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NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Di-Isodecyl Phthalate (DIDP).

The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for di-isodecyl phthalate (DIDP) to cause adverse effects on reproduction and development in humans. DIDP is one of 7 phthalate chemicals evaluated by the NTP CERHR Phthalates Expert Panel. These phthalates were selected for evaluation because of high production volume, extent of human exposures, use in children's products, and/or published evidence of reproductive or developmental toxicity. DIDP is a mixture of branched, C-10 phthalate isomers used to add flexibility to a wide variety of polyvinylchloride (PVC) plastic products such as artificial leather, toys, carpet backing, and pool liners. The results of this evaluation on DIDP are published in a NTP-CERHR monograph which includes: 1) the NTP Brief, 2) the Expert Panel Report on the Reproductive and Developmental Toxicity of Di-Isodecyl Phthalate, and 3) public comments received on the Expert Panel Report. As stated in the NTP Brief, the NTP reached the following conclusions regarding the possible effects of exposure to DIDP on human development and reproduction. First, although DIDP could possibly affect human development if exposures are sufficiently high, there is minimal concern for developmental effects in fetuses and children at current proposed/estimated exposure levels. There is no direct evidence that exposure of people to DIDP adversely affects reproduction or development, but show that oral exposure of pregnant rats to high doses (200 and 1000 mg/kg bodyweight/day) of DIDP can adversely affect fetal development. Human exposure information for DIDP was not available, but it was assumed that the general US population would be exposed to 3-30 mug/kg body weight/day, based upon the range of estimated exposures for DEHP, a more widely used phthalate. Second, there is negligible concern for reproductive toxicity in exposed adults. Studies evaluated showed that, at high exposure levels, there is no evidence of adverse reproductive effects in rats. NTP-CERHR monographs are transmitted to federal and state agencies, interested parties, and the public and are available electronically in PDF format on the CERHR web site (http://cerhr.niehs.nih.gov) and in printed text or CD-ROM from the CERHR (National Institute of Environmental Health Sciences, P.O. Box 12233, MD EC-32, Research Triangle Park, NC; fax: 919-316-4511).

Journal Article↗

NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of 1-Bromopropane (1-BP).

The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for 1-bromopropane to cause adverse effects on reproduction and development in humans. 1-Bromopropane was selected for evaluation due to recent consideration of 1-bromopropane as a replacement chemical for hydrochlorofluorocarbons and chlorinated solvents. 1-Bromopropane is used in spray adhesives and in cleaning metal and electronic components; as a solvent for fats, waxes, or resins; and as an intermediate in the synthesis of pharmaceuticals, insecticides, quaternary ammonium compounds, flavors, or fragrances. The results of this evaluation on 1-brompropane are published in a NTP-CERHR monograph which includes: 1) the NTP Brief, 2) the Expert Panel Report on the Reproductive and Developmental Toxicity of 1-Bromopropane, and 3) public comments received on the Expert Panel Report. As stated in the NTP Brief, the NTP reached the following conclusions regarding the possible effects of exposure to 1-bromopropane on human development and reproduction. No data were available on 1-bromopropane exposures in the general US population. Therefore, conclusions were based on the available occupational exposure data and on studies in humans and laboratory animals. First, there is serious concern for reproductive and developmental effects at the upper end of the human occupational exposure range (18-381 ppm). Adverse developmental and/or reproductive effects have been reported in animal studies at exposure levels of >/=200 ppm. Second, there is minimal concern for reproductive and developmental effects when humans are exposed at the lower end of the human occupational exposure range (0.04-0.63 ppm). This level is at least 300- fold lower than the no effect level identified from reproductive studies in laboratory animals. These conclusions are based upon limited occupational inhalation exposure data. It is likely that worker exposures also occur through dermal contact with 1-bromopropane. However, no information was available on dermal exposures. NTP-CERHR monographs are transmitted to federal and state agencies, interested parties, and the public and are available in electronic PDF format on the CERHR web site (http://cerhr.niehs.nih.gov) and in printed text or CD-ROM from the CERHR (National Institute of Environmental Health Sciences, P.O. Box 12233, MD EC-32, Research Triangle Park, NC; fax: 919-316-4511).

