Toxicological consequences of Aroclor 1254 ingestion by female rhesus (Macaca mulatta) monkeys and their nursing infants. Part 3: post-reproduction and pathological findings

A systematic evidence map for the evaluation of noncancer health effects and exposures to polychlorinated biphenyl mixtures

Assessing health outcomes associated with exposure to polychlorinated biphenyls (PCBs) is important given their persistent and ubiquitous nature. PCBs are classified as a Group 1 carcinogen, but the full range of potential noncancer health effects from exposure to PCBs has not been systematically summarized and evaluated. We used systematic review methods to identify and screen the literature using combined manual review and machine learning approaches. A protocol was developed that describes the literature search strategy and Populations, Exposures, Comparators, and Outcomes (PECO) criteria used to facilitate subsequent screening and categorization of literature into a systematic evidence map of PCB exposure and noncancer health endpoints across 15 organs/systems. A comprehensive literature search yielded 62,599 records. After electronic prioritization steps, 17,037 studies were manually screened at the title and abstract level. An additional 900 studies identified by experts or supplemental searches were also included. After full-text screening of 3889 references, 1586 studies met the PECO criteria. Relevant study details such as the endpoints assessed, exposure duration, and species were extracted into literature summary tables. This review compiles and organizes the human and mammalian studies from these tables into an evidence map for noncancer health endpoints and PCB mixture exposure to identify areas of robust research as well as areas of uncertainty that would benefit from future investigation. Summary data are available online as interactive visuals with downloadable metadata. Sufficient research is available to inform PCB hazard assessments for most organs/systems, but the amount of data to inform associations with specific endpoints differs. Furthermore, despite many years of research, sparse data exist for inhalation and dermal exposures, which are highly relevant human exposure routes. This evidence map provides a foundation for future systematic reviews and noncancer hazard assessments of PCB mixtures and for strategic planning of research to inform areas of greater uncertainty.

Intracellular toxicity exerted by PCBs and role of VBNC bacterial strains in biodegradation

Polychlorinated biphenyls (PCBs) are xenobiotic compounds that persists in the environment for long-term, though its productivity is banned. Abatement of the pollutants have become laborious due to it's recalcitrant nature in the environment leading to toxic effects in humans and other living beings. Biphenyl degrading bacteria co-metabolically degrade low chlorinated PCBs using the active metabolic pathway. bph operon possess different genetic arrangements in gram positive and gram negative bacteria. The binding ability of the genes and the active sites were determined by PCB docking studies. The active site of bphA gene with conserved amino acid residues determines the substrate specificity and biodegradability. Accumulation of toxic intermediates alters cellular behaviour, biomass production and downturn the metabolic activity. Several bacteria in the environment attain unculturable state which is viable and metabolically active but not cultivable (VBNC). Resuscitation-promoting factor (Rpf) and Rpf homologous protein retrieve the culturability of the so far uncultured bacteria. Recovery of this adaptive mechanism against various physical and chemical stressors make a headway in understanding the functionality of both environmental and medically important unculturable bacteria. Thus, this paper review about the general aspects of PCBs, cellular toxicity exerted by PCBs, role of unculturable bacterial strains in biodegradation, genes involved and degradation pathways. It is suggested to extrapolate the research findings on extracellular organic matters produced in culture supernatant of VBNC thus transforming VBNC to culturable state.

Dietary exposure to polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls of the French population: Results of the second French Total Diet Study

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) bioaccumulate through the food chain and are therefore of public health concern. Exposure to these compounds was assessed in the second French Total Diet Study (TDS). Food samples (n=583) were collected to be representative of the whole diet of the population, prepared as consumed, and analyzed. Contamination data were combined with national individual food consumption data. Mean exposure (95th percentile) to PCDD/F+DL-PCBs was assessed to be 0.57 (1.29) pg TEQ(WHO-98) (kg bw)(-1) d(-1) in the adult population and 0.89 (2.02) pg TEQ(WHO-98) (kg bw)(-1) d(-1) in the child and teenager population. Less than 4% of the population exceeded the health-based guidance value for PCDD/F+DL-PCBs. Mean exposure (95th percentile) to the six indicator PCBs (PCB 28, 52, 101, 138, 153, 180) was estimated at 2.71 (7.90) ng (kg bw)(-1) d(-1) in the adult population and 3.77 (11.7) ng (kg bw)(-1) d(-1) in the child and teenager population. Only 2.6% of the adults [CI(95%): 1.9; 3.3] and 6.5% of the children and teenagers [5.2; 7.8] exceeded the health-based guidance value for total PCBs. These results show that the contamination levels in food and therefore the exposure of the general French population to PCDD/Fs and PCBs have declined (by a factor of 3.2 for PCDD/F+DL-PCBs and about three for total PCBs) since the last evaluation, which was conducted using another methodology in 2005 and 2007, and show the efficiency of the European risk management measures which came into force after these evaluations.

