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OCR for page 81
3
Toxicological Testing of
Dispersants and Dispersed Oil
This chapter describes what is known about biological espe-
ciaBy toxicological effects of dispersants and dispersed oils from
laboratory studies; reviews the evidence on oil-induced damage to
organisms and how it is modified by dispersant use; and notes the
applications and limitations of this knowledge (Figure 3-1~. Experi-
ence with of} spill dispersants over the years has resulted in less toxic
formulations. However, some questions pertaining to the effects of
dispersants with and without oil remain, and they are addressed
throughout this chapter.
OVERVIEW OF TOXICOLOGICAL TESTING
Toxicity, the potential of a material to cause adverse effects in
a living organism, is a relative measure (see GIossary). Estimates of
toxicity depend on many experimental physicochemical and biolog-
ical factors. In addition, there are many different testing methods
and variations in the products tested. A related problem has been
the uncertain applicability of toxicity data from one species in one
body of water to another species or area. For example, are species'
sensitivities to dispersed oils in New England waters applicable to
Texan waters? This question, which is of concern to regulators and
industry, is addressed in this chapter.
81
OCR for page 82
82
USING OIL SPILL DISPERSANTS ON THE SEA
DISPERSANTS PETROLEUM OILS
Physicochemical Characteristics Physicochemical Characteristics
Effectiveness of Dispersants Volume, Location of Spill
Toxicology of Components Toxicology of Key Constituents
Exposure of Biota to
Dispersed Oils
l Seawater Temperature
|1
IMPACTS OF DISPERSED OILS
Specific Habitat Vulnerabilities (exposure)
Sensitivities of Individuals and Populations (response)
Community Recovery Potential (recovery)
FIGURE ~1 Factors to consider in the assessment of biological effects of dispersed
oil in marine environments.
The objectives of toxicity testing of dispersants and dispersed
oils in the laboratory are:
~ to provide data on relative acute toxicities of effective prod-
ucts to commonly used test species under standardized conditions so
that dispersant users have a basis for selecting effective and accept-
ably Tow toxicity products;
· ~ . ~ ~
co assure anal c~lspersants do not significantly increase the
acute and chronic toxicities of dispersed petroleum hydrocarbons;
and
.
to determine factors that modify dispersant toxicity, or en-
hance or ameliorate of] toxicity under natural conditions.
Different types of toxicity tests can satisfy these objectives. Tests
are chosen to detect potentially harmful products both rapidly and
reliably. They are not intended to be ecologically realistic or to
predict effects in the field.
In measuring toxicity effects of oils, exposure comparisons may
be made using the integral of concentration multiplied by time of
exposure to 50 percent mortality LC50 (Anderson et al., 1980~; the
results of exposure tests are usually expressed as mg/liter per day
or per hour. Since concentration may also be stated in approximate
terms as parts-per-million (ppm) or parts-per-billion (ppb), and the
exposure period as hours or days, some data on dispersed of]
OCR for page 83
TOXICOL O GICA L TESTINrG OF OIL DISPERSA NTS
83
presented in this chapter will be stated as ppm-hour (ppm-hr) or
ppm 1-day or 2-days. This allows a comparison to be made between
different exposures used by different investigators who use the same
analytical techniques. The exposure-time expression also allows an
exposure to be expressed as concentrations change rapidly in the
field. This concept probably holds during time periods from 1 hr to 4
days for oil and dispersed of} exposures. The use of ppm-hr assumes
that organisms wiB respond in the same manner to a tox~cant if
exposed, for example, to 20 ppm for 1 hr or to 1 ppm for 20 hr. The
concept is approximately valid for some of the data shown in this
chapter.
There are obvious limits to this concept. If the time is short and
the concentration high, the organism may be killed immediately. If
the time is long and the concentration correspondingly lower, many
organisms can tolerate, adapt to, or metabolize hydrocarbons and
~~spersants and survive and recover without apparent adverse effects.
This concept has long been used in radiation exposures. It was
proposed and used by Anderson et al. (1980, 19843, and McAuliffe
(1986, 1987a) used the concept to compare laboratory bioassays that
actuary measured the dissolved hydrocarbons in the water-soluble
fraction and chemically dispersed of! exposures with those measured
in the field.
O
Toxicological Testing Methods
Considerable attention has been paid, especially by regulatory
agencies, to
the choice of suitable exposure regimes (static, continuous
flow);
test species;
acute versus chronic testing;
influence of modifying factors; and
standardized testing protocols.
International workshops on these issues have been held by the
United Nations Food and Agriculture Organisation (FAD) and the
United Nations Environmental Programme (UNEP). Work from the
United Kingdom has included Shelton (1969), Perkins (1972), and
Beynon and Cowell (1974~. Work from the United States has in-
cluded Tarzwell (1969, 1970), ZiDioux et al. (1973), and Becker
et al. (1973~. Canadian work has included Mackay et al. (1981),
Wells (1984), and workshops leading to the Canadian Dispersant
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84
USINrG OIL SPILL DISPERSANTS ON THE SEA
Guidelines, 2d edition, Environment Canada (1984~. FAD has been
represented by White (1976) and UNEP by Thompson (1980 and
private communication).
