DANISH RESEARCHERS CONFIRM SAFETY OF LAS IN BIOSOLIDS
Workshop Findings Contradict Recent Danish Regulations
A recent report on the results of a scientific workshop in Copenhagen, Denmark, concludes that linear alkylbenzene sulfonate (LAS) in sewage sludge does not pose a significant risk to the environment. The results of the report, which includes studies by Danish researchers under Danish environmental conditions, run counter to Danish regulations on LAS and recent statements by the Danish EPA questioning the safety of LAS in sewage sludge (biosolids) applied to farmers’ fields.
In a workshop held in April, researchers from the Danish EPA reviewed new studies on the fate and effects of LAS in biosolids used as fertilizer on farmers’ fields. 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. The Danish government recently implemented regulations limiting the level of LAS in biosolids, despite numerous international studies demonstrating the safety of LAS.
Two Danish research organizations earlier this year completed additional studies measuring the amount of LAS in Danish biosolids and how quickly LAS biodegrades under Danish conditions. The results of these studies presented at the workshop demonstrate that even the highest levels of LAS in biosolids used as fertilizer in Denmark pose no significant risk to the soil or terrestrial environment.
The maximal levels of LAS predicted in soil from use of biosolids in Denmark (1 milligram LAS per kilogram soil dry weight) are lower than the predicted no effect concentration for LAS in soil (5.2 milligrams per kilogram soil dry weight). These studies were conducted by an independent Danish research institute (VKI) and a research agency of the Danish government (DMU).
Other studies conducted by VKI demonstrate that 98-99% of the LAS in biosolids applied to soil is biodegraded within one year, that LAS does not accumulate in soil and that it has low potential to leach into groundwater.
Studies conducted by VKI and another Danish research institute (RISØ) demonstrated that there was no uptake of LAS into the edible part of crops grown on soil fertilized with biosolids.
Biosolids containing LAS have been safely and beneficially used for many years as a low-cost fertilizer in many European and North American countries. In fact, there are no restrictions on the amount
of LAS in biosolids used for fertilizer in any country except for Denmark, which enacted restrictions in 1997 on the level of LAS and three other organic compounds in biosolids permitted for use as fertilizer. Sewage treatment facilities in Denmark that cannot meet these restrictions must incinerate or landfill their biosolids, often at considerable additional taxpayer expense.
The Danish EPA also recently initiated a public campaign encouraging consumers to stop buying products that contain LAS. The agency intends to export this new “regulatory” approach to the European Union and its member countries.
Based on the results of the workshop, CLER, in cooperation with European producers of linear alkylbenzene (LAB) are urging the Danish government to rescind the regulations on LAS in biosolids and to discontinue the campaign against LAS.
The April 19-20, 1999, workshop in Copenhagen was sponsored by The Association of Danish Cosmetics, Toiletries, Soap and Detergent Industries (SPT) in coordination with the Danish Environmental Protection Agency. An executive summary of the report, titled “LAS Risk Assessment for Sludge-Amended Soils,” is available from CLER at 202-737-0171; fax: 202-737-8406. A copy of the full report may be obtained from SPT in Copenhagen (www.spt.dk; email@example.com; phone: 45-39-17-98-39; fax: 45-39-17-97-49).