Inorganic arsenic in food products on the Swedish market and a risk-based intake assessment.

Inorganic arsenic (iAs) and total arsenic (tAs) were determined in common food from the Swedish market. Special focus was on rice, fish and shellfish products. For the speciation of iAs the European standard EN:16802 based on anion exchange chromatography coupled to ICP-MS was used. The two market basket food groups cereals (including rice), and sweets and condiments (a mixed group of sugar, sweets, tomato ketchup and dressings), contained the highest iAs levels (means 9 and 7 µg iAs/kg), whereas other food groups, including fish, did not exceed 2 µg iAs/kg. Varying levels of iAs were found in separate samples of tomato ketchup, 2.4-26 µg/kg, and is suggested to be one reason of the rather high average level of iAs in the food group sweets and condiments. Some specific food products revealed iAs levels much higher, i.e. rice crackers 152 and Norway lobster 89 µg iAs/kg. The intake of iAs via food was estimated by data from two national consumption surveys, performed in 2010-11 (1797 adults) and 2003 (2259 children). The estimated median iAs intakes in adults and children were 0.047 and 0.095 µg/kg body weight and day, respectively. The iAs intake for rice eaters was about 1.4 times higher than for non-rice eaters. Validation of the consumption survey-based iAs intake, using food purchase and market basket data mainly from 2015, resulted in a per capita intake of a similar magnitude, i.e. 0.056 µg/kg body weight and day. The estimated cancer risk for adults using low-dose linear extrapolation is <1 per 100,000 per year.

Comparisons of polybrominated diphenyl ether and hexabromocyclododecane concentrations in dust collected with two sampling methods and matched breast milk samples.

UNLABELLED: Household dust from 19 Swedish homes was collected using two different sampling methods: from the occupant's own home vacuum cleaner after insertion of a new bag and using a researcher-collected method where settled house dust was collected from surfaces above floor level. The samples were analyzed for 16 polybrominated diphenyl ether (PBDE) congeners and total hexabromocyclododecane (HBCD). Significant correlations (r = 0.60-0.65, Spearman r = 0.47-0.54, P < 0.05) were found between matched dust samples collected with the two sampling methods for ∑OctaBDE and ∑DecaBDE but not for ∑PentaBDE or HBCD. Statistically significantly higher concentrations of all PBDE congeners were found in the researcher-collected dust than in the home vacuum cleaner bag dust (VCBD). For HBCD, however, the concentrations were significantly higher in the home VCBD samples. Analysis of the bags themselves indicated no or very low levels of PBDEs and HBCD. This indicates that there may be specific HBCD sources to the floor and/or that it may be present in the vacuum cleaners themselves. The BDE-47 concentrations in matched pairs of VCBD and breast milk samples were significantly correlated (r = 0.514, P = 0.029), indicating that one possible exposure route for this congener may be via dust ingestion. PRACTICAL IMPLICATIONS: The statistically significant correlations found for several individual polybrominated diphenyl ether (PBDE) congeners, ∑OctaBDE and ∑DecaBDE between the two dust sampling methods in this study indicate that the same indoor sources contaminate both types of dust or that common processes govern the distribution of these compounds in the indoor environment. Therefore, either method is adequate for screening ∑OctaBDE and ∑DecaBDE in dust. The high variability seen between dust samples confirms results seen in other studies. For hexabromocyclododecane (HBCD), divergent results in the two dust types indicate differences in contamination sources to the floor than to above-floor surfaces. Thus, it is still unclear which dust sampling method is most relevant for HBCD as well as for ∑PentaBDE in dust and, further, which is most relevant for determining human exposure to PBDEs and HBCD.

Estimated dietary intake of nitrite and nitrate in Swedish children.

