In this study, we identified the main hydroxylated polychlorinated biphenyls (OH-PCBs) and other chlorinated phenolic compounds and we determined their relative concentrations in whole blood from 13 male and 17 female Inuit from northern Quebec, Canada, and from a pooled whole blood sample from southern Quebec. We also determined concentrations of polychlorinated biphenyls (PCBs). Total OH-PCB concentrations were variable among the Inuit samples, ranging over 2 orders of magnitude (0.117-11.6 ng/g whole blood wet weight). These concentrations were equal to and up to 70 times those found for the southern Quebec pooled whole blood sample. Geometric mean concentrations of total OH-PCBs were 1.73 and 1.01 ng/g whole blood for Inuit men and women, respectively, and 0.161 ng/g whole blood for the southern population pool. There are limited data available for comparison, but the levels of OH-PCBs in Inuit are higher than those previously reported in the literature for other populations. There was a significant correlation (p
Exercise behavior, cardiorespiratory fitness, and obesity are strongly influenced by genetic factors. By studying young adult twins, we examined to what extent these interrelated traits have shared genetic and environmental etiologies. We studied 304 twin individuals selected from the population-based FinnTwin16 study. Physical activity was assessed with the Baecke questionnaire, yielding three indexes: sport index, leisure-time index, and work index. In this study, we focused on sport index, which describes sports participation. Body composition was determined using dual-energy X-ray absorptiometry and cardiorespiratory fitness using a bicycle ergometer exercise test with gas exchange analysis. The Baecke sport index was associated with high maximal oxygen uptake adjusted for lean body mass (Vo(2max)[adj]) (r = 0.40), with low body fat percentage (BF%) (r = -0.44) and low waist circumference (WC) (r = -0.29). Heritability estimates for the key traits were as follows: 56% for sport index, 71% for Vo(2max)[adj], 77% for body mass index, 66% for WC, and 68% for BF%. The association between sport index and Vo(2max) was mostly explained by genetic factors (70%), as were both the association between sport index and BF% (71%) and that between sport index and WC (59%). Our results suggest that genetic factors explain a considerable part of the associations between sports participation, cardiorespiratory fitness, and obesity.
We estimated genetic and environmental variance of BMI among 7245 non-pregnant MZ and DZ pairs of the same sex from the population-based Finnish Twin Cohort. The contributions of additive genetic effects, shared and non-shared environmental effects on age-adjusted BMI-variance were estimated by LISREL structural equation models. Genetic effects contribute 72% in men and 66.4% in non-pregnant women of total variance, while 27.8% of variance among men and 33.6% among women is due to non-shared environmental effects. Shared environmental effects were nonsignificant (0% for women and 0.2% for men). Similar values were obtained for hereditary and non-shared environmental effects, when shared environmental effects were not included in the model. The inclusion of pregnant women did not substantially change heritability estimates.
We evaluated alveolar carbon monoxide (CO) levels of 122 male, adult hockey players active in recreational leagues of the Quebec City region (Canada), before and after 10 weekly 90-minute games in 10 different rinks. We also determined exposure by quantifying the average CO level in the rink during the games. Other variables documented included age, pulmonary function, aerobic capacity, and smoking status. Environmental concentrations varied from 1.6 to 131.5 parts per million (ppm). We examined the absorption/exposure relationship using a simple linear regression model. In low CO exposure levels, physical exercise lowered the alveolar CO concentration. However, we noted that for each 10 ppm of CO in the ambient air, the players had adsorbed enough CO to raise their carboxyhemoglobin (COHb) levels by 1 percent. This relationship was true both for smokers and non-smokers. We suggest that an average environmental concentration of 20 ppm of CO for the duration of a hockey game (90 minutes) should be reference limit not to be exceeded in indoor skating rinks.
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Eighteen pairs of monozygotic twins discordant for long-term occupational exposure to organic solvents were examined for disturbances of cardiovascular reflexes. All of the subjects were asymptomatic, and considered themselves healthy. No significant differences were observed between the exposed and the nonexposed twins. The finding suggests that occupational solvent exposure at these particular levels is unlikely to cause disturbances of the autonomic nervous function.
