| 1. |
- Barregård, L, et al.
(författare)
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Cadmium, mercury, and lead in kidney cortex of the general Swedish population: a study of biopsies from living kidney donors.
- 1999
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Ingår i: Environmental health perspectives. - : Environmental Health Perspectives. - 0091-6765 .- 1552-9924. ; 107:11, s. 867-71
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Tidskriftsartikel (refereegranskat)abstract
- Cadmium, mercury, and lead concentrations were determined in deep-frozen kidney cortex biopsies taken from 36 living, healthy Swedish kidney donors (18 males and 18 females), who were 30-71 (mean 53) years of age. Information about occupation, smoking, the presence of dental amalgam, and fish consumption could be obtained for 27 of the donors. The samples (median dry weight 0.74 mg) were analyzed using inductively coupled plasma mass spectrometry, and the results were transformed to wet-weight concentrations. The median kidney Cd was 17 micrograms/g (95% confidence interval, 14-23 micrograms/g), which was similar in males and females. In 10 active smokers, the median kidney Cd was 24 micrograms/g, and in 12 who never smoked, it was 17 micrograms/g. The median kidney Hg was 0.29 micrograms/g, with higher levels in females (median 0.54 micrograms/g) than in males (median 0.16 micrograms/g). Subjects with amalgam fillings had higher kidney Hg (median 0.47 micrograms/g, n = 20) than those without dental amalgam (median 0.15 micrograms;g/g, n = 6), but kidney Hg was below the detection limit in some samples. Nearly half of the samples had kidney Pb below the detection limit. The median kidney Pb was estimated as 0. 14 micrograms/g. This is the first study of heavy metals in kidney cortex of living, healthy subjects, and the results are relatively similar to those of a few previous autopsy studies, indicating that results from autopsy cases are not seriously biased in relation to kidney metal concentrations in the general population. Cd concentrations in those who never smoked were relatively high, indicating considerable Cd intake from the diet in Sweden. The effect of dental amalgam on kidney Hg was as expected, although the reason for the difference in Hg levels between males and females is unclear.
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| 2. |
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| 3. |
- Moberg, L., et al.
(författare)
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Increased blood cadmium levels were not associated with increased fracture risk but with increased total mortality in women: the Malmo Diet and Cancer Study
- 2017
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Ingår i: Osteoporosis International. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 28:8, s. 2401-2408
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to investigate if high levels of blood cadmium at baseline were associated with increased fracture risk during follow-up in middle-aged women. No increased fracture risk was observed during follow-up, but women with higher levels of cadmium had an increased overall mortality. Introduction Exposure to high levels of cadmium has been associated with an increased fracture risk. The aim was to investigate a perceived association between low levels of blood cadmium (B-Cd) at baseline and risk of first incident fracture. Methods From the population-based Malm Diet and Cancer Study Cardiovascular cohort, 2920 middle-aged women with available background questionnaire and B-Cd measurements were included. Women were divided into quartiles (Q) according to their cadmium levels (Cd-Q1 < 0.18 mu g/L, Cd-Q2 0.180.28 mu g/L, Cd-Q3 0.28-0.51 ae g/ L, and Cd-Q4 > 0.51 mu g/L). National registries were analysed for prospective risk of fractures or death. Associations between B-Cd and fracture risk were assessed by survival analysis (Cox regression analysis). Results In total, 998 first incident fractures occurred in women during a follow-up lasting 20.2 years (median) (12.5-21.2 years) (25th-75th percentile). Women in Cd-Q4 were more often current smokers than in Cd-Q1 78.4 vs. 3.3% (p < 0.001) and the number of cigarettes smoked per day correlated with B-Cd (r = 0.49; p < 0.001). The risk of fracture was not associated with baseline B-Cd in adjusted models. The hazard ratio (HR) Cd-Q4 vs. Cd-Q1 was 1.06 (95% confidence interval (CI) 0.89-1.27). In the multivariate Cox regression, independent variables for increased fracture risk were history of gastric ulcer and increasing age, whereas increasing body mass index (BMI) lowered fracture risk. Overall mortality was significantly higher for women with high B-Cd, HR 2.06 (95% CI 1.57-2.69). Conclusions Higher blood levels of cadmium did not increase fracture risk in middle-aged women but reduced overall survival.
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| 4. |
- Thacher, Jesse D., et al.