This study examines the intake of nitrate and nitrite in Swedish children. Daily intake estimates were based on a nationwide food consumption survey (4-day food diary) and nitrite/nitrate content in various foodstuffs. The mean intake of nitrite from cured meat among 2259 children studied was 0.013, 0.010 and 0.007 mg kg(-1) body weight day(-1) in age groups 4, 8-9 and 11-12 years, respectively. Among these age groups, three individuals (0.1% of the studied children) exceeded the acceptable daily intake (ADI) of 0.07 mg nitrite kg(-1) body weight day(-1). The mean intake of nitrate from vegetables, fruit, cured meat and water was 0.84, 0.68 and 0.45 mg kg(-1) body weight day(-1) for children aged 4, 8-9 and 11-12 years, respectively. No individual exceeded the ADI of 3.7 mg nitrate kg(-1) body weight day(-1). However, when the total nitrite intake was estimated, including an estimated 5% endogenous conversion of nitrate to nitrite, approximately 12% of the 4-year-old children exceeded the nitrite ADI. Thus, the intake of nitrite in Swedish children may be a concern for young age groups when endogenous nitrite conversion is included in the intake estimates.

POP levels in breast milk and maternal serum and thyroid hormone levels in mother-child pairs from Uppsala, Sweden.

In experimental studies, it has frequently been observed that the homeostasis of thyroid hormones (THs) is affected by exposure to persistent organic pollutants (POPs), such as dioxins and PCBs. In man, similar effects have been indicated in several epidemiological studies. In order to investigate the possible effect on THs at low background exposures found among the Swedish population the following study was performed. Primiparous women (n=395) in the Uppsala region were recruited between 1996 and 1999. Of these, 325 mothers agreed to donate a serum sample in late pregnancy and breast milk was obtained from 211 women 3 weeks after delivery. Babies were sampled for blood at 3 weeks (n=150) and 3 months (n=115) after birth. In connection to the sampling, questions on personal characteristics were asked. Levels of low (tri- to penta-) chlorinated PCB, di-ortho PCB, p,p'-DDE, (mono-ortho) PCB TEQ and PCDD/DF TEQ were monitored in breast milk and in mother's blood (not PCDD/DF). The results showed that the measured TH levels (thyroid-stimulating hormone - TSH, total tri-iodothyronine - TT3, free thyroxine - FT4) in mothers and children were within the reference range. Some significant associations were seen between POP exposures and TH levels in mother or child after simple regression analysis. Following adjustment for important confounding factors, the significant associations mostly disappeared. However, significantly decreasing TT3 levels with increasing prenatal low-chlorinated PCB exposure were still seen in 3 week old children, and on TT3 in mothers exposed to PCDD/DF. In conclusion, the study clearly shows the importance of adjustment for important confounding factors in the analysis of possible associations between POP exposure and hormonal effects. The remaining associations are weak in both children and mothers and the clinical consequences of these alterations are uncertain. When comparing studies that investigate associations between TH levels and POP levels during the perinatal stage, no obvious between-study concordance was seen regarding the critical dose for hormonal effects to occur.

Brominated flame retardants as possible endocrine disrupters.

Brominated flame retardants (BFR) are endocrine disrupters in experimental systems, both in vitro and in vivo. Although BFR effects on thyroid hormones are well confirmed, studies of effects on oestrogen/androgen systems are fewer but today growing in numbers. The effects of BFR on other hormone systems are still unknown. Hormonal effect levels in animals start from ca 1 mg/kg b.w., but there are exceptions: effects on spermatogenesis, suggesting hormonal causes, have been observed at a low dose (60 microg/kg b.w.) of a polybrominated diphenyl ether (PBDE) congener, BDE-99. It could be concluded that hormonal effects are of importance in risk assessment, and in some cases where effects are seen at low levels safety margins may be insufficient. One additional uncertainty is the lack of reliable human data that could be used to support animal BFR observations. In spite of the recent regulation of PBDE production, levels of both PBDE and of other BFR groups are still present in environmental samples. Thus, we have to deal with the possible effects of human BFR exposure for times to come. In order to reduce BFR exposure, the routes of exposure should be carefully examined and ways to reduce levels in major exposure routes considered.

Levels of nitrate in Swedish lettuce and spinach over the past 10 years.

Monitoring of nitrate in Swedish-produced lettuce and spinach over the past 10 years (1996-2005) showed that more than 95% of the samples were below the maximum levels established by the European Commission in 1997. The good agricultural practices used by Swedish farmers may partly explain these results. Analytical results of organic farming production of lettuce from 2000 showed low nitrate levels compared with conventional production. The 10 years of Swedish experience has shown good compliance with the European Union maximum levels, but even lower nitrate levels may be achieved by organic farming methods, at least regarding fresh lettuce grown under cover.

