An example of the effect of using replacement values for undetected congeners in samples is shown in Table Tuesday 10 April, Morning Registration open. Cool tools for microbial imaging. The TDI was based on the results of a number of studies of developmental toxicity, in which pregnant rats were given TCDD by gavage, and immunological toxicity. This was also the basis for selecting reference laboratories for WHO-coordinated studies of exposure to dioxins in human milk see section 6. Therefore, a method should be developed to allow screening for elevated concentrations e.
1.2 Compounds considered
We invite abstracts on any aspect of retrovirus biology. Depending on the abstracts received, the workshop will be structured around a typical life-cycle of a retrovirus and will cover virus entry and uncoating, genome replication, particle structure, assembly and egress.
Session sponsored by eLIFE The living host provides complex ecological niches for thriving microbial communities. Metagenomic and metataxonomic analyses of these microbiotas, along with fluorescence microscopy, reveal which microbes are present within these communities and provide an indication of their relative abundance.
These data are now informing our understanding of microbial interactions and the living host. This symposium will address aspects of prokaryote, eukaryote and bacteriophage component interactions of the microbiota in relation to health, disease and the immune system. The major sites of microbial colonisation the skin, the gastrointestinal tract and the female genital tract will be included.
Offered papers relating to microbiota interactions in both humans and other animals will be considered for presentation within the symposium. This forum will consider offered papers on all aspects of microbial prokaryotic and eukaryotic metabolism and physiology, including fundamental research on the biochemistry and structure of cells, cell growth and division, cell architecture and differentiation, synthesis and transport of macromolecules, ions and small molecules and the cell cycle; but also on the role of physiology in microbial engineering, signalling and communication, sensing and cellular responses, the molecular mechanisms behind these phenomena and their potential applications.
Fiona Tulloch University of St. Andrews, UK , Hall 7. It is intended to provide a platform for both wet- and dry-lab virologists working in this fast-moving and data-intensive area. Abstracts are invited on any aspect of the scope, causes and consequences of viral diversity, including those relating to the inter- and intra-host evolution, metagenomics, discovery, bioinformatics, phylogenetics, taxonomy and pathogenesis of viruses.
This wide spectrum of topics also includes developments in the methodologies used to study viral diversity. Mushrooms are magical in a way no other microbe is — their amazing macro-structure means they are instantly visible and recognisable, often brightly coloured and decorating autumn forests.
Yet fungi other than yeast and pathogenic strains do not feature in the conference line up of any major microbiology meeting. It is our intention to redress that balance by dedicating this session to a variety of research interests that focus on fungi that form fruiting bodies colloquially known as mushrooms. These include some ascomycetes but are primarily represented by basidiomycetes. We want to look at the ecology of these wonderful organisms, at how endangered they are and the steps being taken to protect them, but also at how they can be used in industry and medicine.
The session will highlight links between fundamental research and its applications in medicine and other industrial purposes — thereby giving the programme broader appeal. Recent years have seen extraordinary advances in the technologies available to study microbial biology. The development of new techniques to probe individual cells and molecules is a major driver of scientific advance.
This session aims to cover and showcase a number of new advanced techniques that have been successfully applied to microbiology, including mass spectrometry imaging, light and electron microscopy and Raman spectroscopy. These have diverse applications which we anticipate will attract a broad audience across all the divisions. Offered papers on all aspects of the genes and genomes of microbes prokaryotes and eukaryotes and their mobile elements will be considered, including their sequencing, transcription, translation, regulation, chromosome dynamics, gene transfer, population genetics and evolution, taxonomy and systematics, comparative genomics, metagenomics, bioinformatics, and synthetic biology.
CLIMB is a cloud-based computing system dedicated to the analysis of microbial bioinformatics data that provides free access to large-scale computing infrastructure for microbial bioinformatics to any UK-based, non-commercial microbial genomics researcher.
Attendees are asked to bring their own laptops to the workshop. This half-day workshop will provide an introduction to CLIMB for any new users, including how to set up and manage accounts and instances, as well as run through the various pipelines that are pre-installed with a CLIMB instance.
In parallel, experienced CLIMB users will also have the opportunity to learn how to launch and configure more bespoke instances and to learn about new functionality being implemented to support very large data analysis and Docker containers. Finally, we will host a structured discussion for users to report their experiences with CLIMB and to help shape the future development of the platform.
Teaching microbiology in higher education. Hall 3 Pre-Conference session: Hall 11a Pre-Conference networking workshop. Are biodegradable plastics the answer? Hall 3 Escherichia coli: Hall 3 The global virome — the scope, causes and consequences of viral diversity. Hall 3 Essential skills: Hall 3 Breaking bad: Hall 3 Emerging model systems.
Hall 3 Models for understanding host—pathogen interactions. Hall 3 Microbial diversity and interactions in the environment. Sandra Junglen University of Bonn, Germany , Hall 1 The global virome — the scope, causes and consequences of viral diversity.
Antibiotics Unearthed — Posters showcase. Hall 3 Lunch and exhibition. Achim Schmalenberger University of Limerick, Ireland , Hall 9 Microbial diversity and interactions in the environment. Hall 3 Drinks reception and poster presentation. Shooters Society quiz and games night. Hall 3 Synthetic ecology: Hall 3 The battle for the ribosome — how viruses manipulate host translation. Hall 3 Microbial metal homeostasis: Alessia Ruggieri Universitäts Klinikum Heidelberg, Germany , Hall 1 The battle for the ribosome — how viruses manipulate host translation.
Hall 11b Essential skills: Annual Conference 10 - 13 April Type Live at Lunch. Session Antibiotics Unearthed — Posters showcase. Community interactions and the living host. Conference Party — Bavarian night. Cool tools for microbial imaging. Drinks reception and poster presentation. Environmental and applied microbiology forum.
Engaging in science policy. Fleming Prize Lecture — How to kill your rivals: Genetics and genomics forum. Hot Topic Lecture — Déjà Flu: Hot Topic Lecture — Plastic waste is a global challenge.
Lunch, exhibition and poster presentations. Marjory Stephenson Prize Lecture — Vaccinia virus: Microbial diversity and interactions in the environment. Microbial physiology, metabolism and molecular biology forum. Microbiology Society Prize Medal Lecture — Metagenomics provides a new view of the tree of life and the roles of candidate phyla bacteria and archaea in subsurface biogeochemistry. Models for understanding host—pathogen interactions.
Passport to Prizes — prize draw. Peter Wildy Prize Lecture — Explorations in microbiology: Society promotion — Journal digests: Society quiz and games night. The battle for the ribosome — how viruses manipulate host translation.
The games microbes play: The global virome — the scope, causes and consequences of viral diversity. The magic of mushrooms in nature and industry. Unilever Colworth Prize Lecture — Translating findings from bacterial whole genome sequencing into clinical practice and public health policy. Negative strand RNA viruses. Positive strand and double strand RNA viruses.
The scope, causes and consequences of viral diversity. Teaching microbiology in higher education This half-day symposium will present several interactive sessions which aim to bring delegates together to discuss and share innovative ways of teaching. Monday 09 April, Afternoon Pre-Conference session: Using digital platforms for teaching in higher education: Coffee break Hall 3. Novel techniques in the lecture theatre: Offered paper - Beyond creation learning and creative teaching: Next steps — what have we learned and what's the output?
Pre-Conference networking workshop Hall 11a. Tuesday 10 April, Morning Registration open. Offered paper - Cutibacterium acnes formerly Propionibacterium acnes is able to tailor its biofilm formation to environmental cues and increase biofilm formation in Staphylococcus species Helen Brown Cardiff University, UK , Hall Offered paper - How do bacteria affect Candida albicans cell wall structure in the gut?
Exhibition and refreshments Hall 3. Flash poster presentation - Investigation of anti-bacterial strategies deployed by a clinical isolate of Serratia marcescens Connor Bowen University of Dundee, UK , Hall Emerging model systems Our understanding of eukaryotic cell biology is based on our ability to manipulate experimental systems.
