Time‐dependent lethal body residues for the toxicity of pentachlorobenzene to Hyalella azteca

Abstract

The study examined the temporal response of Hyalella azteca to pentachlorobenzene (PCBZ) in water-only exposures. Toxicity was evaluated by calculating the body residue of PCBZ associated with survival. The concentration of PCBZ in the tissues of H. azteca associated with 50% mortality decreased from 3 to 0.5 micromol/g over the temporal range of 1 to 28 d, respectively. No significant difference was observed in the body residue calculated for 50% mortality when the value was determined using live or dead organisms. Metabolism of PCBZ was not responsible for the temporal response because no detectable PCBZ biotransformation occurred over an exposure period of 10 d. A damage assessment model was used to evaluate the impact and repair of damage by PCBZ on H. azteca. The toxicokinetics were determined so that the temporal toxicity data could be fit to a damage assessment model. The half-life calculated for the elimination of PCBZ averaged approximately 49 h, while the value determined for the half-life of damage repair from the damage assessment model was 33 h.

Use of solid phase microextraction to estimate toxicity: Relating fiber concentrations to toxicity—part I

“…2 and 3). As expected, the overall equilibrium-equivalent LC50 fiber s and EC50 fiber s for 4-d bio-assays were larger than those for 10-d tests for most of the detected compounds, reflecting the likely difference in toxicokinetic state, with the 10-d exposures being more likely at steady state, and the recognition that sensitivity can increase with increasing exposure [36]. As expected, the overall equilibrium-equivalent LC50 fiber s and EC50 fiber s for 4-d bio-assays were larger than those for 10-d tests for most of the detected compounds, reflecting the likely difference in toxicokinetic state, with the 10-d exposures being more likely at steady state, and the recognition that sensitivity can increase with increasing exposure [36].…”

Response spectrum of pentachlorobenzene and fluoranthene for Chironomus tentans and Hyalella azteca

“…For instance, because H. azteca is known to exhibit size-specific fecundity [14,26], residues required to reduce reproduction were expected to follow growth in terms of endpoint sensitivity. For example, the estimated PCBz concentration required to cause a 50% reduction in growth was 0.87 mol/g, which is similar to or above the reported LR50 values [9,16]. However, for PCBz, no significant re-ductions in reproduction were found at residues up to 0.52 mol/g approaching concentrations that produce 50% lethality 0.71 mol/g [12].…”

Time‐dependent toxicity of dichlorodiphenyldichloroethylene to Hyalella azteca

“…Thus, the build up of damage for nonpolar narcotics in the absence of significant biotransformation, will depend on the rate of elimination and the rate of damage repair. For a series of PAH congeners where biotransformation was found to be small [11] and for pentachlorobenzene with no detectable biotransformation [12], the body residue response relationship was found to be variable temporally and the pentachlorobenzene was more potent than the PAH congeners. The temporal response was described by a damage assessment model that described the change in body residue response as a function of both the toxicokinetics and the toxicodynamics, specifically the rate of damage repair [17].…”