Dietary intake estimations of organohalogen contaminants (dioxins, PCB, PBDE and chlorinated pesticides, e.g. DDT) based on Swedish market basket data.

By use of a Swedish Market basket study from 1999, in which foods were sampled from four regions, the dietary intake of persistent organic pollutants (POPs) was assessed. Based on earlier data, six food groups (fish, meat, dairy products, egg, fats/oils, and pastries; comprising 52 food items) were selected for POP analyses. Homogenates from these six groups were subjected to POP analyses and levels presented on dioxins (PCDD/PCDFs), dioxin-like PCBs, PCB-153, summation operatorPCBs, BDE-47, summation operatorPBDEs, DDE, summation operatorDDTs, HCB, summation operatorHCHs, and summation operatorchlordanes, after adjusting non-quantified levels to 1/2 LOQ. For all compounds, the fish homogenate contained the comparatively highest levels, on a fresh weight basis. Intake calculations based on the six food groups showed that summation operatorPCBs and summation operatorDDTs gave per capita intakes of 615 and 523 ng/day, respectively, that the estimated summation operatorPBDE intake was 51 ng/day and that of dioxins and dioxin-like PCBs was 96 pg WHO-TEQ/day. The estimated mean intakes were below (total-TEQ: 1.3 pg/kgbw/day) or well below (summation operatorDDTs: 8.9 ng/kgbw/day) internationally agreed intake limits (total-TEQ: 2 pg/kgbw/day; summation operatorDDTs: 10,000 ng/kgbw/day). A number of uncertainty factors, including analytical limitations due to low POP levels in food, give reason for caution in the use of the presented intake data. However, the intake estimations of dioxins, summation operatorPCBs and summation operatorPBDEs are well in accordance to calculations of POP intakes in Sweden made by alternate methods.

Methyl mercury and inorganic mercury in Swedish pregnant women and in cord blood: influence of fish consumption.

We studied exposure to methyl mercury (MeHg) in Swedish pregnant women (total mercury [T-Hg] in hair) and their fetuses (MeHg in cord blood) in relation to fish intake. The women were recruited at antenatal care clinics in late pregnancy to participate in an exposure study of environmental pollutants. Fish consumption was evaluated using food frequency questionnaires including detailed questions on fish consumption. In addition, we determined inorganic mercury (I-Hg) and selenium (Se) in cord blood. On average, the women consumed fish (all types) 6.7 times/month (range 0-25 times/month) during the year they became pregnant. They reported less consumption of freshwater fish--species that might contain high concentrations of MeHg--during than before pregnancy. T-Hg in maternal hair (median 0.35 mg/kg; range 0.07-1.5 mg/kg) was significantly associated (R2 = 0.53; p < 0.001) with MeHg in cord blood (median 1.3 microg/L; range 0.10-5.7 microg/L). Both hair T-Hg and cord blood MeHg increased with increasing consumption of seafood (r = 0.41; p < 0.001 and r = 0.46; p < 0.001, respectively). Segmental hair analysis revealed that T-Hg closer to the scalp was lower and more closely correlated with MeHg in cord blood than T-Hg levels in segments corresponding to earlier in pregnancy. We found a weak association between Se (median 86 microg/L; range 43-233 microg/L) and MeHg in cord blood (r = 0.26; p = 0.003), but no association with fish consumption. I-Hg in cord blood (median 0.15 microg/L; range 0.03-0.53 microg/L) increased significantly with increasing number of maternal dental amalgam fillings.

Effects of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) on thyroid hormone and vitamin A levels in rats and mice.

