Pollutant concentrations in placenta.

Unborn children are exposed to environmental pollutants via the placenta, and there is a causal relationship between maternal intake of pollutants and fetal exposure. Placental examination is an effective way for acquiring data for estimating fetal exposure. We analyzed the concentrations of 104 congeners of persistent organic pollutants, seven organotin compounds, five heavy metals, and methylmercury in 130 randomly selected placentas. Additionally, we examined similarities between pollutant concentrations by analyzing correlations between their placental concentrations. Our results yield new information for conducting contaminant risk assessments for the prenatal period. Out of the 117 individual persistent organic pollutants or metals assayed, 46 could be detected in more than half of the placentas. Moreover, dichlorodiphenyldichloroethylene (p,p'-DDE) was found in all placentas. The data indicates that fetal exposure to dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs), p,p'-DDE, and methylmercury depends on the mother's parity, and age. We also conclude that sources of the above four pollutants are similar but differ from the sources of polybrominated diphenyl ethers.

Effects of docosahexaenoic acid and methylmercury on child's brain development due to consumption of fish by Finnish mother during pregnancy: a probabilistic modeling approach.

Fish contains both beneficial substances e.g. docosahexaenoic acids but also harmful compounds e.g. methylmercury. Importantly, the health effects caused by these two substances can be evaluated in one common end point, intelligence quotient (IQ), providing a more transparent analysis. We estimated health effects of maternal fish consumption on child's central nervous system by creating a model with three alternative maternal fish consumption scenarios (lean fish, fatty fish, and current fish consumption). Additionally, we analyzed impacts of both regular fish consumption and extreme fish consumption habits. At the individual level, the simulated net effects were small, encompassing a range of one IQ point in all scenarios. Fatty fish consumption, however, clearly generated a beneficial net IQ effect, and lean fish consumption evoked an adverse net IQ effect. In view of the current fish consumption pattern of Finnish mothers the benefits and risks seem to more or less compensate each other. This study clearly shows the significance of which fish species are consumed during pregnancy and lactation, and the results can be generalized to apply to typical western population fish consumption habits.

State of the art in benefit-risk analysis: medicines.

Benefit-risk assessment in medicine has been a valuable tool in the regulation of medicines since the 1960s. Benefit-risk assessment takes place in multiple stages during a medicine's life-cycle and can be conducted in a variety of ways, using methods ranging from qualitative to quantitative. Each benefit-risk assessment method is subject to its own specific strengths and limitations. Despite its widespread and long-time use, benefit-risk assessment in medicine is subject to debate and suffers from a number of limitations and is currently still under development. This state of the art review paper will discuss the various aspects and approaches to benefit-risk assessment in medicine in a chronological pathway. The review will discuss all types of benefit-risk assessment a medicinal product will undergo during its lifecycle, from Phase I clinical trials to post-marketing surveillance and health technology assessment for inclusion in public formularies. The benefit-risk profile of a drug is dynamic and differs for different indications and patient groups. In the end of this review we conclude benefit-risk analysis in medicine is a developed practice that is subject to continuous improvement and modernisation. Improvement not only in methodology, but also in cooperation between organizations can improve benefit-risk assessment.

State of the art in benefit-risk analysis: consumer perception.