Environmental pollutant Aroclor 1242 (PCB) disrupts reproduction in adult male rhesus monkeys (Macaca mulatta)

Adult male rhesus monkeys (Macaca mulatta) were given oral treatment of either Aroclor 1242 or vehicle (corn oil and glycerol) at a dose of 200 microg/kg body wt/day for 6 months to investigate the effects of the pollutant on plasma testosterone and the morphology of testes and accessory glands. Aroclor 1242 treatment significantly decreased testicular size and testosterone levels in plasma and adversely affected spermatogenic activity by disrupting epithelial organization. All components of the germinal epithelium were greatly reduced. The spermatogonia were either hypertrophied or had shrunken vesiculated cytoplasm with distorted mitochondria and nuclear pyknosis. Changes were milder in the Sertoli cells, where nuclear infoldings were reduced. Characteristic features of treated Leydig cells were the presence of electron-dense and electron-opaque zones, appearing as plaques, cell membrane abnormalities, and high variability in nuclear shape and heterochromatin distribution. All the Aroclor 1242-treated accessory glands contained more connective tissue than their vehicle-treated counterparts. The epithelium contained many layers of irregularly shaped necrotic cells possessing stereocilia in the epididymides, either hypochromic and hypertrophied or hyperchromic and hypotrophied cells in the prostate and shrunken cuboidal cells with elongated nuclei in the seminal vesicles. In conclusion, Aroclor 1242 treatment causes severe structural alterations on gonads and accessory organs in adult male rhesus monkeys, and these effects could be mediated through both estrogen and Ah receptors.

The mammalian testis accumulates lower levels of organochlorine chemicals compared with other tissues

Tissues were obtained from three separate experiments in order to quantify the tissue distribution of organochlorine chemicals that are thought to be potential reproductive toxicants in males: 1) Sprague Dawley rats received 1 microCi of 14C-Aldrin or 14C-Dieldrin (20.6 microCi/micromole) i.p. once a week for three weeks. One week and four weeks after the last injection, tissues were harvested and stored at -80 degrees C. Tissue 14C levels were quantified by scintillation spectrometry. 2) Cis- or trans-nonachlor (0, 0.25, 2.5, 25 mg/kg body weight) were administered daily in corn oil to male rats by gavage for 28 days. Tissues were harvested and frozen at -80 degrees C on the 29th day. Organochlorine residues were extracted and quantified by gas chromatography with electron capture detection. 3) Technical grade toxaphene (0, 0.1, 0.4 or 0.8 mg/kg body weight) was ingested daily by female cynomolgus monkeys of reproductive age for 18 months prior to being mated with control males. Dosing continued during pregnancy and lactation. Their infants received toxaphene via breast milk, and upon weaning, they ingested the same dose as their mothers for 48 to 49 weeks until, at 77 to 80 weeks of age, tissues were harvested and stored at -80 degrees C. Organochlorine residues were extracted and quantified as previously stated. In all three experiments, organochlorine residues in the testis were lower than in most of the other reproductive tract and nonreproductive tract tissues we examined. For example, testicular aldrin and dieldrin levels were <5% the epididymal content; testicular cis- and trans-nonachlor were <25% the epididymal content and, testicular toxaphene levels were <15% of the epididymal content. The reasons for the low degree of accumulation by the testis in comparison with other tissues are unknown. However, the lower testicular content may afford germ cells some protection from the potentially toxic effects of these chemicals.