The ability of the commercial polybrominated diphenyl ether (PBDE) preparation Bromkal 70-5 DE to alter thyroid hormone and vitamin A levels as well as microsomal enzyme activities was compared with that of the commercial polychlorinated biphenyl (PCB) preparation Aroclor 1254 in orally exposed female rats (Sprague-Dawley) and mice (C57BL/6 N). Additional mice were exposed to the PBDE congener 2,2',4,4'-tetrabromodiphenyl ether (DE-47), or to the PCB congener 2,3,3',4,4'-pentachlorobiphenyl (CB-105). For 14 days the animals were given approximately isomolar daily oral doses of Aroclor 1254, CB-105 (both 10 mg/kg body weight), Bromkal 70-5 DE or DE-47 (both at 18 mg/kg body weight). In addition, further groups of rats and mice received a higher dose of Bromkal 70-5 DE, 36 mg/kg body weight. Bromkal 70-5 DE and DE-47 decreased plasma free and total thyroxine (T4) levels in both rats and mice, although with lower potency than that of Aroclor 1254 and CB-105. By contrast, thyroid-stimulating hormone (TSH) levels were not significantly changed in any of the groups. Reduction of hepatic vitamin A levels was seen in rats after Aroclor 1254 and Bromkal 70-5 DE exposure. A similar tendency was seen also in mice, but the effects were significant only for concentration data and not the total amount. Induction ofmicrosomal phase I enzymes, measured as ethoxy, methoxy and pentoxy resorufin O-dealkylase (EROD, MROD, PROD) activities, was greatest after exposure to Aroclor 1254/CB-105 but were also significant in the Bromkal 70-5 DE/DE-47-treated groups. However, induction of uridine diphosphoglucuronosyl transferase (UDPGT) was small and for most groups insignificant. In conclusion, the PBDE compounds studied, although having a lower potency than the PCB compounds, decreased thyroxine and vitamin A levels and induced microsomal enzyme activities. Rats were more sensitive to the observed effects than mice. Microsomal phase I activity might be related, directly or indirectly, to the T4 and vitamin A effects, whereas several factors (such as weak enzyme induction and lack of correlation with altered T4 and vitamin A levels) argue against any UDPGT-related effects.

Polychlorinated biphenyl congeners as markers of toxic equivalents of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans in breast milk.

In breast milk, concentrations of polychlorinated biphenyls (PCBs) are higher than those of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), making PCB analyses less time-consuming and expensive. We searched for PCB "markers" of PCDD/DF concentrations, by studying associations between concentrations of PCB and PCDD/DFs (expressed as toxic equivalents, TEQs) in breast milk from 27 women (primiparas, 22-35 years). These women donated breast milk in 1996-1999 together with 183 other primiparas from Uppsala County, Sweden. Regression analyses showed that both dioxin-like and non-dioxin-like penta- to hepta-chlorinated PCBs could be used as markers of TEQ concentrations in this group of women, in some cases after age adjustment of the regressions. The strong positive association between concentrations of dioxin-like PCB/DD/DFs and non-dioxin-like PCBs will in future epidemiological studies make it difficult to separate Ah receptor-dependent effects from non-Ah receptor-dependent effects. With the use of regression equations and concentrations in breast milk samples collected in 1994, TEQ concentrations were estimated in the 1994 samples. Comparisons between estimated and measured concentrations indicated that associations between concentrations of marker substances and TEQs should be determined separately within each study population, in order to obtain reliable TEQ exposure assessments from PCB markers.

Polybrominated diphenyl ethers: occurrence, dietary exposure, and toxicology.

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in plastics (concentration, 5--30%) and in textile coatings. Commercial products consist predominantly of penta-, octa-, and decabromodiphenyl ether mixtures, and global PBDE production is about 40,000 tons per year. PBDEs are bioaccumulated and biomagnified in the environment, and comparatively high levels are often found in aquatic biotopes from different parts of the world. During the mid-1970--1980s there was a substantial increase in the PBDE levels with time in both sediments and aquatic biota, whereas the latest Swedish data (pike and guillemot egg) may indicate that levels are at steady state or are decreasing. However, exponentially increasing PBDE levels have been observed in mother's milk during 1972--1997. Based on levels in food from 1999, the dietary intake of PBDE in Sweden has been estimated to be 0.05 microg per day. Characteristic end points of animal toxicity are hepatotoxicity, embryotoxicity, and thyroid effects as well as maternal toxicity during gestation. Recently, behavioral effects have been observed in mice on administration of PBDEs during a critical period after birth. Based on the critical effects reported in available studies, we consider the lowest-observed-adverse-effect level (LOAEL) value of the PBDE group to be 1 mg/kg/day (primarily based on effects of pentaBDEs). In conclusion, with the scientific knowledge of today and based on Nordic intake data, the possible consumer health risk from PBDEs appears limited, as a factor of over 10(6) separates the estimated present mean dietary intake from the suggested LOAEL value. However, the presence of many and important data gaps, including those in carcinogenicity, reproduction, and developmental toxicity, as well as additional routes of exposure, make this conclusion only preliminary. Moreover, the time trend of PBDEs in human breast milk is alarming for the future.

