Vol. 8, No. 1 (December 2003) – Preface
Landmark Studies
It is not often that a study appears that can truly be called a landmark, a study that marks a new stage in our scientific understanding. And it is even rarer to have more than one such study in the same journal issue.
Consequently, we at CLER are very pleased to offer four landmark studies in this one issue.
The first study is so big that it takes three papers (Nielsen et al., Doi et al. and McAvoy et al.) to fully report the results. This is the study conducted by the Soap and Detergent Association (SDA) on the major cleaning agents or surfactants used in laundry detergents and household cleaning products – LAS, alcohol ethoxylate and alcohol ether sulfate. The study is landmark because it was conducted on an onsite wastewater treatment system (OWTS), typically a household septic system. Approximately 25% of the U.S. population is served by OWTS, and these are used in over 37% of new housing developments. This means over 25 million U.S. households use OWTS for wastewater treatment, with many more worldwide. Furthermore, the site chosen for study by SDA represents a realistic worst case situation – a household septic system in sandy soil where the groundwater level is so shallow during the rainy season that the effluent from the septic tank flows directly into groundwater, bypassing the unsaturated zone (the region in the soil above the groundwater level where most biodegradation takes place).
The results of the study demonstrate:
- LAS, alcohol ethoxylate and alcohol ether sulfate are readily removed from groundwater in soils below septic system drainfields even in situations with minimal or no unsaturated zones.
- Removal of LAS in subsurface soils is due to both biodegradation and sorption.
- The data are robust enough to be used to develop a mathematical model to predict what happens to other consumer product ingredients in septic systems.
The second study (Belanger et al.) is simply huge in every way. It is a model stream ecosystem (mesocosm) study of the effects of LAS on over 250 species of aquatic organisms over a 56-day observation period. Not only is the study broad in scope and diversity of organisms tested, but also it reviewed all 13 available model ecosystem studies that had previous been conducted on LAS, providing an overview of a vast body of data on LAS. The study is monumental in the conclusion it allows one to reach:
- Because the study contained a diverse and sensitive community of aquatic organisms and used a robust experimental design, the no-observed-effect concentration for LAS in this study (0.268 milligrams per liter) may be considered a predicted no-effect concentration (PNEC) for LAS in the freshwater environment – no “uncertainty factor” need be applied to these results.
The PNEC value defines the safe level of LAS, i.e. any concentration of LAS in freshwater below 0.268 mg/L will have no effects, even with long-term exposures. Consequently the PNEC is a key input for any aquatic safety assessment of LAS. It is truly remarkable to have a PNEC value based on as much high quality data as is the case of LAS.
The Brandt et al. study is a culmination of a number of studies to confirm the safety of LAS in sludge amended soil. Sewage sludge contains residual levels of LAS from sewage treatment and is often used as soil fertilizer or conditioner. In fact, use of sludge as fertilizer is considered the environmentally preferred disposal method because, unlike land filling or incineration, use of sludge as fertilizer allows the recycling of the nutrients present in sludge. Brandt et al. is a real world (field) study conducted under realistic worst case conditions. Specifically, LAS was spiked into the sludge at the highest levels ever found in sludge and spread on a field in rows without mixing into the soil. Microorganisms in the spiked sludge and the soil immediately next to the sludge were then examined for effects of LAS. No long term effects were found. Since previous studies have indicated that microorganisms are the most sensitive soil organisms to LAS, these results confirm that:
- The presence of LAS in sewage sludge used as fertilizer does not pose a risk to the soil.
The final study in this issue (Folke et al.) is landmark because it corrects a troubling misperception – a widely cited but unpublished report that LAS had been found in relatively high concentrations in the marine sediments off the coast of Denmark. Using rigorous analytical methods and monitoring marine sediments in the Baltic Sea as well as in the reported hot spots, the study found:
- The analytical method used in the unpublished report was flawed and greatly overestimated the levels of LAS.
- LAS levels in marine sediments are in fact very low and generally not detectable.
- Hot spots are due to improper sewage treatment practices, such as discharge of untreated sewage, which could be prevented with modern sewage treatment facilities.
These studies demonstrated the high quality of the scientific information available on LAS and the depth of our understanding of the environmental safety of LAS. We in CLER take pleasure in providing these landmark studies, and we hope you will appreciate the value of the scientific effort they demonstrate.
John Heinze, Ph.D.
Editor