Archive for category: Facts

EXECUTIVE SUMMARY

Revised September 2014

The Council for LAB/LAS Environmental Research (CLER) is an organization of scientists and technical specialists representing member companies CEPSA Quimica, S.A. (Madrid), Huntsman Corporation (Houston), Quimica Venoco (Venezuela) and Sasol North America (Houston). CLER’s mission is to evaluate data, conduct research and distribute scientific information on the environmental safety of the world’s number one surfactant, linear alkylbenzene sulfonate (LAS) and the material from which it is produced, linear alkylbenzene (LAB).

For nearly fifty years, LAS has been the major surfactant used in laundry detergents and other cleaning products. Supporting this long history of safe use is an enormous database of environmental research on LAS which includes numerous peer-reviewed scientific publications and extensive data compilations. This research has looked at virtually every environmental compartment that might be exposed to LAS and considered all the components of commercial LAS.

Detergent components such as LAS typically go down the drain after use and flow into municipal sewage treatment plants or domestic septic systems. In some cases, more common in less developed parts of the world, disposal is directly into streams, rivers or the oceans.

Many studies have been conducted in the U.S. and in Europe on what happens to LAS during sewage treatment. Biological breakdown (biodegradation) of LAS actually begins in the raw sewage before it reaches the treatment plant. Once LAS reaches the sewage treatment plant, it is rapidly biodegraded and extensively removed. In modern treatment plants, LAS removal often exceeds 99%.

Treated water from sewage treatment plants is returned to streams, rivers or the oceans. LAS concentrations in the water and sediments of streams, rivers and oceans receiving treated water are very low and pose no risk to the organisms present. Any remaining LAS will continue to biodegrade until it is either incorporated into cell biomass or completely broken down (mineralized) to water, carbon dioxide and sulfate salts.

During sewage treatment, solids are separated from water, and some LAS adsorbs to the solids. These solids, called sludge, can be incinerated, placed in landfills or used as a soil conditioner or fertilizer. LAS does not harm crops planted in soil fertilized with sludge. Residual LAS continues to biodegrade so that yearly applications of sludge to agricultural lands do not cause any buildup of LAS.

LAS is also rapidly biodegraded and efficiently removed in septic systems, thereby protecting groundwater resources.

Commercial LAS contains small amounts of three constituents in addition to LAS itself: linear alkylbenzene (LAB), dialkyltetralin sulfonate (DATS) and methyl-branched alkylbenzene sulfonate (isoLAS). LAB, DATS and isoLAS have been shown to biodegrade rapidly and completely, and are safe for the organisms present in the environment.

Concerns have been expressed about detergent components and other materials that may become attached (adsorbed) to sediments deposited in oxygen free (anaerobic) environments where biodegradation is thought to proceed at a slower pace, if at all. Recent studies have shown that LAS can biodegrade under oxygen limited (anoxic) conditions and also under anaerobic conditions as well. Anoxic environments represent an intermediate environment between oxygen available (aerobic) and anaerobic conditions. Aerobic and anoxic conditions are more prevalent than anaerobic ones. Moreover, LAS levels in the environment are low, or not detectable, and pose no risk to the organisms present. Consequently, anaerobic conditions are not an issue for LAS environmental safety.

Over the years, the environmental safety and acceptability of LAS has been repeatedly confirmed in several major regulatory decisions including qualification as a surfactant raw material in the CleanGredient database, meeting the standards set by the U.S. Environmental Protection Agency Design for the Environment Program, a comprehensive assessment of the available health and environmental data on LAS by the international Organization for Economic Cooperation and Development ( OECD LAS SIDS Dossier), and the 2013 updated HERA Project health and environmental risk assessment of LAS use in household and cleaning products in Europe. In addition, the environmental safety of LAS has been reviewed in a comprehensive 2014 report on the “ Environmental Safety of the Use of Major Surfactant Classes in North America.”

The vast database on LAS, more extensive than on any other surfactant, provides complete and continuing assurance that LAS is environmentally safe and acceptable, and that LAS will be recognized as such for the foreseeable future.

Revised September 2014

In many parts of the world, municipal wastewater treatment facilities are not readily available and wastewater from households is discharged to septic tanks (onsite systems) for treatment. In the U.S., about 20-25 percent of the households, usually at rural locations, utilize onsite treatment of household wastes.¹ Septic systems are also used in major cities in Southeast Asia.² These onsite wastewater treatment facilities are regulated by local governments. In the U.S., the Environmental Protection Agency (EPA) provides guidance and technical assistance to help develop and enhance onsite programs. When properly operated, septic tank treatment of onsite waste is a cost-effective, hygienic method of wastewater treatment.

A study by Cornell University³ indicated that the average U.S. household generates 55 to 75 gallons of waste water per person per day. Sources include toilets, showers, sinks, dishwashers, and washing machines. The diversity of sources means that household wastewater contains a variety of biological and chemical constituents found in sewage, food waste, and assorted household products that are washed or poured down the drain. A typical septic tank may contain more than 100 traceable chemical components, including surfactants (including linear alkylbenzene sulfonate, LAS) contained in laundry and cleaning products.

When LAS was commercially introduced in the early 1960s as a replacement for highly branched alkylbenzene sulfonate (ABS), studies were already being reported on the biodegradation behavior of LAS compared to ABS under septic tank conditions. Results from laboratory benchscale septic tank and drain field studies indicated that LAS was 90 to 95 percent biologically degraded compared to about 35 percent for highly branched ABS under similar conditions.⁴ Over the years, several detailed studies, including studies conducted in the field using established septic tank fields and aquifers which indicated that LAS is rapidly biodegraded and mineralized and completely removed in onsite treatment systems such as septic tanks.^5,6,7,8,9 Key points from these studies are summarized below.

• Relative to effluents from municipal wastewater treatment systems, effluents from onsite systems may contain higher concentrations of LAS and other detergent chemicals. Research has shown that subsurface environments contain significant quantities of heterotrophic microorganisms which are capable of biodegrading a range of detergent chemicals, including LAS.⁷

• The rate and extent of LAS biodegradation was generally unaffected by soil type. Complete biodegradation or mineralization was measured by the use of LAS radiolabeled in the benzene ring with carbon-14 (¹⁴C) as biodegradation of the ring carbon to carbon dioxide (CO₂) and cell biomass is known to represent the last steps in LAS biodegradation. Use of ¹⁴C ring-labeled LAS indicated cumulative values for ¹⁴CO₂ production reached high values (60 to 70%), indicating essentially complete biodegradation of LAS as the remaining amount of radiolabel is expected to be incorporated into cell biomass of the biodegrading organisms. Furthermore the amount of biodegradation was consistent across the range of soils (seven types) tested, indicating that the soil type had little effect on biodegradation. Degradation proceeded without a noticeable lag phase, indicating that soil microbial communities were already adapted to the biodegradation of LAS.⁷

• Biodegradation half-lives (the time required for half the substance to degrade) for LAS were relatively constant and showed little variation as a function of soil type both in mesocosm and field studies. Half-life values ranged from about 1 to 5 days, averaging about 2 days in the majority of samples tested. The half-lives measured for LAS in these studies were comparable to values measured for a naturally occurring fatty acid (stearic acid) and in the range of values reported for LAS biodegradation in the literature.⁷

• Biodegradation of LAS was also assessed in an established septic tank system and an adjoining shallow sand aquifer located near Cambridge, Ontario.⁸ Studies were conducted on soil, aquifer sediment and groundwater samples from a transect of the septic tank effluent plume. LAS was rapidly biodegraded in the vicinity of the discharge, with mineralization half-lives in soil and sediment samples collected near the tile field ranging from 9 to 17 days. Similar results were obtained for ground water. Adaptation was a key process in the system, as illustrated by the rapid biodegradation near the tile field and limited biodegradation at locations far downgradient or upgradient of the system, where little or no LAS. The results demonstrate that properly functioning septic tank systems can effectively remove LAS.

• A study in aimed at determining the sorptive and biodegradable characteristics of LAS using soil obtained below a Florida septic system drainfield has been carried out.⁹ Three distinct soil samples were collected from the septic system drainfield and used in laboratory sorption and biodegradation studies. Different LAS concentrations were added (in ¹⁴C radiolabeled and unlabeled forms) to a series of test vessels that contained upgradient groundwater and the soils collected from the study site. The sorption test was designed to determine the partitioning of LAS between groundwater and soil in each sample. Results indicated that the sorption distribution coefficient (K_d) decreased from 4.02 to 0.43 L/kg and that the rate of ultimate biodegradation (1st-order rate constant k₁) decreased from 2.17 to 0.08/day with increasing distance (0.7-1.2 m vertically below ground surface and 0 to 6.1 m horizontally) from the drainfield. The 3 soils showed 49.8-83.4% LAS mineralization (percentage of theoretical CO₂) over 45- or 59-day test periods. These results demonstrate that subsurface soils in this system have the potential to sorb and biodegrade LAS.

KEY REFERENCES

1. U.S. Environmental Protection Agency, “Septic (Onsite/Decentralized) Systems.” http://water.epa.gov/infrastructure/septic/.

2. Marcotullio, P.J. “Urban water-related environmental transitions in Southeast Asia.” Sustainability Science 2(1), 27-54 (2007)

3. Schwartz, J. J., A.T. Leimely and K. Pratrap, Kalpana. “Water Treatment Notes.” College of Human Ecology, Cornell University, Fact Sheet 16 (June 1997).