PCB and chlorinated pesticide concentrations in swine and bovine adipose tissue in Sweden 1991-1997: spatial and temporal trends.

Results from the Swedish control programme regarding organochlorines in food were used to determine time trends of organochlorine concentrations in adipose tissues from swine (4-8 months old) and bovines (non-dairy, 12-36 months) slaughtered between 1991 and 1997. Moreover, possible regional differences in concentrations were studied, as well as differences in concentrations depending on sex and age of the slaughtered animals. Multiple linear regression indicated that the concentrations of PCB, p,p'-DDE, HCB and alpha-HCH decreased by 4-17% per year, suggesting that the decline in organochlorine concentrations in the Swedish environment and biota reported during the 1970s-1990s also has occurred in meat-producing animals during the 1990s. The concentrations of PCB, DDE and HCB in bovines and PCB and DDE in swine were 1.4-3.8-fold higher in the southern parts of Sweden than in the northern parts of the country, indicating a regional difference in exposure of the animals. The organochlorine concentrations were higher in bovines than in swine, and declined faster in swine than in bovines. Moreover, the concentrations of CB 153 and p,p'-DDE were similar in bovines, but in swine the average concentrations of the two compounds differed two-fold. Apart from possible species differences in metabolism of organochlorines, this may be due to differences in the age at slaughter between swine and bovines, and differences in husbandry of the animals. In the latter case, swine are generally kept inside during their whole life span, whereas bovines are kept outside grazing during the summer period. Finally, a sex-dependent difference in concentrations was indicated in swine, but not in bovines. Our study shows that a lot of information can be 'extracted' from control program results.

Organochlorines and bone mineral density in Swedish men from the general population.

Persistent organochlorines (POCs), such as polychlorinated biphenyls (PCBs) and DDT, are present at relatively high concentrations in food and show estrogenic, anti-estrogenic or anti-androgenic activity in biological test systems. Because bone mineral density (BMD) in men is influenced by sex hormones, we looked for associations between BMD and serum concentrations of POCs in 115 men (mean age 63 years, range 40-75 years) from the general Swedish population. Ten PCB congeners, five DDT isomers, hexachlorobenzene, three hexachlorocyclohexane isomers, trans-nonachlor and oxychlordane were analyzed by gas chromatography. Quantitative bone measurements were performed by dual-energy X-ray absorptiometry at three sites: whole body, the L2-L4 region of the lumbar spine, and the neck region of the proximal femur, as well as by quantitative ultrasound on the left os calcis (broadband ultrasound attenuation (BUA) and speed of sound (SOS)). After adjustment for confounding factors in linear regression analyses we found no strong association between serum concentrations of single POCs and the five BMD and ultrasound variables. When POCs were grouped according to hormonal activity (estrogenic, anti-estrogenic, anti-androgenic) and the study subjects were divided into organochlorine concentration quartiles, a weak association was indicated between increased serum concentrations of p,p'-DDE (antiandrogenic) and decreased BMD, BUA and SOS. This may suggest that p,p'-DDE could cause negative effects on bone density, but the findings might also be due to chance since multiple comparisons were made in the statistical analysis. Overall our results do not suggest that the studied POCs caused major effects on bone density in our study group.

Serum concentrations of organochlorines in men: a search for markers of exposure.