Journal Article↗

The 12 kD FK 506 binding protein FKBP12 is released in the male reproductive tract and stimulates sperm motility.

BACKGROUND: The 12 kD FK506 binding protein FKBP12 is a cytosolic receptor for the immunosuppressant drugs FK506 and rapamycin. In addition to its critical role in drug-induced T-cell immunosuppression, FKBP12 associates physiologically with ryanodine and inositol 1,4,5-trisphosphate (IP3) receptors, regulating their ability to flux calcium. We investigated a role for FKBP12 in male reproductive physiology on the basis of our identification of extremely high levels of [3H]FK506 binding in male reproductive tissues. MATERIALS AND METHODS: [3H]FK506 binding studies were performed to identify tissues enriched with FK506 binding sites. The abundant [3H]FK506 binding sites identified in the male reproductive tract were localized by [3H]FK506 autoradiography. FK506 affinity chromatography was employed to purify FKBP from epididymal fluid. Anti-FKBP12 Western analysis was used to confirm the identity of the purified FKBP. The binding of exogenous FKBP12 to sperm was evaluated by [32P]FKBP12 binding studies and [33P]FKBP12 autoradiography. The effect of recombinant FKBP12 on sperm motility was investigated using a Hamilton Thorne motility analyzer. RESULTS: Male reproductive tissues contained high levels of [3H]FK506 binding. The localization of [3H]FK506 binding sites to the tubular epithelium of the caput epididymis and the lumen of the cauda and vas deferens suggested that FKBP is released in the male reproductive tract. FKBP12 was purified from epididymal plasma by FK506 affinity chromatography. Radiolabeled FKBP12 specifically bound to immature but not mature sperm. In sperm motility studies, FKBP12-treated caput sperm exhibited double the curvilinear velocity of untreated controls. CONCLUSIONS: High levels of FKBP12 are released in the male reproductive tract and specifically associate with maturing sperm. Recombinant FKBP12 enhances the curvilinear velocity of immature sperm, suggesting a role for FKBP12 in motility initiation. The highest concentrations of soluble FKBP12 in the male reproductive tract occur in the lumen of the vas deferens, a site of sperm storage and the conduit for ejaculated sperm. Preservation of mammalian sperm for reproductive technologies may be optimized by supplementing incubation or storage media with FKBP12.

Animals↗

Attitudes towards reproductive issues and carrier testing among adult patients and parents of children with cystic fibrosis (CF).

Assessing the reproductive choices of parents of children with cystic fibrosis (CF) is important in getting a greater insight into the possible needs for counselling of carrier couples in the reproductive decision-making process. Also, parents' reproductive attitudes might indicate critical issues for discussion with regard to introducing general population screening programmes. Data were available from two groups of subjects: 287 adult patients with CF (mean age 27.5 years) and 288 parents of a child with CF (mean age of child 7.7 years) who participated in a Dutch national survey. Attitudes towards reproductive issues and carrier screening and parents' reproductive behaviour were analysed in terms of responses to questionnaires. To avoid having another child with CF, most parents decided against further pregnancies or used other reproductive options. Prenatal diagnosis was used by 72% of parents, whereas 76% of parents planning more children intended using this option. Intention to use prenatal diagnosis was associated with the strength of religious conviction, and was not associated with perceived severity of CF, health of the child, or future therapeutic possibilities. Respondents demonstrated difficulties in deciding to abort for CF. A majority of parents and adult patients supported carrier couple identification within CF families. The results suggest that those most closely involved with CF will accept the reproductive choices of carrier couples identified in population screening programmes.

Abortion, Induced↗

Reproduction trends and the emergence of moral panic.

