RESUMEN
This study uses an individual-based contaminant bioaccumulation model for marine mammals to explore factors controlling the transfer of PCBs from mother to calf via nursing in beluga from the St. Lawrence Estuary. Beluga blubber samples (n = 46), along with four matched milk samples from stranded animals over the 1986-1994 period were used for comparison with modelled results. Based on 68 POPs, including 48 PCBs and 20 other organochlorine compounds, milk:blubber ratios were 0.65 between log K OW 3-6.5, then decreased to 0.1 at log K OW 8. Model simulations based on this relationship indicated females were transferring PCBs that were relatively very hydrophobic and highly chlorinated less readily than their lower chlorinated counterparts, resulting in an enriched concentration of very hydrophobic congeners in nursing females relative to adult males. There was very good agreement between observed and modelled male:female PCB concentration ratios. Four females within our dataset (15 %) had male-like ΣPCB concentrations as well as male-like congener profiles, suggesting that these individuals may have had a reduced or limited nursing history.
Asunto(s)
Ballena Beluga/metabolismo , Hidrocarburos Clorados/metabolismo , Leche/metabolismo , Bifenilos Policlorados/metabolismo , Contaminantes Químicos del Agua/metabolismo , Animales , Canadá , Femenino , LactanciaRESUMEN
Concentrations of metals in hair are used often to develop pharmacokinetic models for both animals and humans. Although data on uptake are available, elimination kinetics are less well understood; stable isotope tracers provide an excellent tool for measuring uptake and elimination kinetics. In the present study, methylmercury concentrations through time were measured in the hair and blood of mink (Neovison vison) during a controlled 60-d feeding experiment. Thirty-four mink were fed a standard fish-based diet for 14 d, at the end of which (day 0), 4 mink were sacrificed to determine baseline methylmercury (MeHg) concentrations. From day 0 to day 10, the remaining mink were fed a diet consisting of the base diet supplemented with 0.513 ± 0.013 µg Me(199) Hg/g and 0.163 ± 0.003 µg Me(201) Hg/g. From day 10 to day 60, mink were fed the base diet supplemented with 0.175 ± 0.024 µg Me(201) Hg/g. Animals were sacrificed periodically to determine accumulation of Me(201) Hg in blood and hair over the entire 60-d period and the elimination of Me(199) Hg over the last 50 d. Hair samples, collected from each mink and cut into 2.0-mm lengths, indicate that both isotopes of MeHg appeared in the hair closest to the skin at approximately day 10, with concentrations in the hair reaching steady state from day 39 onward. The elimination rate of Me(199) Hg from the blood was 0.05/d, and the ratio of MeHg in the hair to blood was 119. A large fraction of MeHg (22% to >100%) was stored in the hair, suggesting that in fur-bearing mammals the hair is a major route of elimination of MeHg from the body.
Asunto(s)
Dieta , Cabello/química , Compuestos de Metilmercurio/sangre , Compuestos de Metilmercurio/metabolismo , Animales , Cabello/crecimiento & desarrollo , Marcaje Isotópico , Masculino , Espectrometría de Masas , Isótopos de Mercurio/química , Visón , Factores de TiempoRESUMEN
An individually based (IB) model to predict PCB concentrations in the bottlenose dolphin population of Charleston, SC, USA, was developed with the aim to gain a better understanding of the bioaccumulation behavior and health risk of dietary PCBs across the population and their prey. PCB concentrations predicted in male and female bottlenose dolphin were in good agreement with observed tissue concentrations corroborating the reliability of the model performance and its utility in gaining a more complete view of risk. The modeled cumulative distribution of ΣPCB concentrations for the population with a breakdown into juvenile, adult male, and female subclasses ranged from 3600 to 144,400 ng/g lipid with 66% to >80% of the population exceeding the established threshold for adverse health effects of 17,000 ng/g lipid. The model estimated that a dietary PCB concentration not exceeding 5.1 ng/g wet wt would be required to reach a condition where 95% of the population would have tissue levels below the health effect threshold. The IB model for PCBs in bottlenose dolphins provides a novel approach to estimating the maximum acceptable dietary concentration for PCBs, a central and important factor to protect these apex predators. The model also enables effective prediction of concentrations in dolphins from fish contaminant surveys which are logistically easier and less costly to collect.
Asunto(s)
Delfín Mular/metabolismo , Dieta , Monitoreo del Ambiente , Modelos Teóricos , Bifenilos Policlorados/metabolismo , Animales , Biotransformación , Calibración , Contaminantes Ambientales/metabolismo , Femenino , Peces/metabolismo , Florida , Geografía , Masculino , Reproducibilidad de los Resultados , Medición de Riesgo , South Carolina , IncertidumbreRESUMEN
The development of an area-based polychlorinated biphenyl (PCB) food-web bioaccumulation model enabled a critical evaluation of the efficacy of sediment quality criteria and prey tissue residue guidelines in protecting fish-eating resident killer whales of British Columbia and adjacent waters. Model-predicted and observed PCB concentrations in resident killer whales and Chinook salmon were in good agreement, supporting the model's application for risk assessment and criteria development. Model application shows that PCB concentrations in the sediments from the resident killer whale's Critical Habitats and entire foraging range leads to PCB concentrations in most killer whales that exceed PCB toxicity threshold concentrations reported for marine mammals. Results further indicate that current PCB sediment quality and prey tissue residue criteria for fish-eating wildlife are not protective of killer whales and are not appropriate for assessing risks of PCB-contaminated sediments to high trophic level biota. We present a novel methodology for deriving sediment quality criteria and tissue residue guidelines that protect biota of high trophic levels under various PCB management scenarios. PCB concentrations in sediments and in prey that are deemed protective of resident killer whale health are much lower than current criteria values, underscoring the extreme vulnerability of high trophic level marine mammals to persistent and bioaccumulative contaminants.