4. Straus, A.E. “Biodegradation of Alkylbenzene Sulfonate in a Simulated Septic Tank and Drain Field.” Science, 142, 244-245 (1963).

5. McAvoy, D.C., C.E. White, B.L. Moore and R.A. Rapaport. “Chemical Fate and Transport in a Domestic Septic System: Sorption and Transport of Anionic and Cationic Surfactants.” Environ. Toxicol. Chem. 13, 213-221 (1994).

6. Soap and Detergent Association (American Cleaning Institute). “Linear Alkylbenzene Sulfonate.” Monograph, 11 pages (1996). Note p. 4. Available at:
http://www.cleaninginstitute.org/assets/1/Page/Linear_AlkylBenzene_Sulfonate.pdf

7. Larson, R.J., T.W. Federle, R.J. Shimp, and R.M. Ventullo. “Behaviour of Linear Alkylbenzene
Sulfonate (LAS) in Soil Infiltration and Groundwater.” Tenside Surfactants Detergents, 26, 116-121(1989).

8. Shimp, R.J., E.V. Lapsins and R.M. Ventullo. “Chemical Fate and Transport in a Domestic Septic System: Biodegradation of Linear Alkylbenzene Sulfonate (LAS) and Nitrilotriacetic acid (NTA).” Environmental Toxicology and Chemistry, 13(2), 205–212 (1994).

9. Doi, J., K.H. Mark, A.J. DeCarvalho, D.C. McAvoy, A.M. Nielsen, L. Kravetz, and M.L. Cano. “Investigation of an Onsite Wastewater Treatment System in Sandy Soil: Sorption and Biodegradation of Linear Alkylbenzene Sulfonate.” Environmental Toxicology and Chemistry 21(12), 2617-2622 (2002).

ADDITIONAL REFERENCES

• Nielsen, A.M., A.J. DeCarvalho, D.C. McAvoy, L. Kravetz, M.L. Cano and D.L. Anderson. “Investigation of an Onsite Wastewater Treatment System in Sandy Soil: Site Characterization and Fate of Anionic and Nonionic Surfactants.” Environmental Toxicology and Chemistry 21(12), 2606-2616 (2002).

• McAvoy, D.C., A.J. DeCarvalho, A.M. Nielsen and M.L. Cano. “Investigation of an Onsite Wastewater Treatment System in Sandy Soil: Modeling the Fate of surfactants.” Environmental Toxicology and Chemistry 21(12), 2623-2630 (2002).

Last updated in August 2014

Revised August 2014

Field studies, which monitor the real-world behavior of a substance, indicate that linear alkylbenzene sulfonate (LAS) biodegrades rapidly and completely and does not accumulate in the environment. Extensive aquatic toxicity and risk assessment data from more than 50 years of use as a detergent surfactant confirm that LAS is safe for aquatic populations, based on levels confirmed through field studies.

• Effective biological treatment, such as activated sludge, removes 99 percent of the LAS present in wastewater, leaving only trace amounts that continue to biodegrade in rivers and streams receiving treated wastewater.^1,2

• “Half-life” refers to the amount of time it takes for microbes to completely break down half the amount of a chemical in water. A study in Rapid Creek, South Dakota, found LAS half-lives ranging from 0.15 to 0.5 days, demonstrating rapid biodegradation following treatment. Using higher test concentrations, a similar study of surface waters near Austin, Texas, confirmed that LAS quickly disappears in the aquatic environment.^3-5

• LAS concentration is further decreased by dilution in the receiving waters where it is found in the 6

• LAS aerobic biodegradation proceeds with degradation of both the alkyl chain and the aromatic ring. Low toxicity sulfophenylcarboxylates (SPCs) are formed as degradation intermediates which are ultimately converted to water, carbon dioxide and sulfate salts.⁶ This degradation route has been demonstrated in sewage treatment plants (STPs) and in laboratory studies using a ¹⁴C ring-labelled commercial product and some pure unlabeled homologues (Nielsen and Huddleston, 1981).⁶

• A 2007 study demonstrated anaerobic biodegradation of LAS for the first time.⁷ The study not only demonstrated degradation of LAS under anaerobic conditions but identified the corresponding microorganisms involved in this process. The study indicated degradation reached 79% in 165 days via generation of sulfophenyl carboxylic acids (SPCs). Spiking experiments indicated that almost all of the added LAS (>99%) was found to be attached to the sediment while the less hydrophobic SPCs were predominant in solution, as their concentration increased progressively up to 3 ppm during the full course of the experiment. Average half-life for LAS was estimated to be 90-days.⁷ (For additional information on anaerobic biodegradation of LAS, see the fact sheet LAS BIODEGRADATION UNDER ANAEROBIC CONDITIONS.

• Using standard laboratory tests to measure aerobic biodegradation, the primary biodegradation (loss of surfactant function) of LAS, measured by MBAS (Methylene Blue Active Substance) or by specific analytical methods such as HPLC (High Performance Liquid Chromatography), in any OECD tests (OECD, 1993), is >99% (EU Commission, 1997).⁶

• The ultimate (complete) biodegradation (or mineralization) measured by DOC (Dissolved Organic Carbon) is in a range going from 80% to >95% for CAS (Continuous Activated Sludge) simulation tests (OECD 303 A), and in the 95-98% range for inherent tests (OECD 302) (EU Commission, 1997). Note that measurements of 80% or more mineralization are considered complete mineralization because the remaining 20% is likely incorporated into bacterial biomass and is not available for conversion to DOC.⁶

• CAS simulation tests (OECD 303 A) were run for the commercial LAS product in the 9-25°C temperature range.⁸ Although acclimation times were significantly different at various temperatures, being longer at lower temperatures, the percent LAS removal, measured by MBAS and HPLC, was always similar and high (>95%) in all cases, indicating that the microorganism community can also reach a proper acclimation and that kinetics are also adequate at low temperatures.^9,10 These results are in agreement with some stream mesocosm studies which concluded that the mineralization of surfactants under realistic environmental conditions, where various algal species are acclimated following natural temperature fluctuations, was at least maintained and often increased during significant seasonal decreases in temperature.⁷

• A comparison between study results and data from a 1973-1986 U.S. monitoring study confirm that LAS is not accumulating in the environment. Even though greater use has increased concentrations of LAS entering sewage treatment plants, LAS concentrations in outgoing water (effluent) have actually diminished. Thus, the low levels of LAS in streams and rivers are not increasing over time, despite greater LAS usage.^1,11

• The U.S. Geological Survey’s Mississippi River monitoring studies indicate that under normal conditions (effective treatment and normal river flow) LAS concentrations rarely exceed 0.005 milligrams per liter (mg/L), due to effective wastewater treatment and continued biodegradation in surface waters.¹² Immediately downstream of sewage treatment plants that discharge into low dilution streams, LAS concentrations averaged 0.043 mg/L.¹

• LAS concentrations in rivers and streams can also be predicted using water quality models such as iSTREEM®.¹³ iSTREEM® predicts mean and low-flow (7Q10) conditions for all U.S. rivers based on per capita daily product use, removal rates by the various types of wastewater treatment plants, and effluent dilutions by the receiving water for each treatment plant. The 7Q10 values represent the lowest 7-day average flow that occurs during a 10-year period. Based on the iSTREEM® model and the extensive monitoring data available on LAS, 90% of the river miles in the U.S. are expected to have LAS concentrations 2

• LAS is one of the most extensively tested chemicals for acute and chronic toxicity to algae, invertebrates and fish. Using laboratory testing, chronic freshwater aquatic toxicity values, based on effects on growth, survival, and reproduction, and evaluated in 19 different species, ranged from 0.23 mg/L (rainbow trout) to 4.15 mg/L (Elimia, snail).² However, under more real-world conditions (as represented by mesocosm testing), an LAS concentration of 0.395 mg/L has no observed effects on the biological population.^2,14 Given the quality of the mesocosm study, as well as the supporting data available from the single-species chronic toxicity values, the mesocosm value of 0.395 mg/L is used as the definitive predicted no effect concentration (PNEC) for risk assessment.²

• Measured LAS concentrations immediately downstream of sewage treatment plants that discharge into low dilution streams averaged 0.043 mg/L.¹ Based on the iSTREEM® model and the extensive monitoring data available on LAS, 90% of the river miles in the U.S. are expected to have LAS concentrations 2 Comparison of these concentrations with the PNEC (predicted no effect concentration) for LAS based on testing of biological populations under real world conditions (0.395 mg/L)² demonstrates that LAS concentrations in rivers and streams, even under worst case conditions, such as low dilution streams immediately downstream of sewage treatment plants, will not harm aquatic organisms.

KEY REFERENCES

1. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

2. Cowan-Ellsberry, C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, D. Versteeg, D. Ferrer and K. Stanton. “Environmental Safety of the Use of Major Surfactant Classes in North America” Critical Reviews in Environmental Science and Technology, 44:17, 1893-1993 (2014).

3. Larson, R.J. and A.G. Payne. “Fate of the Benzene Ring of Linear Alkylbenzene Sulfonate in Natural Waters.” Appl. Environ. Microbiol. 41, 621-627 (1981).