It is difficult to compare disperant formulations or sensitivities
of different species, unless such work is conducted comprehensively
in qualified laboratories (Doe and Wells, 1978; Wells, 1984; Wilson,
private communications. Furthermore, information obtained using
rigorously controlled and standardized testing protocols is desirable
for reliable interpretation of toxicological information. Major com-
ponents and trace contaminants should be known and exposures
verified by analyzing the water in which the organisms are exposed.
Fish, arthropods (usually decapod crustaceans), mollusks (pele-
cypods), annelids (polychaetes), and algae have been the favored
test species. Some researchers have also studied sensitive life stages;
behavioral, biochemical, and developmental responses; and multi-
species interactions, either acute or chronic. Testing of current for-
mulations can be acute (i.e., short term), single-species, lethal, or
sublethal; it is usually done in static rather than flowing systems,
and at ambient temperatures. Some testing includes standard sam-
ples or reference tox~cants.
Dispersant toxicity thresholds are most often reported as nom-
inal concentrations total amount of dispersant or oil divided by
the total volume of water in the experimental chamber- rather than
measured concentrations of materials to which organisms are actu-
ally exposed. This can lead to major errors in some cases. For some
water-immiscible formulations at high concentrations, dispersant in
the bioassay chambers can separate into a floating and dispersed
upper-surface layer, several millimeters thick, and a dissolved sub-
surface fraction during the tests. For example, BPllOOX in static
tests separates like this immediately. Expressing the LC50 or EC50
on the basis of nominal concentration then gives a higher (and in-
correct) value than if the water-soluble fraction were analyzed and
used as the basis. Thus the toxicity of a water-soluble material may
be underestimated. The same problem arises because of the immis-
cibility of water and dispersed oil (as discussed later in this chapter).
For some dispersant formulations, this is an important but generally
unrecognized source of error for toxicity estimates.
Dispersant Screening Procedures for Toxicity: Considerations
The qualities of a good laboratory screening test are that it
is easy to perform and control, and it is reliable, reproducible, and
OCR for page 85
TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
85
adequately sensitive. Because its purpose is to determine the relative
toxicity of one dispersant versus other previously tested dispersants,
practicality and known sensitivity are weighed against ecological
realism. Screening tests are usually conducted with a single species,
but do not yet attempt to simulate interactions of two or more
species, that is, community responses (Cairns, 1983; Mount, 1985~.
Screening tests can include
various test species and life stages;
response parameters other than mortality;
various test materials;
different exposure modes;
varying length of exposure; and
various pass-fai] criteria.
Laboratory tests are poor simulations of natural conditions because
they are conducted under standard controlled conditions. Gener-
aBy, this means exposing animals in the laboratory to more or less
constant concentrations for 2 to 4 days, while in the ocean initial
concentrations of dispersants and dispersed of} would be diluted pro-
gressively and generally rapidly.
Because the effectiveness and toxicity of a dispersant may be
positively correlated, screening tests should consider both criteria in
sequence (Bratbak et al., 1982; Doe and Wells, 1978; Mackay and
Wells, 1983; Nes and Noriand, 1983; Norton et al., 1978; Swedmark
et al., 1973~. Both criteria have already been considered together
when evaluating dispersants for government agencies (Anderson et
al., 1985; Aranjo et al., 1987; Environment Canada, 1984~. Screen-
ing tests should accurately evaluate and accommodate the possibly
greater acute toxicity of more effective dispersants.
For improved accuracy and utility of hazard assessments, future
screening toxicity tests should consider the above factors, the physical
chemistry of the dispersant solutions, and the responses of the test
organisms during short exposures.
Dispersant Screening Procedures in Canada, the
United States, and Other Countries
Until 1982, most countries used a combination of dispersant
and dispersed oil tests, of! and dispersed of} tests, or tests with ah
treatments (WeBs, 1982a). The primary concern was to evaluate the
toxicity of oils upon dispersal. Such an approach was particularly
OCR for page 86
86
USING OIL SPILL DISPERSANTS ON THE SEA
supported by the United Kingdom's sea and beach test.* However,
the inclusion of oils in dispersant tests is experimentally complex
because it introduces a new set of variables associated with the oil and
is subject to errors in interpretation because of immiscibility (Welis,
1982a; Wells et al., 1984a,b). Yet most countries, out of concern
about dispersed of} effects and joint toxicity of of} and dispersant
constituents, have included both of! and dispersant in their tests.
