Adverse Effects of 2,2′,4,4′-Tetrabromodiphenyl Ether on Semen Quality and Spermatogenesis in Male Mice

2,2′,4,4′-Tetrabromodiphenyl ether (BDE47) is an environmental contaminant. To determine the reproductive toxicity, we studied groups of adult male mice and found that the rate of sperm capacitation was decreased significantly in three BDE47-exposed groups (0.0015, 0.045 and 30 mg kg^?1 day^?1). Sperm motility parameters (MOT, PRO, VCL and BCF) after capacitation were also declined in treated groups. Moreover, exposure to BDE47 at concentrations of ≥0.045 mg kg^?1 day^?1 caused increased germ cell loss and apoptosis in some seminiferous tubules. Our results suggest that short-term exposure to low-dose BDE47 may have adverse effects on semen quality and spermatogenesis in adult male mice.     

Toxicity of 3,4,5,3′,4′,5′-hexachlorobiphenyl to mink

Diets supplemented with 0.01 or 0.05 ppm (mg/kg) of 3,4,5,3,4,5-hexachlorobiphenyl (345-HCB) were fed to mink to investigate the toxicological manifestations of this toxic polychlorinated biphenyl congener in a sensitive species. Dietary exposure of mink to 0.05 ppm 3,4,5,3,4,5-hexachlorobiphenyl for 135 days resulted in 50% mortality while no deaths occurred on 0.01 ppm 345-HCB. Clinical signs of toxicity included anorexia, bloody stools, disrupted molting patterns, and thickened, elongated and deformed nails. Ascites and gastric ulcers were present in animals that died. Statistically significant increases in liver, kidney, and adrenal gland weights were found in the 345-HCB-treated mink. Decreases in total and free triiodothyronine concentrations were observed in mink fed the 345-HCB-treated diets and total thyroxine was decreased in the mink fed 0.05 ppm 345-HCB. No consistent histopathologic lesions were found in the thyroid or adrenal glands of the 345-HCB-treated mink, nor were there any statistically significant differences between the 345-HCB-treated and the control mink in serum epidermal growth factor levels, plasma 17-estradiol and progesterone concentrations, hepatic aminopyrine N-demethylase, and benzo()pyrene hydroxylase activities, hypothalamic norepinephrine, dopamine, and serotonin concentrations or in the incorporation of (³H) thymidine by concanavalin-A-stimulated lymphocytes.Published with the approval of the Michigan Agricultural Experiment Station as Journal Article Number11963.     

Cyclic 3′, 5′-adenosine monophosphate and cyclic 3′, 5′-guanosine monophosphate metabolism in malnutrition

When the concentration and turnover of the cyclic nucleotides cyclic 3′, 5′-adenosine monophosphate (cAMP) and cyclic 3′,5′-guanosine monophosphate (cGMP) were measured in the thymus, spleen and cervical lymphnodes of xats subjected to various models of malnutrition, and these same parameters of cAMP alone assessed in their liver, kidney and brain, undernutrition has been found to modify cyclic nucleotide metabolism. When the results on nucleic acid and protein metabolism are taken into consideration with the changes in cyclic nucleotide metabolism, it was noted that the various phases of the cell cycle are prolonged or blocked in the organs of malnourished rats. These data indicate a correlation between cyclic nucleotide metabolism and impaired immune responsiveness seen commonly in undernourished rats.     

Distribution Patterns of Hexachlorocyclohexanes and Other Organochlorine Compounds in Muscles of Fish from a Japanese Remote Lake During 2002–2003

No abstract available.     

Global Gene Expression Analysis in the Livers of Rat Offspring Perinatally Exposed to Low Doses of 2,2′,4,4′-Tetrabromodiphenyl Ether

Background

Polybrominated diphenyl ethers are a group of flame-retardant chemicals appearing increasingly in the environment. Their health effects and mechanisms of toxicity are poorly understood.

Objectives

We screened for the sensitive effects and mechanisms of toxicity of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by analyzing the gene expression profile in rats exposed to doses comparable to human exposure.

Methods

Wistar dams were exposed to vehicle or BDE-47 (0.002 and 0.2 mg/kg body weight) every fifth day from gestation day 15 to postnatal day 20 by injections to caudal vein. Total RNA was extracted from the livers of pups and hybridized to the whole-genome RNA expression microarrays. The list of genes 2-fold differentially expressed was exported to PANTHER and Ingenuity Systems for analysis of enriched ontology groups and molecular pathways.

