Vol. 17, No.1 (August 2020) – Preface

How Does One Determine Safe Environmental Exposure Levels?

When researchers look at data in new ways, advances in science can frequently be made. However, when this new view ignores previous research on the subject, problems can arise. This volume of the CLER Review addresses the issue of Linear Alkylbenzene Sulfonate’s perceived environmental risk (based on a new look at existing data) versus what years of existing research tell us about the actual environmental risk. This volume also highlights the latest research into the fate, aquatic toxicity and environmental safety of LAS.

Determining safe environmental exposure levels, called the Predicted No Effect Concentration or PNEC, is a key component of an environmental safety assessment. In the final step of the assessment, the PNEC is compared to the predicted environmental concentration (PEC) for the environmental compartment. If the PEC is below the PNEC, then exposures are considered to indicate low risk to the environment, the practical definition of “safe.”

LAS (linear alkylbenzene sulfonate) is probably the best studied down-the-drain consumer chemical. LAS has also been at the forefront of the research to develop optimal methods for environmental safety assessments. This issue of The CLER Review highlights a Commentary (“An Amplified Address to Criticisms and Deficiencies Found in a Recent Environmental Effects Assessment of LAS”) and three key supporting studies focused on the latest research and the state of the science in determining the LAS PNEC. 

The Commentary grew out of a letter to the editor (LTE, Dyer et al. 2020) provided in response to an environmental monitoring study that included derivation of PNEC values for comparison to measured levels in the environment (Freeling et al. 2019). Unfortunately the derivation of the PNEC values for LAS and other studied compounds used a short-cut approach that ignored the extensive available documentation for determining PNEC values. Even worse, the response to the letter to the editor (von der Ohe et al. 2020) largely ignored the comments provided by Dyer et al.

Consequently, CLER invited two experts involved with the LTE, Scott Dyer of LeTourneau University, Longview, Texas (USA) and Scott Belanger of The Procter & Gamble Company, Cincinnati, Ohio (USA) to provide a follow-up Commentary for The CLER Review. The result is not only a fuller critique of the short-cut method but also a thorough and understandable review on this important topic. As noted by CLER Board of Directors member Ricky Stackhouse (Sasol (USA) Corporation): “The Commentary is impressive – a lot of really good work.” 

And by the way, the LAS levels in river and streams as measured in the Freeling et al study were below the state-of-the-science PNEC value noted by Dyer and Belanger. This is contrary to the conclusions reached in the Freeling et al study, which concluded that LAS concentrations were above concentrations triggering the need for more environmental monitoring. In contrast, the conclusion of low risk (safety) has been observed in numerous previous studies on LAS, as referenced in Dyer and Belanger.

In addition to the Commentary, this issue includes three studies cited in the Commentary that have not been included previously in The CLER Review:

1) S.E. Belanger et al., “Integration of Aquatic Fate and Ecological Responses to LAS in Model Stream Ecosystems.” This study reports the results of a model stream ecosystem (mesocosm) study, the no-observed-effect concentration (NOEC) derived from the study and comparison to previously published values. The study concludes: “The specific results of the new model ecosystem study presented in this article can be well defended on the basis of a robust experimental design and because the system contained a diverse and sensitive aquatic community.” The NOEC derived from this study supports the PNEC value in the Dyer and Belanger Commentary.

2) Scott Belanger et al., “Future Needs and Recommendations in the Development of Species Sensitivity Distributions: Estimating Toxicity Thresholds for Aquatic Ecological Communities and Assessing Impacts of Chemical Exposures.” This study reviews the state of the science for determining the aquatic PNEC value based on input from academic, government and industry scientists. The method used is a Species Sensitivity Distribution (SSD), and the output of the assessment is the HC5 value, the hazard concentration to 5% of the species in the SSD. The HC5 value, because it protects 95% of the species in the environmental community, provides a starting point for prediction of the PNEC value, including the LAS PNEC value.

3) S.E. Belanger and G.J. Carr, “SSDs Revisited: Part II—Practical Considerations in the Development and Use of Application Factors Applied to Species Sensitivity Distributions.” This study evaluates the use of application factors, also called uncertainty or safety factors, for the derivation of the PNEC from HC5 values. The study concludes that “simulations demonstrate the basis for applications factors in the range of 1 to 5 for well-studies chemicals with high-quality SSDs.” The LAS SSD is specifically discussed with the conclusion that mesocosm and field data consistently demonstrate the HC5s are conservative, further justifying the use of small application factors for high-quality SSDs, such as the LAS SSD.

In addition to these three studies, several studies cited in the Commentary have been published in previous issues of The CLER Review:

Vol. 9: HERA (Human and Environmental Risk Assessment). 2013. Linear Alkylbenzene Sulphonate (CAS No. 68411-30-3). Human and Environmental Risk Assessment on ingredients of household products. 101p.

Vol. 10: OECD (Organization for Economic Cooperation and Development). 2005.  SIDS Dossier. Linear Alkylbenzene Sulfonate (LAS). Sponsor Country: United States of America, January 12, 2005. 201p.

Vol. 13: Dyer et al. 2003.  The influence of untreated wastewater to aquatic communities in the Balatuin River, The Philippines.  Chemosphere 52:43-53.

  McAvoy et al. 2003. Risk assessment approach for untreated wastewater using the QUAL2E water quality model. Chemosphere 52:55-66.

Vol. 14: Cowan-Ellsberry et al.  2014. Environmental safety of the use of major surfactant classes in North America. Crit Rev Environ Sci Technol 44:1893-1993.

Vol. 16: Belanger et al. 2016. Development of acute toxicity Quantitative Structure Activity Relationships (QSAR) and their use in Linear Alkylbenzene Sulfonate Species Sensitivity Distributions. Chemosphere 155:18-27.

  McDonough et al. 2016. Evaluation of anionic surfactant concentrations in US effluents and probabilistic determination of their combined ecological risk in mixing zones. Sci Total Environ 572:434–441.

These studies – the three supporting studies in this issue as well as the seven studies previously published in The CLER Review – strongly support the conclusions of the Dyer and Belanger Commentary that LAS “has been shown in both laboratory and field studies to have a minimal potential risk to the aquatic environment.”

John Heinze, Ph.D.



Dyer SD, McAvoy DC, Belanger SE, Heinze J, Stackhouse R, Sanderson H, Versteeg DJ.  Correcting deficiencies to risk assessment of surfactants by Freeling et al. (2020). Sci Total Environ. 721, 15 June 2020, 135847; available at:

Freeling F, Nikiforos AA, von der Ohe PC, Slobodnik J, Oswald P, Aalizadeh R, Cirka L, Thomaidis NS, Scheurer M. 2019. Occurrence and potential environmental risk of surfactants and their transformation products discharged by wastewater treatment plants. Sci Tot Environ 681:475-487.

Von der Ohe PC, Freeling F, Alygizakis NA, Slobodnik J, Oswald P, Aalizadeh R, Cirka L, Thomaidis NS, Scheurer M.  2020.  Explaining the rationale behind the risk assessment of surfactants by Freeling et al. (2019).  Sci Total Environ. 721, 15 June 2020, 136828; available at: