WASHINGTON -- The presence of the surfactant linear alkylbenzene sulfonate (LAS) in sewage sludge does not pose a significant risk to the environment, according to a recently completed report on the results of a scientific workshop in Copenhagen, Denmark.
The results of the international workshop, which reviewed studies by Danish researchers under Danish environmental conditions, directly contradict the basis for regulations on LAS in Denmark and recent statements by the Danish EPA that argue against the safety of LAS in sewage sludge (biosolids) applied to farmer's fields.
Biosolids have been used for many years as a low-cost fertilizer in many European and North American countries. 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.
There are no restrictions on the levels of LAS in biosolids used for fertilizer in any country except Denmark, which in 1997 enacted restrictions 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 additional taxpayer expense.
Two Danish research organizations, an independent Danish research institute (VKI) and a research agency of the Danish government (DMU), earlier this year completed studies measuring the amount of LAS in Danish biosolids and how quickly LAS biodegrades under Danish conditions. The Danish researchers determined that the maximal levels of LAS predicted in soil from use of biosolids in Denmark are lower than the predicted no effect concentration for LAS in soil.
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 is has low potential to leach into groundwater.
In an international workshop held in April, researchers from the Danish EPA reviewed these new studies which 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.
Despite these new findings, the Danish EPA last month initiated a public campaign encouraging consumers to stop buying products that contain LAS. The agency issued a pamphlet to supermarkets and municipalities throughout Denmark stating that LAS is "poisonous" to the environment. The agency intends to export this new "regulatory" approach to the European Union and its member countries.
"For those who believe that science should be the basis for regulatory action on human health and the environment," said CLER Chairman Tom Grumbles, "the Danish EPA's political campaign against LAS is a shot across bow."
Grumbles continued, "Surfactant manufacturers and their customers throughout Europe have presented sound scientific arguments to EPA, but the science has had little impact on this political decision. We are particularly surprised that the Danish EPA disregarded the studies from its own researchers."
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