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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

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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]

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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

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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

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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.

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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

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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.

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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.

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TOXICOLOGICAL TESTING OF OIL DISPERSANTS MICROBIAL DEGRADATION 155 A potentially important factor for planning dispersant use is whether it will significantly enhance or retard degradationparticu- 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.

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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

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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

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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

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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.

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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.

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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

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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.