Genetic influences on variability of body weight and onset of menarche are well known. To investigate the genetic and environmental contributions to the association of body weight with onset of menarche, we studied Finnish twins from consecutive birth cohorts (the FinnTwin16 study) ascertained from the national population registry, which identifies nearly 100% of all living twins. Baseline questionnaires were mailed to the twins within 60 days of their sixteenth birthday and later to older sibs of the twins. Pairwise response rates (approximately 85% across gender and zygosity) and 30 months of data collection yielded results from 1283 twin pairs. The questionnaires included a survey of health habits and attitudes, a symptom checklist, MMPI personality scales, and a survey of relationships with parents, peers, and the co-twin. Age at menarche was reported by 468 monozygotic (MZ) girls, 378 girls from like-sex dizygotic (FDZ) pairs, 434 girls from opposite-sex (OSDZ) pairs, and 141 older female sibs of the twins. The one-month test-retest reliability of age at menarche in an independent sample (N = 136) of 16-year-olds from a national survey was 0.96. Girls from OSDZ pairs had a significantly higher mean age at menarche (13.33 yr) than FDZ girls (13.13 yr) (difference, 0.20 yr; 95% confidence interval, 0.05-0.35). The MZ correlation for age at menarche was 0.75, the DZ correlation was 0.31, and the sib-twin correlation was 0.32. A bivariate twin analysis of age at menarche and body mass index (wt/ht2) indicated that 37% of the variance in age at menarche can be attributed to additive genetic effects, 37% to dominance effects, and 26% to unique environmental effects. The correlation between additive genetic effects on age at menarche and body mass index was 0.57, indicating a substantial proportion of genetic effects in common.
We studied the cumulative incidence, concordance rate and heritability for diabetes mellitus in a nationwide cohort of 13,888 Finnish twin pairs of the same sex. The twins were born before 1958 and both co-twins were alive in 1967. Data on diabetes were derived through computerized record linkage from death certificates, the National Hospital Discharge Register and the National Drug Register. Records were reviewed in order to assign a diagnostic category to the 738 diabetic patients identified. Of these patients 109 had Type 1 (insulin-dependent) diabetes, 505 Type 2 (non-insulin-dependent) diabetes, 46 gestational diabetes, 24 secondary diabetes, 38 impaired glucose tolerance and 16 remained unclassified. The cumulative incidence of diabetes was 1.4% in men and 1.3% in women aged 28-59 years and 9.3% and 7.0% in men and women aged 60 years and over, respectively. The cumulative incidence did not differ between monozygotic and dizygotic twins. The concordance rate for Type 1 diabetes was higher among monozygotic (23% probandwise and 13% pairwise) than dizygotic twins (5% probandwise and 3% pairwise). The probandwise and pairwise concordance rates for Type 2 diabetes were 34% and 20% among monozygotic twins and 16% and 9% in dizygotic twins, respectively. Heritability for Type 1 diabetes was greater than that for Type 2 where both genetic and environmental effects seemed to play a significant role.
In 1975 and again in 1981, all adult twins in the population-based Finnish Twin Cohort were administered postal questionnaires yielding data on self-reported frequency and quantity of alcohol use. The longitudinal results provide information on the age-to-age stability of social drinking patterns among 13,404 (twin) individuals aged 18 to 43 at baseline; model-fitting the cross-temporal consistency of the twins' reported alcohol use yields unique estimates of the contribution of genetic and environmental factors to their individual age-to-age stabilities. Mean consumption levels did not change between 1975 and 1981. Patterns of social drinking were more stable in older (aged 24-43 at baseline) than younger (aged 18-23 at baseline) adult twins, and were more stable among men than women. Heritabilities were significant at both baseline and follow-up for all three alcohol measures in both genders and both age groups, with a median magnitude of 0.48. Both longitudinal genetic and environmental covariances were significant, and both were generally higher among older pairs. Genetic covariances (median magnitude = 0.68) were significantly higher than environmental covariances (median = 0.36). Analyses of absolute changes in alcohol use revealed heritable influences on the disposition to change. We conclude that genes contribute to both consistency and change in patterns of alcohol use from early to midadulthood.
To study twin resemblance for weight change (delta wt) and to assess the consistency of body mass index (BMI) over 6 years.
6 year follow-up based on identical mailed questionnaires in 1975 (baseline) and in 1981 (follow-up).
5967 same-sexed non-pregnant Finnish twin pairs aged 18-54 in 1975 (1106 male and 862 female monozygotic (MZ) and 2430 male and 1569 female dizygotic (DZ) pairs).
