Reproduction Symposium: does grazing on biosolids-treated pasture pose a pathophysiological risk associated with increased exposure to endocrine disrupting compounds?

Biosolids (processed human sewage sludge), which contain low individual concentrations of an array of contaminants including heavy metals and organic pollutants such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and polychlorinated dibenzodioxins/polychlorinated dibenzofurans known to cause physiological disturbances, are increasingly being used as an agricultural fertilizer. This could pose a health threat to both humans and domestic and wild animal species. This review summarizes results of a unique model, used to determine the effects of exposure to mixtures of environmentally relevant concentrations of pollutants, in sheep grazed on biosolids-treated pastures. Pasture treatment results in nonsignificant increases in environmental chemical (EC) concentrations in soil. Whereas EC concentrations were increased in some tissues of both ewes and their fetuses, concentrations were low and variable and deemed to pose little risk to consumer health. Investigation of the effects of gestational EC exposure on fetal development has highlighted a number of issues. The results indicate that gestational EC exposure can adversely affect gonadal development (males and females) and that these effects can impact testicular morphology, ovarian follicle numbers and health, and the transcriptome and proteome in adult animals. In addition, EC exposure can be associated with altered expression of GnRH, GnRH receptors, galanin receptors, and kisspeptin mRNA within the hypothalamus and pituitary gland, gonadotroph populations within the pituitary gland, and regional aberrations in thyroid morphology. In most cases, these anatomical and functional differences do not result in altered peripheral hormone concentrations or reproductive function (e.g., lambing rate), indicating physiological compensation under the conditions tested. Physiological compensation is also suggested from studies that indicate that EC effects may be greater when exposure occurs either before or during gestation compared with EC exposure throughout life. With regard to human and animal health, this body of work questions the concept of safe individual concentration of EC when EC exposure typically occurs as complex mixtures. It suggests that developmental EC exposure may affect many different physiological systems, with some sex-specific differences in EC sensitivity, and that EC effects may be masked under favorable physiological conditions.

Neural network integration of field observations for soil endocrine disruptor characterisation.

A neural network approach was used to predict the presence and concentration of a range of endocrine disrupting compounds (EDCs), based on field observations. Soil sample concentrations of endocrine disrupting compounds (EDCs) and site environmental characteristics, drawn from the National Soil Inventory of Scotland (NSIS) database, were used. Neural network models were trained to predict soil EDC concentrations using field observations for 184 sites. The results showed that presence/absence and concentration of several of the EDCs, mostly no longer in production, could be predicted with some accuracy. We were able to predict concentrations of seven of 31 compounds with r(2) values greater than 0.25 for log-normalised values and of eight with log-normalised predictions converted to a linear scale. Additional statistical analyses were carried out, including Root Mean Square Error (RMSE), Mean Error (ME), Willmott's index of agreement, Percent Bias (PBIAS) and ratio of root mean square to standard deviation (RSR). These analyses allowed us to demonstrate that the neural network models were making meaningful predictions of EDC concentration. We identified the main predictive input parameters in each case, based on a sensitivity analysis of the trained neural network model. We also demonstrated the capacity of the method for predicting the presence and level of EDC concentration in the field, identified further developments required to make this process as rapid and operator-friendly as possible and discussed the potential value of a system for field surveys of soil composition.

Long term temporal and spatial changes in the distribution of polychlorinated biphenyls and polybrominated diphenyl ethers in Scottish soils.

Long term changes in polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) concentrations in soil from four transects across Scotland were measured in three surveys conducted between 1990 and 2007-9. Overall PCB level declined during this period (22.5 to 4.55 ng/g, p<0.001) but PBDEs increased (0.68 to 2.55 ng/g, p<0.001), reflecting the ban on PCB use in the 1980s while PBDE use increased until about 2004 when the use of penta-mix congener ceased in Europe. The proportion of lighter PCB congeners (28+52) present declined (p<0.001) primarily between 1990 and 1999. However, the proportion of lighter PBDE congeners (47+99) in the soil samples increased (p<0.01) from 1990 to 1999 and declined (p<0.001) thereafter, probably reflecting the introduction of legislation banning penta-BDE products and the degradation of lighter congeners and their translocation. PCBs were slightly higher in two southernmost transects but PBDE concentrations were significantly higher (p<0.001) in the two southern transects than in the two northern transects. This may reflect proximity to areas of high population and industrial activity. It is concluded that temporal and spatial changes in the distribution of PCBs and PBDEs reflect geography, physical processes and legislation.