Are we witnessing a moral panic or a moral evaluation in the responses to the new reproductive technologies? Locating women in reproductive technology is a particularly powerful way into a discussion of values and consequences, intended or unintended. Twelve areas are isolated for discussion beginning with issues of definition and location: What is reproductive and genetic engineering? and How does human reproduction fit into bio-technological developments generally? Next issues are raised about how the new developments are being shaped ideologically and how they are being promoted by the state. A series of legal issues affecting women, men, children, embryos and fetuses follow. The focus then shifts to the way women are ideologically constructed: Why is there an assumption that woman = mother, and mother = heterosexual married or stable cohabiting woman?--and socially controlled: Why assume technological change in human reproductive processes means the basic subordination of women to men will not alter? The usefulness of the new technologies in relieving involuntary childlessness is then queried which leads on to a questioning of whether these developments are qualitatively different from other technologies used in human reproduction. Futuristic concerns such as the importance of the male pregnancy and the social consequences of fully medicalising human reproduction are raised. The last area to be considered is protest by women and suggested alternative approaches to increase the social visibility and recognition of the needs and interest of women in the current and potential use of the new medical and scientific developments.

Female↗

Transcriptomic insights into thermal stress reveal physiological trade-off between thermal stress adaptation and reproductive investment in Spodoptera litura.

Spodoptera litura, a highly polyphagous lepidopteran pest, poses a major threat to agricultural productivity due to its remarkable adaptability to diverse environmental conditions. Although heat stress is known to trigger transcriptional reprogramming in insects, the molecular mechanisms underlying thermal stress responses in S. litura remain poorly understood. In the present study, fourth-instar larvae were exposed to acute heat stress (44 °C) and compared with control conditions (27 ± 1 °C) to investigate heat-induced transcriptional alterations affecting physiology and reproduction. High-quality RNA-Seq data achieved more than 80% mapping efficiency, with a total of 15,782 transcripts were identified. Transcriptome analysis of S. litura larvae showed 323 differentially expressed genes (DEGs), of which 262 genes were significantly upregulated and 61 were downregulated in heat-stressed larvae compared to the control group. The DEGs were associated with stress response, reproduction, signalling, proteostasis, detoxification, oxidative stress, metabolism, development, and chromatin regulation. Heat shock proteins genes, including HSP70, HSP90, and HSP27, together with co-chaperones such as TRET-1, STIP1, and Starvin, were strongly upregulated, indicating enhanced cellular protection against protein damage and oxidative stress under heat stress. Conversely, key reproductive and cell cycle-related genes, including BARR, CAPD2, FEO, CDK2 and MORULA, were significantly downregulated, suggesting reproductive impairment and developmental arrest. RT-qPCR validation corroborated the RNA-Seq findings, demonstrating a heat-induced physiological trade-off that prioritizes survival over reproduction. Consistent with these molecular responses, heat-stressed insects exhibited marked reproductive impairment, including significant reductions in gonadosomatic index, eupyrene sperm bundle count, mating frequency, mating success, female calling behaviour, copulation duration, fecundity, and egg fertility. Collectively, these findings provide comprehensive insights into the molecular basis of thermal adaptation in S. litura and demonstrate that acute heat stress compromises reproductive fitness while activating conserved stress-response pathways that promote short-term survival.

Animals↗

Unmet need for reproductive health in India.

Using data from the National Family Health Survey of 1992-93 and the individual reproductive histories of a cross-section of 70 women from rural Tamil Nadu, this paper exposes the limited extent to which women in India have been able to achieve their reproductive intentions and the failure of health services to meet their considerable reproductive health needs. Of the 70 women, 69 had been unable to achieve their reproductive intentions, not only non-users of contraception but also ever-users, and all 69 had an unmet need for reproductive health services. Sterilisation is often the first and only method of contraception taken up and only after a series of wanted, mistimed and unwanted pregnancies, miscarriages, induced abortions and neonatal and infant deaths. Women who wanted to have more children than they were able to were also found. Given the paradigm policy shift in India from promoting fertility reduction only to meeting women's reproductive and sexual health needs, a more useful concept for measuring 'unmet need' for services in programme planning is required, one such as the HARI index, that would capture the extent to which individual women are achieving their reproductive intentions in good health. Without this, the same problems will only recur in younger women.