Some countries screen dispersants only (e.g., Australia, Canada,
several Asian countries). At least 10 countries employ a toxicity
screening test for dispersants or dispersed oil: Australia, Canada
(linked to effectiveness test), France, Hong Kong (modified U.K. sea
test), Japan, Norway (modified U.K. sea test), Singapore (modi-
fied 1970s Canadian test; Environment Canada, 1973), South Africa
(modified U.K. sea test), United Kingdom, and the United States.
Brazil (Aranjo et al., 1987), Nigeria, the Philippines, and Sweden are
also developing testing approaches (SchaTin, 1987~. Screening meth-
ods and status are listed in Tables 3-1, 3-2, and 3-3; of particular
note are procedures for Australia, Canada, South Africa, the United
Kingdom, and the United States (Table 3-1; reviewed in detail by
Moldan and Chapman, 1983; Thompson, 1985; and WeDs, 1982a). A
number of other countries are thought to be doing tests.
The most frequent combination of test materials are dispersant,
oil, and dispersed oil, that is, dispersant and oil mixture (Table
3-3~. Most tests use seawater, and lethality is the usual toxicity re-
spouse. Many different test species are used, with little uniformity
among countries. Both indigenous and standard species have been
selected, such as local shrimp and Artemia, and in most countries lo-
cal species are used as the standard (rainbow trout, Salmo gairdneri,
in Cana(la; brown shrimp, Crangon crangon, in the United Kingdom;
and mummichog, Fundulus heteroclitus, in the United States). Most
countries have pass-fai} criteria, but they vary. When dispersed of! is
tested in the laboratory, of! composition is variable and differs from
place to place, the water-soluble fraction is normally not separated,
and hydrocarbon exposures are normally not measured. Hence, the
same dispersant submitted to different countries for approval may be
subjected to quite different toxicity screening methods and pass-fai!
· ~
criteria.
*The United Kingdom screens for effectiveness first, and dispersants that pass go
onto the toxicity-testing phase. The work is conducted in two laboratories and is a
phased approach rather than a linked approach.
OCR for page 87
TOXICOLOGICAL TESTING OF OIL DISPERSANTS
TABLE 3-1 Worldwide Survey of Dispersant Toxicity Screening
Geographic
Location
Author/Year
Report/Result
United States
Canada
European Nations
Europe
Finland
France
Norway
Sweden
Battelle Memorial
Institute, 1970
Blacklaw et al., 1971
California State Water
Resources Control
Board, 1971
Becker et al., 1973
McCarthy et al., 1973
U.S. Department
of the Nary, 1973
Exxon Chemical
Company, 1980
Cashion, 1982
Smith and Panic, 1983
Lindstedt-Siva et al.,
1984
Peoria and Smith, 1984
U.S. Environmental
Protection Agency
tEPA), 1984
API, 1985
Pavia and Onstad, 1985
Abbott, 1972
Environment Canada,
1973
Doe and Harris, 1976
Environment Canada,
1976
Harris and Doe, 1977
Wells, 1982a
Abbott, 1984
Environment Canada,
1984
Harris et al., 1986
Trudel and Rose, 1987
Wilson et al., 1973,
1974
Kerminen et al., 1971
Division Qualite
des Eaux, 1979
Auger and Croquette,
1980
CTGREF, Division
Qualite des Eaux,
1981
Norwegian Ministry of
Environment, 1980
Westerngaard, 1983
Lehtinen et al., 1985
Early test procedures developed for
American Petroleum Institute (API)
U.S. Toxicity Test Procedure
Early test procedures developed
for California
Regional U.S. survey for bioassay species
for tests
U.S. EPA standard toxicity tests
U.S. Military Dispersant Specifications
U.S. policies on dispersant use
Draft ASTM Method No.6, dispersed oil
Dispersant use guidelines, California
Use guidelines, ecological considerations,
coast
Use guidelines, California
U.S. revised standard dispersant
toxicity test
API Dispersant Use Guidelines
Use guidelines, California
Ontario guidelines, Ministry of the
Environment
Canadian Dispersant Acceptability
Guidelines
Selection of suitable species for
toxicity tests
Standard Listing of Acceptable
Dispereants, Department of Energy (D OK)
Toxicity methods for screening
dispereants, DOE
Summary/re~riew, toxicity testing
worldwide for regulatory control
Discussion paper, Canadian Dispersant
Acceptability Guidelines
Dispersant Acceptability Guidelines,
2d ed.
Regulatory considerations, acute toxicity
test spp.