Intra-pair correlations of delta wt and BMI, estimates of genetic and environmental components of variance of delta wt and BMI.
Unadjusted mean delta wt was +2.0 (s.d. = 4.6) kg among MZ and 2.1 (4.9) kg among DZ male individuals. Corresponding values among MZ and DZ female individuals were +1.5 (4.4) kg and +1.7 (4.4) kg, respectively. Age and initial BMI together explained 8.0% of the male and 2.3% of the female phenotypic variance of delta wt. The intraclass correlations for delta wt (adjusted for age and initial BMI) for all pairs were 0.29 and 0.07 for MZ and DZ men and 0.25 and 0.05 for MZ and DZ women, respectively. The BMI of the twins increased slightly during the follow-up compared to the baseline values (23.9 (2.7) for MZ and 24.1 for DZ men and 23.0 (3.3) for MZ and 23.2 (3.42) for DZ women). The intra-class correlations for BMI at baseline (0.69 for MZ and 0.34 for DZ men and 0.67 for MZ and 0.29 for DZ women) were almost identical with the correlations at follow-up (0.67 for MZ and 0.32 for DZ men and 0.69 for MZ and 0.29 for DZ women). The intra-class correlations for both BMI and delta wt were consistently higher among pairs living together than among pairs living apart at baseline and at follow-up in both zygosity groups (MZ and DZ). Among pairs living apart at baseline, the longitudinal model for BMI showed that the correlation between genetic effects at baseline and at follow-up was very high (> 0.9 in all age groups among both genders). The correlations for environmental effects ranged from 0.50 to 0.67 during the follow-up period.
Weight changes in adults over a 6-year period appear to be determined by environmental effects rather than genetic factors. However, the genetic component in BMI is considerable and stable over time. Shared environment is likely to contribute to the resemblance of both delta wt and BMI among adult twin pairs, especially among MZ pairs.
Organochlorine compounds bioaccumulate in fishing and hunting products included in the daily diet of many coastal populations. Prenatal and perinatal exposure to large doses of PCBs and PCDFs was shown to be deleterious on fetal and neonatal development, but information is scarce regarding possible effects of chronic low-dose exposure. This study investigates biomarkers of early effects in newborns from women exposed to organochlorines through the consumption of species from marine food chains, in two remote coastal regions of the province of Quebec (Canada). A CYP1A1-dependent enzyme activity (EROD) and DNA adducts were measured in placenta samples obtained from 30 women living on the Lower-North-Shore of the St. Lawrence River and 22 Inuit women from Nunavik (Arctic Quebec). These biomarkers were also assessed in 30 women from a Quebec urban center (Sept-Iles) as a reference group. Prenatal organochlorine exposure was determined by measuring these compounds in umbilical cord plasma. The amount of bulky polycyclic aromatic hydrocarbon (PAH)-related DNA adducts was significantly greater in the Lower-North-Shore group than in the reference group. Placental EROD activity and the amount of less bulky (OC-related) DNA adducts were significantly higher in the Nunavik group than in the reference group. For both biomarkers, smoking was found to be an important confounding factor. Organochlorine exposure was significantly associated with EROD activity and DNA adduct levels when stratifying for smoking. This study confirms that CYP1A1 enzyme induction and DNA adducts in placental tissue constitute useful biomarkers of early effects induced by environmental exposure to organochlorines.
The third Canadian Arctic Human Health Assessment conducted under the Canadian Northern Contaminants Program (NCP), in association with the circumpolar Arctic Monitoring and Assessment Programme (AMAP), addresses concerns about possible adverse health effects in individuals exposed to environmental contaminants through a diet containing country foods. The objectives here are to: 1) provide data on changes in human contaminant concentrations and exposure among Canadian Arctic peoples; 2) identify new contaminants of concern; 3) discuss possible health effects; 4) outline risk communication about contaminants in country food; and 5) identify knowledge gaps for future contaminant research and monitoring. The nutritional and cultural benefits of country foods are substantial; however, some dietary studies suggest declines in the amount of country foods being consumed. Significant declines were found for most contaminants in maternal blood over the last 10years within all three Arctic regions studied. Inuit continue to have the highest levels of almost all persistent organic pollutants (POPs) and metals among the ethnic groups studied. A greater proportion of people in the East exceed Health Canada's guidelines for PCBs and mercury, although the proportion of mothers exceeding these guidelines has decreased since the previous assessment. Further monitoring and research are required to assess trends and health effects of emerging contaminants. Infant development studies have shown possible subtle effects of prenatal exposure to heavy metals and some POPs on immune system function and neurodevelopment. New data suggest important beneficial effects on brain development for Inuit infants from some country food nutrients. The most successful risk communication processes balance the risks and benefits of a diet of country food through input from a variety of regional experts and the community, to incorporate the many socio-cultural and economic factors to arrive at a risk management decision that will be the most beneficial in Arctic communities.