4. Larson, R.J. and R.L. Perry. “Use of the Electrolytic Respirometer to Measure Biodegradation in Natural Waters.” Wat. Res. 15, 697-702 (1981).

5. Nielsen, A.M., L.N. Britton, G.L. Russell, T.P. McCormick and P.A. Filler. “Microbial Mineralization of Dialkyltetralin Sulfonate (DATS) in Soil and Aquatic Systems.” Presented at the 13th Annual Meeting, Society of Environmental Toxicology and Chemistry (Cincinnati, OH, November 8-12, 1992).

6. “Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products – LAS – Linear Alkylbenzene Sulphonate – CAS No. 68411-30-3”, Revised April, 2013, pages 4, 11-14. http://www.heraproject.com/files/HERA-LAS%20revised%20April%202013%20Final1.pdf

7. Lara-Martín, P.A., A. Gómez-Parra, T. Köchling, J.L. Sanz, R. Amils and E. González-Mazo. “Anaerobic degradation of linear alkylbenzene sulfonates in coastal marine sediments.” Environ. Sci. Technol., 41, 3573–3579 (2007).

8. Prats D., P. Varò, M. Rodriguez, E. Sanz, D. Vallejo, C. Lòpez, R. Soto, V.M. Leòn, C. Otero, J. Ferrer, I. Lòpez, G. Cassani. “The effect of temperature in the aerobic biodegradation of anionic and nonionic surfactants,” 10th Giornate CID, Milano, June 4-6.(2003)

9. Prats D., C. Lòpez, D. Vallejo, P. Varò, V.M. Leòn. “Effect of temperature on the biodegradation of LAS and alcohol ethoxylates,” J. of Surfactants and Detergents 9(1): 69-75 (2006).

10. Leòn V.M., C. Lòpez, P.A. Lara-Martìn, D. Prats, P. Varò, E. González-Mazo. “Removal of LAS and their degradation intermediates at low temperatures during activated sludge treatment,” Chemosphere 64, 1157-1166 (2006).

11. Rapaport, R.A. and W.S. Eckhoff. “Monitoring Linear Alkylbenzene Sulfonate in the Environment: 1973-1986.” Environ. Toxicol. Chem. 9, 1245-1257 (1990).

12. Tabor, C.F., Jr., L.B. Barber II and D.D. Runnells. “Anionic Surfactants in the Mississippi River: A Detailed Examination of the Occurrence and Fate of Linear Alkylbenzene Sulfonate.” Preprint extended abstracts, 205th Annual Meeting, American Chemical Society, pp. 52-55 (Denver, CO, March 28-April 2, 1993).

13. Wang, X., M. Homer, S.D. Dyer, C. White-Hull and C. Du. “A river water quality model integrated with a web-based geographic information system.” J. Environ. Manage., 75, 219–228 (2005).

14. Belanger, S. E., J.W. Bowling, D.M. Lee, E.M. LeBlanc, K.M. Kerr, D.C. McAvoy, S.C. Christman and D.H. Davidson. “Integration of aquatic fate and ecological responses to linear alkyl benzene sulfonate (LAS) in model stream ecosystems.” Ecotoxicol. Environ. Saf., 52, 150–171 (2002).

ADDITIONAL REFERENCES

• SIDS INITIAL ASSESSMENT REPORT for Linear Alkylbenzene Sulfonate (LAS), 20th SIAM, Paris, France, April, 2005. http://www.chem.unep.ch/irptc/sids/OECDSIDS/LAS.pdf

Last updated on August 2014

Revised August 2014

Trace amounts of linear alkylbenzene sulfonate (LAS) present after wastewater treatment adsorb onto sediments near treatment plants and subsequently biodegrade. This removal process contributes to high safety margins. Studies conducted on river sediment samples taken near activated sludge treatment plants show only low levels of LAS present, and lab tests confirm that the levels detected have no effects on sediment-dwelling species.

• In laboratory experiments, LAS adsorbed to river sediments biodegrades rapidly and at the same rate as LAS dissolved in river water.¹ Real world monitoring studies confirm that sediment-absorbed LAS is effectively biodegraded.¹

• The LAS adsorbed to sediment has significantly less availability to organisms thereby reducing its toxicity.^2-5

• Comparing the lowest concentration of LAS in water found to change the feeding (filtration) rate in a seven-day test in saltwater mussels (1 milligram LAS per liter of water, 1 mg/L or 1 part per million, ppm) to that found with sediments (281 milligrams LAS per kilogram dry weight of sediment, 281 mg/kg or 281 ppm) shows that 280-fold higher concentrations of LAS are required to produce the same effect in sediment as in water.⁶

• Comparing the safe level, or no observed adverse effect concentration (NOAEC), for LAS in water for long-term survival of midges (2.4 mg/L, 2.4 ppm) to that in sediment (319 mg/kg, 319 ppm) shows that 130-fold higher concentrations of LAS are required to produce the same effect in sediment as in water.⁷

• Half-life refers to the amount of time it takes for half of a chemical substance to biodegrade, or break down, completely. The half-life for LAS in aerobic sediments near sewage treatment plants ranges from less than one day to 5.9 days.^1,8

• Results of recent U.S. monitoring studies also indicate that effective sewage treatment will remove 96 to 99 percent of LAS from wastewater, greatly reducing the amount that enters sediments and eliminating environmental impacts.^9-10 Similar results were observed in Europe, where LAS removal in activate sludge sewage treatment plants of five countries ranged from 98.5 – 99.9%.¹¹

• The safety margin for LAS in sediments can be calculated by comparing predicted LAS levels in sediments (predicted environmental concentrations, PECs) to those levels which would not cause harm to the organisms living in the sediments (predicted no effect concentrations, PNECs). The safety margin is the PNEC divided by the PEC. Any material with a safety margin greater than one is considered safe for the environment.

• For LAS, the PECs are based on real world monitoring studies — actual measured environmental concentrations — not predicted values.

• PNECs are based on concentrations at which no adverse effects are observed, the NOAECs. For the study with saltwater mussels,⁶ the effect observed with LAS in sediments, an increase in the rate of feeding, is not an adverse effect and so testing of LAS concentrations in sediment higher than 281 ppm would be required to determine the NOAEC.

• Considerable PEC and PNEC data has been reported in the 2013 HERA Report on LAS.¹⁸ A sludge PNEC of 49 g/kg_{dw sludge} and a sediment PNEC of 23.8 mg/kg/_{dw sediment} were cited along with a STP PNEC of 5.5 mg/l.

• PNEC/PEC values for LAS may be calculated from the data given in the 2013 HERA Report. These values are 3.2, 4.5 and 20 for LAS in sludge, sediments and STPs, respectively. All of these values are well above a value of 1.00, indicating that LAS poses no real environmental threat in these environmental compartments.¹⁸

• A 80-day chronic test found that the NOAEC for LAS to a freshwater mussel was greater than 750 mg/kg. The lowest NOAEC for LAS in sediment is the value of 319 mg/kg observed with saltwater mussels.^6-7

• U.S. sediments collected under worst-case conditions (areas with low water flow and low effluent dilution) immediately below less efficient tricking filter sewage treatment plants had LAS concentrations ranging from 0.2 to 340 mg/kg.^9-10 Since eight of the nine sediments had LAS concentrations less than 200 mg/kg, most sediments were below levels that could have any harmful effect on the most sensitive sediment-swelling species tested. Consequently, even these worst case sediments generally have margins of safety greater than one and pose little risk to sediment-dwelling organisms.

• U.S. sediments collected under these same worst-case conditions immediately below activated sludge sewage treatment plants had concentrations of LAS ranging from 0.3 to 3.8 mg/kg,^9-10 at least 83 to greater than 1500 times lower than levels that could have any harmful effect on the most sensitive sediment-dwelling species tested.

• Sediments from sampling sites under typical conditions (with average water flow and effluent dilution) show that much lower concentrations of LAS are more typical. Thirty-two of thirty-three Mississippi River sediment samples had LAS concentrations less than 1 mg/kg.¹² The one exception, a sediment with 20 mg/kg LAS, was found in a drainage canal carrying undiluted effluent from the sewage treatment plant of a large city (Minneapolis, Minnesota) to the Mississippi River. Even in this example, the margin of safety is in excess of 15, indicating that worst case Mississippi River sediments pose little risk to sediment-dwelling organisms.

• European studies on sediment samples show similar results to those from the Mississippi river. In a study of sediments near activated sludge treatment plant discharge points in four European countries, LAS levels in 15 sediment samples ranged from 0.2 to 5.3 mg/kg.¹¹ LAS levels in two additional sediment samples were higher, 12-35 mg/kg, due to periodic discharge from storm water tanks of untreated sewage.¹¹

• LAS levels in marine sediments are low. Sediments adjacent to an underwater sewage discharge pipe off the coast of Spain averaged 0.1 mg/kg LAS.¹³ Fifty meters from the discharge, LAS concentrations in sediments were below the detection limit of 0.03 mg/kg.

• Even in the worst case example, where the sediments were periodically contaminated with untreated sewage, the margin of safety is in excess of 8, indicating that sediment levels in Europe pose little risk to sediment-dwelling organisms.

