamination, indicates the need for

congener or isomer specific PCDD/F measurements.

Finally, the marker must have physical and chemical properties (Table III.)

that ensure similar behavior to the compounds of interest in the environment

(e.g., fate, transport and persistence). The least acceptable condition is

that in which the marker molecule is considerably more labile in the

1845

environment than the compounds of interest due to biological and

nonbiological fate processes including metabolism, hydrolysis, photochemistry

and oxidation. In addition, the mobility of the marker should be similar.

In the case of PCDD/F produced in PCP fires, 2,3,7,8-

tetrachlorodibenzo-D-dioxin (TCDD) , OCDD and PCP might be considered as

possible markers. PCP is highly water soluble (Table III.) , readily

photodegraded in natural sunlight (15) , and rapidly metabolized by soil

microbes (16,17) . PCP soil residues are ultimately mineralized.

Volatilization also is important in the dissipation of soil applied PCP (17).

The environmental chemistries of Cl 4 to Cl 8 dioxins and furans are dominated

by low vapor pressures and water solubilities (Table III.), and high

affinities for soil. While PCDD/F are photochemically unstable in organic

microenvironments (e.g., organic solvents, diesel fuel, or pesticide

formulations), their photolability is undetectably slow on soil surfaces due

to poor light penetration. Unlike PeP the microbiological transformations of

PCDD are negligable (18) Environmental half-lives of PCDD/F, including

TCDD and OCDD, are in the 10-12 year range while PCP is reported to be far

less persistent. By this criterion TCDD and OCDD provide acceptable probes

for total PCDD/F contamination while PCP does not.

Table III. Physical and Chemical Properties of PCP, TCDD, and OCDD.

Property PCP TCDD OCDD References

Vapor Pressure (Pa)

Water Solubility (ng/L)

Log Octanol-water

Partition Coefficient

Environmental tl/2

1.3 X 10 -3 4.5 X 10 -6 2.4 X 10 -5 19,20

20,000,000 13 - 19 0.4 21,22,23

1.3 - 4.8

30-50 days

4.5 12 - 13 24,25

i0 - 12 yr I0 - 12 yr 1 6 , 4

1846

Interpretation of the Oroville Community Data.

The OCDD measurements in the Oroville area provide little evidence of

widespread PCDD/F contamination resulting from the fire, or any other event.

In the unlikely case that the deposition of particulate aerosols had

contaminated the community, a relatively uniform OCDD distribution,

particularly in areas of level terrain, would be expected in the near surface

soil. We conclude that there was little or no deposition of combustion

products where the plume tracked to the southwest and then north.

The detection of OCDD at high ppb levels at a single isolated location i0

miles to the north of the fire is probably related to the use of PCP in wood

treatment. The site sampled was within 20 feet of a preservative-treated

telephone pole at a cattle loading platform.

One limitation in using OCDD as a marker is its common occurrence in the

environment. OCDD is the most abundant PCDD/F compound in the environmental

compartments including air (26), sediments (27) and human adipose (28).

Background values as high as 5 ug/kg occur in the U. S. (e.g., in Lake Ontario

sediments). The widespread use of chlorinated phenols in wood preservatives

may give occassional spikes as suspected in the case of the elevated value in

this study. Atmospheric deposition in contrast would be expected to show a

more consistent and extensive contamination pattern.

Applicability of OCDD Screeninq to Fires Involving other Chlorinated Aromatic

Compounds.

Clearly OCDD is the most abundant PCDD/F produced on pyrolysis or combustion

of PCP and its salts. The lower chlorinated phenols, however, are distinctly

different and may produce little if any OCDD on combustion and relatively high

CI4-PCDD (Figure 4.) . Pyrolysis of 2, 4, 5-T herbicide or

2,4,5-trichlorophenol gives an 0.2 to 0.5% yield of TCDD and only traces of

OCDD (30). For chlorinated aromatics where OCDD is a relatively minor

incomplete combustion product compared to other PCDD/F, the utility of OCDD

as a marker should be reevaluated in relation to the goals of the

environmental monitoring program.

1847

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1848

CONCLUSIONS

Environmental contamination from PCP fires is extremely costly due to the

requirement for sophisticated and time-consuming quantitation of PCDD/F

isomers, and the potential for contamination of large areas. After initial

chemical characterization of the pyrolyzed product with rigorous GC/MS

procedures, follow up screening by EC-GLC may prove valuable in identifying

potentially contaminated samples. The use of atmospheric dispersion modeling

and census data to define exposure potentials provides a rational approach to

guide environmental sampling.

ACKNOWLEDGEMENT

We thank Mark Leary, Linda Hennessy, and Jim Papararo of the CDHS, Toxic

Substances Control Division for collecting soil samples. Ted Belsky, Ruth

Chang, and Doug Hayward performed the isomer specific PCDD/F analyses. David

Siegel of the CDHS, Hazard Evaluation Section commented on the TEF estimates.

This work was presented at the 1988 Waste Testing and Quality Assurance

Symposium held in Washington, DC.

LITERATURE CITED

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2. Buser, H.R.; Bosshardt, H. P. J. Assoc. Off. Anal. Chem. 1976, 59, 562.

3. Cull, M.R.; Dobbs, A.J.; Goudot, M.; Schultz, N., Chemosphere 1984, 1/3,

115"7.

4. Rappe, C. Environ. Sci. Technol. 1984, I_88, 78A.

5. Rappe, C.; Marklund, S.; Bergqvist, P.A..; Hansson, M. Chlorinated

Dioxins Dibenzofurans Total Environment Symposium Proceedings, 1982, Edited

by G. Choudhary, L. Keith, and C. Rappe, Butterworth: Boston, Mass, 1983, pp.

91-124.

6. Rappe, C. ; Marklund, S. Pesticide chemistry.: Human Welfare

Environ.,Proc. Int. Congr. Pestic. Chem., 5th 1982, Edited by J. Miyamoto and

P. Kearney, Pergamon: Oxford, UK, 1983, pp. 317-322.

1849

7. Bridle, T.; Afghan, B.; Wilkinson, R.; Carron, J.; Sachdev, A. Proc. -

APCA Annu. Meet. 1984, 77th, l, 84-11.2.

8. Chemical Abstracts I00: 187191.

9. Rappe, C. ; Marklund, S., Chemosphere 1978, 3, 269.

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(Received in Germany 6 June 1988; accepted 7 July 1988)