Results

Oxidoreductase and transferase protein families were enriched in exposed rats as were these biological process categories: carbohydrate metabolism; electron transport; and lipid, fatty acid, and steroid metabolism. Four signaling pathways (cascades of activation of drug-metabolizing enzymes) and 10 metabolic pathways were significantly enriched. Drug-metabolizing enzymes appear to be regulated by BDE-47 through an aryl hydrocarbon receptor–independent mechanism. Direct interaction with retinoid X receptor or its upstream cascade may be involved. The main metabolic effects consisted of activation of metabolic pathways: α- and ω-oxidation of fatty acids, glycolysis, and starch hydrolysis.

Conclusions

Altered expression of genes involved in metabolic and signaling pathways and functions of the organism occurs after perinatal exposure of rat offspring to BDE-47 at doses relevant for the general population.     

Embryotoxicity of 3,3′,4,4′-tetrachloroazobenzene and 3,3′,4,4′-tetrachioroazoxybenzene in the chick embryo

The toxicity of 3,3,4,4-tetrachloroazobenzene (TCAB) and 3,3,4,4-tetrachloroazoxybenzene (TCAOB) to chick embryos was examined. TCAB or TCAOB was dissolved in corn oil and injected into the air cell of fertile chicken eggs. The time of injection had a major effect on embryo mortality as eggs injected with TCAB or TCAOB on the fourth day of incubation had a higher incidence of embryo mortality than eggs injected on days 11–13. Both TCAB and TCAOB were more toxic than all other chemicals that have been tested in the chick embryo with the exception of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Comparing the potency of the two compounds, TCAOB was more potent than TCAB in the chick embryo with an estimated LD₅₀ of 12 ng and 44 ng respectively. Rump edema was the major abnormality observed in embryos treated with either TCAB or TCAOB. Other malformations included altered feather pattern and lack of down, hemorrhage, external viscera, reduced body size, failure to withdraw the yolk sac, beak malformation, dilation of blood vessels, and monomicropthalmia. The results of this investigation suggest that both TCAB and TCAOB are teratogenic in the chick embryo.This work was presented in part at the Annual Meeting of the Society of Toxicology, San Diego, CA, March 1–5, 1981.     

Persistent Organochlorine Pesticide Residues in Fish from Guanting Reservoir, People’s Republic of China

No abstract available.     

From a global crisis to the ‘end of AIDS’: New epidemics of signification

In the past decade, discourses about AIDS have taken a remarkable, and largely unquestioned, turn. Whereas mobilisations for treatment scale-up during the 2000s were premised on perceptions of an ‘epidemic out of control’, we have repeatedly been informed in more recent years that an end to AIDS is immanent. This new discourse and its resulting policies are motivated by post-recession financial pressures, a changing field of global institutions, and shifting health and development priorities. These shifts also reflect a biomedical triumphalism in HIV prevention and treatment, whereby shorter term, privatised, technological, and ‘cost-effective’ interventions are promoted over long-term support for antiretroviral treatment. To explore these changes, we utilise Treichler’s [(1987). How to have theory in an epidemic: Cultural chronicles of AIDS. Durham, NC: Duke University Press] view of AIDS as an ‘epidemic of signification’ to develop a review of ‘End of AIDS’ discourses in recent years. We use this review to investigate the political and philanthropic interests served by efforts to rebrand and re-signify the epidemic. We also hold up these discourses against the realities of treatment access in resource-poor countries, where ‘Ending AIDS’ has not heralded the end of an epidemic per se, but rather the end of external support for treatment programmes, highlighting new difficulties for sustaining treatment in this new era of the epidemic.     

Tissue Distribution of Methylsulfonyl Metabolites Derived from 2,2′,4,5,5′-Penta- and 2,2′,3,4′,5′,6-Hexachlorobiphenyls in Rats