Why new experimentally tractable organisms from key taxa will provide important insights into eukaryotic biology Inaki Ruiz-Trillo Universitat Pompeu Fabra, Spain , Hall 8a. Offered paper - Conserved outer membrane proteins potentially involved in the modulation of intestinal colonisation as possible antigen candidates to prevent enterohaemorrhagic E.
Offered paper - Exploitation of random transposon mutagenesis to reveal conditionally essential genes important for antibiotic resistance Emily Goodall University of Birmingham, UK , Hall 5. Offered paper - One Health genomic surveillance of E.
Microbial diversity and interactions in the environment Session sponsored by MP Biomedicals Our understanding of microbial diversity, both phylogenetic and functional, continues to expand, including the realisation that a key factor in understanding the importance of microbial diversity is the interaction between organisms. Tracking the dynamics of antibiotic resistome in the environment: Offered paper - From glaciers to genomes Vitamins in the sea: Microbial systems ecology for unravelling key functions in situ Paul Wilmes University of Luxembourg, Luxembourg , Hall 9.
Models for understanding host—pathogen interactions The immune system is our main defence against microbial pathogens. Offered paper - Development of a microaerobic mucin-producing human intestinal culture system to investigate the influence of commensal bacteria on enteropathogenic E. Brain infection and activation of neuronal repair mechanisms by human pathogen Listeria monocytogenes in Galleria mellonella Krishnendu Mukherjee University Giessen, Germany , Hall 11a.
The global virome — the scope, causes and consequences of viral diversity Modern sequencing is revealing the existence of huge numbers of viruses, many of which are related to agents that we recognise and many of which are totally new. The genomic underpinnings of eukaryotic virus taxonomy: Offered paper - Evasion of a potent inhibitor by human cytomegalovirus is achieved by utilising an entry pathway independent of heparin sulfate proteoglycans but sensitises it to neutralising antibody responses Matthew J Murray UCL, UK , Hall 1.
Offered paper - Investigations into the dynamics of paramyxovirus infections by high-throughput sequencing Elizabeth Wignall-Fleming University of Glasgow, UK , Hall 1. A small glimpse into the genetic diversity of arthropod-associated viruses Sandra Junglen University of Bonn, Germany , Hall 1. Lunch and exhibition Hall 3. Offered paper - Host-associated niche metabolism controls enteric infection through fine-tuning of type 3 secretion and a co-ordinated suite of effector proteins James Connolly University of Glasgow, UK , Hall Offered paper - Friend or foe: Flash poster presentation - Identification of a staphylococcal complement inhibitor with broad host specificity in equid S.
Offered paper - A new model for investigating the evolution and cell biology of eukaryotes: The role of plasmids in the dissemination of antimicrobial resistance in Escherichia coli Alessandra Carattoli Istituto Superiore di Sanità, Italy , Hall 5.
Offered paper - Comparative genomics of commensal and invasive E. Offered paper - Investigating factors influencing E. Offered paper - The role of the nitrogen stress response in persistence of nitrogen starved non-pathogenic and uropathogenic Escherichia coli Dan Brown Imperial College London, UK , Hall 5.
Offered paper - Genomic insights into the virulence capacity of soil-persistent E. Offered paper - Application of high throughput approaches to study the laboratory-based evolution of E. Soil microbial communities as modulators of ecosystem responses to climate change in drylands Fernando T. Host—pathogen interaction made clear: Modelling Aspergillus infections in larval zebrafish reveals differences in the immune response, pathogen clearance, and infection outcome depending on the specific host—pathogen context Emily Rosowski University of Wisconsin, USA , Hall 11a.
Offered paper - A novel ex vivo skin explant biofilm model for evaluating the effect of photodynamic antimicrobial chemotherapy and iberin treatment towards Pseudomonas aeruginosa biofilms Amal Al-Bakri The University of Jordan, Jordan , Hall 11a. Offered paper - Towards the identification of novel host or bacterial-associated biomarkers to predict sepsis Heather M. May virus taxonomy become a branch of evolutionary studies? Bacteriophages in unlikely places: The genomic ecology and epidemiology of avian influenza and other viruses in natural populations Oliver Pybus University of Oxford, UK , Hall 1.
Drinks reception and poster presentation Hall 3. Society quiz and games night Shooters. Wednesday 11 April, Morning Registration open Hall 1. Offered paper - Differences in plasmidome content of hospital and non-hospital isolates of Enterococcus faecium Anita Schürch University Medical Center, Netherlands , Hall Offered paper - Could adhesins be the key to the difference in pathogenic capabilities between non typeable Haemophilus influenzae NTHi and H.
Offered paper - Fusobacterium nucleatum — friend or foe? Up close and personal with whole genome sequencing: Offered paper - Linking Phenotype to Genotype: Offered paper - The type VI secretion system of Klebsiella pneumoniae: Flash poster presentation - Investigating epigenetic regulation by type I restriction modification in a historic collection of Staphylococcus aureus isolates Rebecca Mekler University of St Andrews, UK , Hall Flash poster presentation - Functional characterisation of p ppGpp synthetases: Flash poster presentation - The diversity and mobility of toxin antitoxin systems in a large dataset of Klebsiella spp.
The different scales of microevolution in enterohaemorrhagic Escherichia coli O and relationship with zoonotic threat David Gally University of Edinburgh, UK , Hall 5.
Offered paper - High resolution mutagenesis analysis of the genetic requirements for anaerobic growth of Escherichia coli in the presence of nitrate Finbar Buttimer University College Cork, Ireland , Hall 5. Offered paper - Ethanolamine metabolism in E. Conclusion and wrap-up Hall 11b.
Copper alloy surfaces collapse bacterial copper homeostasis and reduce infection rates Bill Keevil University of Southampton, UK , Hall 6. A new and emerging HGT locus in Staphylococcus aureus outbreak strains confers hyper resistance to antibacterial copper and promotes macrophage survival Julie Morrissey University of Leicester, UK , Hall 6. Flash poster - A potential novel iron uptake system reserved to Bifidobacterium longum subsp. Flash poster - Mobile genetic element-encoded hypertolerance to copper protects Staphylococcus aureus from killing by host phagocytes Dr.
Zinc at the host—pathogen interface: Offered paper - Who's for TE? The battle for the ribosome — how viruses manipulate host translation The successful replication of all viruses, regardless of whether they have an RNA or DNA genome, relies on the translation of their proteins by the cellular translation machinery.
Flavivirus infection uncouples translation suppression from cellular stress responses Alessia Ruggieri Universitäts Klinikum Heidelberg, Germany , Hall 1. Wednesday 11 April, Afternoon Lunch and exhibition Hall 3. Lineage-specific associations of autotransporters in C.
Offered paper - Comparative pan-genome analysis of Coxiella burnetii reveals limited evolution within genomic groups Claudia Hemsley University of Exeter, UK , Hall Offered paper - A microevolutionary approach using whole genome sequences to estimate the molecular clock in Campylobacter: Shaw Sheffield University, UK.
Offered paper Antimicrobial resistance - Antimicrobial resistance of Campylobacter spp. Are we making an impact? CVN Business Hall 4. Microbial infection forum Offered papers will be presented in areas related to infections caused by prokaryote and eukaryote pathogens of human, veterinary or botanical significance including epidemiology, diagnosis, identification, typing, pathogenesis, treatment, antimicrobial agents and resistance, prevention, virulence factors, host responses and immunity, transmission, and models of infection at the cell, tissue or whole organism level.
Offered paper - Infection with Burkholderia pseudomallei induces cancer-like cellular and molecular changes in trigeminal Schwann cells Seyed Ali Delbaz Griffith University, Australia , Hall 5.