Dispersant use decision-making methods
Review, toxicity tests
Policy on toxicity, fish, early reports
Toxicity protocol
Acceptability list, use guidelines
Toxicity testing protocol
Regulations on dispersant
composition and use
Dispersant policy
Study for criteria for guidelines
87
OCR for page 88
88
USING OIL SPILL DISPERSANTS ON THE SEA
TABLE 3-1 (Continued)
Geographic
Location Author/Year Report/Result
United
Kingdom
Other Countries
Australia
Moore, 1968
Jeffery and Nichols,
1974
Blackman et al., 1978
Lloyd, 1980
Norton and Franklin,
1980
Norton, private
. ~ .
communication
Wilson, 1981
Franklin and Lloyd,
1982
Lloyd, priorate
. i.
communication
Wilson, 1984
Henry, 1971
Thompson, 1985
Thompson and
McEnnally, 1985
Linden, 1981
Bahrain
Hong Kong Thompson and Wu,
1981
Ministry of Transpor-
tation, 1974
White, private
communication
Port of Singapore
Authority, 1976
South Africa McGibbon, priorate
communication
Moldan and Chapman,
1983
Japan
Singapore
International Agencies
FAO White, 1976
IPECA
IMO
Early paper, U.K. dispersal experience
in ports
List of approved dispersants and
rationale
Procedure for U.K. screening, sea and beach
tests
U.K. role of toxicity tests, registration
and notification
Methods, dispersant toxicity, sea and
beach tests
U.K. methods, dispereant toxicology
Toxicity tests, rationale for choice
Toxicity, 2S oil-dispersant mixtures,
sea and beach tests
U.K., MAFF toxicity approach
U.K. policies on dispersant use, risk
analysis
Policy, dispereant use, early report
Program, effect and toxicity of dispersants
Resource atlas for spill countermeasures
Fisheries, use recommendations
Toxicity testing/ecreening methods
Testing standards, toxicity
Testing method
Toxicity testing methods
Dispereant testing program
Review, toxicity methods
International Petroleum
Industry En~riron-
mental Conservation
Association, 1986
IMO/UNEP International Maritime
Organization, 1982
Hayward, 1984
IMO Organization, 1986
Course, methods for oils and
dispereants
Statement of environmental concerns,
fate and effects
Guidelines, environmental
considerations
Bonn Agreement, toxicity test methods
Hong Kong, acceptance list
KEY: ASTM--American Society for Testing and Materials; FAO--Food and Agriculture
Organisation of the United Nations; MAFF--Ministry of Agriculture, Fisheries, and Food;
and UNEP--United Nations Environment Programme.
OCR for page 89
89
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OCR for page 154
154
USING OIL SPILL DISPERSANTS ON THE SEA
Dispersed of] was about twice as toxic to chum salmon fry compared
with dissolved hydrocarbons from untreated oil.
Coonstripe shrimp, sand lance, and Pacific herring larvae
were about the same sensitivity. Artemia nauplli and an isopod were
also affected to about the same degree by dissolved hydrocarbons
from dispersed oil.
Summary
The laboratory studies summarized above, comparing lethal and
sublethal toxicities of dispersed of} to various organisms, demonstrate
the wide range of responses that may occur when dispersants have
been used to treat oil, and the many factors influencing the responses.
In general, the results fall into three categories:
1. those employing nominal concentrations (total of} per unit
volume), which find that dispersed of] is more toxic; many (nearly 30
percent) of the tests (usually the earlier ones) fall into this category.
Test results stemming from use of this technique are in error, and
much data are of little use.
2. those analyzing for the water-soluble fraction, which find no
difference in toxicity between physically and chemically dispersed oil;
and
3. those comparing dispersant to dispersed of] toxicity that find
dispersed of] to be more toxic when a relatively nontoxic dispersant
is used, and find dispersant alone to be more toxic when a toxic
formulation is used.
When the WSF of the of} has been analyzed, there is seldom
evidence for synergism (i.e., greater than additive toxicity) between
of] and dispersant components, validating the general conclusion that
of] is as acutely toxic as dispersed oil.
These laboratory studies also demonstrate some of the difficulties
of accurately controlling the exposure of organisms to complex or-
ga~ic mixtures in small tank systems. Such experimental approaches
have been used because they are suitable for specific test organisms,
and because they offer some control over experimental variables. It
is recognized that such approaches do not simulate field conditions.
To date, laboratory studies have been most valuable in exploring the
types of responses and the duration of effects under "high exposure"
conditions, and offering guidance to the design and conduct of field
studies on dispersed oils.
OCR for page 155
TOXICOLOGICAL TESTING OF OIL DISPERSANTS
MICROBIAL DEGRADATION
155
A potentially important factor for planning dispersant use is
whether it will significantly enhance or retard degradation—particu-
larly microbial degradation of spiced oil. The ultimate fate of
spired petroleum depends primarily on the ability of microorganisms
to use spilled hydrocarbons as sources of carbon and energy (NRC,
1985).
AH marine waters appear to contain mixed natural microbial
populations with the genetic ability to grow on petroleum hydrocar-
bons. However, ocean waters that have continuous of} inputs, as from
seeps or discharges from populated areas, are likely to have greater
numbers and types of oil-degrading microorganisms. Biodegradation
begins after evaporative losses have ceased and continues for a week
to a year. Evidence suggests that chemical or mechanical disper-
sion in the water shortens the time period during which microbial
degradation assists of} removal.