KEY REFERENCES

1. Larson, R.J., T.M. Rothgeb, R.J. Shimp, T.E. Ward and R.M. Ventullo. “Kinetics and Practical Significance of Biodegradation of Linear Alkylbenzene Sulfonate in the Environment.” J. Am. Oil Chem. Soc. 70, 645-657 (1993).

2. Hand, V.C. and G.K. Williams. “Structure-Activity Relationships for Sorption of Linear Alkylbenzene Sulfonates.” Environ. Sci. Technol. 21, 370-373 (1987).

3. Di Toro, D.M., L.J. Dodge and V.C. Hand. “A Model for Anionic Surfactant Sorption.” Environ. Sci. Technol. 24, 1013-1019 (1990).

4. Hand, V.C., R.A. Rapaport and C.A. Pittinger. “First Validation of a Model for the Adsorption of Linear Alkylbenzene Sulfonate to Sediment and Comparison to Chronic Effects Data.” Chemosphere 21, 741-750 (1990).

5. Orth, R.G., R.L. Powell, G. Kutey and R.A. Kimerle. “Impact of Sediment Partitioning Methods on Environmental Safety Assessment of Surfactant.” Environ. Toxicol. Chem. 14, 337-343 (1995).

6. Bressan, M., R. Brunetti, S. Castellato, G.C. Fava, P. Giro, M. Marin, P. Negrisolo, L. Tallandini, S. Thomann, L. Tosoni, M. Turchetto and G.C. Campesan. “Effects of Linear Alkylbenzene Sulfonate (LAS) on Benthic Organisms.” Tenside Surf. Det. 26, 148-158 (1989).

7. Kimerle, R.A., “Aquatic and Terrestrial Ecotoxicology of Linear Alkylbenzene Sulfonate,” Tenside Surf. Det. 26, 169-176 (1989).

8. Nielsen, A.M., L.N. Britton, C.E. Beall, T.P. McCormick and G.L. Russell, “Biodegradation of Coproducts of Commercial Linear Alkylbenzene Sulfonate,” Environ. Sci. Technol. 31, 3397-3404 (1997).

9. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

10. Rapaport, R.A. and W.S. Eckhoff. “Monitoring Linear Alkyl Benzene in the Environment: 1973-1986.” Environ. Toxicol. Chem. 9, 1245-1257 (1990).

11. Waters, J., and T.C.J. Feijtel, “AIS/CESIO Environmental Surfactant Monitoring Program: outcome of five national Pilot studies on Linear Alkylbenzene Sulfonate,” Chemosphere 30, 1939-1956 (1995).

12. Tabor, C.F., and L.B. Barber, II, “Fate of Linear Alkylbenzene Sulfonate in the Mississippi River,” Environ. Sci. Technol. 30, 161-171 (1996).

13. Prats, D., F. Ruiz, B. Váquez, D. Zarzo, J.L. Berna and A. Moreno, “LAS Homolog Distribution Shift During Wastewater Treatment and Composting: Ecological Implications,” Environ. Toxicol. Chem. 12, 1599-1608 (1993).

14.“Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products – LAS – Linear Alkylbenzene Sulphonate – CAS No. 68411-30-3”, Revised April, 2013

ADDITIONAL REFERENCES

• Takada, H. and R. Ishiwatari. “Behavior of Linear Alkylbenzenesulfonates in River Water (R. Tamagawa; Chofu dam).” Japanese Journal of Water Pollution Research 11, 569-576 (1988).

• Cowan-Ellsberry C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, D. Versteeg D. Ferrer, and K. Stanton. “Environmental Safety of the Use of Major Surfactant Classes in North America,” Critical Reviews in Environmental Science and Technology, 44:17, 1893-1993, DOI:10.1080/10739149.2013.803777

• SIDS INITIAL ASSESSMENT REPORT for Linear Alkylbenzene Sulfonate (LAS), SIAR, 20th SIAM, Paris, France, April, 2005 (Revised August 2014)

Updated August 2014

Biosolids, commonly called sewage “sludge,” are produced during wastewater treatment, especially in activated sludge treatment plants, the most commonly used type of wastewater treatment plants (WTP) in North America and Europe. Linear alkylbenzene sulfonate (LAS) can become attached (adsorbed) to sewage sludge before it enters wastewater treatment and, while continuing to biodegrade, can be present in sewage sludge following treatment. Similarly, LAS from sludges can sometimes be found in soil mixtures shortly after treated sludges are applied to agricultural lands as fertilizer. Concentrations of LAS in these “sludge-amended soils” rapidly decrease with time. Studies show that LAS levels typically found in treated sludge are safe. Thirty years of hazard assessments show that any trace amounts of LAS present and breaking down in soil do not harm plants, earthworms and soil bacteria.

• About 30 percent of the LAS entering a sewage system adsorbs onto sewage sludge before treatment.^1-5 A final step in sewage treatment is to reduce excess sludge using either an anaerobic or an aerobic (less common) digester.

• In sewage sludge that has been treated in an anaerobic digester, the calculated median LAS concentration is 5.6 grams per kilograms dry weight sludge (5.6 g/kg_dw sludge) (15.1 g/kg_dw sludge at the 95th highest percentile). During sludge transportation to farmland, sludge storage, or application on agricultural soil, aerobic conditions are restored and rapid degradation of LAS resumes.⁶

• Typical LAS concentrations in aerobic sludge are dw sludge.^2,6

• In sludge-amended soils, LAS has a maximum half-life of one week (primary biodegradation), where half-life is the time it takes for half the substance to breakdown. Monitored concentrations were around 1 milligram (mg = 0.001 g)/kg_dwsoil (maximum 1.4 mg/kg_dw soil) at harvesting time 30 days later. No accumulation in soil and no bioaccumulation in plants could be detected experimentally.⁶

• Accurate data for degradation of LAS in sludge-amended soil under realistic field conditions indicate its degradation in soil is increased by the presence of crop plants with soil concentrations decreasing from 27 mg/kg_dw to 0.7-1.4 mg/kg_dw soil at harvesting time after 30 days (half-life 7

• Results from several monitoring studies of LAS concentrations in soil are available for various soil types, sludge application rates, and averaging times.⁶ LAS concentrations in sludge-amended soils were reviewed concluding that they were generally below 20 mg/kg soil, depending on the application rate or sampling time after sludge application.⁸ At sludge application rates less than 5 tons per hectare per year (5 t/ha/y), 30 days after its application, LAS concentrations in soil are expected to be in the low mg/kg range. With sludge application rates higher than those used in the normal agricultural practice (6-10 t/ha/y), LAS concentrations in an experimental field of soil-pots with rapes dropped from an initial measured value of 27 mg/kg_dw soil to 0.7-1.4 mg/kg_dw soil at harvest time after 30 days.⁷

• LAS effect levels for test crops (including sorghum, wheat, corn and sunflower) range from 167 mg/kg to more than 407 mg/kg (for most plant species tested). These levels are three to several hundred times higher than even initial concentrations of LAS present before degradation in sludge-amended soils.⁹

• LAS has no observable effect on earthworm test species (Eisenia foetida and Lumbricus terrestris) at concentrations up to 250 mg/kg and 613 mg/kg, respectively. Again, these levels are much higher than even the initial levels in sludge-amended soils.⁹

• No significant effects to the microbial community were observed after prolonged exposure to heterogeneous LAS distributions in agricultural soil following sludge amendment.⁶

• A sludge PNEC of 49 g/kg_dw sludge, also called the sludge quality standard (SQS), of LAS can be back-calculated from the soil PNEC, taking into account the exposure of sewage sludge on agricultural soil and the soil PNEC of 35 mg/kg_dw soil.¹⁰

• Real world concentrations of LAS in sludge and in sludge-amended soil do not exceed the PNEC values discussed above, indicating that current uses of LAS are safe and do not pose a risk to organisms present in sludge or soil.

KEY REFERENCES

1. Matthijs, E. and H. de Henau. “Adsorption and Desorption of LAS.” Tenside Surf. Det. 22, 299-304 (1985).

2. McAvoy, D. C., W. S. Eckhoff and R. A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

3. Rapaport, R. A. and W. S. Eckhoff. “Monitoring Linear Alkyl Benzene Sulfonate in the Environment: 1973-1986.” Environ. Toxicol. Chem. 9, 1245-1257 (1990).

4. Takada, H. and R. Ishiwatari. “Linear Alkylbenzene in Urban Riverine Environments in Tokyo: Distribution, Source and Behavior.” Environ. Sci. Technol. 21, 875-883 (1987).

5. Cowan, C.E., R.J. Larson, T.C. Feijtel and R.A. Rapaport. “An Improved Model for Predicting the Fate of Consumer Product Chemicals in Wastewater Treatment Plants.” Wat. Res. 27, 561-573 (1993).

6. Cowan-Ellsberry, C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, D. Versteeg, D. Ferrer and K. Stanton. “Environmental Safety of the Use of Major Surfactant Classes in North America.” Critical Reviews in Environmental Science and Technology, 44, 17, 1893-1993, DOI:10.1080/10739149.2013.803777.

7. Mortensen G.K., H. Elsgaard, P. Ambus, E.S. Jensen and C. Groen. “Influence of Plant Growth on Degradation of LAS in Sludge-Amended Soil.” J. Environ. Quality 30, 1266-1270 (2001).