Offered paper - Lineage and strain specific differences in the in vitro and in vivo pathogenicity of bovine adapted Staphylococcus aureus Dagmara Niedziela Teagasc, Ireland and University College Dublin, Ireland , Hall 5. Offered paper - Modelling the interactions of pathogenic and commensal strains of Mannheimia haemolytica with bovine airway epithelial cells Daniel Cozens University of Glasgow, UK , Hall 5.
Offered paper - Real-time optical imaging of bacteria for point-of-care diagnosis of infection in the clinic Beth Mills University of Edinburgh, UK , Hall 5.
Offered paper - Investigating Campylobacter jejuni interactions with endoplasmic reticulum in intestinal epithelial cells resulting in induction of the unfolded protein response Abdi Elmi London School of Hygiene and Tropical Medicine, UK , Hall 5. Offered paper - Metallophilic macrophage receptor blockade: Offered paper - Characterising emerging mutations in a stressed population of a biotechnologically-relevant E.
Flash poster presentation - Associative bacteria of Medicago lupulina L. Flash poster presentation - Novel mechanisms for overcoming phosphate limitation in rhizosphere-dwelling Flavobacteria spp. Flash poster presentation - Incorporation of Vibrio vulnificus into phytoplankton-based marine aggregates for oyster uptake Cam Hubert University of Exeter, UK , Hall 11a. Flash poster presentation - Feature selection from microbial profiles via a genetic algorithm Nisha Puthiyedth University of Saskatchewan, Canada , Hall 11a.
The transcription and translation landscapes during human cytomegalovirus infection Noam Stern-Ginossar Weizmann Institute of Science, Israel , Hall 1. Thursday 12 April, Morning Registration open. The epidemiology of Leptospirosis in Italy: Sheppard Bath University, UK. Environmental and applied microbiology forum This forum focuses on any area in environmental, ecological, applied and industrial microbiology, including non-human host—microbe communities and interactions, marine and freshwater microbiology, soil and geomicrobiology, air-, cryo- and extremophile microbiology, climate change, biotechnology, bio-processing and bio-engineering, food microbiology, and other applied and industrial microbial processes, including microbe-mediated biodegradation and bioremediation.
Offered paper - Bioprospection of an oleaginous endophytic fungus, Phomopsis sp. Offered paper - Landfill sites: The experimental investigation of the relationship between bacterial adhesion upon a range of surfaces under different shear stresses within a microfluidic device.
Offered paper - Comparison of biofilm and bulk water bacterial community throughout the drinking water treatment process Cara Wray Newcastle University, UK , Hall 5. Engaging in science policy Scientists can play an important role informing policy-making, whether providing scientific evidence and solutions to policy-makers to help address grand challenges such as antimicrobial resistance or climate change, or informing science policy on research skills, funding, and infrastructure.
Refreshments and networking Hall 11b. Offered paper - Disentangling bacterial virulence mechanisms: Offered paper - Knowing the Enemy: How does Pseudomonas aeruginosa regulate carbon flux through its glyoxylate shunt?
Offered paper - Biocide exposure induces changes in susceptibility, pathogenicity, and biofilm formation in uropathogenic Escherichia coli Emma Henly Sheffield Hallam University, UK , Hall 1. Offered paper - Antibiotics Unearthed: Offered paper - How does paper beat rock in rock-paper-scissors?
Quantifying interactions in a small, evolving microbial community Sara Mitri University of Lausanne, Switzerland , Hall 8a. Clinical virology This workshop will involve a range of clinical virology cases or short papers which relate to studies relevant to clinical virology network.
Utilisation of chimeric haemagglutinin bearing lentiviral pseudotypes to dissect head and stalk directed antibody responses George Carnell University of Kent, UK , Hall 4. Production and application of reference materials in outbreak scenarios: Bacterial co-infections in patients with a range of viral respiratory tract infections — an under recognised clinical problem Temi Lampejo King's College Hospital, UK , Hall 4. Offered paper - Merkel cell polyomavirus miRNA targeting of the host-cell immune response during virus replication results in the attenuation of neutrophil chemotaxis Pouria Akhbari University of Exeter, UK , Hall 11a.
Offered paper - Terminal depth single-molecule sequencing of capped transcripts reveals host-pathogen dynamics in human macrophages Sara Clohisey The Roslin Institute, UK , Hall 7. Offered paper - Elucidation of novel interactions between respiratory syncytial virus Rsv and human airway epithelium predictive of severe Rsv disease Dean Coey Queen's University Belfast, UK , Hall 7.
Turkington University of Zurich, Switzerland , Hall 7. Offered paper - Absent to active: Offered paper - Characterising an unexpected role for the ubiquitin-like protein ISG Positive strand and double strand RNA viruses We invite abstracts on any aspect of the biology of positive strand and double strand RNA viruses. Offered paper - Reverse genetic analysis of strain variation and virulence in deformed wing virus of honey bees Olesya Gusachenko University of St Andrews, UK , Hall 8b.
Offered paper - Handing out freebies: Retroviruses We invite abstracts on any aspect of retrovirus biology. All mice were observed for 35 days before necropsy.
Decreased body-weight gain, increased liver weight and thymic and splenic atrophy were observed in both strains of mice Birnbaum et al. None of the animals at the lowest dose died, while 8.
The toxicity of TCDD and related coplanar chemicals in short-term studies is characterized, depending on the route and species, by similar biological and toxicological effects. In studies of the porphyrinogenic potential of various chlorinated dioxins, furans and coplanar PCBs, groups of five female B6C3F 1 mice were treated on 5 days per week for 13 weeks by gavage with concentrations related by TEFs to doses of TCDD of 0, 0. Analysis of hepatic tissue for highly carboxylated porphyrins and CYP 1A1 and 1A2 induction indicated that the binding affinity of the congeners to the Ah receptor in vivo was related to CYP 1A2 induction, which was in turn correlated to hepatic porphyrin accumulation.
The LOELs associated with significant increases in total hepatic porphyrin content were: Induction of hepatic porphyrins by the mono- ortho -substituted PCBs was greater than that estimated from the TEFs assigned to them, which was considered to be related in part to non-Ah receptor-dependent induction of CYP 2B1 and delta -aminolaevulinic acid synthetase van Birgelen et al.
The deaths occurred only at the highest dose, four females dying during the 13 weeks of treatment and two males and two females dying between 14 and 49 days during the week post-dosing observation period. The NOEL was thus 0. Groups of six male and six female rats of the same strain were fed diets containing a variety of penta- and hexachlorinated dioxins and dibenzofurans, separately and in a mixture, for 13 weeks: Male and female Fischer rats were given oral doses of TCDD designed to generate a liver concentration of 0.
After an initial loading dose of 0. Induction of this gene has not been associated with various treatments designed to induce hepatocellular proliferation Fox et al. Hepatic EROD activity was significantly increased in all treated groups when compared with controls, with similar induction at the low, intermediate and high doses.
When the tumour promoting ability of the three treatments was assessed relative focal volume of ATPase-deficient preneoplastic liver tissue , similar results were obtained after modelling the toxic equivalents for liver with TCDD and the dioxin mixture; however, the response to the latter was about twofold lower at the highest dose. The authors concluded that TEFs based on enzyme induction in vitro provide only an approximation of the tumour promoting ability of dioxin congeners and gave an overestimate of the response to the HpCDD Schrenk et al.
On the basis of the measured end-points deaths, hepatic EROD induction, decreased plasma T4 concentration, haematological indices , the TEF for this congener was estimated to be 0. In an experiment of a similar design, groups of 20 rats of the same strain were given total toxic equivalents of 0, 0. Whereas there was a significant, dose-dependent increase in hepatic EROD activity even at the lowest toxic equivalents 0.
Overall, the effects seen with the toxic equivalent mixture, TCDD or 1,2,3,6,7,8-HxCDD alone were comparable mortality rate, growth reduction, hepatic enzyme induction, haematological effects , providing support for the TEF and additivity concept for chlorinated dioxins Viluksela et al. The most sensitive effects, seen at the lowest dose, included hepatic CYP 1A1 and 1A2 induction and significant decreases in thymus weights and hepatic retinol concentration. At the higher doses, differences in liver, kidney and spleen weights and decreases in plasma T3 and free T4 concentrations were seen.