The exposure of swimmers to chloroform (CHCl3) was investigated in indoor swimming pools of the Quebec City region along with the associated carcinogenic risk. Six training sessions involving 52 competition swimmers (11 to 20 yr old) were conducted in 3 different pools, while 12 adult leisure swimmers attended 5 sessions, each held in a different pool. For each session, water and ambient air CHCl3 concentrations were measured and CHCl3 levels in alveolar air samples (CHCl3 ALV) collected from swimmers prior to entering the swimming pool premises and after 15, 35, and 60 min of swimming. Mean water concentrations varied from 18 microg/L to 80 microg/L, while those in air ranged from 78 microg/m3 to 329 microg/m3. Multiple linear regression analyses revealed that CHCl3 ALV values in competition swimmers were strongly correlated to ambient air and water levels, and to a lesser degree to the intensity of training. Only ambient air concentration was positively correlated to CHCl3 ALV in the leisure group. Concentrations of CHCl3 metabolites bound to hepatic and renal macromolecules, estimated using a physiologically based pharmacokinetic (PBPK) model, were 1.6 and 1.9 times higher for the competition swimmers than for the leisure swimmers, respectively. The highest hepatic concentration predicted in competition swimmers, 0.22 microg CHCl3 equivalents/kg of tissue, was at least 10,000 times lower than the smallest no observed effect level for liver tumors in animals. Data indicate that the safety margin is therefore very large, for competitive swimmers as well as for leisure swimmers.
We investigated whether BMI predicts type 2 diabetes in twins and to what extent that is explained by common genetic factors.
This was a population-based twin cohort study. Monozygotic (n = 4,076) and dizygotic (n = 9,109) non-diabetic twin pairs born before 1958 answered a questionnaire in 1975, from which BMI was obtained. Information on incident cases of diabetes was obtained by linkage to nationwide registers until 2005.
Altogether, 1,332 twins (6.3% of men, 5.1% of women) developed type 2 diabetes. The HR for type 2 diabetes increased monotonically with a mean of 1.22 (95% CI 1.20-1.24) per BMI unit and of 1.97 (95% CI 1.87-2.08) per SD of BMI. The HRs for lean, overweight, obese and morbidly obese participants were 0.59, 2.96, 6.80 and 13.64 as compared with normal weight participants. Model heritability estimates for bivariate variance due to an additive genetic component and non-shared environmental component were 75% (men) and 71% (women) for BMI, and 73% and 64%, respectively for type 2 diabetes. The correlations between genetic variance components (r (g)) indicated that one fifth of the covariance of BMI and type 2 diabetes was due to shared genetic influences. Although the mean monozygotic concordance for type 2 diabetes was approximately twice the dizygotic one, age of onset of diabetes within twin pair members varied greatly, irrespective of zygosity.
A 28-year follow-up of adult Finnish twins showed that despite high trait heritability estimates, only a fraction of covariation in BMI and incident type 2 diabetes was of genetic origin.
High organochlorine concentrations have been found among the Inuit in eastern Canada and in Greenland. The present study was undertaken to assess the exposure to organochlorines in relation to age, sex, and diet in a general population sample of Inuit from Greenland. Survey data and plasma concentrations of 14 polychlorinated biphenyl (PCB) congeners and 16 pesticides, including 5 toxaphene congeners, were recorded in a random population survey of 408 adult indigenous Greenlanders. In a two-stage design, the survey response rate was 66%, and 90% of those randomly selected for blood testing participated. This was equivalent to an overall response rate of 59%. The median plasma concentration of the sum of PCB congeners was 13.3 microg/L; the lipid-adjusted value was 2109 microg/kg. The PCB concentration was twice as high as among the Inuit of Nunavik, Canada, 25 times higher than in a control group from southern Canada, and several times higher than the values found in European studies. Concentrations were similarly elevated for all PCB congeners and pesticides. The PCB congener pattern was similar to previous observations from the eastern Canadian Arctic and Greenland. Concentrations showed statistically significant positive associations with age, marine diet, and male sex in multiple linear regression analyses. The exceptionally high plasma concentrations of several organochlorines among the Inuit of Greenland are attributed to a lifelong high intake of seafood, in particular marine mammals. Concentrations of PCB adjusted for the consumption of marine food increased until approximately 40 yr of age, which is equivalent to the birth cohorts of the early 1950s. The age pattern indicates that bioaccumulation of PCB started in the 1950s, which is a likely date for the introduction of the compounds into the Arctic environment.