Birth Intervals↗

Population genetic consequences of extreme variation in sexual and clonal reproduction in an aquatic plant.

Most plants combine sexual reproduction with asexual clonal reproduction in varying degrees, yet the genetic consequences of reproductive variation remain poorly understood. The aquatic plant Butomus umbellatus exhibits striking reproductive variation related to ploidy. Diploids produce abundant viable seed whereas triploids are sexually sterile. Diploids also produce hundreds of tiny clonal bulbils, whereas triploids exhibit only limited clonal multiplication through rhizome fragmentation. We investigated whether this marked difference in reproductive strategy influences the diversity of genotypes within populations and their movement between populations by performing two large-scale population surveys (n = 58 populations) and assaying genotypic variation using random amplified polymorphic DNA (RAPDs). Contrary to expectations, sexually fertile populations did not exhibit higher genotypic diversity than sterile populations. For each cytotype, we detected one very common and widespread genotype. This would only occur with a very low probability (< 10-7) under regular sexual recombination. Compatibility analysis also indicated that the pattern of genotypic variation largely conformed to that expected with predominant clonal reproduction. The potential for recombination in diploids is not realized, possibly because seeds are outcompeted by bulbils for safe sites during establishment. We also failed to find evidence for more extensive movement of fertile than sterile genotypes. Aside from the few widespread genotypes, most were restricted to single populations. Genotypes in fertile populations were very strongly differentiated from those in sterile populations, suggesting that new triploids have not arisen during the colonization of North America. The colonization of North America involves two distinct forms of B. umbellatus that, despite striking reproductive differences, exhibit largely clonal population genetic structures.

Canada↗

[Reproductive medicine in Germany--peculiarities and dilemmas].

BACKGROUND: Technological progress, as well as increasing success, of reproductive medicine may lower the threshold for childless couples to initiate infertility therapy. However this development may aggravate unsolved problems (e. g. multiple births) and may not increase the pregnancy rate, due to the present unsatisfactory legal situation in Germany (e. g. ban on selective blastocyst culture). METHODS: Based on a systematic review of the literature, we studied actual problems of German reproductive medicine under three public health-related topics: (1) the decline in population in Germany, (2) criteria for success in reproductive medicine and (3) new treatment options in the light of legal and ethical aspects. RESULTS: In Germany (and other industrial nations), reproductive medicine has emerged parallel to an ever-increasing rate of childlessness. Today, 2 % of all births result from treatments using the techniques of reproductive medicine. Nevertheless, the actual extent of involuntary childlessness is lower (below 8 %) than commonly suggested (between 10 and 15 %). Frequently, the success of treatment depends upon a series of treatment cycles and is, especially in Germany, accompanied by a high rate of multiple births (more than 30 %). Hence, a more adequate success rate may be the healthy, i. e., term, singleton baby. The use of selective blastocyst culture, currently not permitted in Germany, could further improve therapy or, at least, reduce patient stress and discomfort. CONCLUSION: Reproductive medicine, as seen from a public health perspective, needs to pursue patient-oriented requirements more in-depth. An open discussion of new technologies which could improve reproductive health but are at present not permitted, would be imperative.

Germany↗

Genetics of reproduction and its evolutionary significance.

