Single‐substance and mixture toxicity of five pharmaceuticals and personal care products to marine periphyton communities

Abstract

The single-substance and mixture toxicity of five pharmaceuticals and personal care products (fluoxetine, propranolol, triclosan, zinc-pyrithione, and clotrimazole) to marine microalgal communities (periphyton) was investigated. All compounds proved to be toxic, with median effective concentration values (EC50s) between 1,800 nmol/L (triclosan) and 7.2 nmol/L (Zn-pyrithione). With an EC50 of 356 nmol/L, the toxicity of the mixture falls into this span, indicating the absence of strong synergisms or antagonisms. In fact, a comparison with mixture toxicity predictions by the classical mixture concepts of concentration addition and independent action showed a good predictability in the upper effect range. However, the mixture provoked stimulating effects (hormesis) in the lower effect range, hampering the application of either concept. An independent repetition of the mixture experiment resulted in a principally similar concentration-response curve, again with clear hormesis effects in the lower range of test concentrations. However, the curve was shifted toward higher effect concentrations (EC50 1,070 nmol/L), which likely is due to changes in the initial species composition. Clear mixture effects were observed even when all five components were present only at their individual no-observed-effect concentrations (NOECs). These results show that, even with respect to mixtures of chemically and functionally dissimilar compounds, such as the five pharmaceuticals and personal care products investigated, environmental quality standards must take possible mixture effects from low-effect concentrations of individual compounds into consideration.

Assessing triclosan-induced ecological and trans-generational effects in natural phytoplankton communities: a trait-based field method

“…Additionally, our data show that some populations had a significantly higher growth for low doses (below 10 lg L -1 ) with the trend decreasing at higher levels (Table 1). This is consistent with previous reports of TCS showing hormetic responses at sub-lethal doses in periphyton (when present in mixture with other pharmaceutical and personal care products) (Backhaus et al 2011;Brown et al 2012). It may be argued that if smaller cells are more sensitive to exposure (as hypothesised here), they may also be more sensitive to low dose hormetic effects.…”

“…Pulse exposure (48 h duration) to TCS at 60 lg L -1 has shown to cause higher Chl-a content after 7 days and increased mortality of diatoms and bacteria in biofilms, consequently reducing biodiversity (Proia et al 2011). At lower doses (similar to those used in our study), TCS treatment has resulted in stimulation of pigment content at community level (hormetic effects) in one study (Backhaus et al 2011), and non-significant differences in biomass yields with marked shifts in the community structure (reduced species richness) at higher concentrations (Wilson et al 2003). The lack in detection of biodiversity effects in our study may be the result of insufficient resolution of the statistical clustering method on the actual diversity of the phytoplankton, or of low statistical replication of experimental treatments (n = 3).…”

“…Three bottles were spiked with 1 mL solution of ethanol dissolved TCS at 0.05, 0.5 and 5 mg L -1 to obtain the final concentrations of 0.1, 1 and 10 lg L -1 , respectively. These concentrations reflected the environmental range of TCS exposure at the lower end of waste water treatment effluent levels and at the higher end of surface water levels (Singer et al 2002;Fernandes et al 2011;Bedoux et al 2012), and fall within the range of sensitivity for phytoplankton species and communities (DeLorenzo et al 2008;Backhaus et al 2011). The fourth bottle was spiked with 1 mL of ethanol (vector control).…”

Medicines, shaken and stirred: a critical review on the ecotoxicology of pharmaceutical mixtures

“…This was explained by the fact that four of the components (sulfamethoxazole, EE2, diclofenac, ibuprofen) were classified as acting primarily as baseline toxicants in algae and hence sharing an identical mode of action in this organism-although they belong to different chemical groups and therapeutical classes. The mixture toxicity of five pharmaceuticals and personal care products (fluoxetine, propranolol, triclosan, zinc-pyrithione and clotrimazole) to marine benthic microalgal communities (periphyton) was investigated by Backhaus et al [48], describing an almost identical mixture toxicity prediction by CA and IA. The observed mixture toxicity was largely in line with the conceptual expectations in the upper effect range.…”

Ecotoxicology: The Challenges for the 21st Century

“…However, the science on the toxicity of chemical mixtures focuses primarily on the effects of mixtures at an individual level [53]. The few studies available at higher hierarchical levels are mainly oriented toward communities of algae and microorganisms [54,55]. Efforts to understand how a complex ecosystem may respond to mixtures of chemicals with different modes of action on the different taxonomic groups of living organisms are still lacking [50].…”