Two remote maritime populations were evaluated for their biological exposure to organochlorines in 1989-1990. Because of their high intake of seafood, these two populations have high biological levels. One hundred nine breast milk samples from Inuit women from Arctic Québec were analyzed to determine levels of polychlorodibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) including non-ortho, mono-ortho, and di-ortho congeners. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEqs) for PCBs were 3.5 times higher in Inuit milk samples than in 96 Caucasian milk samples. Among the 185 fishermen from the Lower North Shore of the Gulf of the St. Lawrence River, we evaluated 10 highly exposed fishermen for their coplanar PCB blood levels. Total TEqs were 900 ng/kg for highly exposed individuals with 36 ng/kg for controls. In these two nonoccupationally exposed populations, coplanar PCBs make a larger contribution to the TEq than PCDDs and PCDFs. However, the mono-ortho penta CB No. 118 is the major contributor for the total toxicity.
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The authors conducted a survey during 1992 to evaluate blood levels of lead and mercury in Inuit adults of Nunavik (Arctic Quebec, Canada). Blood samples obtained from 492 participants (209 males and 283 females; mean age = 35 yr) were analyzed for lead and total mercury; mean (geometric) concentrations were 0.42 micromol/l (range = 0.04-2.28 micromol/l) and 79.6 nmol/l (range = 4-560 nmol/l), respectively. Concentrations of omega-3 fatty acid in plasma phospholipids--a biomarker of marine food consumption--were correlated with mercury (r = .56, p
This study identifies, in genetically informative data, familial and socioregional environmental influences on abstinence from alcohol at age 16.
Data are from FinnTwin 16, a population-based study of five consecutive birth cohorts of Finnish twins (N = 5,747 twin individuals), yielding 2,711 pairs of known zygosity. Measures of alcohol use, embedded into a health-habits questionnaire, were taken from earlier epidemiological research with nontwin Finnish adolescents. The questionnaire was administered sequentially to all twins as they reached age 16. Separate questionnaires, including measures of alcohol use and screening questions for alcohol problems, were received from 5,243 of the twins' parents.
Abstinence from alcohol to age 16 exhibits very significant familial aggregation, largely due to nongenetic influences. Abstinence rates are influenced by socioregional variation, sibling interaction effects and parental drinking patterns. Sibling and parental influences are greater in some regional environments than in others: the relative likelihood that a twin abstains, given that the co-twin does, or that both parents do, is shown to be modulated by socioregional variation.
Environmental contexts affect the likelihood of maintaining abstinence from alcohol to midadolescence, and socioregional variation modulates influences of siblings and parents. The results illustrate how genetically informative data can inform prevention research by identifying target variables for intervention efforts.
The nature of the association between body height and educational attainment found in previous studies remains to be clarified. The aim of this study was to examine factors contributing to this association by using a large Finnish twin data set (8798 adult twin pairs) gathered by questionnaire in 1981. A bivariate twin analysis was used to determine whether the genetic and environmental factors behind body height and educational attainment correlate with each other. A high heritability was found for body height (h2 = 0.78 in men and h2 = 0.75 in women), and a moderate heritability for education (h2 = 0.47 and h2 = 0.43, respectively). Shared environmental effects were also important in body height (c2 = 0.12 in men and c2 = 0.11 in women) and education (c2 = 0.36 and c2 = 0.43, respectively). A high correlation (r(c) = 0.77 in men, r(c) = 0.58 in women) of shared environmental factors education and body height, and weaker correlations (r = 0.11 and r = 0.08, respectively) of unshared environmental factors were found. The correlation of genetic factors between these two characteristics was not statistically significant. The results suggest that the association between body height and education is due mainly to nongenetic family factors.