Vol. 5, No. 1 (December 1999) — Preface
Science as the Basis for Environmental Regulations
The soap and detergent industry have long supported the principle that science should provide the basis for environmental regulations. Regulations not based on science consume public resources without the assurance of any benefit to the environment. Indeed, this is the very reason CLER was formed 12 years ago – to provide scientific information on the environmental safety of linear alkylbenzene (LAB) and linear alkylbenzene sulfonate (LAS), the most widely used cleaning agent (surfactant) in laundry detergents worldwide.
Consequently, when the Environmental Protection Agency of Denmark announced in May 1996 that they intended to set strict restrictions on the amount of LAS allowed in the solid wastes of sewage treatment plants (biosolids or sewage sludge) permitted for use as agricultural fertilizer, it drew considerable attention from CLER, our sister organization in Europe (ECOSOL), the Danish soap and detergent association (SPT) and the international detergent and surfactant industries (AISE & CESIO). Re-use of biosolids as a fertilizer is generally considered the environmentally preferred method for disposal, provided that the biosolids do not contain harmful levels of heavy metals, other potentially toxic compounds or pathogenic microorganisms. Because laundry detergents that contain LAS and other substances are washed down the drain into sewage systems, residual levels of these substances can be detected in biosolids from sewage treatment facilities.
But what is the basis for the Danish EPA’s concern? After all:
- Biosolids containing LAS have been safely used for many years as fertilizer in Denmark, other countries of Europe and in North America.
- Numerous scientific studies have demonstrated that LAS rapidly biodegrades in biosolids-amended soil and does not build up in the soil with repeated application.1
- A terrestrial risk assessment of LAS published in 1990 reported that LAS levels in biosolids-amended soil were far below levels that would harm earthworms or food crops.2
- No other country has restrictions on levels of LAS in biosolids.
This issue of THE CLER REVIEW contains six studies that address the concerns regarding LAS in biosolids used as fertilizer and demonstrate the safety of LAS:
- The first study, by Cavalli and Valtorta (“Surfactants in sludge-amended soil”) reports that the Danish restrictions on LAS in biosolids do not follow the agreed upon European rules for conducting a terrestrial risk assessment. The study concludes that, even using Denmark’s rules for calculating LAS levels in biosolids-amended soil, LAS “does not present any immediate cause for concern as regards risk to the terrestrial environment.”
- The next paper (Madsen and others, “Studies on the fate of linear alkylbenzene sulfonates (LAS) in sludge and sludge-amended soil”) is the extended abstract of a study conducted by the Water Quality Institute of Denmark (VKI), an independent research organization. It was presented at a recent science workshop organized by SPT in coordination with the Danish EPA. Laboratory studies conducted by VKI demonstrate that LAS in biosolids is rapidly biodegraded during aerobic treatment (sludge stabilization or composting). Modeling studies based on Danish conditions predict worst case initial LAS concentrations in soil of no more than 10 milligrams LAS per kilogram dry weight of soil (10 parts per million). These studies also indicate that the LAS from biosolids-amended soil will be almost completely (98-99%) biodegraded within one year. Further, LAS “is not expected to accumulate in soil” and has “low leaching potential.”
- The third paper (Holmstrup and others, “Effect and risk assessment of linear alkylbenzene sulfonates (LAS) in sludge-amended soils”) is also an extended abstract of a study presented at the same science workshop. The study, conducted by a research agency of the Danish government (DMU), indicates that even an average LAS soil concentration of 5 to 15 parts per million (ppm) LAS “is unlikely to cause long-term adverse effects in the agricultural soil ecosystem.” Such high average concentrations do not occur in Denmark since Madsen and others have shown that, even under worst case conditions, initial LAS concentrations do not exceed 10 ppm and LAS rapidly biodegrades in soil.
- The next paper (J. Solbé, “Linear alkylbenzene sulfonate (LAS) risk assessment for sludge-amended soils”) is the official proceedings of the Denmark science workshop. One of the key findings is that even at the highest concentration of LAS in biosolids in Denmark, LAS is not predicted to cause a problem because of its rapid biodegradation in soil (half-lives less than 2S days) and also the legal restrictions in Denmark on the amount of biosolids that can be applied to soil. Consequently, the workshop found no scientific basis for restrictions on LAS levels in biosolids used as fertilizer in Denmark.
- The fifth paper (Denger and Cook, “Linear alkylbenzene sulfonate (LAS) bioavailable to anaerobic bacteria as a source of sulfur”) reports that some bacteria found in the environment can remove the sulfur-containing sulfonate group of LAS under sulfur starvation conditions even in the absence of oxygen (anoxic conditions). The Danish EPA has indicated that one of the reasons for their concern with LAS is that it does not undergo biodegradation under anoxic conditions (anaerobic biodegradation). The surprising new findings of this study demonstrate that LAS can undergo at least partial anaerobic biodegradation under sulfur depleted conditions. Furthermore, sulfur depleted conditions are increasingly being reported in agricultural soils. Consequently, even anoxic conditions in soil may not be a barrier to LAS biodegradation.
- The final paper (“Anaerobic biodegradation of surfactants”) is the executive summary and position paper of an AISE-CESIO report on the use of anaerobic biodegradation as a pass/fail criteria for environmentally preferred labeling (eco-labeling) of detergents. The Danish EPA is recommending that consumers buy laundry detergents with a particular eco-label seal as a strategy for reducing the levels of LAS in biosolids by reducing sales of detergents containing LAS. Laundry detergents containing LAS are not eligible for the eco-label due to requirements that all surfactants demonstrate anaerobic biodegradation in a specific laboratory test. The AISE-CESIO report concludes that the lack of anaerobic biodegradation does not seem to correlate with any apparent environmental problem for detergent ingredients such as LAS, which undergo rapid aerobic biodegradation. Consequently, eco-labels and regulatory schemes that use anaerobic biodegradability as a pass/fail criteria are not science based.
- A major conclusion of these studies is that there is no scientific basis for the restrictions of LAS levels in biosolids in Denmark, or by extension, anywhere else in the world. And there is no scientific basis for the concerns about anaerobic biodegradability of LAS or its safety for the terrestrial ecosystem. Consequently, the actions taken by the Danish authorities regarding LAS are examples of regulatory activity that appear to based on policy rather than science. These actions could result in consuming public resources without providing known benefit to the environment.
John E. Heinze, Ph.D.
1. Marcomini, A. and W Giger, Behavior of LAS in Sewage Treatment, Tenside Surf. Det. 25:226-229 (1988); Bema, J.L., F. Ferrer, A. Moreno, D. Pmts and F.R. Bevia, The Fate of LAS in the Environment, Tenside Surf. Det. 26:101-107 (1989); Figge, K., and R Schöberl, LAS and the Applicaton of Sewage Sludge In Agriculture, ibid. 26: 122-128 (1989); Hoft, M.S., E. Matthijs and J. Waters, The Concentration and Fate of Linear Alkyl Benzene Sulfonate in Sludge Amended Soils, Wat Res. 23:749-759 (1989); Prats, D., F. Ruiz, B. Váquez, D. Zarzo, J.L. Berna and A. Moreno, “LAS Homologue Distribution Shift During Wastewater Treatment and Composting: Ecological Implications,” Env. Toxicol. Chem. 12:1599-1608 (1993).
2. Mieure, J.P., J. Waters, M.S. Hoft and E. Matthijs, Terrestrial Safety Assessment of Linear Alkyl Benzene Sulfonate, Chemosphere 21:251-262 (1990).