PROBLEM: To provide an evolutionary perspective on reproductive problems. METHOD OF STUDY: A broad range of evolutionary and reproductive data in the literature were analyzed. RESULTS: Evolutionary considerations provide some insight into two aspects of human reproduction. First, the inefficiency of the reproductive process (20-35% of fertilized ova yield successful pregnancies) may reflect the stress placed on the reproductive process by the relatively short evolutionary time between the hunter--gatherer and settled agricultural patterns of human life. Second, the immaturity of the immune response of the human newborn is most likely a consequence of its delivery while still in the embryonic/fetal stage of development. Delivery at this time is necessitated by the rapid development of the human brain in utero. CONCLUSIONS: The attempts to develop reproductive technologies should take into account the fundamental limits on the human reproductive process. A variety of in utero preventive and therapeutic techniques should be developed to provide the newborn with enhanced resistance to infectious diseases or to correct congenital defects. All new procedures should be thoroughly investigated and proved before being put into clinical practice.

Animals↗

How the magnitude of clinical severity and recurrence risk affects reproductive decisions in adult males with different forms of progressive muscular dystrophy.

The reproductive history of 177 male patients affected with Becker (BMD) (n=69), limb-girdle (LGMD) (n=54), and facioscapulohumeral (FSHMD) (n=54) muscular dystrophy (MD) was analysed according to severity of the disease (BMD>LGMD>FSHMD) and magnitude of recurrence risk (RR) (high for FSHMD, intermediate for BMD, and low for LGMD). Additionally, 62 male patients were interviewed on psychosocial issues, in order to disentangle the factors influencing reproductive decisions among patients affected with MD. Among male adults, significantly more FSHMD than LGMD or BMD patients were married and had children. Age specific reproductive outcome was 0.31-0.32 for BMD, 0.51-0.62 for LGMD, and 0.58-1.02 for FSHMD, reflecting the influence of the disease's severity. High RRs did not significantly diminish reproduction after genetic counselling or correlate with less prospective desire for children. Instead, early onset, severity of the disease, and past reproductive history were found to diminish reproductive outcome after genetic counselling, and prospective family planning was also found to be influenced by past reproductive history as well as by emotional/sexual dysfunction with the opposite sex.

Adult↗

Reproductive health needs of adolescent males in rural Pakistan: an exploratory study.

This is the first study done to explore reproductive health needs of adolescent males in Pakistan. The purpose of this exploratory study was to obtain qualitative information on existing knowledge and perceptions on puberty and reproductive health needs and to identify effective communication channels for imparting reproductive health education to adolescent males. Seventy-eight unmarried adolescent males participated in the survey, conducted through in-depth interviews by a semi-structured questionnaire using purposive sampling, in eight rural districts in Pakistan. The study pointed out that there existed misconceptions and gaps in knowledge regarding puberty and reproductive health. These young men also have poor knowledge about sexually transmitted diseases dynamics. The communication between parents or siblings on the said issues was found to be poor and they mainly get information from friends followed by the media. The majority showed interest in getting quality information. Multiple entry points and settings can be used to enhance access to information and services. In-school adolescents could be effectively approached through teachers and peer group. Out-of-school adolescents could be reached via media and local health care providers. The results imply that there is a dire need for reproductive health education for adolescent males and suggestions from this study might be utilized when initiating any reproductive health educational service for male adolescents in rural areas in Pakistan. Future efforts should thus focus on assuring access to timely, comprehensive and high-quality reproductive health education for all teenagers and reducing gaps in access related to gender and school attendance.

Adolescent↗

Major advances associated with reproduction in dairy cattle.

The purpose of this overview is to review some of the major advances in reproductive technologies, and how they may be applied to meet the challenge of enhancing reproductive efficiency in the high-producing dairy cow of the 21st century. The current population of high-producing dairy cows is considered to be subfertile, as characterized by low pregnancy rates and high rates of embryonic mortality. Coordinated systems of reproductive management have been developed based upon a thorough understanding of the endocrine, cellular, and molecular factors controlling ovarian and uterine function. These systems will partially restore herd reproductive performance. Advances in other reproductive technologies offer possibilities for wider use of superior germplasm. Technologies such as sexed semen, cloning, transgenesis, and preimplantation genetic diagnosis offer the potential to enhance the influence of superior animals on production of food for human consumption. However, at this time, additional research is needed to counteract the higher rates of embryonic and fetal mortality associated with some of these technologies. Furthermore, use of genomics, proteomics, and bioinformatics in the study of reproduction will undoubtedly provide investigators with a greater understanding of the limitations to efficient reproductive processes in the subfertile lactating dairy cow.