Analysis of single marker substances in serum could provide cost-effective assessment of human exposure to complex mixtures of organochlorines. We studied the serum concentrations of 10 polychlorinated biphenyl (PCB) congeners and 11 chlorinated pesticides and some of their metabolites in samples collected from 120 Swedish men (mean age 63 years, range 40-74 years) from the general Swedish population. The median concentrations of individual PCB congeners increased in the order PCB 52 < PCB 101 < or = PCB28 < PCB 105 < PCB 167 < PCB 156 < PCB 118 < PCB 138 < PCB 180 < PCB 153. The concentrations of o,p'-DDT, o,p'-DDE, p,p'-DDD, alpha-HCH and gamma-HCH were in most cases below the quantification limit (2-4 ng/g lipid). Among the other chlorinated pesticides the median concentration increased in the order oxychlordane (12 ng/g lipid) < p,p'-DDT < trans-nonachlor < beta-HCH < HCB < p,p'-DDE (586 ng/g lipid). The observed concentrations of PCB and chlorinated pesticides were in the same range as those found in similar groups of men from Sweden and Norway, but lower than those found in male populations with recent occupational exposure or high environmental exposure. Strong relationships were found between the concentrations of single mono- and di-ortho PCB congeners and groups of PCB congeners in serum. In our group of men PCB 153 was a good marker substance for the concentration of sigma PCB and sigma di-ortho PCB concentrations in serum. Moreover, among the mono-ortho PCB congeners analyzed, PCB 156 could be used as a marker for the sigma mono-ortho PCB TEQ concentrations in serum in the studied group. No useful marker substances were found among DDT compounds and other chlorinated pesticides and metabolites, except for trans-nonachlor which predicted the concentration of the metabolite oxychlordane fairly well.

Hydroxylated polychlorinated biphenyls: distribution in the pregnant mouse.

1. In the pregnant C57BL mouse the disposition of a single, intravenous low dose of 14C-labelled 4-hydroxy-3,5,3',4'-tetrachlorobiphenyl (4-OH-TCB) or 4-hydroxy-3,5,2',3',4'-pentachloro-biphenyl (4-OH-PeCB1) was monitored by liquid scintillation counting and whole-body autoradiography. The compounds were placentally transferred and accumulated in the foetal tissues (e.g. plasma and liver). Also, maternal accumulation was observed in selected tissues, including liver, adrenal gland, adipose tissue and yolk sac placenta. 2. The foetal concentration of both hydroxy-PCBs increased with time up 24 h post-exposure and the foetal plasma concentration with at this time-point two-fold of that in maternal plasma. Chemical analysis of maternal plasma and liver showed no metabolism of the administered compounds. 3. In the pregnant C57BL mouse at late gestation, exposure to 4-OH-TCB generally resulted in a higher foetal and maternal tissue retention than did 4-OH-PeCB1. The estimated elimination half-lives (t 1/2) of 4-OH-TCB in maternal liver and plasma were 69 and 13 h respectively, and for 4-OH-PeCB1 were 17 and 13 h. 4. No differences in foetal tissue concentration of 4-OH-TCB were observed between the C57BL, and NMRI mouse. In contrast, earlier studies have shown that the PCB congener CB-77, the parent compound of 4-OH-TCB, resulted in a C57BL/NMRI foetal ratio of 1:5.

Hydroxylated polychlorinated biphenyls: placental transfer and effects on thyroxine in the foetal mouse.

1. At day 17 of pregnancy, 1 day after maternal intravenous administration (5-50 mumol/kg body wt) of 4-OH-3,5,3',4'-tetrachlorobiphenyl (4-OH-TCB; a CB-77 metabolite), a limited dose-dependent decrease was found both in foetal and maternal total thyroxine (T4) levels (76-81% of control at 50 mumol/kg). Similarly, a 50 mumol/kg dose of a 4-OH-3,5,2',3',4'-pentachlorobiphenyl (4-OH-PeCB1) decreased total T4 levels, whereas 4-OH-2,3,5,3',4'-pentachlorobiphenyl (4-OH-PeCB2) showed no clear effect (both 4-OH-pentaCBs are CB-105 metabolites). Earlier administration (gestation day 10 or 13) of the 4-OH-PCBs had no effect on total T4 at day 17. 2. Placental transfer of 14C-4-OH-TCB to the foetal compartment was dose-related and accumulated mainly in foetal plasma at levels 2-fold those in the maternal plasma at the dose interval 0.5-5.0 mumol/kg body wt, whereas at higher doses (20 and 50 mumol/kg body wt) the foetal and maternal plasma levels were similar. A break-point in the foetal dose/plasma concentration curve at 5.0 mumol/kg indicates saturation of a high-affinity ligand binding above this dose. 3. There was an extensive accumulation of radioactivity in the maternal liver after 14C-4-OH-TCB administration (20-30% of the administered dose). In spite of this the investigated compounds resulted in a small or no effect on EROD/MROD activity in maternal liver and these enzyme activities were not detectable in either exposed or control foetal liver.