Biodegradation appears to be limited primarily to paraffinic and
aromatic fractions, although studies by Rontani et al. (1986) have
shown some degradation of asphaltenes. To date there is no evidence
of biodegradation of polar fractions, or nitrogen-, sulfur-, and oxygen-
containing compounds (WestIake, 1982~.
Dispersants applied effectively increase the rate and possibly the
extent of biodegradation by
· creating more of} surface area;
· reducing the tendency of of} to form tar bans or mousse
(Gunke} and Gassman, 1980; Daling and Bran~vik, 1988~; and
· enabling dispersed oil droplets to remain in the water column
instead of beaching or sedimenting (Gilfi~n et al., 1985~.
They may also diminish biodegradation rates by
· adding new bacterial substrate (the dispersant) that microbes
might preferentially attack over the oil; or
· increasing concentrations of dispersed of] and dispersant in
the water column, which may have temporary toxic or inhibitory
effects on the natural microbial populations.
Creation of new surface area is the most important factor relat-
ing to biodegradation. Because chemical dispersion of oil increases
surface-to-volume ratios of the oil, and because degradation occurs
at the oil-water interface, the use of dispersants should enhance the
environmental conditions required for suitable microbial growth.
OCR for page 156
156
USING OIL SPILL DISPERSANTS ON THE SEA
Ideally, key questions relating to possible differences in the rate
and extent of degradation of chemically dispersed and nondispersed
of} should be addressed by direct field comparisons. However, these
comparisons are extremely difficult to accomplish (Green et al.,
1982~. As a result, knowledge of dispersed of! degradation is lim-
ited mainly to laboratory studies, pond and mesocosm studies, and
information on physical and chemical changes that are known to
occur mainly when dispersants act on spilled oil.
Laboratory Studies
Laboratory studies are useful for observing such important phe-
nomena as mechanisms of degradation; changes over time of type and
numbers of oleocIasts petroleum-degrading bacteria (AtIas, 19SS;
Lee et al., 1985~; relative degradability of various petroleum compo-
nents; biodegradability of various commercial dispersants; effects of
nutrient supplements; and enhancement or retardation of degrada-
tion rates with dispersant use. Laboratory studies, including innocu-
lations of field collections, have shown that degradation rates can be
enhanced or inhibited when dispersed of} is added to culture vessels.
For example:
.
TraxIer and Bhattacharya (1978) found that chemical dis-
persants significantly enhanced bacterial degradation of petroleum
hydrocarbons.
· Traxier et al. (1983) found that dispersed of} was more ef-
fectively metabolized by hydrocarbon-utilizing microorganisms than
either untreated of} or dispersant alone.
· Mulkins-Phillips and Stewart (1974) found only slightly en-
hanced degradation upon dispersion.
· Bunch and HarIand (1976) found no difference between un-
treated of} and dispersed oil.
Gatellier et al. (1973) found either enhancement or inhibition
depending on the dispersant used.
Zeeck et al. (1984), using 900 ppm (an extremely high con-
centration) of dispersants, inhibited bacterial growth or decreased
glucose uptake rates.
These widely varying and even apparently conflicting results are
not conflicting, however, given differences in laboratory techniques,
exposure concentrations and durations, nutrient availability in the
culture, temperature, and dispersants and oils tested. Generally, the
OCR for page 157
TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
157
experiments showing inhibition used dispersant concentrations that
exceeded the range found in field tests.
The biodegradable nature of some commonly used dispersants
has been reported from several laboratory studies (Cretney et al.,
1981; Gunkel, 1974; Traxler and Bhattacharya, 1978~. Because
some dispersants are preferentially utilized over the of} as the carbon
source, some experiments have shown initial of! degradation rates in
the laboratory to be inhibited by the addition of dispersants (Bunch
et al., 1983; Foght and WestIake, 1982; Foght et al., 1983; Mulkins-
PhiDips and Stewart, 1974~. Griffiths et al. (1981) reported decreased
uptake of labeled glucose that appeared to be dependent on disper-
sant concentration. These dispersant-oi} concentrations were higher
than would usually be observed in situ, although Griffiths et al.
(19S1) reported one experiment that showed a 10 percent decrease
observed at 1 ppm. Generally, inhibition has not been important in
pond or mesocosm studies.
The extent to which laboratory studies of biodegradation rate
and extent can be extrapolated to the marine environment is severely
limited. Major problems include the confining conditions of test
vessels and the need to add nutrient supplements. Hydrocarbon
degradation rates from laboratory experiments have been several
orders of magnitude higher than in situ rates. Conversely, toxic or
inhibitory effects are likely to be magnified in the laboratory because
the dispersant and dispersed of} mixtures in the test vessels are not
able to dilute as they would in nature.