Benefit and risk perception with respect to food consumption, have been a part of human daily life from beginning of time. In today's society the food chain is long with many different types of actors and low degree of transparency. Making informed food choices where knowledge of benefits and risks is part of the decision making process are therefore complicated for consumers. Thus, to understand how consumers perceive benefits and risks of foods, their importance in relation to quality evaluations are aspects that need to be addressed. The objective of this paper is to discuss state of the art in understanding consumer perceptions of benefits and risks of foods in order to improve understanding of consumer behaviour in the food domain. Risks may be associated with both acute and long term consequences, some of which may have serious effects. Perceived risks are connected to morbidity and mortality along two dimensions relating to unknown risk, and to which extent the risk is dreaded by the consumer. Unfamiliar, uncertain, unknown, uncontrollable, and severe consequences are some factors associated with risk perception. Novel food processing techniques, for instance, score high on several of these parameters and are consequently regarded with suspicion and perceived as risky by consumers. On a daily basis, benefits of foods and food consumption are more important in most consumers' minds than risks. Benefits are often associated with food's ability to assuage hunger, and to provide pleasure through eating and socialising. In addition, two main categories of benefits that are important for acceptance of product innovations are health and environmental benefits. Benefit and risk perception of foods seem to be inversely correlated, so when something is perceived as being highly beneficial, it is correspondingly perceived as having low risk. However, slightly different paths are used in the formation of these perceptions; benefit perception is based on heuristics and experience, while risk perception is to a larger extent the result of cognitive information processing. Consumers are particularly conservative when it comes to perception and acceptance of foods compared to other products. Benefit-risk evaluations tend to be skewed towards acceptance of all that is traditional and well-known (benefits), and rejection or suspicion towards anything that is novel or highly processed (risks) regardless of actual risk. Knowledge of how consumers perceive benefits and risks of foods, may contribute to understanding benefit-risk perception in other areas related to personal, societal or environmental perspectives.

State of the art in benefit-risk analysis: economics and marketing-finance.

All market participants (e.g., investors, producers, consumers) accept a certain level of risk as necessary to achieve certain benefits. There are many types of risk including price, production, financial, institutional, and individual human risks. All these risks should be effectively managed in order to derive the utmost of benefits and avoid disruption and/or catastrophic economic consequences for the food industry. The identification, analysis, determination, and understanding of the benefit-risk trade-offs of market participants in the food markets may help policy makers, financial analysts and marketers to make well-informed and effective corporate investment strategies in order to deal with highly uncertain and risky situations. In this paper, we discuss the role that benefits and risks play in the formation of the decision-making process of market-participants, who are engaged in the upstream and downstream stages of the food supply chain. In addition, we review the most common approaches (expected utility model and psychometrics) for measuring benefit-risk trade-offs in the economics and marketing-finance literature, and different factors that may affect the economic behaviour in the light of benefit-risk analyses. Building on the findings of our review, we introduce a conceptual framework to study the benefit-risk behaviour of market participants. Specifically, we suggest the decoupling of benefits and risks into the separate components of utilitarian benefits, hedonic benefits, and risk attitude and risk perception, respectively. Predicting and explaining how market participants in the food industry form their overall attitude in light of benefit-risk trade-offs may be critical for policy-makers and managers who need to understand the drivers of the economic behaviour of market participants with respect to production, marketing and consumption of food products.

State of the art in benefit-risk analysis: introduction.

Risk-taking is normal in everyday life if there are associated (perceived) benefits. Benefit-Risk Analysis (BRA) compares the risk of a situation to its related benefits and addresses the acceptability of the risk. Over the past years BRA in relation to food and food ingredients has gained attention. Food, and even the same food ingredient, may confer both beneficial and adverse effects. Measures directed at food safety may lead to suboptimal or insufficient levels of ingredients from a benefit perspective. In BRA, benefits and risks of food (ingredients) are assessed in one go and may conditionally be expressed into one currency. This allows the comparison of adverse and beneficial effects to be qualitative and quantitative. A BRA should help policy-makers to make more informed and balanced benefit-risk management decisions. Not allowing food benefits to occur in order to guarantee food safety is a risk management decision much the same as accepting some risk in order to achieve more benefits. BRA in food and nutrition is making progress, but difficulties remain. The field may benefit from looking across its borders to learn from other research areas. The BEPRARIBEAN project (Best Practices for Risk-Benefit Analysis: experience from out of food into food; http://en.opasnet.org/w/Bepraribean) aims to do so, by working together with Medicines, Food Microbiology, Environmental Health, Economics & Marketing-Finance and Consumer Perception. All perspectives are reviewed and subsequently integrated to identify opportunities for further development of BRA for food and food ingredients. Interesting issues that emerge are the varying degrees of risk that are deemed acceptable within the areas and the trend towards more open and participatory BRA processes. A set of 6 'state of the art' papers covering the above areas and a paper integrating the separate (re)views are published in this volume.

State of the art in benefit-risk analysis: food microbiology.