8. Solbè J, J.L. Berna, L. Cavalli, T.C.J. Feijtel, K.K. Fox, J. Heinze, S.J.Marshall, and W. de Wolf (2000),” Terrestrial Risk Assessment of LAS in Sludge-Amended Soils.” 5th CESIO World Surfactant Congress, V.2: 1433-1438, May-June, Firenze, Italy.

9. Mieure, J.P., J. Waters, M.S. Holt and E. Mathijs. “Terrestrial Safety Assessment of Linear Alkylbenzene Sulfonate.” Chemosphere 21, 251-262 (1990).

10. Schowanek D, H. David, R. Francaviglia, J. Hall, H. Kirchmann, P.H. Krogh, S. Smith, N. Schraepen, S. Smith, and T. Wildemann. “Probabilistic Risk Assessment for LAS in Sewage Sludge Used on Agricultural Soil.” Regulatory Toxicology and Pharmacology 49: 245–259 (2007).

ADDITIONAL REFERENCES

• SIDS INITIAL ASSESSMENT REPORT for Linear Alkylbenzene Sulfonate (LAS), SIAR, 20th SIAM, Paris, France, April, 2005.

• “Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products – LAS – Linear Alkylbenzene Sulphonate – CAS No. 68411-30-3”, Revised April, 2013

Last updated in August 2014

August 2014

Untreated wastewater discharge is a common occurrence in many parts of the world, and yet there is very little data to form an environmental risk assessment. Conducting widespread monitoring studies of these types of locations on a global basis would be a tremendously ambitious and costly undertaking. Fortunately, two studies focused on developing a risk assessment for untreated wastewater discharged to the Balatuin River in The Philippines have been carried out and reported in two publications.

The first paper, by Dyer et al., focuses on the influence of physical and chemical factors — including levels of LAS — on aquatic communities in the river, including algae, invertebrates, and fish.¹ The study included nine sampling sites (6 along the Balatuin River and three point sources) spread over approximately 10 miles. The sample sites ranged from residential areas that had piggeries and included direct discharge household wastes from bathing, washing of clothes including use of laundry products containing LAS, household cleaning, human wastes (urine and feces) and other solids and plastics as well. Key points that emerged from the study of the Balatuin River are:

• The study found that the critical factors impacting aquatic communities were low dissolved oxygen (DO) levels and high ammonia concentrations.

• Perhaps not surprising was the observation that river water quality was poorer at sampling points located in highly populated areas, likely due to higher waste loading at these sites.

• Sampling sites down river from those with the poorer water quality exhibited higher levels of dissolved oxygen and hence improved water quality, due in part to the purification process of the river itself.

• An initial risk assessment may be conducted for LAS concentrations in down-river sampling sites. The first step was to determine a Predicted No Effect Concentration (PNEC) for aquatic organisms. For LAS there is an extensive database and the PNEC for the most sensitive 5% of the aquatic population (PNEC_0.05) – in other words, a PNEC that protects 95% of the aquatic population – can be determined. The PNEC_0.05 for LAS with an average alkyl carbon chain length of C12 (C₁₂-LAS) was determined to be 245 micrograms LAS per liter (245 μg/L) or (0.245 milligrams/L (0.245 mg/L).

• The concentration of LAS measured at six sampling sites on the Balatuin River ranged from 0.003 mg/L to 0.12 mg/L.

• Measured LAS concentrations in the Balatuin River are below the PNEC_0.05 indicating no adverse effect from the presence of LAS in the river water at any of the six sampling sites.

The second study, by McAvoy et al., reports the results of a risk assessment model developed for untreated wastewater discharge containing consumer product ingredients.² The model involves an impact zone concept in which the river can be thought of as a natural wastewater treatment system. After the river has recovered via “self-purification” (biodegradation of bulk organic compounds (BOD), conversion of ammonia to other compounds, etc.), it can be assessed by traditional risk assessment methods, focusing on DO and ammonia concentrations as critical parameters. This model (the QUAL2E model³) was validated using data obtained from the same river discussed above (the Balatiun River located in the Philippines near the same sampling sites as discussed in the Dyer paper). Sampling sites ranged over an approximately seven miles stretch of the river.

• A key takeaway is that the data show that LAS biodegrades faster than BOD, the biodegradation of which is a key driver of low DO levels. Consequently, LAS concentrations are not critical factors which influence the risk assessment. LAS is certainly present in untreated wastewater. But this risk assessment shows that standard water quality parameters — DO, ammonia, and BOD — are in fact the critical factors for an aquatic risk assessment.

• The model simulation did an excellent job of predicting the observed LAS river water concentrations. This rate loss rate of LAS is very similar to a field derived loss rate determined by Fox et al.⁴ and a laboratory derived value by Peng et al.⁵ further supporting its use. A maximum LAS concentration of 150 μg/L was predicted below a direct discharge site and by the time that parcel of water had reached the last sampling site in the study the LAS concentration was predicted to be 3 μg/L. This change accounts for a 98% loss of LAS over a 14 kilometer stretch of river and is similar to the removal in activated sludge wastewater treatment (McAvoy et al.,⁶).

• The 2- and 3-phenyl position isomers were being lost at a much greater rate than the inner 5- and 6-phenyl isomers within the impact zone. This shift in isomer distribution is similar to what is observed during activated sludge wastewater treatment where the primary removal mechanism of LAS is by biodegradation.^7,8 The similarity in the shift in the positional isomers is further evidence that the observed LAS removal in river water is due to biodegradation.

• To determine the concentration of LAS that would interfere with the self-purification process, the key processes involved need to be identified. These are digestion of BOD (ultimately leading to increasing DO) and nitrification of ammonia. Bressan et al.⁹ reported a no observed effect concentration (NOEC) for LAS of greater than 200 mg/L for activated sludge (BOD) digestion and a NOEC of greater than 100 mg/L for nitrifying bacteria. Consequently, a conservative estimate of the self- purification PNEC for LAS is 100 mg/L.

• Based on the model simulation, the highest predicted LAS concentration in the impact zone was 150 μg/L. Using this value for the impact zone Predicted Environmental Concentration (PEC) and the PNEC of 100 mg/L yields a risk quotient (PEC/PNEC) of 0.0015, which indicates low risk and no cause of concern.

KEY REFERENCES

1. Dyer, S.D., C. Peng, D.C. McAvoy, N.J. Fendinger, P. Masscheleyn, L.V. Castillo and J.M.U. Lim, “The Influence of Untreated Wastewater to Aquatic Communities in the Balatuin River, The Philippines.” Chemosphere 52, 43-53 (2003).

2. McAvoy, D.C., P. Masscheleyn, C. Peng, S.W. Morrall, A.B. Casilla, J.M.U. Lim and E.G. Gregorio, “Risk Assessment Approach for Untreated Wastewater Using the QUAL2E Water Quality Model.” Chemosphere 52, 55-66 (2003).

3. Brown, L.C. and T.O. Barnwell. “The Enhanced Stream Water Quality Models QUAL2E and QUAL2E-UNCAS: Documentation and User Manual.” U.S. Environmental Protection Agency, Report No. EPA/600/3–87/007 (1987).

4. Fox, K., M. Holt, M. Daniel, H. Buckland and I. Guymer. “Removal of Linear Alkylbenzene Sulfonate from a Small Yorkshire Stream: Contribution to GREAT-ER project #7c”. The Science of the Total Environment 251/252, 265–275 (2000).

5. Peng, C.G., T. Arakaki, K.H. Jung and E. Namkung, E.. “Biodegradation of Household Chemicals in River Water Under Untreated Discharge Conditions”. In: Proceedings of IAWQ Ecohazard Specialty Conference, Otsu City, Japan (1999).

6. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport “Fate of Linear Alkylbenzene Sulfonate in the Environment”. Environmental Toxicology and Chemistry 12, 977–987 (1993).

7. Di Corcia, A., L. Capuani, F. Casassa, A. Marcomini and R. Samperi. “Fate of Linear Alkylbenzenesulfonates, Coproducts, and their Metabolites in Sewage Treatment Plants and in Receiving River Waters.” Environmental Science and Technology 33 (22), 4119–4125 (1999).

8. Morrall, S.W., W.M. Begley, J.M. Rawlings, W.S. Eckhoff and D.J. Versteeg. “Use of Isomer Distributions to Characterize the Environmental Fate of LAS.” In: Proceedings of the CESIO 5th World Surfactant Congress, May 29–June 2, Firenze, Italy, pp. 1468–474 (2000).

9. Bressan, M., R. Brunetti, S. Casellato, G.C. Fava. P. Giro, M. Marin, P. Negrisolo, L. Tallandi, S. Thomann, L. Tosoni, and M. Turchetto. “Effects of linear alkylbenzene sulfonate (LAS) on benthic organisms. Tenside Surfactant Detergents 26 (2), 148-158 (1989)

Last updated in August 2014

Commercial linear alkylbenzene sulfonate (LAS) consists of 85 to 98% LAS and three other constituents: linear alkylbenzene (LAB), dialkyltetralin sulfonate (DATS) and methyl branched alkylbenzene sulfonate (isoLAS). Like LAS, the three other constituents undergo biodegradation and are extensively removed during sewage treatment. Trace amounts remaining in treated wastewater and sludge biodegrade rapidly and completely in the environment and pose no risk to plants and animals. These results, together with the extensive data on LAS, demonstrate the environmental safety of commercial LAS.

