title: Environmental Fate, Aquatic Toxicology and Risk Assessment of Polymeric Quaternary Ammonium Salts from Cosmetic Uses
Creators: name: Cumming, Janet L
Publisher: name: Griffith University
Year: 2008
Subjects: subject: aquatic toxicology
subject: polymeric quaternary ammonium salts
subject: polyquaterniums
subject: cosmetics
subject: wastewater treatment plants
subject: risk assessment

description: The consumption of household and personal care products in Australia is similar to that of more highly regulated agricultural and veterinary chemicals. One class of chemical used in cosmetic applications, polymeric quaternary ammonium salts (polyquaterniums), is thought to have adverse effects on aquatic organisms. These polymers belong to a larger class of polymers, cationic polyelectrolytes, that are widely used in industry, largely for water treatment, and that have been extensively studied and regulated. The cosmetic polyquaterniums, however, have not been subject to the same scrutiny, even though differences in, or expectations of, their behaviour are known to exist. The aim of this study was to examine the fate and toxicity of some cosmetic polyquaterniums, and particularly to examine the impact of the presence of the anionic surfactant, sodium dodecyl sulphate, that is often complexed with the polyquaterniums in cosmetic formulations on fate and toxicity. The polyquaterniums studied consisted of six samples of Polyquaternium-10 of provided by Amerchol (The Dow Chemical Company, Midland, MI U.S.A.), five samples of three polyquaterniums (Polyquaternium-11, Polyquaternium-28, Polyquaternium-55) provided by International Specialty Products (ISP, Wayne, New Jersey, USA), and polydimethyldiallyl ammonium chloride (poly(DADMAC), Polyquaternium-6), widely used in water treatment but less commonly in cosmetic applications purchased from Sigma-Aldrich (Castle Hill, NSW, Australia). The four-step risk assessment paradigm (hazard identification, exposure assessment, hazard assessment, risk characterisation) provided the framework for this study. Metachromatic polyelectrolyte titration was used to analyse polyquaterniums in aqueous solution. Although the method is generally not viable in the presence of other ions due to interference, it was found to be viable in the presence of the anionic surfactant sodium dodecyl sulphate. Further, the method was found to work with the supernatant following a sorption experiment involving humic acid. It was not possible to titrate solutions following exposure to bentonite, or in solutions prepared for toxicity tests. Metachromatic Colloid Titration was found to be useful in determining the charge density of the polyquaterniums, and in measuring the concentration of polyquaterniums of known charge density. To establish the extent of exposure of vulnerable aquatic organisms to polyquaterniums released from cosmetic usage, it is necessary to estimate the concentration of polyquaterniums in the aquatic environment. The volume usage of polyquaterniums was estimated from available published data and standard emission scenarios used in the risk assessment of new and existing chemicals. The partitioning of the polyquaternium from the aqueous to the biosolid phase from wastewater treatment plants was estimated from the determination of the partition coefficient between water and humic acid. The latter was assumed to be a suitable surrogate for the biosolids. The fate of polyquaterniums in wastewater treatment plants was modelled using a fugacity approach based on a typical wastewater treatment plant. The import/manufacture volume of polyquaterniums for cosmetic uses was estimated to be between 20 and 60 tonnes per annum. The partition coefficient for polyquaterniums between the aqueous phase and humic acid was lower than expected, generally between 100 and 1000 for the polyquaterniums in this study. Fugacity modelling results suggested that the partitioning of polyquaterniums to the solid phase in wastewater treatment may be less than the default values normally assumed in regulatory risk assessment. Therefore, the estimate of the predicted environmental concentration (PEC) of polyquaterniums in Australian waters is between 0.7 µg/L and 40 µg/L depending on the assumptions and methodology used. Effects assessment, or hazard assessment, is concerned with determining the capacity of the cosmetic polyquaterniums to cause harm to aquatic organisms in the environment. In this study, the aim was to determine if the hazard of the polyquaternium from cosmetic usage is the same as that of the better studied water treatment polymers; and if the complexing of the polyquaternium with the anionic surfactant makes any difference to the toxicity. One species from each of three trophic levels, viz fish, crustacean and algae were selected. Using assessment factors developed for the risk assessment of new chemicals, the environmental concentration likely to be hazardous to the most sensitive species was estimated. The polyquaterniums studied were found to be just as hazardous to the most sensitive species for a typical cosmetic polyquaternium when complexed with the anionic surfactant. The lowest concentration at which a toxic effect occurred was for 50% growth inhibition for algae, 0.3 mg/L for the most toxic polyquaternium. With assessment factors, and using the concentration at which cosmetic polyquaterniums were likely to be hazardous to aquatic organisms, the predicted no effect concentration (PNEC) was estimated to be between 0.3 µg/L and 1.2 µg/L. The risk characterisation process combines the information obtained from the effects and exposure assessments to evaluate the nature of the potential risk. Commonly, the level of risk is estimated based on the PEC/PNEC ratio. In this study, using point estimates and probabilistic methods (Monte Carlo Simulation), the risk of polyquaterniums from cosmetic uses was estimated. Based on the behaviour and toxicity determined in this study, there may be some risk to aquatic organisms from individual polyquaterniums at even low import volumes. As a class of compounds, polyquaterniums from cosmetic uses may present a significant risk to environmental waters in Australia. Sensitivity analysis showed that the prediction of risk was most sensitive to those parameters for which the least amount of data was available, such as the import volume and dilution to receiving waters. A recently developed method of estimating potential risk based on the concept of an Environmental Threshold of No Concern (ETNC), was applied to the use of cosmetic polyquaterniums in Australia. Using the fugacity model approach, the usage volume at which the environmental concentration would exceed the critical threshold was estimated. The volume was found to be significantly lower than the estimated usage determined by either of the methods employed in estimating the current usage volume. While some problems remain in identifying the risk from polyquaterniums to the Australian environment, particularly those associated with the difficulties of quantifying polymers in environmental samples, this thesis has made substantial progress in the risk assessment. Particularly, it has been shown that the use of default assumptions that are largely unsubstantiated, and the sensitivity of the methodology to information that is often unavailable, may result in an estimation of risk that may not be able to protect vulnerable environments.