Over the past years benefit-risk analysis (BRA) in relation to foods and food ingredients has gained much attention; in Europe and worldwide. BRA relating to food microbiology is however a relatively new field of research. Microbiological risk assessment is well defined but assessment of microbial benefits and the weighing of benefits and risk has not been systematically addressed. In this paper the state of the art in benefit-risk analysis in food microbiology is presented, with a brief overview of microbiological food safety practices. The quality and safety of foods is commonly best preserved by delaying the growth of spoilage bacteria and contamination by bacterial pathogens. However, microorganisms in food can be both harmful and beneficial. Many microorganisms are integral to various food production processes e.g. the production of beer, wine and various dairy products. Moreover, the use of some microorganisms in the production of fermented foods are often claimed to have beneficial effects on food nutrition and consumer health. Furthermore, food safety interventions leading to reduced public exposure to foodborne pathogens can be regarded as benefits. The BRA approach integrates an independent assessment of both risks and benefits and weighs the two using a common currency. Recently, a number of initiatives have been launched in the field of food and nutrition to address the formulation of the benefit-risk assessment approach. BRA has recently been advocated by EFSA for the public health management of food and food ingredients; as beneficial and adverse chemicals can often be found within the same foods and even the same ingredients. These recent developments in the scoping of BRA could be very relevant for food microbiological issues. BRA could become a valuable methodology to support evaluations and decision making regarding microbiological food safety and public health, supplementing other presently available policy making and administrative tools for microbiological food safety management.

State of the art in benefit-risk analysis: food and nutrition.

Benefit-risk assessment in food and nutrition is relatively new. It weighs the beneficial and adverse effects that a food (component) may have, in order to facilitate more informed management decisions regarding public health issues. It is rooted in the recognition that good food and nutrition can improve health and that some risk may be acceptable if benefit is expected to outweigh it. This paper presents an overview of current concepts and practices in benefit-risk analysis for food and nutrition. It aims to facilitate scientists and policy makers in performing, interpreting and evaluating benefit-risk assessments. Historically, the assessments of risks and benefits have been separate processes. Risk assessment is mainly addressed by toxicology, as demanded by regulation. It traditionally assumes that a maximum safe dose can be determined from experimental studies (usually in animals) and that applying appropriate uncertainty factors then defines the 'safe' intake for human populations. There is a minor role for other research traditions in risk assessment, such as epidemiology, which quantifies associations between determinants and health effects in humans. These effects can be both adverse and beneficial. Benefit assessment is newly developing in regulatory terms, but has been the subject of research for a long time within nutrition and epidemiology. The exact scope is yet to be defined. Reductions in risk can be termed benefits, but also states rising above 'the average health' are explored as benefits. In nutrition, current interest is in 'optimal' intake; from a population perspective, but also from a more individualised perspective. In current approaches to combine benefit and risk assessment, benefit assessment mirrors the traditional risk assessment paradigm of hazard identification, hazard characterization, exposure assessment and risk characterization. Benefit-risk comparison can be qualitative and quantitative. In a quantitative comparison, benefits and risks are expressed in a common currency, for which the input may be deterministic or (increasingly more) probabilistic. A tiered approach is advocated, as this allows for transparency, an early stop in the analysis and interim interaction with the decision-maker. A general problem in the disciplines underlying benefit-risk assessment is that good dose-response data, i.e. at relevant intake levels and suitable for the target population, are scarce. It is concluded that, provided it is clearly explained, benefit-risk assessment is a valuable approach to systematically show current knowledge and its gaps and to transparently provide the best possible science-based answer to complicated questions with a large potential impact on public health.

State of the art in benefit-risk analysis: environmental health.