LAS

• Commercial LAS consists of 85 to 98% LAS.

• Monitoring studies at 50 U.S. sewage treatment plants show that LAS is 99% removed in activated sludge plants and is highly removed even in less efficient trickling filter (77% removal) and rotating biological contactor (96% removal) plants. LAS is efficiently biodegraded by activated sludge (See “LAS Biodegradation and Removal in Sewage Treatment”).

• LAS concentrations in rivers, streams and sediments are well below levels that would affect the environment. These trace levels of LAS continue to biodegrade completely (See “LAS Biodegradation and Safety in Rivers and Streams” and “LAS Biodegradation and Safety in Sediments”).

• LAS in the solids (sludges) from sewage treatment plants biodegrades rapidly and completely when sludges are used as a soil conditioner or fertilizer (See “LAS Biodegradation and Safety in Sludge and Soils”).

LAB

• Linear alkylbenzene (LAB) is the material used to produce LAS. Sulfonation of LAB yields LAS and a small amount of unsulfonated LAB, typically less than 0.5%.

• Monitoring studies at 10 U.S. sewage treatment plants show that LAB is 98% removed in activated sludge plants and is highly removed even in less efficient trickling filter (80% removal) and rotating biological contactor (89% removal) plants. LAB is efficiently biodegraded by activated sludge.¹

• LAB concentrations in rivers, streams and sediments are well below levels that would affect the environment. These trace levels of LAB continue to biodegrade completely.¹

• LAB in the solids (sludges) from sewage treatment plants biodegrades rapidly and completely when sludges are used as a soil conditioner or fertilizer.²

DATS

• Dialkyltetralin is formed in LAB when a second bond is formed between the alkyl chain and the benzene ring. Depending on the manufacturing process used to make LAB, commercial LAS contains less than 1% to 8% DATS. Improvements in process technology in recent years have reduced the DATS content to less than 5%.³

• Monitoring studies at 10 U.S. sewage treatment plants show that DATS biodegrades and is 95% removed in activated sludge plants. DATS is highly removed even in less efficient trickling filter (63% removal) and rotating biological contactor (85% removal) plants.^4,5

• DATS concentrations in rivers, streams and sediments are well below levels that would affect the environment.^4,5 These trace levels of DATS continue to biodegrade rapidly and completely.^6,7

• DATS in sewage sludge mixed with soil, called sludge-amended soil, also biodegrades rapidly and completely.^6,7

IsoLAS

• IsoLAS, which has a methyl branch in the otherwise linear alkyl chain, occurs due to methyl branching present in the kerosene feedstock and methyl branch formation during manufacturing. Depending on the process used to make LAB, commercial LAS contains less than 1% to about 6% isoLAS.

• Because the methods for analysis of environmental levels of LAS do not distinguish between LAS and isoLAS, monitoring studies have included isoLAS in the LAS levels reported.

• Monitoring studies have shown that LAS and isoLAS are removed at comparable rates (99% removal) in activated sludge plants.^3,8 LAS and isoLAS are highly removed even in less efficient trickling filter (77% removal) and rotating biological contactor (96% removal) plants.⁹

• High rates of removal are also observed in European sewage treatment plants.^10-12

• Confirmation that isoLAS biodegrades as rapidly and completely as LAS comes from recent studies with isoLAS molecules^13,17) and from a study which specifically analyzed for isoLAS intermediates during biodegradation of commercial LAS.¹⁴

• LAS and isoLAS concentrations in rivers, streams and sediments are well below levels that are known to affect plants and animals in these environments.^4,9,15 Branching of surfactants tends to decrease toxicity;¹⁶ thus isoLAS would be expected to show even less toxicity that LAS.

• The trace levels of isoLAS in the environment will continue to biodegrade rapidly and completely.¹⁴

KEY REFERENCES

1. Gledhill, W.E., V.W. Saeger and M.L. Trehy. “An Aquatic Environmental Safety Assessment of Linear Alkylbenzene.” Environ. Toxicol. Chem. 10, 169-178 (1991).

2. Holt, M.S. and S.L. Bernstein. “Linear Alkylbenzenes in Sewage Sludges and Sludge Amended Soils.” Wat. Res. 26, 613-624 (1992).

3. ECOSOL (2005), Statistics, Brussels.

4. Rapaport, R.A., R.J. Larson, D.C. McAvoy, A.M. Nielsen and M.L. Trehy. “The Fate of Commercial LAS in the Environment.” 3rd CESIO International Surfactants Congress & Exhibition — A World Market, Section E, 78-88 (London, June 1-5, 1992).

5. Trehy, M.L., W.E. Gledhill, J.P. Mieure, J.E. Adamova, A.M. Nielsen, H.O. Perkins and W.S. Eckhoff. “Environmental Monitoring for Linear Alkylbenzene Sulfonates, Dialkyltetralin Sulfonates and their Biodegradation Intermediates.” Environ. Toxicol. Chem., 15, 233-240 (1996).

6. Nielsen, A.M., L.N. Britton, G.L. Russell, T.P. McCormick and P.A. Filler. “Microbial Mineralization of Dialkyltetralin Sulfonate (DATS) in Soil and Aquatic Systems.” SETAC 13th Annual Meeting, Abstract 543 (Cincinnati, OH, Nov. 8-12, 1992).

7. Nielsen, A.M., L.N. Britton, G.L. Russell, T.P. McCormick and P.A. Filler. “Microbial Mineralization of Dialkyltetralin Sulfonate (DATS) in Soil and Aquatic Systems.” 1st SETAC World Congress, Abstract 244 (Lisbon, March 28-31, 1993).

8. SIDS INITIAL ASSESSMENT REPORT for Linear Alkylbenzene Sulfonate (LAS), SIAR, 20th SIAM, Paris, France, April, 2005

9. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

10. Cavalli, L., A. Gellera and A. Landone. “LAS Removal and Biodegradation in a Wastewater Treatment Plant.” Environ. Toxicol. Chem. 12, 1777-1788 (1993).

11. Sánchez Leal, J., M.T. García, R. Tomás, J. Ferrer and C. Bengoechea. “Linear Alkylbenzene Sulfonate Removal.” Tenside Surf. Det. 31, 253-256 (1994).

12. Waters, J. and T.C.J. Feijtel. “AIS/CESIO Environmental Surfactant Monitoring Program: Outcome of Five National Pilot Studies on Linear Alkylbenzene Sulfonate (LAS).” Chemosphere 30, 1939-1956 (1995).

13. Nielsen A.M., L.N. Britton, C.E. Beall, T.P. McCormick and G.L. Russell. “Biodegradation of Co-products of Commercial LAS,” Environ. Sci. Technol. 31, 3397-3404 (1997).

14. Cavalli, L., G. Cassani, M. Lazzarin, C. Maraschin, G. Nucci and L. Valtorta. “Iso-branching of LAS, Prolonged “living” biodegradation test on commercial LAS,” Tenside Surf. Det. 33: 393-398 (1996).

15. Kimerle, R.A. “Aquatic and Terrestrial Ecotoxicology of Linear Alkylbenzene Sulfonate.” Tenside Surf. Det. 26, 169-176 (1989).

16. Talmage, S.S. “Environmental and Human Safety of Major surfactants: Alcohol Ethoxylates and Alkylphenol Ethoxylates.” pp. 81-83 (Lewis, Boca Raton, 1994).

17. Dunphy J, T.W. Federle, N. Itrich, S. Simonich, P.K. Kloepper-Sams, J. Scheibel, T. Cripe, and E. Matthijs “Environ. Profile of Improved Alkyl Benzene Surfactants,” 5th CESIO World Surfactants Congress V.2: 1489-1497, May-June, Firenze, Italy (2000).

ADDITIONAL REFERENCES

• “Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products – LAS – Linear Alkylbenzene Sulphonate – CAS No. 68411-30-3”, Revised April, 2013

• Cowan-Ellsberry C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, H. Versteeg, D. Ferrer, and K. Stanton, K., “Environmental Safety of the Use of Major Surfactant Classes in North America,” Critical Reviews in Environmental Science and Technology, 44:17, 1893-1993 (2014) DOI:10.1080/10739149.2013.803777.

Last updated August 2014

Revised August 2014

Strictly anaerobic conditions are often defined, for the purpose of laboratory testing, as those in which oxygen is totally excluded. Linear alkylbenzene sulfonate (LAS) can reach several compartments in the environment that are characterized as “anaerobic,” including surface water sediments, septic system tile fields, and landfills where sewage sludge may be disposed. However, recent studies suggest these “anaerobic” environments are actually anoxic, or oxygen-limited, indicating that oxygen diffuses into them but is consumed at a faster rate than it enters.

For a chemical such as LAS, this distinction is significant, for LAS biodegrades in anoxic environments and, once initial biodegradation has occurred, LAS will continue to biodegrade even in strictly anaerobic conditions. Field study data also support this finding, detecting far lower levels of LAS in the environment than laboratory studies conducted under strictly anaerobic conditions would predict. Field studies also confirm that, after more than 50 years of use, LAS has not accumulated in these environments, providing further scientific support for aerobic metabolism through oxygen diffusion into natural anaerobic environments.