Thyroid hormone status was assessed in rats in a short-term assay for tumour promotion. While there was no effect on T3 concentration, that of serum TSH was increased by about 2. Histological changes in the thyroid included diffuse follicular hyperplasia; in rats at 3. The effects induced were similar to those in rats, including deaths at the highest dose.
The NOEL for changes in organ and body weights and clinical effects was 0. Most of the long-term experiments designed to determine the toxicity of dioxin and coplanar chemicals were conducted with various rodent species or non-human primates. The carcinogenic effects assessed in long-term studies are summarized in Table 4.
Dose-dependent increases in the incidence of both ulcerative skin lesions and amyloidosis were observed at the two lower doses and a decreased lifespan in mice at the highest dose. An increased incidence of liver tumours hepatomas and hepatocellular carcinomas was observed at the intermediate dose, but a similar increase at the highest dose was not significant Tóth et al. Among those reported were ear-duct carcinoma, renal adenocarcinoma, skin angiosarcoma, Leydig-cell adenoma, fibrosarcoma, squamous-cell carcinoma of the skin and lung, glioblastoma, astrocytoma, cholangiocarcinoma and lymphocytic leukaemia.
No tumours were found at the lowest dose Van Miller et al. The Committee noted that the small number of animals used and the high mortality rates limit interpretation of this study. Groups of 50 Sprague-Dawley rats of each sex 86 rats of each sex as vehicle controls were fed diets formulated with TCDD to provide a dose of 0, 0. Body weight and food consumption were measured throughout the study; haematological examinations and urinary analyses were performed on eight rats of each sex per group after 3, 12 and 23 months.
Serum samples were collected twice during the study. The biochemical and histopathological examinations were extensive. Increased incidences of hepatocellular carcinoma, squamous-cell carcinomas of the lung, hard palate and tongue were observed at the highest dose. TCDD not only affected the incidence rates of cancer but had additional toxicological effects, particularly at the highest dose, which included increased mortality females only , decreased body-weight gain, splenic and thymic atrophy, hepatic degeneration and necrosis.
On the basis of increased urinary excretion of porphyrins and delta -aminolaevulinic acid and hyperplastic nodules in the liver in females at 0.
Animals at the higher dose showed marginal signs of toxicity Bowman et al. Several short—term assays for genotoxicity with TCDD covering various end-points gave primarily negative results.
Thioguanine selection resulted in a weakly positive response Rogers et al. Sister chromatid exchange and micronuclei were found in human lymphocytes treated with TCDD, in the absence or presence of alpha -naphthoflavone Nagayama et al. TCDD also transformed AdSVimmortalized cells but not primary human epidermal keratinocytes, as revealed by growth in soft agar, and increased foci formation, cell density and the carcinogenic response in nude mice.
OCDD did not induce mutations in S. When administered concomitantly with O -tetradecanoylphorbol acetate, TCDD increased the cell transforming capacity of peritoneal macrophages in mice in a dose-dependent manner Massa et al. TCDD enhanced alpha -naphthoflavone-induced sister chromatid exchange frequency in cultured rat lymphocytes Lundgren et al. It did not induce sister chromatid exchange, micronuclei or chromosomal aberrations in mouse bone marrow Meyne et al.
TCDD increased the mutagenic and recombinogenic activity of N- ethyl- N -nitrosourea in the mouse spot test by twofold Fahrig, In lacI transgenic rats, TCDD increased neither the mutation frequency nor the mutation spectrum in the liver Thornton et al. Similarly, TCDD did change the spontaneous spectrum of H- ras codon 61 point mutations in mouse liver, nor did it affect the mutation spectrum of H- ras mutations in hepatocellular adenomas and carcinomas after treatment of mice with vinyl carbamate Watson et al.
In a three-generation study of reproductive toxicity, male and female Sprague-Dawley rats 16 males and 32 females in the control and high-dose groups; 10 males and 20 females at the low and intermediate doses were maintained on diets containing TCDD designed to deliver a dose of 0, 0.
The F 1b and F 2 litters were mated when the animals were about days of age to produce the F 2 and F 3 generations, respectively. Fertility, litter sizes and neonatal survival were severely decreased for animals at the highest dose at the F 0 matings and in ensuing generations at the intermediate dose. Although slight effects were seen on pup survival and renal morphology at the low dose, they did not occur consistently across all generations. The NOEL was 0. The steady-state body burdens of TCDD of the rats at the two lower doses were estimated to have been 0.
After a second breeding, in which 14 treated males and seven treated females at 1. Groups of 10—12 female B6C3F 1 mice were treated by gavage with various dioxin, furan and PCB congeners once every 3 weeks for five dosing periods to assess the survival of autotransplanted endometrial lesions. Endometrial tissue was transplanted during the second dosing period. Whereas the weights of the lesions appeared to decrease with increasing dose of TCDD, the weights were still higher than those of controls.
No significant effects were seen on ovarian or uterine horn weights, but the thymus weights were decreased and the liver weights increased at the two higher doses of PCDF. The size of the maintenance doses was based on a reported elimination half-life of 3 weeks for adult rats.
The dams were killed after weaning, and 20 male pups per group were either assessed at 70 or days of age for sexual development sex organ weights, sperm analysis or bred to untreated females on postnatal day No effects were seen on reproductive performance mating, pregnancy, fertility. At the highest dose, the serum testosterone concentration was decreased at adulthood, and permanent changes in the testicular tubuli were found, including pyknotic nuclei and the occurrence of cell debris in the lumen.
Mounting and intromission latencies were significantly increased at the lowest and highest doses. The rats were killed 24, 48, 56 and 72 h later study termination , and body weight, ovarian weights, ovulation status and serum prolactin, luteinizing hormone and follicle-stimulating hormone were measured.
After 7 months of treatment, the monkeys were bred to untreated males, produced the F 1 generation and were bred again after 27 months on diet.
The total amount of TCDD ingested by the mothers was estimated to have been ng after While there was no indication of maternal toxicity at the time, analysis of the monkeys 10 years after termination of the study revealed a dose-dependent increase in the frequency and severity of endometriosis, and three monkeys at the higher dose died due to severe peritoneal endometriosis.
As there was a high concentration of coplanar PCBs in the blood of monkeys in which endometriosis was originally diagnosed, there may have been an unknown source of exposure to PCBs that caused the reported lesions Rier et al.
The average dietary concentration of PCBs was reported to be 7. The average doses of TCDD delivered were 0, 0. Laparoscopic examinations were conducted on all monkeys at 1, 3, 6 and 12 months study termination.
The surviving endometrial strips in animals at the lowest dose actually regressed in size. The serum concentrations of interleukin IL -6 were significantly decreased, while those of IL-6 soluble receptor were increased in monkeys at the highest dose at termination, with a 2.
Dioxins, and specifically TCDD, induce a distinct series of developmental effects, including fetal mortality, structural malformations and postnatal functional alterations, in a variety of species at doses below those associated with maternal toxicity. These effects are thought to be due in part to interactions with the Ah receptor and its related transcriptional factor, ARNT, the expression of which appears to be involved in aspects of normal embryonic development Kozak et al.
In most species tested to date, TCDD can induce significant embryolethality early or late resorptions, abortions, stillbirths , which is usually associated with indications of maternal toxicity.
The timing of dosing and the age of the embryo or fetus have been shown to be major determinants of TCDD-induced prenatal mortality. Characteristic, sensitive indications of the teratogenicity of TCDD in responsive strains of mice include induction of cleft palate and hydronephrosis at doses not associated with maternal toxicity.
While cleft palate in the absence of fetal or maternal toxicity usually occurs only in mice, common effects in rats and hamsters include renal malformations, oedema and gastrointestinal haemorrhage. The ability of most coplanar chemicals to induce frank developmental effects is related to their binding affinity to the Ah receptor.