Environmental health assessment covers a broad area: virtually all systematic analysis to support decision making on issues relevant to environment and health. Consequently, various different approaches have been developed and applied for different needs within the broad field. In this paper we explore the plurality of approaches and attempt to reveal the state-of-the-art in environmental health assessment by characterizing and explicating the similarities and differences between them. A diverse, yet concise, set of approaches to environmental health assessment is analyzed in terms of nine attributes: purpose, problem owner, question, answer, process, use, interaction, performance and establishment. The conclusions of the analysis underline the multitude and complexity of issues in environmental health assessment as well as the variety of perspectives taken to address them. In response to the challenges, a tendency towards developing and applying more inclusive, pragmatic and integrative approaches can be identified. The most interesting aspects of environmental health assessment are found among these emerging approaches: (a) increasing engagement between assessment and management as well as stakeholders, (b) strive for framing assessments according to specific practical policy needs, (c) integration of multiple benefits and risks, as well as (d) explicit incorporation of both scientific facts and value statements in assessment. However, such approaches are yet to become established, and many contemporary mainstream environmental health assessment practices can still be characterized as relatively traditional risk assessment.

Associations between congenital cryptorchidism in newborn boys and levels of dioxins and PCBs in placenta.

In animal studies, exposure to dioxins has been associated with disrupted development of the male reproductive system, including testicular maldescent. Some polychlorinated biphenyls (PCBs) have also dioxin-like effects. In addition, one previous case-control study has reported an association between congenital cryptorchidism and colostrum PCB levels. We performed a case-control study to evaluate whether congenital cryptorchidism in boys was associated with increased levels of dioxins or PCBs in placenta reflecting foetal exposure. In addition, associations between placenta levels of these chemicals and reproductive hormone levels in boys at 3 months were studied. Placentas were collected in a Danish-Finnish joint prospective cohort study on cryptorchidism (1997-2001). The boys were examined for cryptorchidism at birth and at 3 months. Altogether, 280 placentas [112 Finnish (56 cases, 56 controls) and 168 Danish (39 cases, 129 controls)] were analysed for 17 toxic polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and 37 PCBs (including 12 dioxin-like PCBs). Infant serum samples taken at 3 months were analysed for reproductive hormones. No significant differences between cases and controls were observed in either country in dioxin WHO-TEq levels (median 9.78 vs. 8.47 pg/g fat, respectively, in Finland, and 11.75 vs. 10.88 pg/g fat in Denmark) or PCB WHO-TEq levels (median 2.12 vs. 2.15 pg/g fat in Finland, 2.34 vs. 2.10 pg/g fat in Denmark) or total-TEq levels (median 11.66 vs. 10.58 pg/g fat in Finland, 13.94 vs. 13.00 pg/g fat in Denmark). Placenta WHO-TEq levels of dioxins were not associated with infant reproductive hormone levels at 3 months. In Finland, PCB WHO-TEq levels in placenta associated positively with infant LH levels. WHO-TEq levels of dioxins and PCBs and total-TEq levels were higher in Danish than Finnish samples. In conclusion, no association between placenta levels of dioxins or PCBs and congenital cryptorchidism was found. Significant country differences in chemical levels were observed.

Looking beyond borders: integrating best practices in benefit-risk analysis into the field of food and nutrition.

An integrated benefit-risk analysis aims to give guidance in decision situations where benefits do not clearly prevail over risks, and explicit weighing of benefits and risks is thus indicated. The BEPRARIBEAN project aims to advance benefit-risk analysis in the area of food and nutrition by learning from other fields. This paper constitutes the final stage of the project, in which commonalities and differences in benefit-risk analysis are identified between the Food and Nutrition field and other fields, namely Medicines, Food Microbiology, Environmental Health, Economics and Marketing-Finance, and Consumer Perception. From this, ways forward are characterized for benefit-risk analysis in Food and Nutrition. Integrated benefit-risk analysis in Food and Nutrition may advance in the following ways: Increased engagement and communication between assessors, managers, and stakeholders; more pragmatic problem-oriented framing of assessment; accepting some risk; pre- and post-market analysis; explicit communication of the assessment purpose, input and output; more human (dose-response) data and more efficient use of human data; segmenting populations based on physiology; explicit consideration of value judgments in assessment; integration of multiple benefits and risks from multiple domains; explicit recognition of the impact of consumer beliefs, opinions, views, perceptions, and attitudes on behaviour; and segmenting populations based on behaviour; the opportunities proposed here do not provide ultimate solutions; rather, they define a collection of issues to be taken account of in developing methods, tools, practices and policies, as well as refining the regulatory context, for benefit-risk analysis in Food and Nutrition and other fields. Thus, these opportunities will now need to be explored further and incorporated into benefit-risk practice and policy. If accepted, incorporation of these opportunities will also involve a paradigm shift in Food and Nutrition benefit-risk analysis towards conceiving the analysis as a process of creating shared knowledge among all stakeholders.