Tampons, dioxins, and endometriosis

Concern has been expressed that rayon tampons contain dioxins as a result of chlorine bleaching and, further, that the dioxins in tampons may increase the risk of endometriosis. Rayon tampons do not contain 2,3,7,8-tetrachlorodibenzo-p-dioxin, the chemical commonly meant when the generic term "dioxin" is used. In addition, rayon tampons contain only trivial amounts of dioxin-like environmental contaminants, similar to the amounts contained in unbleached cotton tampons. The amount of dioxin-like material that is theoretically available from tampons is at least six orders of magnitude lower than estimated daily food exposure levels to these contaminants. The evidence for a causal relationship between environmental exposure to dioxins and endometriosis is inconsistent. Prediction of the effective dioxin dose based on the most suggestive of the primate studies on endometriosis does not raise concerns about typical human food exposures to these compounds, let alone the considerably lower levels that could be present in tampons.

Effects of polychlorinated biphenyls on development and reproduction

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article, which constitutes the release of an important section of the Toxicological Profile for Polychlorinated Biphenyls (ATSDR 2000) into the scientific literature, focuses on the developmental and reproductive effects of this group of synthetic organic chemicals (PCBs) in humans and animals. Information on other health effects, toxicokinetics, mechanisms of toxicity, biomarkers, interactions, chemical and physical properties, potential for human exposure, and regulations and advisories is detailed in the profile. Interested readers are encouraged to consult the original toxicological profile for more information. Profiles can be requested from ATSDR's Information Center by telephone (1-888-42-ATSDR [1-888-422-8737] or E-mail: (atsdric@cdc.gov).

Consequences of Aroclor 1254 ingestion on the menstrual cycle of rhesus (Macaca mulatta) monkeys

A group of 80 female rhesus (Macaca mulatta) monkeys were randomly distributed to four similar test rooms (20 monkeys/room) and then randomly allocated to one of five test groups (four females/test group/room). The objective of the study was to ascertain the toxicological and reproductive effects of Aroclor 1254 ingestion at dose levels of 0, 5, 20, 40 or 80 microg Aroclor 1254/kg body weight per day (Arnold et al., 1993a,b, 1995, 1996, 1997). It was deemed necessary to establish the menstrual patterns for all the monkeys both before and after the start of dosing so as to provide an appropriate baseline from which potential treatment effects could be ascertained. The data presented herein were obtained during the first 3 years after the start of dosing, or the study's pre-mating phase. At the end of the first 2 years of dosing, the monkeys attained a qualitative pharmacokinetic steady state regarding the levels of polychlorinated biphenyls in their adipose tissue. Upon termination of the study, a number of monkeys were found to have endometriosis, adenomyosis or uterine leiomyomas (Arnold et al., 1996, 1997). These monkeys were designated as having gynecological abnormalities which were considered to be a factor in the analysis of the menstrual data. The menstrual data (i.e. menses frequency, cycle length and menses duration) were subjected to a statistical assessment to see whether year, quarter, gynecological abnormalities or dose of Aroclor 1254 had any effect on menses frequency, menstrual cycle length (i.e. the first day of menses until the day prior to the start of the next menses) and/or menses duration (i.e. the number of days of haemorrhagic discharge). The only consistent statistically significant effect found was that gynecological abnormalities increased menses duration (P<0.05) in all 12 quarters of the premating observation period. This effect was significant during both the pre- (P=0.0004) and post- (P< or =0.0001) pharmacokinetic steady-state intervals. While there was some indication of seasonality regarding menstrual cycle length and menses duration when these data were compared on a quarterly basis during the first 2 years of the study (P=0.043; P< or =0.0001, respectively), this effect was not evident during the third year (P=0.21; P=0.31, respectively). In particular, the effect of quarter on menses cycle length was most evident during the first year, with the shortest cycles occurring during the first or spring quarter and the longest in the third or fall quarter. However, menses duration was shortest in the first quarter during the first 2 years and tended to peak in the second quarter of all 3 years, while generally diminishing in the third and fourth quarters. There was also an increase in menses duration with increasing time on test for all groups. In addition, Aroclor 1254 treatment appeared to have some effect on menses duration when menses duration was plotted against dose group, but the effect was not statistically significant (P>0. 05). It was concluded that the ingestion of Aroclor 1254 at dose levels up to 80 microg/kg body weight/day by rhesus monkeys did not have any appreciable biological effect on menstrual frequency, menstrual cycle length or menses duration. However, gynecological abnormalities significantly increased menses duration during the three-year observation period.

Toxicological consequences of feeding PCB congeners to infant rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys

In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).