Mesoscale Studies
Pond and mesoscale experiments are seen by many researchers
as a way to increase substantially the realism of oil-dispersant ex-
periments. They suffer some of the same shortcomings as laboratory
studies (e.g., a limited water volume), but to a lesser extent. Key
results of several experiments are summarized below. They con-
sistently show enhanced oil degradation rates of dispersed of] over
undispersed of] (see Chapter 4~.
In CEPEX bag experiments reported by Cretney et al. (1981)
and Green et al. (1982), biodegradation was greatly increased in the
dispersed oil bag. Microbial oxidation of the n-alkane component
of the of! was completed within 15 days, a rate at least an order of
OCR for page 158
158
USING OIL SPILL DISPERSANTS ON THE SEA
magnitude higher than for undispersed of} (Green et al., 1982~. Fur-
thermore, only 0.1 percent of the dispersed of! reached the sediment
during these 15 days, and it was in an advanced state of bacterial
decomposition. At the surface slick in the CEPEX experiments,
microbial degradation had not begun by the end of the 15 days.
In Seafluxes enclosure studies of dispersant and dispersed oil-
stimulated bacterial production, Lee et al. (1985) observed increased
glucose uptake rates in enclosures with dispersant and dispersed oil.
Biodegradation was more important than abiotic processes in the
removal of low volatility n-alkanes of dispersed of! in the Seafluxes
enclosure.
In freshwater pond experiments, alkane degradation rates of
test oils were substantially increased in dispersed of] ponds versus
undispersed oil ponds (Dutka and Kwan, 1984; Dutka et al., 1980;
Green et al., 1982; Scott et al., 1984~. Heterotrophic bacterial counts
increased tenfold in oil-dispersant ponds versus oil-only ponds. Also,
substantially less of} was found in the sediments of the pond treated
with dispersants than in the oil-only ponds after ~ year (Scott et al.,
1984).
In seawater pond experiments, Marty et al. (1979) compared
dispersed and nondispersed of] in 20-m2 (24 x 103 liters) basins
filled with lagoon seawater. Four months after the first treatment,
dispersed slicks were no longer visible, while the untreated reference
slick did not appear significantly different. Nutrients were not added
to the lagoon seawater. Dispersant concentrations were 13 to 130
ppm, significantly higher than manufacturers found in field tests,
even immediately after dispersion.
In dispersant-only tests, oil-degrading bacteria increased by 4 to
100 times those in the seawater only (Marty et al., 1979~. Although
bacterial populations doubled in the oil-only basin after 14 hr of
contact, in the dispersant-treated ponds a doubling was not evident
until the fifth day of treatment. Despite the delay, microbial popu-
lations and extent of degradation were significantly enhanced in the
dispersant tanks after 4 months.
Microbial Field Studies
Bunch (1987) studied the effects of chemically dispersed crude
of} on bacterial numbers and microheterotrophic activity in the water
column and sediments of selected bays at the BIOS experiment site,
Cape Hatt, Northwest Territories, from 1980 to 1983. In the release
OCR for page 159
TOXICOLOGICAL TESTING OF OIL DISPERSANTS
159
of dispersed of} in 1981, there was a transient decrease in Vmax (max-
imum velocity) of glutamic acid uptake in water samples. Bacterial
numbers were unaffected.
In vitro experunents with water samples demonstrated that a combination
of petroleum and dispersant, or disperse alone, reduced the Vmax of
glutamic acid uptake to a greater extent than petroleum alone.
In addition, total organic carbon and bacterial numbers tem-
porarily increased in the sediments impacted by dispersed oils, re-
covering to normal (control) values by the second year. Effects on the
water column were considered inconsequential or marginally delete-
rious, while effects on the sediment were indirect, long-term, and
likely of marginal significance to microheterotrophic activity.
Summary
Some laboratory studies and all mesocosm studies have shown
increased oil biodegradation rates when dispersants are used. Tem-
porary inhibition of biodegradation with dispersed of} also has been
observed in the laboratory, but appears to occur only at dispersed
of} concentrations higher than would occur in the field. Data from
pond and mesocosm studies strongly indicate that effective use of
dispersants would enhance the biodegradation rate of spilled oil.
With limited field data (Bunch et al., 1983, 1985) available, and
because biodegradation may be slow or incomplete under some field
conditions, this conclusion requires additional verification by field
studies.
The primary objectives of dispersant use are to enhance dilution
effects, to get of} off the water surface, and to prevent stranding of
oil. Hence, any rate enhancement of biodegradation probably should
be viewed simply as a secondary benefit to the primary objectives.
Finally, on the question of whether dispersants enhance the ex-
tent of biodegradation, available information suggests that refractory
compounds would remain undegraded regardless of the addition of
dispersants (Lee and Levy, 1986~. One aspect of this question that
has not been quantified is the extent to which dispersants prevent tar
bad formation. Prevention of tar bass and large mousse accumula-
tions possibly could be an important advantage of chemically dispers-
ing oil, because tar balls, especially large ones, trap biodegradable
hydrocarbons, and mousse accumulations do not break up before
stranding and eventually become buried in intertidal and shallow
subtidal sediments (Jordan and Payne, 1980; NRC, 1985~.
