Screening level mixture risk assessment of pharmaceuticals in STP effluents

Abstract

We modeled the ecotoxicological risks of the pharmaceutical mixtures emitted from STP effluents into the environment. The classic mixture toxicity concept of Concentration Addition was used to calculate the total expected risk of the analytically determined mixtures, compare the expected impact of seven effluent streams and pinpoint the most sensitive group of species. The risk quotient of a single, randomly selected pharmaceutical is often more than a factor of 1 000 lower than the mixture risk, clearly indicating the need to systematically analyse the overall risk of all pharmaceuticals present. The MCR, which is the ratio between the most risky compound and the total mixture risk, varies between 1.2 and 4.2, depending on the actual scenario and species group under consideration. The mixture risk quotients, based on acute data and an assessment factor of 1 000, regularly exceed 1, indicating a potential risk for the environment, depending on the dilution in the recipient stream. The top 10 mixture components explain more than 95% of the mixture risk in all cases. A mixture toxicity assessment cannot go beyond the underlying single substance data. The lack of data on the chronic toxicity of most pharmaceuticals as well as the very few data available for in vivo fish toxicity has to be regarded as a major knowledge gap in this context. On the other hand, ignoring Independent Action or even using the sum of individual risk quotients as a rough approximation of Concentration Addition does not have a major impact on the final risk estimate.

Simplifying environmental mixtures—An aquatic exposure‐based approach via land use scenarios

“…There was also evidence to suggest that predicted mixture risks can be attributed to relatively few compounds in many cases. The latter has been observed more frequently based on measured environmental concentrations (e.g., Backhaus and Karlsson ; Vallotton and Price ). One of the common characteristics of mixture risk assessments is a difference in the availability of ecotoxicity data for the compounds involved in causing the potential risk.…”

Mixtures of chemicals are important drivers of impacts on ecological status in European surface waters

“…The results of recent analyses of monitoring data provide some additional insights that are relevant for practice. That is, although the studies show that mixture impacts are important, they also show that frequently some chemicals have a relatively dominant role (e.g., [15,[29][30][31]). This was also found in scenario studies [32].…”

Regulatory assessment and risk management of chemical mixtures: challenges and ways forward

“…The hazard of chemical mixtures can be assessed by testing the whole mixturebearing in mind that it is not feasible to test all possible combinations of chemicals in mixturesor based on the concentration and effect information of the individual components of the mixture. One of the main challenges in the toxicological assessment of mixtures is the need to address data gaps: whole mixture effect data are available for a limited number of mixtures only, and single chemical hazard, dose-response, and Mode of Action (MoA) information needed in component-based approaches is often lacking for many chemical classes (Backhaus and Karlsson 2014;Evans et al 2015;Bopp et al 2016Bopp et al , 2018a.…”

“…Using the MCR, the "nature of concern" of a mixture and related risk management actions can be decided on (Section 5.1). A review of case studies ) showed that the MCR was usually ranging between 1.2 and 5.8, depending on the number of analyzed compounds Backhaus and Karlsson 2014;De Brouwere et al 2014;Price et al 2014), that is, the number of chemicals that drive the mixture risk is usually low. In all the examples, the MCR decreased with increasing HI, indicating that the higher the predicted risk, the lower the number of substantially contributing chemicals.…”

“…Several studies show that usually risks from chemical mixtures are driven by a limited number of mixture components. Backhaus and Karlsson (2014) investigated environmental risks from pharmaceuticals detected in waste water treatment plant effluents across Europe and identified that at maximum 10 compounds usually explained more than 95% of the overall risk. Posthuma et al (2016) found for Dutch rivers that 5-10 compounds are usually responsible for nearly the whole toxic pressure.…”