• Although several studies have demonstrated that LAS requires oxygen to biodegrade^1-7, more recent studies by Lara-Martin^30,1,32 have shown that LAS truly degrades in anaerobic sulfate-reducing marine sediment. Laboratory experiments, performed on anoxy marine sediments spiked with 10-50 ppm of LAS, showed that degradation is feasible, reaching a value of 79% in 165 days, with a half-life time of ca. 90 days.

• Anaerobic biodegradation of LAS was also observed in the field with several marine sediment samplings at anoxy depths in the sedimentary column. LAS concentrations in pore waters decreased sharply and the biodegradation intermediates (SPC) reached the maxima. These observations provide the first real evidence of partial degradation of LAS under anaerobic conditions.^30,31

• A more recent paper provides for the first time an anaerobic biodegradation pathway for LAS.³²

• Standard laboratory tests on anaerobic biodegradability, while predicting fate with no oxygen present, do not reflect the behavior of LAS in real-world environments, which are typically subject to oxygen diffusion.

• Laboratory studies show that LAS will biodegrade under anoxic conditions, presumably by using available oxygen that diffuses into these environments.^8-10 River sediments, landfills and subsurface soils are examples of such environments.

• Extensive U.S. monitoring studies found no LAS accumulation on sediments below sewage treatment plant outfalls. In fact, the studies show that the LAS on sediments continues to biodegrade.^11-13

• A comprehensive Mississippi River Survey found only very low levels of LAS and biodegradation intermediates in sediments downstream from wastewater treatment plants. Concentrations ranged from less than 0.01 to 5 milligrams per kilogram (mg/kg).¹⁴

• Studies in Japan also revealed degradation of LAS in sediments. LAS concentrations in river sediments around outfalls decreased 90 percent in upper estuaries and almost completely (below 0.01 mg/kg) 10 kilometers offshore.^15-17

• The vertical distribution of LAS in Japanese lake sediments showed seasonal variations attributed to biodegradation activities.^18,19 LAS levels in Japanese lake sediments decreased with increasing depths, indicating biodegradation even though the conditions might be considered anaerobic.¹⁹

• Studies involving a German landfill, an ostensibly anaerobic environment, receiving LAS-containing sludge, revealed a 98 percent LAS removal rate over a period of 10 to 11 years.²⁰

• In an extensive series of studies on a domestic septic system, including the subsurface soil and groundwater, LAS was shown to be rapidly and extensively biodegraded by the microbial populations in the soil. In fact, no LAS was detected below the top 2 inches (5 centimeters) of soil in the septic tank percolation field.^21-25

• Subsurface soils beneath a drainage field and pond receiving laundromat wastewater were also shown to be effective in biodegrading LAS. No LAS has been detected in the ground-water below the site, despite 25 years of LAS use.^26,27

• Studies show that exposure of LAS to oxygen for five to six hours during the treatment process yielded LAS biodegradation products that continued to break down in an anaerobic digester. This indicates that, once aerobic biodegradation of LAS is initiated, it can continue in anaerobic conditions.^27,28

KEY REFERENCES

1. Swisher, R.D. Surfactant Biodegradation. (Marcel Dekker, New York, 1987).

2. Little, A.D. “Environmental and Human Safety of Major Surfactants. Volume 1. Anionic surfactants. Part 1. Linear Alkylbenzene Sulfonates.” Final Report To: The Soap and Detergent Association, Ref. 65913 (New York, February, 1991).

3. Painter, H.A. and T.F. Zabel. “Review of the Environmental Safety of LAS.” Water Research Centre, CO-1659-M/1/EV8658 (Medmenham, UK, 1988).

4. McEvoy, J. and W. Giger. “Determination of Linear Alkylbenzene Sulfonates in Sewage Sludge by High Resolution Gas Chromatography/Mass Spectrometry.” Environ. Sci. Tech. 20, 376-383 (1986).

5. Janicke, W. and G. Hilge. “Biodegradability of Anionic/Cationic Surfactants Under Aerobic and Anaerobic Conditions of Wastewater and Sludge Treatment.” Tenside Surf. Det. 16, 472-482 (1979).

6. Oba, K.Y., Y. Yoshida and S. Tomiyama. “Biodegradation of Synthetic Detergents: I. Biodegradation of Anionic Surfactants Under Aerobic and Anaerobic Conditions.” Yukgaku 16, 517-523 (1967).

7. Federle, T.W. and B.S. Swab. “Mineralization of Surfactants in Anaerobic Sediments of a Laundromat Wastewater Pond.” Water Res. 26, 123-127 (1992).

8. Pflugmacher, J. “Degradation of Linear Alkylbenzenesulfonates (LAS) Under Laboratory and Field Conditions Using a New HPLC Detection Method.” UWSF-Z. Umweltchem. Oekotox. 4, 329-332 (1992).

9. Britton, L.N. and A.M. Nielsen. “Relevance of Aerobic Biodegradability Testing to Environmental Fate.” 1st SETAC World Congress, Abstract 102P (Lisbon, March 28-31, 1993).

10. Heinze, J.E. and L.N. Britton. “Anaerobic Biodegradation: Environmental Relevance.” Proceedings of the 3rd World Conference on Detergents: Global Perspectives. (ed. A. Cahn) 235-239 (AOCS Press, Champaign, Illinois, 1994).

11. Rapaport, R.A. and W.S. Eckhoff. “Monitoring Linear Alkylbenzene Sulfonate in the Environment: 1973-1986.” Environ. Toxicol. Chem. 9, 1245-1257 (1990).

12. Rapaport, R.A., R.J. Larson, D.C. McAvoy, A.M. Nielsen and M. Trehy. “The Fate of Commercial LAS in the Environment.” 3rd CESIO International Surfactants Congress & Exhibitions — A World Market, Proceedings Section E, 78-87 (London, June 1-5, 1992).

13. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

14. Tabor, C.F. Jr., L.B. Barber and D.D. Runnells. “Anionic Surfactants in the Mississippi River: A Detailed Examination of the Occurrence and Fate of Linear Alkylbenzene Sulfonate.” 205th Annual Meeting, American Chemical Society, Division of Environmental Chemistry, preprint extended abstracts, pp. 52-55 (Denver, March 28-April 2, 1993).

15. Takada, H. and R. Ishiwatari. “Linear Alkylbenzenes in Riverine Environments in Tokyo: Distribution, Source and Behavior.” Environ. Sci. Tech. 21, 875-883 (1987).

16. Takada, H., N. Ogura and R. Ishiwatari. “Seasonal Variations and Modes of Riverine Input of Organic Pollutants to the Coastal Zone: I. Flux of Detergent-derived Pollutants to Tokyo Bay.” Environ. Sci. Tech. 26, 2517-2523 (1992).

17. Takada, H., R. Ishiwatari and N. Ogura. “Distribution of Linear Alkylbenzenes (LABs) and Linear Alkylbenzene Sulfonate (LAS) in Tokyo Bay Sediments.” Estuarine, Coastal and Shelf Science 35, 141-156 (1992).

18. Amano, K. and T. Fukushime. “On the Longitudinal and Vertical Changes in Lake Estuarine Sediments.” Water Sci. Tech. 20, 143-153 (1988).

19. Amano, K., T. Fukushime and O. Nagasugi. “Diffusive Exchange of Linear Alkylbenzene Sulfonate (LAS) Between Overlying Water and Bottom Sediment.” Hydrobiologia 0, 1-9 (1991).

20. Marcomini, A., P.D. Capel, T. Lichtensteiger, P.H. Brunner and W. Giger. “Behavior of Aromatic Surfactants and PCBs in Sludge-Treated Soil and Landfills.” J. Environ. Quat. 18, 523-528 (1989).

21. Larson, R.J., R.W. Federle, R.J. Shimp and R.M. Ventullo. “Behavior of Linear Alkylbenzene Sulfonate in Soil Infiltration and Groundwater.” Tenside Surf. Det. 26, 116-121 (1989).

22. Robertson, W.D., E.A. Sudicky, J.A. Cherry, R.A. Rapaport and R.J. Shimp. “Impact of a Domestic Septic System on an Unconfined Sand Aquifer.” Contaminant Transport in Groundwater. (eds. Kobus & Kenzelbach) 105-112 (Balkema, Rotterdam 1989).

23. Shimp, R.J., E.V. Lapsins and R.M. Ventullo. “Chemical Fate and Transport in a Domestic Septic System: Biodegradation of Linear Alkylbenzene Sulfonate (LAS) and Nitrilotriacetic Acid (NTA).” Environ. Toxicol. Chem. 13, 205-212 (1994).

24. McAvoy, D.C., C.E. White, B.L. Moore and R.A. Rapaport. “Chemical Fate and Transport in a Domestic Septic System: Sorption and Transport of Anionic and Cationic Surfactants.” Environ. Toxicol. Chem. 13, 213-221 (1994).

25. Shutter, S.B., E.A. Sudicky and W.D. Robertson. “Chemical Fate and Transport in a Domestic Septic System: Application of a Variably Saturated Model for Chemical Movement.” Environ. Toxicol. Chem. 13, 223-231 (1994).

26. Federle, T.W. and G.M. Pastwa. “Biodegradation of Surfactants in Saturated Subsurface Sediments: A Field Study.” Ground Water 26, 761-770 (1988).

