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GLERL 2000 Milestone Reports
GOAL: SUSTAIN HEALTHY COASTS
OBJECTIVE 2: Promote Clean Coastal Waters to Sustain Living Marine resources and to Ensure Safe Recreation, Healthy Seafood, and Economic Vitality
PM: Develop better tools, predictive models, and understanding related to water quality and coastal ecosystems management.
Milestone: Determine the utility of the critical body-residue approach for improving assessment of contaminant impacts for non-persistent high volume commercial products such as selected surfactants, an important component of laundry detergents.
Scientist: Peter Landrum, GLERL
Purpose: This work is a collaborative effort between GLERL, Ohio State University (Dr. Susan Fisher), and the Proctor and Gamble Co. The research examined the use of body residues as a measure of dose for compounds that are not persistent in the environment, specifically the surfactant, 2-phenyl C12 linear alkylbenzene sulfonate (LAS). Despite the low persistence, these compounds are used in huge quantities in various detergent formulations. Thus, even if small amounts survive waste-water treatment, they could pose a risk to aquatic organisms. Further, the compounds are discharged to a wide range of aquatic environments. LAS is a particle sorptive compound, so organisms that ingest settling particles from discharges may be at the highest risk, since benthic organisms often receive a large portion of their exposure through ingestion of contaminated particles. Establishing the exposure on a body residue basis accounts for all routes of exposure. Developing better methods for assessing the hazard of chemicals and the exposure of aquatic organisms will lead to improved management of contaminants and protection of the health of the ecosystem.
Efforts: Chironomus riparius, midge larvae were exposed to LAS for periods ranging from 4 d through to emergence as adults. Toxicity was measured as mortality, fecundity, and development time by exposing midges to aqueous concentrations of LAS. The concentrations of LAS in the midges at the different periods of exposure were used as the measure of dose. The body-residue approach for assessing exposure has been demonstrated to allow improved assessment of exposure from multiple sources. Compounds acting through a narcosis mechanism of action are found to be acutely lethal at 2-8 mmol/kg and chronically lethal at 0.2-.8 mmol/kg for fish. Other mechanisms of action require lower concentrations. These studies were performed with compounds that are not rapidly metabolized. It was expected that LAS would be biotransformed and that the impact of biotransformation on the use of the body-residue approach could be evaluated. However, in the midge larvae, no biotransformation of the LAS was found. Therefore, it was possible to examine the impact of the accumulated LAS residue without having to account for biotransformation.
LAS was acutely toxic after 4 d exposure and exhibited an LR50 of 1.17(0.31-4.32) mmol/ kg. The lethality increased and after 30 d, a substantial portion of the lifetime of these organisms, the LR50 decreased to 0.28 (0.19-0.53) mmol/kg. By examining the relationship between exposure time and internal concentration to produce 50% mortality (Figure 1), it is possible to estimate the concentration required to result in a similar level of mortality at say 90% of the life span of the organism. The toxic dose at 90% of the lifespan would be about 0.08 mmol/kg based on the relationship in Figure 1. This approach suggests that levels could be set for regulatory protection based on body residues if the proper database were available. Note this level is similar to the level of some chronic effects for LAS, specifically developmental times of the midges were significantly increased at 0.085 (0.07 - 0.11) and 0.47 (0.03-0.64) mmol/kg for males and females respectively. Some of the highest concentrations of LAS found in the environment are in a range that could lead to chronic effects based on the measured bioconcentration factor of 182 and the chronic effects data generated here. The amount of data in this study is small and there is significant variability in the measurements. Thus, before setting limits additional work would be required. Further, these tests also need to be with the LAS sorbed to sediment to determine if the material is biologically available. Overall, the body-residue approach allowed examination of effects without accounting for exposure to LAS sorbed to food as well as the concentration in the water under the current exposure conditions.
Figure 1. Lethal body residue for 50% of the population versus exposure duration.
Customers: This work is important to the detergent industry, as demonstrated by the partial support of this work by Proctor and Gamble. The work is also important to the regulatory community and the public seeking to protect the environment. The work is provided directly to Proctor and Gamble and is being presented at national scientific meetings and will be published in the open literature.
Significance: The body-residue approach for evaluating exposure to assess toxicity is still in the developmental phase. There have been significant advancements in the field over the past several years. This approach is expected to improve assessment of the bioaccumulation of contaminants by organisms. To date the bioaccumulation data required by regulatory mandate can only be evaluated relative to background, a reference site, or against an FDA action limit. From an ecosystem protection perspective, evaluation of these bioaccumulation data is limited and the development of the body-residue effects model will make them more useful.
Success: The project was completed as expected. The only limitation was the absence of biotransformation by this organism. Thus, the impact of biotransformation on the body-residue approach could not be tested. The development of both acute and chronic data for this important commercial compound will allow the regulatory community an improved approach to determine if the integrated exposure to this important benthic organism is at toxic levels. This allows for integration of multiple routes and multiple durations of exposure to be incorporated into assessments.
Next Steps: Both the USEPA and the USACOE have developed documents indicating a need for developing data to allow assessment of body residues in terms of effects on organisms. This information will also be extremely useful for the Office of Response and Restoration, NOS. Research on the conditions and utility of the body residue approach will continue. Specifically, a collaborative project with the USACOE is planned to use this approach to develop an improved method for assessing contaminant mixtures from sediment exposures.
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Last updated: July 9, 2002 mbl