The time courses of fecal excretion and tissue distribution of metabolites derived from 2,2′,4,5,5′-pentachlorobiphenyl (CB101) and 2,2′,3,4′,5′,6-hexachlorobiphenyl (CB149) were investigated in male Wistar rats. The metabolism of both congeners involved primarily hydroxylation at the 3-position, and methylthiolation at the 4-position. Metabolites distributed in tissue were dominated by different ratios of 3- and 4-methylsulfonyl (MeSO₂) metabolites. The 3-/4-MeSO₂ metabolite ratios in liver and adipose tissue for both congeners were 0.41–0.61 at day 4, and then increased to 0.85–1.00 for up to day 42. In contrast, the ratios in lung were 0.03–0.04, and then decreased to 0.01. Compared to the unchanged PCBs at day 42, the distribution ratios of 3-MeSO₂ metabolites were greater in the order of liver (0.46 for CB101 and 0.21 for CB149) > kidney > blood > lung > adipose tissue, whereas those of 4-MeSO₂ metabolites were in the order of lung (9.50 for CB101 and 4.00 for CB149) > kidney > blood > liver > adipose tissue, indicating the different binding affinity of 3-MeSO₂ metabolites in liver from that of 4-MeSO₂ metabolites in lungs of rats. Furthermore, the structure-tissue affinity relationship for 3-MeSO₂ metabolites was investigated, following the administration of 11 3-MeSO₂-PCB congeners to rats. The results indicated that the retention potential of 3-MeSO₂ metabolites in the liver largely depends on the ortho-chlorine substitution in the biphenyl ring rather than the degree of chlorination. Received: 17 July 1998/Accepted: 11 January 1999     

Tissue Distribution Kinetics of 2,2′,4,4′,5,5′-Hexachlorobiphenyl in Ringdoves After Oral Dosing

Ring doves were provided contaminated food spiked with [¹³C]-2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) over a period of 63 days. Animals were sacrificed after 0.33, 0.5, 1, 2, 4, 8, 18, 36 and 63 days following access to contaminated food. At each time point, chemical concentrations in blood, liver, brain, gonad, adipose and remaining whole carcass was determined. Whole body concentrations of PCB 153 increased linearly with time over the experiment indicating that the birds did not reach steady state with their food after 63 days. Tissue/plasma concentration ratios were plotted as a function of time to determine time to inter-tissue steady state for fast and slowly perfused tissues. Liver, brain and gonad achieved steady state concentrations with plasma in less than 3 days, whereas fat and carcass tissues required 9.7 and 11.5 days, respectively. The results indicate that inter-tissue distribution kinetics for PCBs in birds is relatively rapid and completed within a little over a week following exposure to a contaminated diet.     

Toxicities of 2,2′,4,4′- and 3,3′,4,4′-tetrachlorobiphenyls to house flies at different ages and enzyme levels

Two tetrachlorobiphenyls (2,2,4,4-tetraCB and 3,3,4,4-tetraCB) had different effects on the longevity of adult female house flies (Musca domestica), depending on enzyme levels at dosing. Twenty-four-hour acute toxicities of the two tetrachlorobiphenyls were also compared with one trichlorobiphenyl (2,2,5-triCB) at different enzyme levels. 2,2,4,4-tetraCB killed more than 90% of the flies within 12 h at the highest dose (1,667 ppm, g/g); however, the toxicity of the moderate dose (1,250 ppm) was age-dependent and greater in 1- and 15-day-old flies and lower in 5-day-old flies. Daily mortality patterns of the lower doses (390 and 833 ppm) were similar to the control. LT₅₀s (time for 50% death) were also different in different age groups at the moderate dose. The toxicity of 3,3,4,4-tetraCB was similar to the control in all age groups, with a slight increase in the early mortalities and a decrease in the LT₅₀s at the highest (1,200 ppm) dose.The twenty-four-hour lethality of 2,2,4,4-tetraCB was very high, even at the lower doses in 1- and 15-day-old flies. Lower doses were least toxic at day 5, when the levels of cytochrome P₄₅₀ enzymes were at the highest. On the other hand, the acute toxicity of 2,2,5-triCB increased from 5 and 15% in 1- and 15-day-old flies, respectively, to about 50% in 5-day-old flies, suggesting bioactivation of 2,2,5-triCB. The acute toxicity of 3,3,4,4-tetraCB was negligible in all ages of house flies.     

Biological Activity and Physicochemical Parameters of Marine Halogenated Natural Products 2,3,3′,4,4′,5,5′-Heptachloro-1′-Methyl-1,2′-Bipyrrole and2,4,6-Tribromoanisole