Asunto(s)
Exposición a Riesgos Ambientales , Monitoreo del Ambiente/métodos , Cadena Alimentaria , Bifenilos Policlorados/toxicidad , Contaminantes Químicos del Agua/toxicidad , Orca/metabolismo , Animales , Organismos Acuáticos/efectos de los fármacos , Organismos Acuáticos/metabolismo , Colombia Británica , Relación Dosis-Respuesta a Droga , Especies en Peligro de Extinción , Sedimentos Geológicos/análisis , Invertebrados/efectos de los fármacos , Invertebrados/metabolismo , Modelos Biológicos , Océanos y Mares , Fitoplancton/efectos de los fármacos , Fitoplancton/metabolismo , Bifenilos Policlorados/metabolismo , Medición de Riesgo , Salmón/metabolismo , Contaminantes Químicos del Agua/metabolismo , Zooplancton/efectos de los fármacos , Zooplancton/metabolismoRESUMEN
Polychlorinated biphenyl (PCB) concentrations declined rapidly in environmental compartments and most biota following implementation of regulations in the 1970s. However, the metabolic recalcitrance of PCBs may delay responses to such declines in large, long-lived species, such as the endangered and highly PCB-contaminated resident killer whales (Orcinus orca) of the Northeastern Pacific Ocean. To investigate the influence of life history on PCB-related health risks, we developed models to estimate PCB concentrations in killer whales during the period from 1930 forward to 2030, both within a lifetime (approximately 50 years) and across generations, and then evaluated these in the context of health effects thresholds established for marine mammals. Modeled PCB concentrations in killer whales responded slowly to changes in loadings to the environment as evidenced by slower accumulation and lower magnitude increases in PCB concentrations relative to prey, and a delayed decline that was particularly evident in adult males. Since PCBs attained peak levels well above the effects threshold (17 mg/kg lipid) in approximately 1969, estimated concentrations in both the northern and the more contaminated southern resident populations have declined gradually. Projections suggest that the northern resident population could largely fall below the threshold concentration by 2030 while the endangered southern residents may not do so until at least 2063. Long-lived aquatic mammals are therefore not protected from PCBs by current dietary residue guidelines.
Asunto(s)
Exposición a Riesgos Ambientales/efectos adversos , Bifenilos Policlorados/toxicidad , Orca , Animales , Colombia Británica , Residuos de Medicamentos/análisis , Exposición a Riesgos Ambientales/análisis , Monitoreo del Ambiente/métodos , Contaminantes Ambientales/toxicidad , Femenino , Geografía , Masculino , Océano Pacífico , Factores de Riesgo , Contaminantes Químicos del Agua/toxicidadRESUMEN
Individual- and population-based models were developed to simulate the bioaccumulation of persistent organic pollutants (POPs) over the lifetime of ringed seals (Phoca hispida) and account for the effects of age, growth, body condition and sex (including gestation, birth and lactation). Lactational transfer was described using a milk to blubber partition coefficient, which was shown to be a function of Kow (KMB=1/(1.676+1.293.10(-7).Kow) r2=0.60, n=32, p<0.001). Simulations showed that nursing mothers could transfer between 5% and 40% of their burden of low and high KMB contaminants, respectively, to their milk over 40 days of lactation. The models were calibrated using a POPs dataset for 50 seals (29 males, 21 females) from Arviat, Nunavut. They were initially calibrated for a group of eight highly recalcitrant PCB congeners (e.g. PCBs 153, 180) assuming a baseline elimination rate (ke) of about 0.03 year-1. For congeners more prone to biotransformation a satisfactory fit could only be reached by iteratively increasing ke to values ranging from 0.05 to 2.5 year-1 for PCBs 187 and 18, respectively; thus the models became a means for estimating ke. Estimated ke values were correlated with a calculated index of susceptibility to biotransformation (ke=0.0284/Rrelr2=0.98, n=20, p<0.001). This relationship was used to estimate ke values used in simulations to hind-cast temporal trends of SigmaPCB, SigmaDDT, SigmaCHL, alphaHCH, betaHCH in ringed seal populations and to predict potential future trends. Results of these simulations showed good agreement with measured concentrations in seals from two locations in the Canadian Arctic (Holman Island, NWT and Arctic Bay, Nunavut) collected between 1972 and 2001. The models show that the combined effects of rapid juvenile growth, a fast rate of population turnover and substantial capacity to eliminate many POPs result in fairly rapid responses to changes in contaminant loading, thus making ringed seals an effective choice for monitoring spatial and temporal trends of POPs in the Arctic marine ecosystem.