Decreased maternal body-weight gain was seen only in mice treated with TCDD on day 10 of gestation, whereas the relative liver weight was increased at all doses of TCDD.
There was a trend towards a decrease in maternal body-weight gain in mice treated with retinoic acid on day 10 and increased relative liver weight after treatment on both days 10 and The increase in relative liver weight seen in mice treated with both chemicals was similar to that seen with TCDD alone.
All treated groups had 6—20 litters. Hydronephrosis was seen in all groups treated with TCDD, with a dose-dependent increase in severity. The median effective dose ED 50 for this lesion was estimated to be 3. Combined treatment with the two chemicals had no effect on either TCDD-induced hydronephrosis or retinoic acid-induced skeletal anomalies, but they had an interactive effect on cleft palate induction. Significant increases in relative liver weights were seen in maternal animals at all doses, but there were no effects on litter size, litter weight or fetal mortality.
Various structural end-points associated with the developing urogenital system of rodents have been shown to be extremely sensitive to perturbation by TCDD and coplanar chemicals. Additional maternal rats were treated with a single oral dose of 0, 0. After this time and until sexual maturity postnatal day , no significant differences were seen for either parameter. Although there was a trend towards decreased plasma testosterone and dihydrotestosterone concentrations in male offspring from postnatal day 32—, none of the changes was significant.
Male offspring from litters in the above study, standardized on postnatal day 1 to five pups of each sex per litter from dams treated with graded doses of TCDD on day 15 of gestation, were also assessed for sexual behaviour on postnatal days 56—63, 70—77 and — While the number of intromissions required before ejaculation was not significantly affected, the number of mounts required before ejaculation was slightly increased in all groups during testing on postnatal days — Hepatic EROD activity, when determined on postnatal day , was not significantly increased at any dose Mably et al.
Male pups isolated after lactation were assessed for various aspects of the development of the reproductive system on postnatal day 32, 39, 63 and juvenile, pubertal, postpubertal and sexually mature, respectively. Although slight decreases in paired testis weights were observed at all doses except 0. The weight of the right epididymis was decreased in a dose-dependent manner at a maternal dose as low as 0.
The weights of the cauda epididymis were lower than those of controls at all doses after puberty postnatal days 63 and No significant effects were seen on cauda epididymal sperm motility or morphology. The plasma concentration of follicle-stimulating hormone was slightly reduced only on postnatal day 32 at all maternal doses except 0. When the male offspring were mated with control females on postnatal day 70, no effects were observed on fertility, gestation index, litter size or pup survival Mably et al.
Some male pups were retained for assessment of reproductive organ weights and sperm counts at 15 months of age. On postnatal days 49 and 63, most of the developmental affects in male offspring occurred at the highest dose and included decreased numbers of epididymal sperm postnatal day 49 and 63 and decreased weights of the cauda epididyma postnatal day 63 , ventral prostate and seminal vesicle postnatal day The onset of puberty was delayed by about 2 and 4 days at the two higher doses, respectively.
However, when the results were combined with those of a previous study Gray et al. These effects of low doses of dioxin and coplanar chemicals on the developing male reproductive system are usually not paralleled by decreased reproductive capacity or androgen status. Also, in general, the effects of TCDD and related coplanar chemicals on the urogenital tract during fetal and neonatal development of rodents, although dependent on the timing and age of the fetus, can be achieved by low doses in utero alone.
Not only male reproductive tract development but also various aspects of male sexual behaviour can be affected by perinatal exposure to low doses of TCDD and coplanar PCBs. In the experiments by Mably et al. Similarly, in Long Evans rats Gray et al. While demasculinization of sexual behaviour was reproducible in three strains of rat, it was not seen in hamster offspring.
Feminization of male sexual behaviour, as assessed by increased intensity and duration of lordosis, was also observed in male Holtzman rats at maternal doses of TCDD as low as 0. Alteration of defeminization of sexual behaviour by TCDD has been shown to require exposure during lactation or after parturition. In rats and hamsters, single maternal doses as low as 0. Female offspring from the study of Gray et al. Additional females were mated to control males on postnatal day for assessment of fertility.
On postnatal day 70, the age of onset of vaginal opening was delayed in pups of dams at 0. After mating on postnatal day , no significant differences were seen in treated animals with respect to fertility, but the time to pregnancy of offspring of dams at the highest dose was increased by three estrous cycles when compared with controls 4. Significantly increased numbers of female offspring at 0. Cleft phallus and changes in the urethral opening position have also been observed in rats given other estrogen-like chemicals diethylstilbestrol, RU , estradiol Gray et al.
After parturition, the litters were standardized to four pups of each sex, and the female offspring were monitored for sexual development, estrous cycle and fertility. This effect was thought to be related to the decreased fertility rate of female progeny treated on day 8 when they were entered into a continuous breeding phase five successive litters. Whereas the fertility rates of females treated on day 15 were similar to those of controls up to the fourth litter but significantly reduced by the fifth litter , the fertility rate of females treated on day 8 was reduced by the second litter and throughout the duration of the breeding phase.
Although overall fertility and fecundity in the first litter produced by females treated on day 15 were not affected, the high prevalence of vaginal threads caused greater difficulty in mating with control males, as illustrated by the increased number of mounts without intromission and increased ejaculation latency.
After parturition and lactation, the female offspring were monitored for various developmental landmarks until maturity postnatal day — After mating of the female offspring on postnatal day —, a variety of parameters, including fertility, weaning index, number of implants, litter size and pup survival, were significantly reduced in the treated animals.
TCDD treatment also increased the frequency of F 1 female offspring with mild hypospadias or cleft phallus 0. The litters were standardized on postnatal day 1 to four of each sex, and development was assessed after interim sacrifices on postnatal days 23 males only , 44, 65, —, males only and females only. Duration of gestation, prenatal mortality, litter size and dam weight were not affected by TCDD, and no effect was seen on postnatal pup mortality or pup weight gain throughout the experiment.
TCDD also accelerated the average time to eye opening by about 1 day and decreased thymus weights not dose-dependent on postnatal day 44 in male but not female offspring. No urogenital tract malformations were seen in female offspring, and the time to vaginal opening was not affected. For comparison, the single dose of 0. In a study designed to determine the most sensitive effect of TCDD on the rodent male reproductive system, groups of six pregnant Holtzman rats were given a single oral dose of TCDD at 0, TCDD had no effect on the body-weight gain of dams during gestation or on the weight of male pups during the assessment period.
Maternal treatment with TCDD also had no effect on the relative testis or epididymal weights, daily sperm production, cauda epididymal sperm reserve or serum luteinizing hormone, follicle-stimulating hormone or testosterone concentrations of male offspring.
Semi-quantitative reverse transcription polymerase chain analysis indicated that the levels of androgen receptor mRNA in this organ were significantly reduced in all treated groups on postnatal day 49 but not on postnatal day Administration of TCDD at any dose resulted in a dose-dependent increase in 5 alpha -reductase type 2 mRNA and a decrease in androgen receptor mRNA in the ventral prostate of rats killed on day 49 but not in those killed on day , with no adverse sequelae at the lowest dose of Although the authors postulated that the decreased size of the ventral prostate was due to the decrease in androgen receptor mRNA, previous results Gray et al.
There is currently limited experimental evidence for an Ah receptor-based mechanism of action for dioxin-induced neurotoxicity. Central nervous system functioning and neurobehaviour have been assessed in some animal models. Pregnant Wistar rats were treated by subcutaneous injection with a loading and maintenance dosing regime designed to approximate human perinatal exposure.
After an initial dose of TCDD at 0, 1 or 0. After a slight initial decrease in body weight on postnatal day 7, the body weights of pups of dams on the low-dose regimen were comparable to those of controls. Greater percentages of the TCDD-treated offspring than controls acquired a righting reflex on postnatal day 5 or 6, but they showed a delayed ability to remain on a rotating rod. The activity of 3-month-old female offspring was significantly reduced after treatment with TCDD in comparison with controls after an amphetamine challenge.