Reduction potential of urban PM2.5 mortality risk using modern ventilation systems in buildings.

UNLABELLED: Urban PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 microm) is associated with excess mortality and other health effects. Stationary sources are regulated and considerable effort is being put into developing low-pollution vehicles and environment-friendly transportation systems. While waiting for technological breakthroughs in emission controls, the current work assesses the exposure reductions achievable by a complementary means: efficient filtration of supply air in buildings. For this purpose infiltration factors for buildings of different ages are quantified using Exposures of Adult Urban Populations in Europe Study (EXPOLIS) measurements of indoor and outdoor concentrations in a population-based probability sample of residential and occupational buildings in Helsinki, Finland. These are entered as inputs into an evaluated simulation model to compare exposures in the current scenario with an alternative scenario, where the distribution of ambient PM2.5 infiltration factors in all residential and occupational buildings are assumed to be similar to the subset of existing occupational buildings using supply air filters. In the alternative scenario exposures to ambient PM2.5 were reduced by 27%. Compared with source controls, a significant additional benefit is that infiltration affects particles from all outdoor sources. The large fraction of time spent indoors makes the reduction larger than what probably can be achieved by local transport policies or other emission controls in the near future. PRACTICAL IMPLICATIONS: It has been suggested that indoor concentrations of ambient particles and the associated health risks can be reduced by using mechanical ventilation systems with supply air filtering in buildings. The current work quantifies the effects of these concentration reductions on population exposures using population-based data from Helsinki and an exposure model. The estimated exposure reductions suggest that correctly defined building codes may reduce annual premature mortality by hundreds in Finland and by tens of thousands in the developed world altogether.

Comparison of acute toxicities of indolo[3,2-b]carbazole (ICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in TCDD-sensitive rats.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatic hydrocarbons are environmental toxicants that act via the AH receptor (AHR). In vitro studies have demonstrated that some indole derivatives present in cruciferous vegetables also bind to the AHR. One of the highest AHR binding affinities is exhibited by indolo[3,2-b]carbazole (ICZ). Since exposure to these dietary indoles is quantitatively far larger than that to halogenated aromatic compounds, their potential toxic risks have raised concern. In the present study, we compared the effects of ICZ with those of a single dose of 20 microg/kg TCDD in the most TCDD-sensitive rat strain (Long-Evans [Turku AB]) (L-E). Whereas TCDD elicited the expected toxicity syndrome, ICZ, either as a single subcutaneous dose (63.5, 127 or 508 microg/kg) or with repeated sc dosing (508 microg/kg for 5 days) failed to reproduce any toxic impacts of TCDD. Furthermore, a simultaneous ICZ treatment (63.5 or 127 microg/kg for 10 days) did not interfere with TCDD (20 microg/kg; single exposure) action. A moderate hepatic induction of CYP1A1 could be triggered by repeated intragastric administration of ICZ (127 microg/kg for 4 days, the last treatment 2.5 h prior to termination). In control experiments in a reconstituted yeast system, ICZ potently and dose-dependently activated L-E rat AHR function demonstrating that it represents a bona fide high-affinity ligand for the rat receptor in vivo. Thus, the present study does not support the view that dietary exposure to ICZ would present a hazard of AHR-mediated adverse health effects to humans.

Assessing the public health benefits of reduced ozone concentrations.