Animals↗

Use of prostaglandin F2 alpha as a postpartum reproductive management tool for lactating dairy cows.

This study compared three programs for reproductive management of the postpartum period for reproductive performance and net economic benefit within three dairy herds (n = 1624 cows). Cows on one program received PGF alpha injection at 25 to 32 d postpartum for reproductive therapy, and cows on a second program received additional PGF2 alpha at 39 to 46 d postpartum for synchronization of estrus. These programs were compared with a postpartum program of rectal palpation based on veterinary intervention. Survival analysis indicated that cows receiving PGF2 alpha for reproductive therapy and synchronization of estrus had an 11% higher rate of first AI and 10% higher rate of pregnancy than did cows receiving the rectal palpation. No differences existed between the cows receiving rectal palpation and those receiving the PGF2 alpha. Because overall conception rates and conception rates at first AI did not differ among programs, the improved reproductive performance of cows receiving PGF2 alpha for both therapy and synchronization may be attributed to greater synchronization of estrus, which resulted in improved estrus detection. A partial budget indicated that the PGF2 alpha programs were less expensive than the rectal palpation program. When PGF2 alpha was used for postpartum reproductive therapy and synchronization of estrus, reproductive performance and net economic benefit were increased compared with those of the other programs.

Animals↗

Assessing the burden of sexual and reproductive ill-health: questions regarding the use of disability-adjusted life years.

The use of the disability-adjusted life year (DALY) as the unit in which to calculate the burden of disease associated with reproductive ill-health has given rise to considerable debate. Criticisms include the failure to address the problem of missing and inadequate epidemiological data, inability to deal adequately with co-morbidities, and lack of transparency in the process of ascribing disability weights to sexual and reproductive health conditions. Many of these criticisms could be addressed within the current DALY framework and a number of suggestions to do so are made. These suggestions include: (1) developing an international research strategy to determine the incidence and prevalence of reproductive ill-health and diseases, including the risk of long-term complications; (2) undertaking a research strategy using case studies, population-based surveillance data and longitudinal studies to identify, evaluate and utilize more of the existing national data sources on sexual and reproductive health; (3) comprehensively mapping the natural history of sexual and reproductive health conditions--in males and in females--and their sequelae, whether physical or psychological; (4) developing valuation instruments that are adaptable for both chronic and acute health states, that reflect a range of severity for each health state and can be modified to reflect prognosis; (5) undertaking a full review of the DALY methodology to determine what changes may be made to reduce sources of methodological and gender bias. Despite the many criticisms of the DALY as a measurement unit, it represents a major conceptual advance since it permits the combination of life expectancy and levels of dysfunction into a single measure. Measuring reproductive ill-health by counting deaths alone is inadequate for a proper understanding of the dimensions of the problem because of the young age of many of the deaths associated with reproductive ill-health and the large component of years lived with disability from many of the associated conditions.

Cost of Illness↗

Zambia moves towards reproductive health.