The influence of interview on decision making and selection of prospective veterinary undergraduate students.

Interviews form part of the selection process in many veterinary programmes worldwide. This study aimed to evaluate the influence of the interview on veterinary selection decisions. An admissions cycle of interviews of 181 shortlisted school-leaving applicants to veterinary medicine was investigated. Selection panel pairs (from cohorts of 5 chairs and 11 cointerviewers) independently evaluated applicants before interview on the basis of their written application. Applicants were then interviewed and selectors repeated their evaluations, both independently and after joint discussion. Results of the preinterview and postinterview evaluations of the applicants were analysed statistically. There was slight to moderate agreement between the chair and cointerviewer on selection decisions/rankings taken before interview, but substantial agreement after interview. Agreement between postinterview decisions/rankings and consensus decisions/rankings postinterview was extremely high. Applicant attributes that had the most influence on selection decisions were: 'communication skills', 'overall knowledge gained from work experience' and 'ability to think on their feet'. There was significantly more agreement possible between interviewers with regard to selection decisions based on interview assessment compared with preinterview assessment of written applications. This study suggests that interviews may be a useful and important aid in decision making for selecting the candidates perceived as most suitable for this veterinary programme.

Short- and long-term temporal changes in soil concentrations of selected endocrine disrupting compounds (EDCs) following single or multiple applications of sewage sludge to pastures.

Temporal changes in soil burdens of selected endocrine disrupting compounds were determined following application to pasture of either sewage sludge or inorganic fertilizer. Soil polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations were not altered. Changes in concentrations of diethylhexyl phthalate (DEHP) and PBDEs 47 and 99 differed with season but concentrations remained elevated for more than three weeks after application, when grazing animals are normally excluded from pasture. It is concluded that single applications of sewage sludge can increase soil concentrations of some, but not all classes of EDCs, possibly to concentrations sufficient to exert biological effects when different chemicals act in combination, but patterns of change depend on season and soil temperature. Analysis of soil from pasture subjected to repeated sludge applications, over 13 years, provided preliminary evidence of greater increases in soil burdens of all of the EDC groups measured, including all of the PBDE congeners measured.

Concentrations and geographic distribution of selected organic pollutants in Scottish surface soils.

Concentrations of selected persistent organic pollutants (POPs) representing three chemical classes (polycyclic aromatic hydrocarbons (PAH), polybrominated diphenyl ethers (PBDE) and polychlorinated biphenyls (PCB) and the organic pollutant diethylhexyl phthalate (DEHP), were determined in surface soil samples (0-5 cm) collected at 20 km grid intersects throughout Scotland over a three-year period. Detectable amounts of all chemical classes and most individual congeners were present in all samples. There were no consistent effects of soil or vegetation type, soil carbon content, pH, altitude or distance from centres of population on concentrations which exhibited extreme variation, even in adjacent samples. It is concluded that soil POPs and DEHP concentrations and associated rates of animal and human exposure were highly variable, influenced by multiple, interacting factors, and not clearly related to local sources but possibly related to wet atmospheric deposition and the organic carbon content of the soil.

Effects of exposure to environmental chemicals during pregnancy on the development of the male and female reproductive axes.