Lack of effects of some individual polybrominated diphenyl ether (PBDE) and polychlorinated biphenyl (PCB) congeners on human lymphocyte functions in vitro.

The structural similarities between polybrominated diphenyl ethers and immunotoxic halogenated aromatic compounds suggest that the polybrominated diphenyl ethers might affect the immune system. The present study was undertaken to investigate the immunological effects of some purified PBDE-congeners on human lymphocyte function in vitro. Polychlorinated biphenyl congeners were also included in the study. Mitogen-induced DNA synthesis and immunoglobulin synthesis by lymphocytes from blood donors were examined following polybrominated diphenyl ether or polychlorinated biphenyl exposure in vitro in order to determine the immunotoxic potential of these substances. No effects on mitogen-induced proliferation or immunoglobulin synthesis were observed after exposure of cells to concentrations up to 10(-5) M. The negative findings in this study indicate that certain functions of human peripheral lymphocytes, i.e. proliferation and immunoglobulin synthesis, are insensitive to the direct action of polybrominated diphenyl ethers and polychlorinated biphenyls. Our results are in accordance with other recent studies in which no effects on immunological parameters were demonstrated by exposure of lymphocytes to polyhalogenated aromatic hydrocarbons in vitro.

Milk transfer and neonatal uptake of coplanar polychlorinated biphenyl (PCB) congeners in mice.

The selective accumulation of 3,3',4,4'-tetrachlorobiphenyl metabolites in late gestational foetal blood and soft tissues in mice as a result of administration of different coplanar polychlorinated biphenyl (PCB) congeners, is reported elsewhere. The situation in the nursing neonate after maternal exposure to the same congeners is now studied: The 14C-labelled congeners 3,3',4,4'-tetrachlorobiphenyl (IUPAC number CB-77),3,3',4,4'5-pentachlorobiphenyl (IUPAC number CB-126), 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC number CB-169) (all three non-ortho congeners) and 2,3,3',4,4'-pentachlorobiphenyl (IUPAC number CB-105) (mono-ortho congener) were injected intravenously in lactating mice at day 11 post partum. One day and four days later, milk and neonatal/maternal tissues and plasma radioactivity was monitored by liquid scintillation counting (dose: 2.0 mumol (20-50 microCi)/kg body weight). In milk, CB-126, -169 and -105 showed higher levels (1450-2520 pmol/ml; one day after administration) than did CB-77 (580 pmol/ml), and in neonates, the relative whole-body levels of radioactivity (CB-169 and -105 highest) were related to the levels seen in milk (probably the consequences of their metabolic persistence). The comparably high 14C-concentration found in neonatal liver (about 15,000 pmol/kg) after CB-126 administration and in plasma (880 pmol/ml) after CB-77 administration could be explained by binding to specific proteins. In general, neonatal mice had two to seven times higher plasma levels than those of their mothers. These results indicate that CB-126, -169 and -105 are transferred via milk to neonates in considerable quantity and are deposited mainly in neonatal liver, whereas CB-77 is transferred in a comparably lower amount and accumulated in neonatal plasma. The lower 14C-levels in the NMRI mothers and offspring (about half of C57BL values in maternal and neonatal plasma), could possibly be explained by a differentiated metabolism of CB-77 in these two strains.

Foetal uptake of coplanar polychlorinated biphenyl (PCB) congeners in mice.