Physicochemical parameters (vapor pressure, water solubility, Henrys law constant) and biological activities of two halogenated natural products frequently detected in marine samples and food were determined. Synthetic 2,3,3,4,4,5,5-heptachloro-1-methyl-1,2-bipyrrole (Q1) and 2,4,6-tribromoanisole (TBA) were available in pure form. The physicochemical parameters were in the range of anthropogenic chlorinated compounds of concern. The aqueous solubilities at 25°C (S_w,25) of Q1 and TBA were 4.6 g/L and 12,200 g/L, respectively, whereas subcooled liquid vapor pressures were 0.00168 Pa (Q1) and 0.06562 Pa (TBA) as measured by the gas chromatographic–retention time technique. Q1 was negative by established test systems for the determination of ethoxyresorufin-O-deethylase (EROD) induction and by sulforhodamine B assay. EROD induction potency was at least 10^–7 times lower than that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). At a relatively high concentration (20 M), Q1 inhibited specific binding of 2 nM [³H]TCDD to the in vitro-expressed human aryl hydrocarbon receptor (AHR) by 18%; lower concentrations showed no effect. Molecular modeling showed that Q1 is nonplanar, consistent with its relatively modest affinity as an AHR ligand. When tested for cell-growth inhibitory/cytocidal activity in human tumor cells, Q1 was only marginally, if at all, active with an IC₅₀ value >50 M compared with five to ten times lower IC₅₀ values for potent cytotoxins tested in the test system used. Furthermore, standard pesticide tests on insecticidal, herbicidal, and fungicidal activity did not provide any significant activity at highest concentrations. For TBA, the results in all tests were comparable with Q1. The SRB assay was also applied to the halogenated natural product 4,6-dibromo-2-(2,4-dibromo)phenoxyanisole, but no toxic response was found. Although it was apparent that Q1 and TBA had been proven to have relatively low biological activity in all tests performed, further research is necessary to clarify whether metabolites of the compounds eventually may possess a risk to humans or other living organisms. Nevertheless, the role of Q1 in nature remains uncertain.     

Building a Consensus on Community Health Workers’ Scope of Practice: Lessons From New York

Objectives. We evaluated efforts in New York to build a consensus between community health workers (CHWs) and employers on CHWs’ scope of practice, training standards, and certification procedures.Methods. We conducted multiple-choice surveys in 2008 and 2010 with 226 CHWs and 44 employers. We compared CHWs’ and employers’ recommendations regarding 28 scope of practice elements. The participatory ranking method was used to identify consensus scope of practice recommendations.Results. There was consensus on 5 scope of practice elements: outreach and community organizing, case management and care coordination, home visits, health education and coaching, and system navigation. For each element, 3 to 4 essential skills were identified, giving a total of 27 skills. These included all skills recommended in national CHW studies, along with 3 unique to New York: computer skills, participatory research methods, and time management.Conclusions. CHWs and employers in New York were in consensus on CHWs’ scope of practice on virtually all of the detailed core competency skills. The CHW scope of practice recommendations of these groups can help other states refine their scope of practice elements.Under the Affordable Care Act (Pub L No. 111-148), the landmark health care reform legislation signed into law by President Obama, millions of Americans will have access to quality, affordable health care. However, cultural, language, or other vulnerabilities can prevent millions of people from benefiting from this care. Community health workers (CHWs) are in a unique position to help. CHWs can break down barriers so that people can receive the health care services they need, and they can assist them in benefiting fully from those services.1 A growing number of studies have shown that CHWs can help ensure equitable access to care, decrease health care costs, and improve outcomes, including self-management of chronic diseases such as asthma or diabetes.1–13 The valuable role CHWs can play is clear, and many groups are now working to outline the details of their roles across a spectrum of conditions and communities.In addition to the critical questions of how and for whom CHWs can most effectively provide these services, attention needs to be paid to ensuring that the CHW workforce is structured to respond to this demand. Surveys of the CHW workforce have concluded that although there may be as many as 120 000 CHWs in the United States today,14 there are no national standards defining what a CHW does as a member of the health care team or what criteria might be used to qualify CHWs for reimbursement through sustainable funding such as Medicaid. National organizations such as the American Association of Community Health Workers and the American Public Health Association (APHA) have been working to support the development of CHW workforce standards,15 and the Bureau of Labor Statistics has established a standard occupational code for CHWs.16 The APHA CHW Section’s definition of a CHW is increasingly recognized as the nationally accepted definition:

Community Health Worker (CHWs) are frontline public health workers who are trusted members of and/or have an unusually close understanding of the community served. This trusting relationship enables CHWs to serve as a liaison/link/intermediary between health/social services and the community to facilitate access to services and improve the quality and cultural competence of service delivery. CHWs also build individual and community capacity by increasing health knowledge and self-sufficiency through a range of activities such as outreach, community education, informal counseling, social support, and advocacy.15