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160
USING OIL SPILL DISPERSANTS ON THE SEA
SEABIRDS AND MARINE MAMMALS
Despite concerns of coastal resource managers and of] spill re-
sponse teams about the effects of of} spills on seabirds and marine
mammals, far more research has been conducted on the effects of
oil and dispersed of] on intertidal and subtidal invertebrates, plants,
and fish. Because of high susceptibility to damage and high visibility
when oiled, however, much recent public policy consideration has
been given to seabirds and marine mammals. Unfortunately, many
of the critical questions regarding damage to marine mammals and
seabirds by of} and possible mitigation by dispersants have not yet
been addressed.
There are two primary effects of of] on seabirds and marine
mammals (Leighton et al., 1985; NRC, 1985~:
1. toxic effects resulting from direct ingestion of of! from the
water, or indirectly from grooming or preening; and
2. effects on the water-repellency of feathers or fur needed for
thermal insulation.
Research on toxic effects of ingestion is reviewed below.
Seabeds
The few studies of direct toxicity of of} and dispersants to seabirds
(Table 3-16; Peakall et al., 1987) show that dispersant and crude of!
reduce hatching success and lower resistance to infection to about
the same extent, and sometimes less than, of} ~one. Studies have
been primarily on avian reproduction and physiology. The effects
of of} alone on embryos and early development are well known, and
the effects of oil-dispersant mixtures have been studied at various
stages of the reproductive cycle. Generally, crude oil and Corex~t
9527 mixtures and crude oil alone are similarly toxic to bird eggs,
based on nominal concentrations.
Work with other species, such as mallard ducks and herring gulls
(Table 3-16), also shows a wide range of sensitivities, particularly
with duck eggs. For example, Albers (1979) tested Prudhoe Bay
crude oil, Corexit 9527, and mixtures (5: l and 30:1) on the hatch-
ability of mallard eggs (Anas platyrhynchos) over 6 to 23 days. All
produced diminished hatchability at the 20-pl dose level per egg (ex-
ternal surface). The oil, dispersant, and 5:1 mixture had similar
effects, but the 30:1 mixture was significantly less toxic. At reduced
dosage, only the Cored mixture caused significant effects.
OCR for page 161
161
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OCR for page 162
162
USING OIL SPILL DISPERSANTS ON THE SEA
The results of coating experiments are important to note, par-
ticularly for breeding birds, which may transfer dispersant and oil
back to their nests. For example, a field study with Leach's storm
petrels (Butier et al., 1988) showed no effects of internal dosing with
Pru~hoe Bay crude of} or mixtures with Corex~t 9527 (10:1), but
the highest dose of externally applied dispersant-oi] mixture (1.5 m]
per bird) significantly increased the percentage of brooding birds de-
serting the nesting burrow. No significant effects were seen with of]
alone. Hatching success was decreased to the same extent with both
oil and dispersant-oil treatment.
A mathematical model for the exposure of diving and surface-
feeding seabirds to surface oil and dispersed subsurface oil (Peakall
et a]., 1987) led to the conclusion that the exposure resulted from
the surface slick, and that "a highly effective dispersant significantly
reduces of} exposure for both types."
The literature review by Peakall et al. (1987) on dispersed of!
effects on seabirds concluded that the hazard of chem~caDy dispersed
of] to seabirds depended primarily on differing exposures under nat-
uraDy and chemically dispersing conditions. Their evaluation of the
toxicology, based on sublethal responses at the biochemical and phys-
iolog~cal level, showed similar responses to of} components, with and
without dispersants.
Other studies have examined the toxicity of dispersed oils to
seabirds; these include Butler et al. (1979, 1982, 1987), Albers (1980),
Lambert and PeakaD (1981), Miller et al. (1981, 1982), PeakaD and
Miller (1981), Butler and Peakall (1982), Trudel (1984), and Ekker
and Jenssen (1986~. Collectively these studies, including those by
PeakaD et al., show the range of responses of birds to of} and dispersed
oils, the similarity in responses to of] and dispersed oils, and the
obvious need to reduce surface oiling for bird protection.
There are also occasional concerns regarding the direct effects
of the dispersants themselves on seabirds, both on adults and on
eggs and young at the nest. These effects, although perhaps fewer
than those produced by of] itself, include direct accidental spraying
of birds with dispersants (from aircraft) and the potential increased
risk of oiling to seabirds from slicks that have spread after dispersant
application.
The seabird-dispersant issue, following from the above summary,
seems to be one of exposure to the dispersant and the dispersed oil,
rather than one of enhanced toxicity of the oil as perceived until
recently.
