Field studies should be used, whenever possible, to validate laboratory predictions of environmental exposures and the safety of chemicals. Laboratory tests are designed to be easily replicated but only generally representati ve of environmental conditions, and have been shown through recent studies using linear alkylbenzene sulfonate (LAS) as a test substance to greatly underestimate real-world safety. Use of field studies that closely simulate or monitor real-world condition s to support or refine assessments based on laboratory measurements ensures that standards and regulations based on safety assessment are appropriately protective of the environment. LAS provides a practical case study for comparison of laboratory and fie ld safety assessment studies. It has been used in large volumes for 30 years and is the most widely tested detergent ingredient in use today, offering an extensive data base of laboratory tests and field studies covering all parts of the environment.
- Laboratory tests to determine levels of chemicals in water typically use analytical methods that provide a measure of total concentration in an aquatic environment. These measurements predict the amount of exp osure aquatic organisms have to a chemical, and are compared against levels shown to be harmful to test organisms. The exposure level compared against the toxic effect level determines environmental safety.
- Most laboratory analytical methods, however, test only for total concentration and not for the amount of a chemical that is both present and available to aquatic species. This is an important distinction for surfactants like LAS which tend to attach (adsorb) to sediment or particulate matter suspended in water, or interact with dissolved chemicals naturally present in water, such as humic acids.
- When adsorbed on sediments, a significant portion of the total LAS concentration is essentially removed from the water, and aquatic organisms are exposed to much smaller levels, and, thus, potential toxicity is reduced. The laborato ry methods typically used do not reflect this removal, and as a result, overestimate exposure, toxicity and relative risk to aquatic organisms.(1,2)
- In one laboratory study, LAS concentrations in clean water were predicted to have impacts on certain sensitive test organisms. However, LAS adsorbed into sediment was shown not to pose any risk even at concentrations 10 times the predicted level of toxicity.(3)
- An experimental stream study at the U.S. Fish and Wildlife Service's laboratory in Columbia, Missouri, found no observable effect concentrations (NOECs) for fish and insects to be greater than 0.36 milligrams per liter (mg/L). This result, compared with data from numerous laboratory studies, demonstrated that the laboratory studies yielded valid, but conservative, safety assessments.(4)
- Even field studies can provide understated estimates of safety. LAS, for instance, is a mixture of different-sized molecules (alkyl chain lengths), the longer alkyl chain lengths having greater potential to be toxic than the s horter alkyl chains. These longer alkyl chain molecules, however, are more rapidly removed.(1,5-8) Because field studies do not include the preferential removal of the longer alkyl chain LAS molecules, they overestimate potential risk to the en vironment by a factor of two to four. Nonetheless, field studies still provide the most reliable measure of environmental safety and should be used, when available, instead of relying on laboratory findings alone.
KEY REFERENCES
2. Hand, V. C., R. A. Rapaport and C. C. Pittinger. "First Validation of a Model for the Adsorption of Linear Alkylbenzene Sulfonate (LAS) to Sediment and Comparison to Chronic Effects Data." Chemosphere 21, 741 (1990).
3. Bressan, M. et al. "Effects of Linear Alkylbenzene Sulfonate (LAS) on Benthic Organisms." Tenside Surf. Det. 26, 148-158 (1989).
4. Fairchild, J. F., F. J. Dwyer, T. W. La Point, S. A. Burch and C. G. Ingersoll. "Evaluation of a Laboratory-Generated NOEC for Linear Alkylbenzene Sulphonate in Outdoor Experimental Streams." Environ. Toxicol. Chem. 12, 1763-1775 (1 993).
5. Divo, C. "A Survey on Fish Toxicity and Biodegradability of Linear Sodium Alkylbenzene Sulfonates." The 12th World Congress of the International Society for Fat Research (Milan, 1974).
6. Kimerle, R. A. and R. D. Swisher. "Reduction of Aquatic Toxicity of Linear Alkylbenzene Sulfonate (LAS) by Biodegradation." Water Research. 11, 31-37 (1977).
7. Brown, V. M., F. S. H. Abram and L. J. Collins. "The Acute Lethal Toxicity of an LAS Surfactant and Its Residues and Degradation Products." Tenside Surf. Det. 15, 57-59 (1978).
8. Moreno, A. and J. Ferrer. "Toxicity towards Daphnia during Biodegradation of Various LAS." Tenside Surf. Det. 28, 129-131 (1991).
- Orth, R. G., R. L. Powell, G. Kutey and R. A. Kimerle. "Impact of Sediment Partitioning Methods on Environmental Safety Assessment of Surfactants." Environ. Toxicol. Chem. 14, 337-343 (1995).
Last updated on October 1995
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INDEX OF CLER FACT SHEETS
- Executive Summary
- Recent Developments
- LAS Biodegradation and
Removal In Sewage Treatment
- LAS Biodegradation and
Safety in Rivers and Streams
- LAS Biodegradation and
Safety in Sediments
- LAS Biodegradation and
Safety in Sludge and Soils
- LAS Biodegradation and
Safety Under Anaerobic Conditions
- Biodegradation and
Safety of Commercial LAS
- Environmental and Other
Benefits of Replacing ABS With LAS
- Test Methods for Biodegradation
- Laboratory Versus Field
Safety Assessment Studies
- Oleochemical and Petrochemical Surfactants