Setting workforce standards begins with the establishment of a scope of practice, the roles and tasks performed by practitioners, along with the usual education and competencies required for that practice. In 1998 the National Community Health Advisor Study (NCHAS), a milestone review of CHW roles and activities, listed 7 basic roles, 8 core skills or competencies, and 7 additional qualities supporting accomplishment of these CHW roles17; however, these elements need to be reviewed and tailored as appropriate to ensure that they capture context-specific roles. Establishment of a scope of practice for credentialing is a state responsibility, and 17 states are now in the process of establishing standards for CHWs.1,18,19As is the case with members of any other profession establishing standards for itself, CHWs should lead in identifying appropriate scope of practice roles, and this is the approach that has been adopted in New York.1 In 2005, the Mailman School of Public Health and the CHW Network of NYC began an academic–community partnership to elicit CHWs’ views on establishing practice and training standards. We learned that although CHWs felt they were recruited for qualities such as dedication to the community and trust, often employers valued a wholly different skill set that included informal counseling, teaching, and promotion of behavior change. CHWs saw themselves in terms of “who” they were in the community, whereas employers viewed them according to “what” they could do.20 We concluded that if there is to be agreement on scope of practice, it is critical that each group, CHWs and their employers, agree on both the “who” and “what” questions.To develop a consensus scope of practice, we set out to determine CHWs’ perceptions of the most appropriate set of roles and skills for their profession, as well as potential employers’ perceptions of those roles and skills. We used a community-based participatory research approach to simultaneously obtain input from CHWs and employers on these topics that could be used in achieving a consensus, and here we report on the recommendations derived from this multiyear process.     

Short-Term Distribution, Metabolism, and Excretion of 2,2′,5-Tri-, 2,2′,4,4′-Tetra-, and 3,3′,4,4′-Tetrachlorobiphenyls in Prepubertal Rats

The excretion and tissue retention of three ¹⁴C-labeled lower chlorinated biphenyls were examined in prepubertal male and female Sprague-Dawley rats following IV administration. Urine and feces were collected individually at different time intervals up to 72 h for pharmacokinetic analyses. After 72 h, different organs were removed and extracted in acetone:hexane (1:1, v/v) to determine radioactivity. Within the first 10 h after dosing, 2,2′,5-trichlorobiphenyl (PCB 18) was rapidly excreted in urine (8–18% of the administered dose), whereas only 0.6–0.8% of 2,2′,4,4′-tetrachlorobiphenyl (PCB 47) and 0.3–0.8% 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) were found in urine during this time period. The half-life of elimination was shortest for PCB 18 (37.5 to 49.2 h). The half-lives for PCB 47 and PCB 77 were 351 to 672 h and 152 to 186 h, respectively. The cumulative total excretion (urinary + fecal) of PCB 18 within 72 h was 51–62%, of PCB 77 was 22–25%, and of PCB 47 was 7–10%. No parent PCBs were detected in urine. PCB 47 accumulated preferentially in adipose tissues (subcutaneous fat > mesenteric fat); relatively high levels of PCB 47 were also found in adrenals, ovaries, lungs, liver, and skin. The highest concentration of PCB 77 was found in serum, followed by adipose tissues. Very low concentrations of PCB 18 were found in most tissues; the highest being found in serum, followed by ovaries and adrenal glands. This study suggests that prepubertal rats retain higher short-term serum levels and have lower excretion rates than adult rats. Received: 3 February 1998/Accepted: 16 August 1998     

Trans-3′-hydroxycotinine as a main metabolite in urine of smokers

Summary Nine mal smokers smoked three types of cigarettes that differed in mainstream nicotine. The experiment was carried out in three runs, each consisting of 7 d when smoking was allowed and 5 d when it was not allowed. Urine fractions were collected throughout the whole period of the experiments. As assumed, nicotine and four of its known metabolites, i.e., cotinine, nicotine-N-oxide, nornicotine, and N-methyl-nicotinum ions were found in the urine. In addition, trans-3- hydroxycotinine was determined. The amount of this metabolite was well in excess of those of nicotine and cotinine in the urine. The serum concentration trans-3-hydroxycotinine was found to be second to serum cotinine.     

Alternative Sources of Omega-3 Fats: Can We Find a Sustainable Substitute for Fish?