OCR for page 163
TOXICOL O GICA L TESTING OF OIL DISPERSA NTS
Marine Mammals
163
Effects of of} spins on marine mammals include physical fouling,
thermal and compensatory imbalance due to oil coatings, uptake,
storage and depuration of hydrocarbons, changes in enzymatic activ-
ity in the skin, interferences with swimming, occasional mortalities,
eye irritation and lesions, and oiling of young (Engelhardt, l9SS).
Reviews by Geraci and St. Aubin (1980), Smiley (1982), Engel--
hardt (1983, 1985), and NRC (1985) describe the effects of oiling
on the fur of sensitive marine mammals (sea otters), based on lab-
oratory and mesocosm toxicology experiments and observations of
oiled animals in the field. More than a twofold increase in thermal
conductance (over baseline), and therefore a 50 percent reduction
in insulating capacity, has been reported for polar bears (Hurst and
Oritsland, 1982), sea otter pups and fur seals (Kooyman et al., 1977),
live adult sea otters (Costa and Kooyman, 1982), and sea otter pelts
(Hubbs Marine Research Institute, 1986; Kooyman et al., 1977~.
Dispersants have been used experimentally like "shampoos" to
remove crude of! from marine mammal fur, but such attempts re-
moved natural skin oils along with the crude oil, thus destroying the
fur's water-repellency (Williams, 1978~. Surface-active agents, such
as those used in dispersants, can increase the Nettability of fur or
feathers, which in turn allows cold water to penetrate and increase
the thermal conductance of the pelt. This is particularly dangerous
to animals that are buoyed or insulated by their fur or feathers. In the
case of the sea otter, unless grooming can quickly repair the damage,
cold water leaks through the fur and against the skin, causing fatal
chilling. If the animal grooms excessively, however, it can scratch
away large amounts of underfur, further complicating the restoration
of body insulation (McEwan et al., 1974~.
Direct toxicity is also a potential problem. Polar bears died from
toxic effects of oil ingested during grooming (Engelhardt, 1981) as
did river otters examined after an oil spill at Sullom Voe, Shetland
Islands (Richardson, 1979~.
To date, only Hubbs Marine Research Institute (1986) has ad-
dressed chemically dispersed oil effects. The critical work by the
American Society for Testing and Materials (ASTM, 1987) reviews
the literature on oil damage and other human disturbances to marine
mammals, but cites none regarding the effects of dispersed oil.
Attempts to remove oil or dispersed oil from sea otter pelts
showed that any residue of oil or dispersant left on the fur, even
if the fur was dry, permitted water to penetrate into the fur upon
OCR for page 164
164
USING OIL SPILL DISPERSANTS ON THE SEA
immersion (Hubbs Marine Research Institute, 1986~. This confirmed
the earlier studies of the damaging effects of increased wettability of
sea otter fur after contact with crude oils, detergents, and dispersants
(Costa and Kooyman, 1982~.
Research on thermal responses was conducted by rubbing fresh
oil or 5-day weathered Santa Barbara crude oil on adult California sea
otter pelts (Hubbs Marine Research Institute, 1986~. Fresh oil alone,
or with Correct, easily penetrated the fur, which quickly saturated
upon immersion in water. Thermal conductance was more than
twice as high as in untreated control pelts. There was no difference
in conductance between fresh crude alone or with of} combined with
the dispersant. Based on such sparse information, oil dispersant
chemicals may not reduce the physical threat of spilled of! to some
fur-insulated sea mammals.
Smiley (1982) stated that
Nonetheless, dispersion of large oil slicks is probably a useful countermeasure
tool, assuming that both the floating oil and the applied chemical are
effectively diffused into the water column. The risks of direct fouling and
of inhalation toxicity when swimming at the sea surface would be reduced,
especially in cold icy situations where natural weathering And evaporation
of oil slicks is slow.
In addition, the ASTM (1987) concluded that
Use of chemical dispersants and mechanical methods is recommended to
prevent these habitats from being contaminated or to reduce contamination.
. . . Because sea otters and polar bears are very sensitive to oil contamination,
dispersant use is recommended even if application must occur near or in a
habitat used by these animals.
However, available data do not seem to support this recommen-
dation, and Smiley's conclusion assumes complete dispersion and
disappearance of surface of} after dispersant application, which may
not occur.
In view of the enormous public interest in, and concern for, the
fate of seabirds and marine mammals, it is surprising that so little
research with dispersants has been done with these animals, and
that the conclusions on the use of dispersants for protecting these
animals can only be tentative. Clearly, there is a great need for
more laboratory and field studies, particularly in order to determine
whether the use of dispersants wiD lessen the adherence and impact of
of] on the fur of marine mammals and the feathers of birds. Thus far
the data only appear to indicate that there is no difference between
the effects of oft with dispersants or alone.
Representative terms from entire chapter:
chemically dispersed