There is a large body of literature describing effects of environmental chemicals (ECs), many of them anthropogenic with endocrine-disrupting properties, on development in rodent laboratory species, some of which lead to impaired reproduction and adverse health. This literature joins extensive human epidemiological data and opportunistic wildlife findings on health effects of ECs. In contrast, the effect of endocrine disruption on foetal development and reproductive performance in domestic species is less extensively documented. This applies both to domestic farm and to companion species even though the former is critical to food production and the latter share our homes and many aspects of the modern developed human lifestyle. In domestic species, the nature of chemicals exposure in utero and their consequences for animal health and production are poorly understood. A complication in our understanding is that the pace of development, ontogeny and efficiency of foetal and maternal hepatic and placental activity differs between domestic species. In many ways, this reflects the difficulties in understanding human exposure and consequences of that exposure for the foetus and subsequent adult from epidemiological and largely rodent-based data. It is important that domestic species are included in research into endocrine disruption because of their (i) wide variety of exposure to such chemicals, (ii) greater similarity of many developmental processes to the human, (iii) economic importance and (iv) close similarities to developed world human lifestyle in companion species.

Potential barriers to veterinary student access to counselling and other support systems: perceptions of staff and students at a UK veterinary school.

Considerable evidence suggests that veterinary surgeons' mental health is often poorer than comparable populations and that the incidence of suicide is higher among veterinary surgeons than the general public. Veterinary students also appear to suffer from high levels of anxiety and stress, and may possess inadequate coping strategies when faced with adversity. Veterinary students may find it difficult to access central university support systems due to their heavy workload and geographical isolation on some veterinary campuses. A previous study of University of Edinburgh fourth-year veterinary students found that support services located several miles from the main veterinary campus was a barrier to students accessing counselling services. Consequently, a pilot project was initiated, which provided a counselling service at the University of Edinburgh's rural Easter Bush veterinary campus one afternoon a week during 2010. As part of the evaluation of this service, web-based questionnaires were delivered via e-mail to all veterinary staff and students towards the end of the 12-month pilot period to evaluate perceptions of barriers to student counselling and to investigate student-valued support services. Questionnaire responses were received from 35 per cent of veterinary students and 52 per cent of staff. Stigmatisation of being unable to cope was a potent inhibitor of seeking support within the veterinary environment, but counselling was perceived as valuable by the majority of staff and students. Provision of an on-site counselling service was considered important for increasing ease of access; however, students viewed friends and family as their most important support mechanism. Workload was cited as the main cause of veterinary student stress. The majority of staff and student respondents perceived veterinary students as having an increased need for counselling support compared with other students.

Foetal and post-natal exposure of sheep to sewage sludge chemicals disrupts sperm production in adulthood in a subset of animals.

Exposure to ubiquitous, environmental chemicals (ECs) has been hypothesized as a cause for declining male reproductive health. Understanding the long-term effects of EC exposure on reproductive health in humans requires animal models and exposure to 'real life', environmentally relevant, mixtures during development, a life stage of particular sensitivity to ECs. The aim of this study was to evaluate the effects of in utero and post-natal exposure to environmentally relevant levels of ECs, via sewage sludge application to pasture, on the adult male sheep testis. Hormones, liver concentrations of candidate ECs and Sertoli and germ cell numbers in testes of adult rams that were exposed to ECs in sewage sludge in utero, and until weaning via maternal exposure, and post-weaning via grazing pastures fertilized with sewage sludge, were quantified. Evaluated as a single group, exposure to sludge ECs was without significant effect on most parameters. However, a more detailed study revealed that 5 of 12 sludge-exposed rams exhibited major spermatogenic abnormalities. These consisted of major reductions in germ cell numbers per testis or per Sertoli cell and more Sertoli cell-only tubules, when compared with controls, which did not show any such changes. The sludge-related spermatogenic changes in the five affected animals were significantly different from controls (p < 0.001); Sertoli cell number was unaffected. Hormone profiles and liver candidate EC concentrations were not measurably affected by exposure. We conclude that developmental exposure of male sheep to real-world mixtures of ECs can result in major reduction in germ cell numbers, indicative of impaired sperm production, in a proportion of exposed males. The individual-specific effects are presumed to reflect EC effects on a heterogeneous population in which some individuals may be more susceptible to adverse EC effects. Such effects of EC exposure in humans could have adverse consequences for sperm counts and fertility in some exposed males.

