January 2000
SIX STUDIES DEMONSTRATE SAFETY OF LAS IN SOIL
Six international studies on the safety of linear alkylbenzene sulfonate (LAS) in biosolids (sewage sludge) used as fertilizer appear in the latest issue of The CLER Review (Vol. 5, No. 1), the journal of the Council for LAB/LAS Environmental Research (CLER).
The Review includes the report from a 1999 international workshop held in Copenhagen, in cooperation with the Danish Environmental Protection Agency, that found no significant risk to the environment from LAS in biosolids. The workshop report, written by John Sólbe of Unilever (UK), notes 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 25 days).
Dr. John Heinze, technical director of CLER and editor of The CLER Review, noted that a major conclusion of all six studies is that “there is no scientific basis for the restrictions of LAS levels [in biosolids] anywhere in the world.”
Other highlights in the Review include:
A report that the Danish restrictions on LAS in biosolids do not adhere to the accepted European Union rules for conducting a terrestrial risk assessment.
A report on laboratory studies by the Water Quality Institute of Denmark (VKI) demonstrating that LAS in biosolids is rapidly biodegraded during aerobic treatment (sludge stabilization or composting).
A study, conducted by a research agency of the Danish government (DMU), indicating that even an average LAS soil concentration of 5 to 15 parts per million “is unlikely to cause long-term adverse effects in the agricultural soil ecosystem.”
A study demonstrating that LAS can undergo at least partial anaerobic biodegradation under sulfur depleted conditions.
An executive summary and position paper on a new European report on the use of anaerobic biodegradation as a pass/fail criterion for environmentally preferred labeling (ecolabeling) of detergents.