In this paper we examine scientific evidence and related uncertainties in two steps of benefit-cost analyses of ozone reduction: estimating the health improvements attributable to reductions in ozone and determining the appropriate monetary values of these improvements. Although substantial evidence exists on molecular and physiologic impacts, the evidence needed to establish concentration-response functions is somewhat limited. Furthermore, because exposure to ozone depends on factors such as air conditioning use, past epidemiologic studies may not be directly applicable in unstudied settings. To evaluate the evidence likely to contribute significantly to benefits, we focus on four health outcomes: premature mortality, chronic asthma, respiratory hospital admissions, and minor restricted activity days. We determine concentration-response functions for these health outcomes for a hypothetical case study in Houston, Texas, using probabilistic weighting reflecting our judgment of the strength of the evidence and the possibility of confounding. We make a similar presentation for valuation, where uncertainty is due primarily to the lack of willingness-to-pay data for the population affected by ozone. We estimate that the annual monetary value of health benefits from reducing ozone concentrations in Houston is approximately $10 per person per microgram per cubic meter (24-hr average) reduced (95% confidence interval, $0.70-$40). The central estimate exceeds past estimates by approximately a factor of five, driven by the inclusion of mortality. We discuss the implications of our findings for future analyses and determine areas of research that might help reduce the uncertainties in benefit estimation.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on bone in two rat strains with different aryl hydrocarbon receptor structures.

Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic environmental contaminants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent dioxin. Here, we studied the effects of TCDD on bone. Two rat strains, Han/Wistar (H/W) and Long-Evans (L-E), were used because they exhibit a 1000-fold sensitivity difference in acute lethality of TCDD, which difference is related to the aryl hydrocarbon receptor (AHR). TCDD inhibited the tibial growth dose dependently, the effect being manifested at lower doses in the more sensitive L-E strain. In H/W rats the effect of TCDD was seen only at the high dose of 170 microg/kg (p < 0.05), whereas in the sensitive L-E rats a significant reduction of bone growth was already seen at 1.7 microg/kg (p < 0.01). This reduction was caused by the smaller tibial size because the diaphyseal bone mineral density (BMD) did not change. The three-point bending breaking force of the tibia was significantly reduced in H/W rats at 170 microg/kg (p < 0.05), but tibial stiffness was lower already at the dose of 17 microg/kg (p < 0.05). In the sensitive L-E strain, both breaking force and stiffness were reduced at the dose of 17 microg/kg (p < 0.001). These results indicate that TCDD dose-dependently interferes with bone growth, modeling, and mechanical strength. The altered transactivation domain of AHR is associated with a lower sensitivity of bone to TCDD in H/W rats, suggesting that AHR plays a role in modulating the effects of dioxins on bone.

In utero/lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure impairs molar tooth development in rats.

Developmental defects caused by dioxins are causing increasing concern since they occur at low dose levels and are usually permanent. In this study we examined the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at low in utero/lactational exposure levels on rat tooth development in three rat lines, denoted A, B, and C, that differ in their TCDD sensitivity and aryl hydrocarbon receptor structure. These rat lines are derived from TCDD-resistant Han/Wistar (Kuopio) and TCDD-sensitive Long-Evans (Turku/AB) rats by selective breeding. The main target teeth were the third molars, since their development spans from the perinatal period to about 6 weeks after birth. Pregnant dams were exposed to 0.03-1 microg/kg TCDD on gestation day 15. Pups exposed in utero and lactationally were euthanized at the age of 5 or 10 weeks and the jaws were examined. The eruption of the third molar was observed by stereomicroscopy and the jaws were further radiographed. TCDD at 1 microg/kg completely prevented the development of the third lower molars in 60% of males and 50% of females in the most sensitive rat line, C, while only 6% or less of the pups in the more resistant lines A and B were lacking this target tooth. TCDD exposure also dose-dependently diminished the proportion of third molars erupted at the age of 5 weeks. The size of molars was dose-dependently reduced in all rat lines. The third lower molars were most severely affected, and the reduction was significant already at 0.03 microg/kg in line A and at 0.1 microg/kg in lines B and C. The results indicate that impaired tooth development is one of the most sensitive endpoints of TCDD-induced toxicity.

High fish-specific dioxin concentrations in Finland.

Dioxin concentrations in a population that frequently eat fish from the Baltic Sea are comparable to those seen in inhabitants of Seveso, Italy, after the accidental release of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 1976. Individual variations in the congener patterns in human beings are similar to congener patterns in the fish species consumed.