Effect of duration of exposure to sewage sludge-treated pastures on liver tissue accumulation of persistent endocrine disrupting compounds (EDCs) in sheep.

Liver tissue concentrations of selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) were determined in groups of Texel ewes and lambs following exposure to pastures fertilised with either sewage sludge (Treated; T) or inorganic fertiliser (Control; C). Lambs were slaughtered at the age of 6 months, in each of 3 years, while ewes were slaughtered at 5 to 6 years of age having been exposed to the respective pastures for approximately 6, 18 or 30 months, during the same, respective years, immediately before slaughter. Mean liver concentrations of very few of the chemical classes were elevated in either ewe or lamb tissue as a result of exposure of the animals to sewage sludge. Mean concentrations, in lamb liver, of chemicals of each of the classes differed significantly, but inconsistently, between years, reflecting temporal variations in exposure, although the pattern of annual change differed with individual chemical. On the other hand, in ewes, liver concentrations of many chemicals increased, significantly and consistently, with increasing duration of exposure. It was concluded that the increases in tissue concentrations with increased duration of exposure were unlikely to be sufficient to be of concern to consumers and that tissue burdens cannot be linked, easily, with the physiological effects reported previously for animals similarly exposed.

Perceptions of clients and veterinarians on what attributes constitute 'a good vet'.

The perceptions of veterinarians and small animal (SA) clients on what attributes constitute 'a good veterinarian' were examined by a questionnaire survey. The respondents were asked to record how important they considered 20 attributes for a veterinary surgeon to have on a five-point scale from 'not at all important' to 'very important'. In addition, they were asked to list which attributes they considered to be the three most important attributes in a veterinary surgeon; finally, they were asked whether there were any additional attributes that they considered to be highly desirable in a veterinary surgeon. In total, 407 SA clients, 243 SA veterinarians and 61 non-SA veterinarians completed the questionnaire. There were significant differences in the proportion of clients who considered an attribute to be 'very important' compared with SA veterinarians for 12 of the 20 attributes (P<0.005). A larger proportion of clients considered 'confidence', 'knowledge about veterinary medicine and surgery', 'cleanliness', 'good at explaining technical terms', 'patience', 'clear about cost of treatment', 'ability to work in a team', 'honesty', 'politeness', 'decisiveness', 'good with animals' and 'good practical skills' to be 'very important' attributes than the SA veterinarians; a larger proportion of SA veterinarians considered 'good communication skills' to be a 'very important' attribute than the clients.

Geographic variation in tissue accumulation of endocrine disrupting compounds (EDCs) in grazing sheep.

Muscle tissue was collected from ewes and lambs derived from farms throughout Scotland and sample concentrations of five endocrine disrupting compound groups were determined. Farms of origin were categorised according to geographic region. There were few statistically-significant differences with region or distance from cities. However, the magnitude of the difference between the highest and lowest mean values in ewe muscle from different regions exceeded 30% for 13 of the 15 compounds that were consistently detected in muscle, with animals derived from the industrialised region having the highest mean values for 11 of the 13 compounds. A less marked trend was apparent in the lamb muscle (8 of 13 highest were in the industrialised region). The physiological effects of such small differences in exposure to mixtures of pollutants remain to be determined.

Maternal and fetal tissue accumulation of selected endocrine disrupting compounds (EDCs) following exposure to sewage sludge-treated pastures before or after conception.