Monkeys treated with TCDD showed an increased overall level of behavioural arousal, including increased self-directed behaviour, when compared with controls. No significant relationship was observed between any of the behavioural parameters and the concentration of TCDD in the body fat of the infants.
Similar effects were not seen when a second cohort of offspring obtained after the maternal animals had been on control diet for 16 months were tested. A further group of infant rhesus monkeys one female, four males was obtained after the maternal animals had been on the TCDD-containing diet for Cognitive testing of the monkeys in both groups was conducted when they were about 14 months of age. Monkeys exposed perinatally to TCDD took a significantly longer time to learn the first reversal of a shape discrimination—reversal problem than controls 47 versus 27 trials.
No significant effect of TCDD was seen for subsequent reversals up to eight. In addition, no significant effect was seen on learning of spatial or colour reversal problems or in the ability to respond to a delayed spatial alternation test.
The performance of offspring on a shape discrimination—reversal problem was not correlated to the concentration of TCDD in their adipose tissue. TCDD-induced thymic atrophy has been observed after perinatal exposure in all species examined Holladay et al.
TCDD-induced thymic atrophy is probably of less clinical significance in adult animals, as no correlation has been established between effects on the thymus and functional immune suppression. The reported acute ED 50 values for thymic atrophy in adult animals vary considerably among species: Several hypotheses have been proposed to explain the mechanism by which TCDD induces thymic atrophy.
TCDD administered orally at 0. Similar results were obtained when T-cell responsiveness was tested with an antigenic challenge with conalbumin, suggesting that TCDD acts at a time when T cells are in the process of differentiating in response to antigenic challenge, as TCDD had no effect on naïve or resting T cells that had not been challenged with an antigenic stimulus.
On the basis of these results, the authors suggested that the observed immunotoxic effects of TCDD may be mediated partly through the presence of the Fas molecule in activated T cells and that MHC phenotype may also play an important role Rhile et al. TCDD affects both cellular and humoral immunity. Its effects on T-cell function are characterized by changes in several end-points, including delayed-type hypersensitivity DTH responses, rejection of skin allografts, generation of cytotoxic T lymphocytes and lymphoproliferative responses of lymphocytes to mitogens and specific antigens in vitro.
The effects on T-cell function occur at concentrations three orders of magnitude lower than those that affect thymus cellularity. Species differ in their sensitivity to TCDD, guinea-pigs being more sensitive than rodents. Differences in DTH response have also been observed in the same species challenged with different antigens.
TCDD-induced effects on the cytotoxic T lymphocyte response of spleen cells have been found less consistently. Generation was inhibited at all doses. On the basis of mechanistic studies in vitro, the authors concluded that the cellular basis for suppression of the cytotoxic T lymphocyte response was induction of T-suppressor cells in the thymus which act selectively against the cytotoxic T lymphocyte response Clark et al.
The mechanism by which TCDD affects the cytotoxic T lymphocyte response therefore remains to be elucidated. Specifically, TCDD at a dose as low as 1. Differences among species in the primary response to antigens have also been observed. The plaque-forming cell response in mice was significantly suppressed, with an ED 50 value of 0.
The mechanism responsible for the observed differences between the two species in their response to T cell-dependent and T cell-independent antigens remains to be elucidated Smialowicz et al. Differences in the response to various antigens after exposure to TCDD have also been observed within the same species.
The effects of TCDD on host resistance to various infectious agents, including bacteria, viruses and parasites, has been well documented. Increased mortality in response to S. None of the doses compromised the ability of mice to combat infection by H.
Increased parasitic infestation has been reported after administration of TCDD. The ability of hosts to combat viral infection was compromised at doses of TCDD lower than those that affected resistance to bacteria and parasites. Mice given an intraperitoneal injection of TCDD at 0. An even lower LOEL of 0.
The mortality rates of mice given TCDD was statistically significantly higher than that of controls, but the rate at doses of 0. TCDD did not alter the replication or clearance of the virus in these mice Burleson et al. Young animals are reported to be highly sensitive to prenatal or neonatal exposure to TCDD. The LOEL for increased mortality of offspring due to endotoxin was the lowest dose, that for decreased thymus weight was 2.
A single dose of TCDD at 0. Exposure during both gestation and lactation was required for suppression of the DTH response Gehrs et al. Further experiments with TCDD at 0, 0. Thus, doses of TCDD as low as 0. All rats were killed 3 days after the last feeding. Stimulation of IL-2 production by spleen cells was also reduced, but only in the group treated for days. Both groups showed decreased conconavalin A-induced expression of IL-2 receptors by splenic T-cells in vitro Badesha et al.
In summary, immunotoxic effects of TCDD have been observed in several species at multiple targets in the immune system. The severity of TCDD-induced immunotoxic effects varies among species and depends largely on the end-point investigated.
The effects on the thyroid observed in experimental animals after exposure to dioxins or coplanar chemicals usually involve decreases in free and total T4 in serum, with no compensatory effects on TSH or T3 Brucker-Davis, Dose-dependent decreases in plasma T4 concentration were observed in groups of eight female Sprague-Dawley rats given diets supplemented with TCDD at a concentration of 0, 0.
The LOEL was 0. Thyroid hormone status was assessed in rats from a short-term assay for tumour promotion. After initiation with N -nitrosodiethylamine at 70 days of age, female Sprague-Dawley rats were treated by gavage every 2 weeks for 30 weeks with TCDD at doses designed to deliver 0, 0.
While there was no effect on T3 concentration, that of TSH in serum was increased approximately 2. Significant positive correlations have been observed between TCDD-induced decreases in plasma T4 concentration and concomitant induction of hepatic UGT1, indicating that TCDD functions predominantly at an extrathyroidal level Schuur et al. Further evidence for a mechanism of action that does not directly involve the thyroid gland was obtained in the long-term bioassay in which male and female Sprague-Dawley rats were given TCDD at doses of 0.
Indications of reduced T4 protein binding decreased ratio of total: Various hydroxylated metabolites of PCBs have been shown to competitively displace T4 binding to human transthyretin but not to T4-binding globulin Lans et al.
Four of seven rats at the highest dose died, and decreased body-weight gain was seen at the three higher doses. Treatment had no effect on the weight gain of dams during gestation, on litter size or on pup survival or growth during lactation. No sex-specific differences were seen with respect to enzyme induction Seo et al.
Characteristic symptoms of vitamin A deficiency have been observed in experimental animals and wildlife species after exposure to TCDD and various coplanar chemicals. The mechanism of action appears to be persistent impairment of the ability of liver stellate cells to store vitamin A due to inhibition of lecithin: The initial kinetic effects after exposure to TCDD involve increased mobilization of vitamin A from hepatic storage sites, probably by retinal ester hydrolysis Kelley et al. Additional control groups consisted of rats maintained on a vitamin A-free diet for 12 or 26 days.
The relative kidney weights were significantly increased only at the lowest dose. The concentrations of retinol and retinal palmitate in kidney were increased at doses of TCDD of 3. The activity of acyl coenzyme A: Groups of six male and six female Sprague-Dawley rats were fed diets containing various concentrations of dioxins and furans for 13 weeks, and hepatic retinol concentrations were determined at sacrifice.
The estimated median effective dietary concentrations of TCDD for reducing hepatic retinol were 0. The estimated relative potency factors for hepatic vitamin A depletion corresponded to the values for indices of toxicity in short-term tests thymic atrophy, body-weight reduction, liver lesions. Dietary intake of a variety of chlorinated dioxins and furans for 13 weeks thus reduced hepatic vitamin A concentrations in a dose-dependent manner Fattore et al.
As retinol is transported in blood bound to a complex of retinol binding protein and transthyretin, destabilization of this complex could reduce the binding ability of retinol, with subsequent elimination by renal glomerular filtration.