Changes in food intake and food selection in rats after 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) exposure.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on food selection were studied in TCDD-resistant Han/Wistar and TCDD-sensitive Long-Evans rats and their crosses. The rats were offered a selection diet consisting of chocolate, cheese, and chow, and TCDD was given at the same time or 4 or 16 days later. TCDD persistently reduced the chocolate intake. When the selection diet was started at the time of or less than 11 h after TCDD exposure, TCDD almost completely prevented the intake of chocolate and also cheese in all strains already on the first day, while controls started to consume large amounts of both foods. This may be due to conditioned taste aversion. The effect on food selection with familiar foods seemed to reduce fat intake, while protein and carbohydrate intakes were more variable. There were no major strain differences in the chocolate intake inhibition despite a 1000-fold sensitivity difference in TCDD lethality.

Liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in TCDD-sensitive and TCDD-resistant rat strains.

Risk assessment of dioxins is currently based on induction of liver tumors in rats. The toxicity of dioxins is characterized by large sensitivity differences among animal species and even strains of the same species, which complicates the risk assessment. The significance of these differences in dioxin-induced carcinogenicity is not known. We therefore studied the liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the sensitive Long-Evans (L-E) and the resistant Han/Wistar (H/W) rats differing >1000-fold in their sensitivity to the acute lethaity of TCDD. Female rats were partially hepatectomized, initiated with nitrosodiethylamine, and treated with TCDD for 20 weeks. Altered hepatic foci (AHF) were stereologically quantitated using glutathione S-transferase P as a marker. AHF were significantly (P < 0.001) and dose dependently increased in L-E rats at 10 and 100 ng/kg/day, but in H/W rats only at 1000 ng/kg/day and above, indicating a remarkable (approximately 100-fold) sensitivity difference between L-E and H/W rats. The same sensitivity difference but 10-fold less foci were observed between nonhepatectomized/noninitiated L-E and H/W rats. Induction of AHF was related to hepatotoxicity but not to cytochrome P4501A1 activity in the liver. Liver TCDD concentrations were similar in both strains. H/W rats are exceptionally resistant to induction of AHF by TCDD, and the resistance is associated with an altered transactivation domain of the aryl hydrocarbon receptor. Genetic differences may account for significant interindividual/intraspecies sensitivity differences in dioxin-induced carcinogenesis. Understanding the role of transactivation domain of the aryl hydrocarbon receptor in carcinogenesis is therefore likely to improve dioxin risk assessment.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on liver phosphoenolpyruvate carboxykinase (PEPCK) activity, glucose homeostasis and plasma amino acid concentrations in the most TCDD-susceptible and the most TCDD-resistant rat strains.

Reduced gluconeogenesis due to decreased activity of key gluconeogenic enzymes in liver, together with feed refusal, has been suggested to play an important role in 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD)-induced lethality in rats. This study was carried out to further analyse the toxicological significance of reduced gluconeogenesis by comparing dose-responses and time-courses of effects of TCDD on the activity of phosphoenolpyruvate carboxykinase (PEPCK) in liver, liver glycogen concentration as well as plasma concentrations of glucose and amino acids in both genders of TCDD-sensitive Long-Evans (L-E) rats and TCDD-resistant Han/Wistar (H/W) rats. A dose-dependent decrease in PEPCK activity was observed in H/W rats, but in L-E rats the activity was not decreased. However, TCDD impaired the strong increase in liver PEPCK activity observed in pair-fed controls of the L-E strain. Liver glycogen concentrations were severely decreased in L-E rats and moderately in H/W rats. This effect seems to be secondary to reduced feed intake, since a similar decrease was seen in pair-fed controls. Decreases in plasma glucose concentrations were also more profound in L-E rats than in H/W rats, but pair-fed controls were generally less affected. Circulating concentrations of amino acids were markedly increased in TCDD-treated L-E rats, which is likely to reflect increased mobilization of amino acids and their decreased metabolism in liver. Reduction of liver PEPCK activity cannot account for the sensitivity difference of these two strains of rats in terms of mortality. Nevertheless, the response of both strains of TCDD-treated rats regarding gluconeogenesis is different from that seen in pair-fed controls and suggesting that impairment of this pathway contributes to the development of the wasting syndrome.