The Council for LAB/LAS Environmental Research (CLER) is an organization of scientists and technical specialists representing member companies Huntsman Corporation (Houston), Petresa (Madrid), Sasol North America (Houston), Quimica Venoco (Venezuela) and Repsol YPF (Argentina). 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 thirty 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. This research has looked at virtually every part of the environment that might be exposed to LAS and considered all the components of commercial LAS. Moreover, the research on LAS has revealed important lessons about test methods and environmental acceptability.
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 re aches 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 reduced (mineralized) to materials harmless to the environment (carbon dioxide, water 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 plan ted in soil fertilized with sludge. Residual LAS continues to biodegrade so that yearly applications of sludge to agricultural lands does not cause any build up of LAS.
LAS is also rapidly biodegraded and efficiently removed in septic systems, thereby protecting groundwater resources.
Commercial LAS contains 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 ra pidly 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, which represent an intermediate environment between oxygen available (aerobic) and anaerobic conditions. Aerobic and anoxic conditions seem to be much m ore common 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 a problem for LAS environmental safety.
Because there is so much real world data on LAS, results from field and monitoring tests on LAS can be used to evaluate how well laboratory test methods predict real world results. This information is important to know since pass/fail r esults in laboratory tests are sometimes used for regulatory or environmental labeling purposes. The real world studies on LAS have shown that reliance on laboratory tests greatly underestimates the environmental safety of LAS.
In addition to the results from studies on biodegradation and environmental safety, the environmental acceptability of detergent components can be evaluated from an examination of the resources and energy consumed and the air, water and solid wastes produced in their manufacture. A systematic compilation of the total resources, energy and wastes involved, called a Life Cycle Inventory, is a massive undertaking that has only been attempted for the major cleaning agents (surfactants). Com parison of the results indicates that no surfactant can claim to be superior for the environment. Contrary to statements made by some suppliers of vegetable (oleochemical) based surfactants, petrochemical based surfactants such as LAS are just as environm entally acceptable as oleochemical based surfactants.
In fact, the environmental safety and acceptability of LAS has been recently confirmed in several major regulatory decisions. This includes environmental labeling decisions on laundry detergents in Europe, a rigorous environmental safet y assessment in The Netherlands, a comprehensive safety assessment on LAB by the Organization for Economic Cooperation and Development (OECD) and a health and environmental safety assessment on LAS by the UK Department of the Environment.
This database on LAS, more extensive than on any other surfactant, provides complete assurance that LAS is environmentally safe and acceptable, and that LAS will be recognized as such for the foreseeable future.
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