In the study of van der Plas et al. However, only the mixture reduced plasma retinol concentrations, presumably by the generation of hydroxylated PCB metabolites and effects on retinol binding protein—transthyretin binding. Various hydroxylated metabolites of coplanar PCBs have been shown to bind with high affinity to transthyretin, resulting in inhibition of T4 binding to this protein and disruption of the transthyretin—retinol binding protein complex Brouwer et al.
The epidemiological studies on dioxins include studies of the exposure of workers producing phenoxy herbicide and chlorophenols, studies of the population exposed in the industrial accident in Seveso, Italy, studies of persons exposed during application of herbicides and particularly cohorts of personnel in the US Air Force in Viet Nam, commercial applicators and case—control studies of exposure of communities.
The most informative epidemiological studies are those of the population of Seveso who were accidentally exposed to dioxins in , those of workers producing chlorophenols and chlorophenoxy herbicides contaminated with dioxins and US Air Force applicators. Considerable effort has been made to characterize the exposure of these populations to TCDD, which was 10— times higher than that of the general population.
The populations included in these studies are shown in Table 5. Populations included in the most informative epidemiological studies of the effects of exposure to dioxin. The incidence of and mortality from cancer were investigated in the population of Seveso that was exposed during the industrial accident in The contaminated area was subdivided into three zones zone A, zone B and zone R , according to the average concentration of TCDD measured in soil samples.
The mortality rate during —91 and cancer incidence rates for the period —86 have been reported Bertazzi et al. The rate of death from cancer in general was not increased over the period of observation. However, 15 years after the accident, the mortality rate from cancer was increased in men among the inhabitants of zone A and the inhabitants of zone B, with a rate ratio of 1.
Increases were also seen in the rate of death from rectal cancer rate ratio, 2. Lymphohaematopoietic neoplasms occurred at an excess rate in males and females rate ratio, 1. The mortality rate from Hodgkin disease was high during the first year observation period rate ratio, 4. No cases of soft-tissue sarcoma were observed in zones A and B, although 0. The study populations considered overlap in many instances.
Figure 8 shows the relationships among the various publications considered relevant to this evaluation. In an accident at a BASF plant producing trichlorophenol in Ludwigshafen, Germany, in , a total of employees men, 4 women were identified as having been involved directly or in subsequent clean-up, repair or maintenance activities Zober et al. The cumulative dose of TCDD at the time of exposure was calculated from a model for each person.
The cohort was observed for deaths and cancer incidence until , and the rate of mortality from cancer was found to increase with increasing exposure Figure 9. Mortality rates from cancers of the digestive system and respiratory tract also tended to increase with increasing exposure. Similar results were obtained for cancer incidence. A joint analysis of dose of TCDD and cigarette smoking showed a relationship between the dose and the occurrence of all cancers combined among current cigarette smokers but not among non-smokers.
The study did not include the persons involved in the BASF accident. It included workers from a Boehringer-Ingelheim plant in Hamburg, for whom results have been reported in several publications Manz et al. The concentrations of TCDD were measured in the blood of workers in three of the four plants Kogevinas et al.
The mortality rate was increased in the whole cohort from all cancers combined deaths; standardized mortality ratio [SMR], 1. An outbreak of chloracne in led to a halt in the production of trichlorophenol and 2,4,5-trichlorphenoxyacetic acid. In , production was resumed, with a new process that reduced the formation of TCDD. The vital status of all persons who had been permanent employees at the plant for at least 3 months between 1 January and 31 December men, women was investigated through to Manz et al.
The causes of death were ascertained from medical records or, when medical records were not available, from death certificates. The concentrations of TCDD were measured in samples of serum or adipose tissue from workers in various production departments, mainly after the plant had closed in The rate of mortality from all cancers combined among men was increased in comparison with the rate for the general population 93 deaths; SMR, 1.
The increase was greatest for men who had started work at the plant before , who had the heaviest exposure to TCDD on the basis of the history of the plant and subsequent serum measurements, and who had remained employed at the plant for many years. The mortality rates of female workers were further investigated by Nagel et al. The rate of death from breast cancer was higher than expected 10 cases; SMR, 2. The mortality rates of male workers were investigated through Flesch-Janys et al.
The concentrations of various PCDD and PCDF congeners were measured in adipose tissue or whole blood from workers, and the values for each worker at the end of exposure were calculated on the basis of a one-compartment first-order kinetics model. In some departments, workers had been exposed to other carcinogens, such as dimethyl sulfate and benzene. No data were reported on deaths from cancers at specific sites.
From Flesch-Janys et al. Rates of mortality from all causes, all cancers and ischaemic heart disease IHD in relation to exposure to dioxins, Boehringer plaint, Germany. Mortality rates among workers employed between and in the synthesis and formulation of phenoxy herbicides and chlorophenols in The Netherlands were examined Bueno de Mesquita et al.
In one of the plants, where the main compound produced was 2,4,5-trichlorphenoxyacetic acid and its derivatives, an accident in , which caused a release of PCDDs, including TCDD. In a second factory, 4-chloro- ortho -toloxy acetic acid, 4-chloromethyl phenoxypropionic acid and 2,4-D were produced.
The study involved men working in manufacture at the two plants exposed to phenoxy herbicides, not exposed ; in addition, workers who had probably been exposed to TCDD during the industrial accident and clean-up were examined.
The study was later extended to and enlarged persons, including women Hooiveld et al. In this factory, the mortality rates from all causes deaths; SMR, 1. Excess numbers of deaths from cancers of the urinary bladder four deaths; SMR, 3.
When the workers were subdivided into three categories of low, medium and high exposure according to the serum concentrations of TCDD predicted from a model, the relative risks for death from all causes, all cancers and lung cancer were significantly increased for workers with medium and high exposure and were highest for the group with the heaviest exposure Figure From Hooiveld et al. Mortality rates from all causes, all cancers and ischaemic heart disease in relation to exposure to TCDD predicted from a model, The Netherlans.
The cohort comprised men and included most workers in the USA likely to have been exposed to TCDD during manufacture principally of trichlorophenol and 2,4,5-trichlorphenoxyacetic acid.
Extrapolation to the date at which these workers had been employed, assuming a half-life of 7. In the latest update, of mortality rates through Steenland et al. An exposure matrix was used to estimate the degree of exposure to TCDD in the whole cohort. The SMR for all cancers combined was 1. A statistically significant, positive, linear trend in risk for all cancers combined and for lung cancer was found with increasing exposure Figure The SMR for all cancers combined for the group with the heaviest exposure was 1.
The excess cancer risk was limited to the workers with the heaviest exposure, which was likely to have been — times higher than that experienced by the general population and similar to the doses of TCDD used in studies in experimental animals. From Steenland et al. An international cohort of workers exposed to phenoxyacetic acid herbicides and chlorophenols was set up by the IARC Saracci et al.
The cohort was updated and expanded with the data of Fingerhut et al. The length of follow-up differed by plant, but workers at most of the European plants were followed through —92, and those in the USA through This study represents the largest cohort of TCDD-exposed workers and includes groups with heavy exposure to TCDD and cohorts with little or very little exposure.
The risks for all cancers combined and for soft-tissue sarcomas and lymphomas increased with time since first exposure. In a direct comparison of persons exposed to higher chlorinated PCDDs and those exposed to lower chlorinated PCDDs or none, the rate ratio for all cancers combined was 1. Increased risks were found for breast cancer in both women and men, endometrial cancer and testicular cancer Table 6.
The increased mortality rate from breast cancer was confined to female workers in the Boehringer plant in Germany nine deaths; SMR, 2. Two of three deaths from endometrial cancer similarly occurred among women who had worked in this plant. Standardized mortality ratios SMRs for selected tumours in the 21 workers in the IARC international cohort study who had been exposed to phenoxy acetic acid herbicides or chlorophenols, by exposure to TCDD or higher chlorinated dioxins, — A panel of three industrial hygienists estimated the exposure of the workers to 21 chemicals or mixtures, and a cumulative exposure score was calculated for each person and chemical, on the basis of estimated intensity and duration of exposure in years.
