Aquatic toxicity of sertraline to Pimephales promelas at environmentally relevant surface water pH

Abstract

Abstract-Researchers recognize that ionization state may influence the biological activity of weak acids and bases. Dissociation in aqueous solutions is controlled by the pK a of a compound and the pH of the matrix. Because many pharmaceuticals are implicitly designed as ionizable compounds, site-specific variability in pH of receiving waters may introduce uncertainty to ecological risk assessments. The present study employed 48-h and 7-d toxicity tests with Pimephales promelas exposed to the model weak base pharmaceutical sertraline over a gradient of environmentally relevant surface water pHs. The 48-h experiments were completed in triplicate, and the average lethal concentration values were 647, 205, and 72 mg/L sertraline at pH 6.5, 7.5, and 8.5, respectively. Survivorship, growth, and feeding rate (a nontraditional endpoint linked by other researchers to sertraline's specific mode of action) were monitored during the 7-d experiment. Adverse effects were more pronounced when individuals were exposed to sertraline at pH 8.5 compared to pH 7.5 and 6.5. The pH-dependent toxicological relationships from these studies were related to in-stream pH data for two streams in the Brazos River basin of central Texas, USA. This predictive approach was taken because of the scarcity of environmental analytical data for sertraline. The results of this study emphasized temporal variability associated with in-stream pH linked to seasonal differences within and between these spatially related systems. Relating site-specific pH variability of surface waters to ionization state may allow researchers to reduce uncertainty during ecological risk assessment of pharmaceuticals by improving estimates of biological effects associated with exposure.

Organic Contaminants in Marine Mammals

“…Valenti et al (2009) reported similar toxicity-pH observations with juvenile fathead minnows exposed to sertraline. Further, Valenti et al (2009) performed a time-to-death fathead minnow study with 500 Ilg/L of sertraline, and estimated associated LT50 values of >48,31.9, and 4.9 h at pH treatment levels of 6.5, 7.5, and 8.5, respectively.…”

“…Valenti et al (2009) reported similar toxicity-pH observations with juvenile fathead minnows exposed to sertraline. Further, Valenti et al (2009) performed a time-to-death fathead minnow study with 500 Ilg/L of sertraline, and estimated associated LT50 values of >48,31.9, and 4.9 h at pH treatment levels of 6.5, 7.5, and 8.5, respectively. Such observations support the findings of Nakamura et al (2008) because if more non ionized sertraline exists at higher pH treatment levels, then sertraline should be more bioavailable and more readily absorbed by juvenile fathead minnows, resulting in the observed more rapid onset of mortality at increasingly higher pHs.…”

Uptake from water, biotransformation, and biliary excretion of pharmaceuticals by rainbow trout

“…The uptake rate of ionized compounds is lower than that of neutral compounds [11][12][13], although ionized molecules may also be absorbed by ion carriers [13]. In fish, as in humans, a mixed variety of anionic, cationic, and neutral transporters affects the active or passive uptake and elimination of xenobiotics [29].…”

“…Ionization usually decreases the uptake, bioconcentration, and toxicity of acidic and basic chemicals because of the loss of pure lipophilic characteristics [11][12][13].…”

Bioaccumulation and trophic dilution of human pharmaceuticals across trophic positions of an effluent-dependent wadeable stream

“…For example, uptake and elimination of ionizable pharmaceuticals (over 70% of drugs are ionizable) by fish [12,13] and invertebrates [14] are modified by surface water pH [13,[15][16][17]. Unfortunately, environmental modelling approaches for predicting fate, transport, exposure and bioaccumulation, which were designed to address historical contaminants (e.g.…”