Liver concentrations of selected pollutant classes were determined in groups of sheep fetuses and their dams, at 55 (Experiment 1) and 110 (Experiment 2) days of gestation (term = 145 d) following exposure, throughout their breeding lives and after mating, to pasture treated with either inorganic fertiliser (control, CC) or with sewage sludge (treated, TT). In a unique study designed to separate the respective contributions of environmental sources and mobilised tissue to the available EDC burden, in additional groups of animals, pollutant burdens at 110 days gestation were assessed following exposure to the respective treatments, either throughout their breeding lives until mating, but not thereafter (TC), or only between mating and slaughter (CT) (Experiment 3). With very few exceptions, maternal and fetal liver concentrations of diethylhexyl phthalate (DEHP) and selected polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDE) and polycyclic aromatic hydrocarbons (PAHs) were not significantly affected by sludge exposure in any group. In some cases, maternal and fetal tissue EDC concentrations were different but the differences were not consistent, and maternal and fetal concentrations of none of the classes of chemical were significantly correlated. It was not possible to identify a single chemical, or class of chemical, that may be responsible for previously observed physiological effects of exposure to sludge-treated pastures. It is concluded that exposure of sheep to pastures fertilised with sewage sludge was not associated with increased liver concentrations of EDCs, irrespective of the stage of development at which they were measured and of maternal tissue mobilisation and EDC release during gestation. Thus, retrospective measurements of EDC tissue burdens could not be used to accurately assess earlier fetal EDC insults.

Effects of environmental pollutants on the reproduction and welfare of ruminants.

Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.

Foetal hypothalamic and pituitary expression of gonadotrophin-releasing hormone and galanin systems is disturbed by exposure to sewage sludge chemicals via maternal ingestion.

Animals and humans are chronically exposed to endocrine disrupting chemicals (EDCs) that are ubiquitous in the environment. There are strong circumstantial links between environmental EDC exposure and both declining human/wildlife reproductive health and the increasing incidence of reproductive system abnormalities. The verification of such links, however, is difficult and requires animal models exposed to 'real life', environmentally relevant concentrations/mixtures of environmental contaminants (ECs), particularly in utero, when sensitivity to EC exposure is high. The present study aimed to determine whether the foetal sheep reproductive neuroendocrine axis, particularly gondotrophin-releasing hormone (GnRH) and galaninergic systems, were affected by maternal exposure to a complex mixture of chemicals, applied to pasture, in the form of sewage sludge. Sewage sludge contains high concentrations of a spectrum of EDCs and other pollutants, relative to environmental concentrations, but is frequently recycled to land as a fertiliser. We found that foetuses exposed to the EDC mixture in utero through their mothers had lower GnRH mRNA expression in the hypothalamus and lower GnRH receptor (GnRHR) and galanin receptor (GALR) mRNA expression in the hypothalamus and pituitary gland. Strikingly, this, treatment had no significant effect on maternal GnRH or GnRHR mRNA expression, although GALR mRNA expression within the maternal hypothalamus and pituitary gland was reduced. The present study clearly demonstrates that the developing foetal neuroendocrine axis is sensitive to real-world mixtures of environmental chemicals. Given the important role of GnRH and GnRHR in the regulation of reproductive function, its known role programming role in utero, and the role of galanin in the regulation of many physiological/neuroendocrine systems, in utero changes in the activity of these systems are likely to have long-term consequences in adulthood and represent a novel pathway through which EC mixtures could perturb normal reproductive function.

Evaluation of suicide awareness programmes delivered to veterinary undergraduates and academic staff.

In an effort to increase suicide awareness skills among veterinary undergraduates, a three-hour suicide awareness workshop (safeTALK) was delivered to third-year Royal (Dick) School of Veterinary Studies undergraduates as part of their professional development curriculum. Students were able to opt out of the session by contacting the course organisers. A total of 26 of 151 (17 per cent) third-year students attended the workshop, and 17 completed a feedback questionnaire. The vast majority of the students reported that after completing the workshop they were more likely or much more likely to recognise the signs of a person at risk of suicide, approach a person at risk of suicide, ask a person about suicide, and connect a person at risk of suicide with help. Five veterinary academics attended a two-day Applied Suicide Intervention Skills Training (ASIST) course, and all reported that the course was effective in improving suicide awareness and intervention skills.

Influence of prenatal nutrition and obesity on tissue specific fat mass and obesity-associated (FTO) gene expression.