Soft-tissue sarcoma was also associated with exposure to TCDD odds ratio, 5. From Kogevinas et al. This review does not cover studies of phenoxy acetic acid herbicide applicators, including US Air Force personnel who applied Agent Orange, numerous community based case—control studies on soft-tissue sarcoma, malignant lymphoma and other neoplasms, and studies of persons exposed to unspecified combinations of pesticides and herbicides or to herbicides not contaminated by PCDDs e.
The available information indicates that, in these studies, the concentrations of TCDD were lower and, in most cases, considerably lower than that to which industrial workers and the population of Seveso were exposed. In one Swedish case—control study Nygren et al. In a study of the most heavily exposed commercial sprayers in New Zealand Smith et al. Lower values were observed among commercial sprayers in Australia Johnson et al. The findings of studies of cancer risk among persons evaluated in community-based studies and of applicators are contradictory Figure The large discrepancies are probably due to misclassification of exposure, as most of the persons classified as exposed in these studies probably had TCDD burdens very similar to or only slightly higher than those of persons classified as unexposed.
From Johnson Figure Relative risks in 15 case-control studies of soft-tissue sarcoma and exposure to phenoxyacetic acid herbicides, chlorophenols and dioxins. One case—control study on liver cancer was conducted in Hanoi, Viet Nam.
An increased risk for hepatocellular carcinoma OR, 8. The incidence of cancer among persons aged 0—19 years in Seveso, Italy, was analysed separately Pesatori et al. Given the small number of cases, the three contaminated zones and the two sexes were grouped. Seventeen cases were observed relative risk, 1. Two cases of ovarian cancer were found, with none expected.
Two thyroid gland cancers among girls gave a relative risk of 4. The incidence of lymphatic and haematopoietic neoplasms was increased nine cases; relative risk, 1. These excess risks were highly statistically significant, and any effect of chance can be excluded.
The risk tended to be higher for workers with the heaviest exposure. Increased risks with time since first exposure were observed in those studies in which latency was evaluated Kogevinas et al. The risks for certain cancers were increased in some studies lymphomas, multiple myeloma, soft-tissue sarcoma, lung cancer, liver cancer, breast cancer, testicular cancer, endometrial cancer , but, overall, the results were not consistent among studies, and no particular cancer appears to predominate.
Mortality rates from all neoplasms in selected industrial cohorts with heavy exposure to polychlorinated dibenzodioxins and furans. In examining the findings on cancer risk in the most informative epidemiological studies, a number of issues should be noted.
The excess risks observed were highly statistically significant, and any effect of chance could be excluded. In addition, the studies were prospective and were well conducted. Nevertheless, the results must be evaluated with caution, given that the overall risks are not very high and that the strongest evidence is for industrial populations.
Furthermore, there are very few precedents of carcinogens that affect the risk for all cancers with no clear excess for any specific cancer IARC, Finally, the strongest evidence comes from studies of persons whose exposure was two to three orders of magnitude higher than that of the general population.
In order to extrapolate to the general population, models must be used, with the assumption of similar effects at high and low doses. At present, the real dilemma is not whether dioxins are or are not carcinogenic but, rather, the size of the risk associated with the very low exposure of the general population. Most of the available epidemiological studies, however, focused on mortality from cancer and were not designed to evaluate morbidity, e.
Epidemiological evidence exists for only few of these effects and, in contrast to the experimental evidence, is inconsistent for most effects other than cancer. The evidence in humans is currently conclusive only for dermatological effects and temporary increases in liver enzyme concentrations, and there is increasing evidence for an association with cardiovascular disease.
Effect Epidemiological evidence Dermatological effects chloracne Proven association Gastrointestinal effects and liver enzymes Temporary increases in liver enzymes proven Cardiovascular disease and changes in lipid concentrations Positive associations in most studies of heavy exposure, but results not entirely consistent: While there was clear evidence that dioxins and coplanar chemicals can cause a variety of adverse reproductive effects in experimental animals, the evidence for human populations was limited, except for the two episodes of rice oil poisoning in South-East Asia.
Accidental consumption of rice oil contaminated with heat-degraded PCBs occurred in two separate episodes, in Japan in and in Taiwan Province of China in Large numbers of persons were exposed.
Analysis of the rice oils in question showed that other chlorinated compounds, including polychlorinated terphenyls, naphthalenes, quarterphenyls and furans, were present, in addition to the PCBs Chen et al. A number of attempts have been made to determine whether US Air Force personnel involved in spraying TCDD-contaminated herbicides during the Viet Nam War had higher rates of adverse reproductive outcomes for a review, see Environmental Protection Agency, a. While there have been no strong indications of decreased fertility rates or an increased risk for adverse birth outcomes, such as spontaneous abortion, stillbirths or intrauterine growth retardation, some results suggest higher rates of birth defects, both total and specific Centers for Disease Control, ; Michalek et al.
A number of the studies lack consistency and may have involved reporting bias or exposure misclassification Wolfe et al. When all birth outcomes total, of women from the affected areas in Seveso in —82 were reviewed, no significant increase in the frequency of total or specific birth defects was observed Mastroiacovo et al.
The authors noted that most of the participants were from outside the two zones with the heaviest TCDD contamination. Both US Air Force personnel involved in spraying in Viet Nam and workers in the USA employed in factories producing TCDD-contaminated herbicides chloro-phenoxyacetic acid derivatives have undergone assessment for circulating gonadotropins and sperm characteristics. In the former group, current serum concentrations of testosterone, follicle-stimulating hormone and luteinizing hormone and testicular abnormalities, sperm count, sperm abnormalities and testicular volume were not associated with current or back-extrapolated serum TCDD concentrations Henriksen et al.
In addition to the variety of developmental abnormalities observed in children born to mothers who consumed poisoned rice oil Yusho and Yu-Cheng; see below , about twice as many women affected in the Yu-Cheng incident reported abnormal menstrual flow 14 years after poisoning when compared with neighbourhood control women Yu et al. More Yu-Cheng-affected women also reported having had a stillbirth after 4.
Since the initial report that long-term exposure to low doses of TCDD was associated with endometriosis in non-human primates Rier et al. A retrospective study is under way to examine these effects in women in Seveso. Among 79 women attending an infertility clinic in Jerusalem, detectable concentrations of TCDD were found in the blood of eight of 44 with endometriosis 0.
In Belgium, endometriosis was diagnosed by laparoscopy in 42 of women who were undergoing treatment for infertility in — Further evidence for a link between TCDD and endometriosis is provided by experimental studies.
An initial report from Seveso indicated that the sex ratio of children born to parents who had lived in zone A, with the highest level of TCDD contamination, was altered in favour of females Mocarelli et al. Of the births that occurred from 9 months after the accident to 7 years later, about twice as many children were female 26 males, 48 females. During —94, the sex ratio apparently reverted to normal 60 males, 64 females. In a follow-up study Mocarelli et al. A biological explanation of this phenomenon has not yet been provided.
General decreases in the normal male: Comparable analyses in other populations exposed to dioxins, PCBs or PCDFs in studies of oil poisoning and herbicide spraying in Viet Nam have not provided support for these findings Michalek et al. Of births between —85 to women who were identified from the Yu-Cheng registry, approximately equal numbers of males and females 68 and 69 were born Rogan et al.
Neurodevelopmental effects in children have been examined mainly in relation to exposure to mixtures of organochlorinated compounds, predominantly PCBs Ribas et al The most characteristic symptoms observed at birth in the infants of mothers certified as Yusho patients was a gray—dark-brown skin and gingival pigmentation, which usually resolved within 2—5 months.
Although limited follow-up has been reported of infants exposed in this incident perinatally, one group of 13 children has been described as being apathetic and hypotonic, with lower IQs, 7 years after the event Harada,