Earlier studies (Darnerud et al. 1986) have shown that the Ah-receptor binding polychlorinated biphenyl (PCB) congener 3,3',4,4'-tetrachlorobiphenyl (IUPAC number CB-77) accumulated as hydroxy and methylsulphone metabolites in late gestational mice foetuses. In the present paper the foetal accumulation potential in mice of other dioxin-like PCB congeners was studied: 3,3',4,4',5-pentachlorobiphenyl, 3,3',4,4',5,5'-hexachlorobiphenyl and 2,3,3',4,4'-pentachlorobiphenyl (IUPAC numbers CB-126, CB-169, CB-105, to some extent dioxin-like) were compared to results of CB-77 (all congeners 14C-labelled and in equimolar doses (2.0 mumol/kg body wt.)). CB-77 resulted in the comparatively strongest foetal 14C-accumulation, when measured in plasma or whole body homogenate four days after administration (day 17 of pregnancy); the plasma 14C-values (calculated as pmol/g wet wt.) were 760, 130, 60 and 40 for CB-77, -126, 105 and -169, respectively, and the CB-77 derived radioactivity in the foetal compartment was 3.6% of administered dose (i.e. a considerable portion of the remaining maternal body radioactivity). Thin-layer chromatography (TLC) results, suggesting extensive CB-77 metabolism and foetal metabolite uptake, support earlier findings. The effects of CB-77 and CB-169 on foetal 7-ethoxyresorufin-O-deethylase (EROD) activities (day 17 of gestation; two days after 5 mg/kg body wt. dose (14.0-17.0 mumol/kg body wt.)) was about 20 times lower than of CB-126. In the dam, high radioactivity levels were observed in the liver and fat (highest concentrations found in CB-126 and CB-105, respectively). Strain comparison-foetal 14C-uptake (four days after administration of CB-77) in C57BL mice was almost five times higher than in NMRI-may be correlated to earlier observed differences in EROD activities between these strains. The present results indicate that congener and strain differences exist regarding both foetal and maternal distribution patterns of coplanar PCB congeners and point out the difference in foetal disposition between CB-77 and the other studied congeners.

Binding of a 3,3', 4,4'-tetrachlorobiphenyl (CB-77) metabolite to fetal transthyretin and effects on fetal thyroid hormone levels in mice.

The present study was conducted in order to study the effect of the PCB congener 3,3', 4,4'-tetrachlorobiphenyl (CB-77) on fetal thyroxin homeostasis in the mouse, and to examine a possible underlying mechanism behind the effect. C57BL mice were treated with 14C-labelled or unlabelled CB-77 (1 or 10 mg/kg body wt.) on day 13 of gestation, and control animals were treated with corn oil. The experiment was terminated at 4 days after exposure. Maternal and fetal plasma and livers, and whole fetuses for homogenate preparation, were collected and analysed for total radioactivity, in vitro binding of 125I-thyroxin to plasma transthyretin (TTR; a thyroxin-transporting protein), and free and total thyroxin (FT4, TT4) levels. Maternal plasma, fetal plasma and homogenates were also analyzed for presence of CB-77 and metabolites. Results showed a dose-dependent uptake of radioactivity in plasma and liver, fetal plasma 14C-levels being about five-times higher in 10 mg/kg dosed animals as after 1 mg/kg. Fetal; plasma levels of total radioactivity were four- to nine-times above maternal levels and corresponded to only one compound, the metabolite 4-OH-3,3', 4',5-tetrachlorobiphenyl (4-OH-tCB). 4-OH-tCB was the major metabolite also in whole fetuses, with only small amounts of the parent compound (approximately 15% of the 4-OH-tCB) and traces (approximately 6%) of two other metabolites, 2-OH-3,3, 4,4'-tetrachlorobiphenyl and 5-OH-3,3', 4,4'-tetrachlorobiphenyl. Polyacrylamide gel electrophoresis confirmed that the 14C-radioactivity in fetal plasma was bound to TTR, and revealed that in vitro binding of 125I-T4 to fetal TTR was reduced to 50% of control values in treated animals (10 mg/kg body wt.). Fetal plasma FT4 and TT4 levels were significantly decreased (64 and 55% of control fetuses) after 10 mg/kg treatment. In conclusion, exposure of pregnant mice to CB-77 results in the accumulation of the metabolite 4-OH-tCB in fetal mouse plasma. The metabolite binds to TTR and is accompanied by a significant decrease in fetal plasma T4 levels. A causative correlation between TTR binding and effects on T4 levels is suggested.