The recent discovery of an association between body composition, energy intake and the fat mass and obesity-associated (FTO) gene represents a promising new therapeutic target in obesity prevention. In a well, pre-established large animal model, we investigated the regulation of FTO gene expression under conditions either leading to obesity or increased risk of obesity related disorders: i) a sedentary 'Western' lifestyle and ii) prenatal exposure to nutrient restriction. Pregnant sheep were either fed to fully meet their nutritional requirements throughout gestation or 50% of this amount from early-to-mid gestation. Following weaning, offspring were either made obese through exposure to a sedentary obesogenic environment or remained lean. A significant positive relationship between placental FTO gene expression and fetal weight was found at 110 days gestation. In both the newborn and adult offspring, the hypothalamus was the major site of FTO gene expression. Hypothalamic FTO gene expression was upregulated by obesity and was further increased by prenatal nutrient restriction. Importantly, we found a strong negative relationship between the hypothalamic FTO gene expression and food intake in lean animals only that may imply FTO as a novel controller of energy intake. In contrast, FTO gene expression in the heart was downregulated in obese offspring born to nutrient restricted mothers. In addition, FTO gene expression was unaffected by obesity or prenatal diet in insulin-dependent tissues, where it changed with age possibly reflecting adaptations in cellular energetic activity. These findings extend information gained from human epidemiology and provide new insights into the regulation of in vivo energy metabolism to prevent obesity.

Anthropogenic pollutants: a threat to ecosystem sustainability?

Pollutants, including synthetic organic materials and heavy metals, are known to adversely affect physiological systems in all animal species studied to date. While many individual chemicals can perturb normal functions, the combined actions of multiple pollutants are of particular concern because they can exert effects even when each individual chemical is present at concentrations too low to be individually effective. The biological effects of pollutants differ greatly between species reflecting differences in the pattern of exposure, routes of uptake, metabolism following uptake, rates of accumulation and sensitivity of the target organs. Thus, understanding of the effects of pollutants on wildlife and ecosystems will require detailed study of many different species, representing a wide range of taxa. However, such studies can be informed by knowledge obtained in more controlled conditions which may indicate likely mechanisms of action and suitable endpoint measurements. Responses may be exacerbated by interactions between the effects of pollutants and environmental stressors, such as under-nutrition or osmotic stresses and so changes in such variables associated with climatic changes may exacerbate physiological responses to pollutant burdens.

Accumulation of endocrine disrupting compounds in sheep fetal and maternal liver tissue following exposure to pastures treated with sewage sludge.

Fetal tissue concentrations of endocrine disrupting compounds (EDCs), and their relationship to maternal tissue concentrations, are largely unknown, in any species. In particular, the patterns of accumulation in the respective tissues following increased rates of environmental exposure are little known. This study was designed to determine fetal and maternal tissue concentrations of selected EDCs in sheep exposed to background, environmental concentrations of EDCs (pastures treated with inorganic fertiliser; Control; C) or to elevated, environmental concentrations (sludge-treated pastures; Treated; T). Mean log concentrations of diethylhexyl phthalate (DEHP) were similar in adult and fetal livers but there was a significant interaction between stage of development (maternal or fetal) and treatment reflecting the fact that mean concentrations were lower (P < 0.05) in C than T fetuses but not adults. Relative concentrations of polychlorinated biphenyls (PCB) in maternal and fetal tissue differed with congener; concentrations of congener 101 were higher (P < 0.05) in fetal tissue. Neither maternal nor fetal liver concentrations of any of the PCB congeners differed significantly with treatment. Polybrominated diphenyl ethers (PBDE) in the tissue were represented primarily by congeners 47 and 99. PBDE 99 concentrations were higher in maternal than fetal tissue (P = 0.01). None differed with treatment in either maternal or fetal tissues. Concentrations of many polycyclic aromatic hydrocarbons (PAH) were higher in maternal tissue but none differed with treatment in either adult or fetuses. It is concluded that sheep fetal liver EDC concentrations are variably related to those of their dams and in some cases appear to be selectively accumulated in fetuses. Differential accumulation of individual pollutants may have important implications for the assessment of risk from exposure.