Several events in Zambia this year have marked the development of an integrated approach to reproductive health. A team met in March to draw up a national safe motherhood policy, plus strategies and guidelines. These were completed by April and are being distributed for comments. Clinical guidelines for safe motherhood in health centers have also been developed. These aim to reduce mortality and morbidity among mothers and infants by helping health workers to provide quality care to women at every stage of pregnancy and delivery. A reproductive health workshop was held in Ngwerere in May to create awareness of the concept of reproductive health, identify reproductive health problems in the area, propose solutions and outline activities. The 75 participants included community health workers, community leaders, teachers, youth leaders, and community members, as well as health workers and policymakers. The workshop was conducted in the local language so that those present were able to participate fully. June 1997 saw the official launch of Zambia's new policy framework, guidelines and strategy on family planning within reproductive health. The country's Minister of Health, Dr. Katele Kalumba, said the family planning guidelines were a sign of the government's commitment to providing a basic health care package for all Zambians. To promote widespread discussion of the whole concept of reproductive health, local newspapers printed feature articles with the headline "Let's talk reproductive health." The articles raised a variety of sensitive issues that ranged from safe sex and adolescent sexuality to safe motherhood and HIV prevention. Plans are going ahead in Zambia for drawing up a national training curriculum for safe motherhood and family planning. The curriculum for health workers will cover both pre-service and in-service training.

Africa↗

Reproductive genetics, gender and the body: 'please doctor, may I have a normal baby?'.

This paper's purpose is to highlight key sociological issues, that come to light when 'the body' becomes a theoretical site in reproductive genetics. By positioning the body as a central feature in this analysis, the paper: (1) describes how a mechanistic view of the body continues to be privileged in this discourse and the effects of this view; (2) examines how reproductive limits are practised on the gendered body through a feminised regime of reproductive asceticism and the discourse on shame; and (3) explores the social effects and limitations of reproductive genetics in relation to disability as a cultural representation of impaired bodies. The central assumption concerning reproductive genetics are that it appears within surveillance medicine as a part of a disciplinary process in society's creation of a genetic moral order, that it is mobilised by experts for the management of reproductive bodies and that it constructs a limited view of the body. Thus, the way reproductive genetics operatives tends to hide the fact that what may appear as 'defective genes' is a result of a body's interaction not only with the environment but also gendered social practices valorised by difference as well as rigid definitions of health and illness. The research is from a 1995-96 European study of experts interviewed in four countries.

Attitude of Health Personnel↗

Multigeneration reproductive toxicity assessment of 60-Hz magnetic fields using a continuous breeding protocol in rats.

Male and female reproductive functions have been proposed as possibly sensitive targets for the biological effects of 60-Hz (power frequency) magnetic fields (MF). However, experimental data relevant to this hypothesized association are very limited. In the present study, the "reproductive assessment by continuous breeding" design was used to identify possible effects of MF exposure on reproductive performance, fetal development, and early postnatal growth in rats. Groups of age-matched Sprague-Dawley rats (40 breeding pairs/group) were exposed continuously (18.5 hr per day) to linearly polarized, transient-free 60-Hz MF at field strengths of 0 Gauss (G; sham control), 0.02 G, 2.0 G, or 10.0 G. An additional group of 40 breeding pairs received intermittent (1 hr on/1 hr off) exposure to 10.0 G fields. F0 breeding pairs were exposed to MF or sham fields for 1 week prior to mating, during a 14-week period of cohabitation, and during a 3-week holding period after cohabitation. The duration of the cohabitation period was selected to be sufficient for the delivery of five litters in the sham control group. Pups from the final F1 litter from each breeding pair were exposed to MF or sham fields until sexual maturity, were cohabitated in MF or sham fields for 7 days with nonsiblings from the same exposure group, and were held in the MF or sham fields for 22 days to permit delivery of F2 pups for evaluation. No evidence of exposure-related toxicity was identified in any rat in the F0, F1, or F2 generations. Fetal viability and body weights in all litters of groups exposed to MF were comparable to those of sham controls. No significant differences between sham controls and MF-exposed groups were seen in any measure of reproductive performance (litters/breeding pair, percent fertile pairs, latency to parturition, litter size, or sex ratio) in either the F0 or F1 generation. Exposure of Sprague-Dawley rats to 60-Hz MF strengths of up to 10.0 G either during their peak reproductive period (F0) or during gestation and throughout their life span (F1) has no biologically significant effects on reproductive performance. These results do not support the hypothesis that exposure to pure, linearly polarized 60-Hz MF is a significant reproductive or developmental toxicant.

Animals↗