27. Birch, R.R., W.E. Gledhill, R.J. Larson and A.M. Nielsen. “Role of Anaerobic Biodegradability in the Environmental Acceptability of Detergent Materials.” 3rd CESIO International Surfactants Congress & Exhibition — A World Market, Proceedings Section E, 26-33 (London, June 1992).

28. Larson, R.J., T.M. Rothgeb, R.J. Shimp, T.E. Ward and R.M. Ventullo. “Kinetics and Practical Significance of Biodegradation of Linear Alkylbenzene Sulfonate in the Environment.” J. Amer. Oil. Chem. Soc. 70, 645-657 (1993).

29. Leòn V.M., E González-Mazo, J.M. Forja Pajares and A. Gómez-Parra, “Vertical distribution profiles of LAS and their long-chain intermediate degradation products in coastal marine sediments,” Environ. Tox. Chem. 20: 2171-2178 (2001).

30. Lara-Martín, P.A., Gómez-Parra, A., Köchling, T., Sanz, J.L., Amils, R., and González-Mazo, E. “Anaerobic degradation of linear alkylbenzene sulfonates in coastal marine sediments.” Environ. Sci. Technol. 41, 3573–3579 (2007)

31. Lara-Martín P.A., A. Gómez-Parra, T. Köchling, J.L. Sanz, and E. Gónzalez-Mazo. “Field and laboratory evidences regarding the anaerobic degradation of LAS,” vol. 2, paper O-E11, CESIO 2008: 7th World Surfactants Congress, Paris, France: 22-25 June 2008.

32.Lara-Martín P.A., A. Gómez-Parra, J.L. Sanz, and E. Gónzalez-Mazo. “Anaerobic degradation pathway of linear alkylbenzene sulfonates (LAS) in sulphate-reducing marine sediments,” Environ. Sci. Technol. 44, 1670-1676 (2010).

ADDITIONAL REFERENCES

• Thurman, E.M., L.B. Barber, Jr. and D.J. LeBlanc. “Movement and Fate of Detergents in Groundwater.” Hydrol., 1, 143-161 (1986).

• Field, J.A., L.B. Barber, II, E.M. Thurman, B.L. Moore, D.L. Lawrence and D.A. Peake. “Alkylbenzenesulfonates and Dialkyltetralinsulfonates in Sewage-Contaminated Groundwater.” Environ. Sci. Tech. 26, 1140-1145 (1992).

• “Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products – LAS – Linear Alkylbenzene Sulphonate – CAS No. 68411-30-3”, Revised April, 2013, pages 4, 11-14.

• Cowan-Ellsberry C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, D. Versteeg, D. Ferrer and K. Stanton. “Environmental Safety of the Use of Major Surfactant Classes in North America,” Critical Reviews in Environmental Science and Technology, 44:17, 1893-1993 (2014).

Last updated on August 2014

There are two types of alkylbenzene sulfonates, ABS (branched alkylbenzene sulfonate) and LAS (linear alkylbenzene sulfonate). LAS had not been discovered when ABS was first introduced as a detergent surfactant in the late 1940s. While ABS has served consumers well, foam-related environmental problems began to appear in surface waters, groundwater, drinking water and in wastewater treatment plants. Investigation of these problems led to the discovery that ABS is resistant to biodegradation.^1,2,3 This resistance caused ABS to be known as non-biodegradable or a “hard detergent.” LAS is known as biodegradable or a “soft detergent” because it quickly and completely biodegrades^2,3,4 and does not cause such environmental problems.

Environmental Benefits

As ABS was replaced with LAS beginning in the mid-1960s, extensive data, compiled in the book by R.D. Switzer⁵, have confirmed the positive environmental effects. Among the well-documented examples:

United States: Surfactant concentrations in river waters dramatically decreased. The Illinois River at Peoria, Illinois, was highly polluted because of sewage and industrial plant effluents and storm water runoff from the greater Chicago area. From 1959 to 1965, the average MBAS (Methylene Blue Active Substance) concentration in the river was 0.54 parts per million (ppm). The MBAS test measures anionic surfactants (including LAS and ABS) and related anionic substances. These substances generally affect the taste of water and cause foaming at concentrations above 0.5 ppm. Consequently, the U.S. and other countries adopted standards for water quality of MBAS < 0.5 ppm. In the year following the conversion to LAS, the average MBAS value dropped to 0.22 ppm. By the spring of 1968, it had dropped even lower, averaging 0.05 ppm. In addition, analytical work showed that only 20 percent of the MBAS present was actually LAS. A U.S. monitoring study of 50 river sites directly below wastewater treatment plants showed that the average LAS concentration was 0.035 ppm.⁶ Furthermore, 90% of over 500,000 U.S. river miles in the U.S. have less than 0.004 ppm LAS.

England: When ABS was replaced with LAS in England, the surfactant concentration in river waters dropped by a factor of five. By 1966, surfactant levels had reached the lower limits of analytical detection. Today they are almost certainly lower. These changes occurred even though the volume of detergents used, and therefore the amount entering the environment, had greatly increased.

Germany: From 1958 to 1964, MBAS residues in surface waters of the Rhine River basin increased constantly, paralleling the rapid increase in ABS consumption. The conversion to LAS in 1964 resulted in the immediate reduction of MBAS levels. Average MBAS concentrations continued to drop until pre-1958 levels were observed by the late 1970’s. This overall reduction occurred despite a population increase of approximately 6 million people and a two-fold increase in detergent consumption over 1958 levels. From 1978 to 1987 the MBAS levels dropped to below 0.05 ppm. LAS specific analyses suggest that only about 0.01 ppm LAS is currently present in the Rhine River.

Japan: Similar results were observed in Japan. One example is that of the Tama River, which passes through heavily populated areas and receives large quantities of untreated domestic sewage. Even though the levels of organic pollutants in the river had reached the 8-10 ppm BOD level by the early 1980’s, the yearly average MBAS residues had steadily decreased from a high of about 2.5 ppm in 1968 to 0.3 ppm in 1981 as a result of the use of LAS.

Thailand: In July-August 1983, the average MBAS residual over the 10-48 kilometer zone of the Chao Phraya River was 0.34 ppm. After switching to LAS, the average value over the same zone had decreased by 72 percent to 0.095 ppm by July of 1984.

Thus while there is extensive evidence that ABS causes environmental problems, there is now also overwhelming evidence that these problems are solved by changing to the use of LAS. This remains true regardless of geographical location, climate or environmental conditions.

Processing

The same plant process units, transfer and storage equipment, and similar operating conditions can be used for LAS as is used for ABS. No new plant investment or other significant changes are required in switching to the biodegradable LAS.

Performance Advantages

Both the cleaning power and the foam properties of LAS are equal or superior to ABS under most washing conditions. These performance advantages offer the detergent manufacturer possibilities of reducing the level of active ingredient and/or phosphate in the detergent product without sacrificing performance. (The actual amount of these reductions will depend, of course, on the particular formulation and the local washing conditions.) The detergency performance advantage of LAS over ABS is due to two factors. First the carbon distribution of LAS is at the optimum for performance (C12 average). This is not the case for ABS which gives optimum performance at C13 average. Second, LAS is less sensitive to water hardness than ABS in, for example, Latin American washing conditions.⁷ This greater cleaning property of LAS offers the detergent formulator possibilities for either a superior cleaning product or for surfactant and phosphate reductions in the detergent product when changing from ABS to LAS.

Conclusion

The change for ABS to LAS detergents has not only eliminated the environmental problem of non-biodegradability, but has given manufacturers and consumers a superior product with performance benefits. This has been thoroughly documented in countries throughout the world that have changed from ABS to LAS. As a result, LAS has become the leading detergent active ingredient in the world.

Key References

1. Sallee, E. M., J.D. Fairing, R.W. Hess, R. House, P.M. Maxwell, F.W. Melpolder, F.W. Middleton, J. Ross, W.C. Woelfel, and P.J. Weaver. “Determination of trace amounts of alkyl benzene-sulfonates in water.” Anal.Chem., 28, 1822–1826 (1956).

2. Swisher, R.D., Surfactant Biodegradation, Second Ed., Marcel Dekker, New York, 1987, pp. 1-2.

3. Cowan-Ellsberry, C., S. Belanger, P. Dorn, S. Dyer, D. McAvoy, H. Sanderson, D. Versteeg, D. Ferrer and K. Stanton. “Environmental Safety of the Use of Major Surfactant Classes in North America” Critical Reviews in Environmental Science and Technology, 44:17, 1893-1993 (2014).a>

4. Serrano, L.I., C.A.P. Velasco and A.S.C. Malagon. “Ultimate Biodegradation of Commercial Linear Alkylbenzene Sulphonates (LAS) under ISO 14593 Headspace CO2 Test: Compliance with EU Detergent Regulation 648/2004.” Tenside Surf. Det. 48, 390-394 (2001).

5. Swisher, R.D., ibid., pp. 5-6 and section 5.XI.E (pp. 400-401) and tables and references therein.

6. McAvoy, D.C., W.S. Eckhoff and R.A. Rapaport. “Fate of Linear Alkylbenzene Sulfonate in the Environment.” Environ. Toxicol. Chem. 12, 977-987 (1993).

7. Matheson, K.L. “Detergency Performance Comparison between LAS and ABS Using Calcium Sulfonate Precipitation Boundary Diagrams.” J. Am. Oil Chem. Soc. 62, 1269-1274 (1985).

Revised August 2014