Increasing demand for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) containing fish oils is putting pressure on fish species and numbers. Fisheries provide fish for human consumption, supplement production and fish feeds and are currently supplying fish at a maximum historical rate, suggesting mass-scale fishing is no longer sustainable. However, the health properties of EPA and DHA long-chain (LC) omega-3 polyunsaturated fatty acids (PUFA) demonstrate the necessity for these oils in our diets. EPA and DHA from fish oils show favourable effects in inflammatory bowel disease, some cancers and cardiovascular complications. The high prevalence of these diseases worldwide indicates the requirement for alternative sources of LC-PUFA. Strategies have included plant-based fish diets, although this may compromise the health benefits associated with fish oils. Alternatively, stearidonic acid, the product of α-linolenic acid desaturation, may act as an EPA-enhancing fatty acid. Additionally, algae oils may be a promising omega-3 PUFA source for the future. Algae are beneficial for multiple industries, offering a source of biodiesel and livestock feeds. However, further research is required to develop efficient and sustainable LC-PUFA production from algae. This paper summarises the recent research for developing prospective substitutes for omega-3 PUFA and the current limitations that are faced.     

Enantiomeric Enrichment of 2,2′,3,3′,6,6′-Hexachlorobiphenyl (PCB 136) in Mice After Induction of CYP Enzymes

Several PCB congeners, present in commercial PCB formulations, are chiral. These PCBs can undergo enantiomeric enrichment in many animal species and in humans due to currently uncharacterized enantioselective biotransformation processes. To investigate if certain cytochrome P-450 enzymes (CYPs), such as CYP2B’s, are responsible for this enantiomeric enrichment, we investigated the enantioselective disposition of (±)-PCB 136 in female mice after induction of different CYP enzymes by pretreatment with corn oil alone, β-naphthoflavone (CYP1A’s), phenobarbital (CYP2B’s), or dexamethasone (2B’s and 3A’s), followed by oral PCB administration. PCB 136 levels were significantly lower in phenobarbital- and, to a lesser extent, in dexamethasone-pretreated animals, presumably due to the induction of PCB 136 metabolizing enzymes. Although (+)-PCB 136 was enriched in all tissues, none of the pretreatments altered the enantioselective disposition of PCB 136 in a manner that suggests a particular CYP subfamily as the cause of the enrichment of (+)-PCB 136. Fecal PCB levels and enantiomeric fraction values changed over time in a manner consistent with slower digestive motility in the mice pretreated with phenobarbital and dexamethasone. Overall, this study does not support the hypothesis that metabolism by CYP2B enzymes is responsible for the enrichment of (+)-PCB 136 in mice.     

Influence of Fishing Technique on Organochlorine Pesticide Accumulation in Fish and its Possible Human Health Risk in the Republic of Bénin

In Bénin different techniques are used for large-scale commercial fishing, Acadjas (enclosures constructed in the river) and Whédos (holes made in the river banks). This study aimed at assessing the extent of contamination related to these fishing techniques. Fish contained residues of DDT and its metabolites, α-endosulfan, dieldrin, aldrin, endrin and lindane. Pesticide levels were similar in fish from Acadjas and Whédos, except for higher α-endosulfan levels in fish from the Whédos. Comparing pesticide intake levels through fish consumption with tolerable daily intake levels showed that in all cases risk for human health is low.     

Chronic toxicity and bioaccumulation of 2,5,2′,5′- and 3,4,3′,4′-tetrachlorobiphenyl and Aroclor® 1242 in the amphipodHyalella azteca

The addition of 100 (g/L of Aroclor^® 1242 (A1242) or 2,5,2,5-tetrachlorobiphenyl (TeCB) during 10 week chronic toxicity tests withHyalella azteca resulted in complete mortality. There were no effects on survival, growth, or reproduction after addition of 30 g/L. Toxic effects were observed at tissue levels of between 30 and 180 g/g on a wet weight basis, and tissue levels appear to be a better indicator of toxicity than levels in water. No toxic effects were observed after additions of up to 2,700 g/L of the coplanar congener 3,4,3,4-TeCB.H. azteca has the ability to avoid accumulating in excess of 140 g/g 3,4,3,4-TeCB. The amount taken up was proportional to the amount added in water up to 100 g/L, but was constant at higher additions, possibly accounting for its relatively low toxicity. The low toxicity of the coplanar congener, as compared to the non-coplanar 2,5,2,5-TeCB, is in direct contrast to the high toxicity of coplanar PCB congeners to mammals and may be associated with slower rates of aromatic hydrocarbon metabolism in amphipods. Polychlorinated biphenyl levels measured in amphipods from Lake Ontario are approximately 100-fold below levels associated with toxicity inH. azteca, but are above levels which, through biomagnification up the food chain, lead to salmonid residues in excess of 2 g/g, a tolerance limit for human consumption.