(författare)
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Occupational noise exposure and risk of incident stroke: a pooled study of five Scandinavian cohorts
- 2022
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Ingår i: OCCUPATIONAL AND ENVIRONMENTAL MEDICINE. - : BMJ. - 1351-0711 .- 1470-7926. ; 79:9, s. 594-601
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To investigate the association between occupational noise exposure and stroke incidence in a pooled study of five Scandinavian cohorts (NordSOUND). Methods We pooled and harmonised data from five Scandinavian cohorts resulting in 78 389 participants. We obtained job data from national registries or questionnaires and recoded these to match a job-exposure matrix developed in Sweden, which specified the annual average daily noise exposure in five exposure classes (L-Aeq8h): <70, 70-74, 75-79, 80-84, >= 85 dB(A). We identified residential address history and estimated 1-year average road traffic noise at baseline. Using national patient and mortality registers, we identified 7777 stroke cases with a median follow-up of 20.2 years. Analyses were conducted using Cox proportional hazards models adjusting for individual and area-level potential confounders. Results Exposure to occupational noise at baseline was not associated with overall stroke in the fully adjusted models. For ischaemic stroke, occupational noise was associated with HRs (95% CI) of 1.08 (0.98 to 1.20), 1.09 (0.97 to 1.24) and 1.06 (0.92 to 1.21) in the 75-79, 80-84 and >= 85 dB(A) exposure groups, compared with <70 dB(A), respectively. In subanalyses using time-varying occupational noise exposure, we observed an indication of higher stroke risk among the most exposed (>= 85 dB(A)), particularly when restricting analyses to people exposed to occupational noise within the last year (HR: 1.27; 95% CI: 0.99 to 1.63). Conclusions We found no association between occupational noise and risk of overall stroke after adjustment for confounders. However, the non-significantly increased risk of ischaemic stroke warrants further investigation.
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| 5. |
- Andersson, Eva M., 1968, et al.
(författare)
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Is Cadmium a Risk Factor for Breast Cancer - Results from a Nested Case-Control Study Using Data from the Malmo Diet and Cancer Study
- 2021
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Ingår i: Cancer Epidemiology Biomarkers & Prevention. - 1055-9965. ; 30:9, s. 1744-1752
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Tidskriftsartikel (refereegranskat)abstract
- Background: Some studies have shown that cadmium (Cd) is associated with breast cancer risk. One hypothesis is that Cd has estrogen-like properties. This case-control study investigated the association between breast cancer risk and blood Cd (BCd) levels. Methods: All breast cancers in the Malmo Diet and Cancer cohort were identified through linkage to the Swedish Cancer Registry, baseline (1991-1996) through 2014. Two controls per case were selected from the same cohort. BCd was analyzed at baseline. Associations were analyzed using logistic regression. Results: Mean BCd was 0.51 mg/L among 1,274 cases and 0.46 among 2,572 controls. There was an overall increased risk of breast cancer [OR, 1.18; 95% confidence interval (CI), 1.05-1.36] per mg/L of BCd. An increased risk was, however, only found at high BCd [OR, 1.34 (95% CI, 1.05-1.73)] for BCd more than 1.20 mg/L. The group with the highest BCd was mainly smokers. A spline indicated that at BCd less than 1.0 mg/L, the OR was not increased. The association with BCd was stronger in current smokers and at body mass index (BMI) above 25, while no modification due to receptor status was found. Conclusions: The results indicated increased risk of breast cancer only for high Cd exposure, which occurred mainly among smokers. This made it difficult to disentangle the effects of smoking and Cd, despite inclusion of smoking habits in the models. Impact: This study provides support for reducing Cd exposure through smoking cessation and dietary choice. On the population level, preventive measures against Cd pollution are warranted.
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| 6. |
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| 7. |
- Barregård, Lars, 1948, et al.
(författare)
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Normal variability of 22 elements in 24-hour urine samples - Results from a biobank from healthy non-smoking adults.
- 2021
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Ingår i: International journal of hygiene and environmental health. - : Elsevier BV. - 1618-131X .- 1438-4639. ; 233
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Tidskriftsartikel (refereegranskat)abstract
- Urine is often used for biomonitoring the exposure to elements. However, most studies report concentrations in spot urine samples, which may not accurately mirror the "gold standard" of complete 24-h (24h) urine samples. There are relatively few data published for 24h samples, and little information on the within- and between person variability.The present study aimed at assessing variability within and between individuals in 24h excretion for a number of elements in adults from the general population and the typical 24h excretion of these elements. In addition, we assessed concentrations adjusted for creatinine and specific gravity (SG), and associations between elements.60 healthy non-smokers (31 women and 29 men) from Sweden, aged 21-64 years, collected all urine during 24h (split into six separate samples) on two occasions, about one week apart. Concentrations of As, Br, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, P, Pb, S, Sb, Se, Sn, U, V, W, and Zn in urine were analyzed by inductively coupled plasma sector-field mass spectrometry (ICP-SF-MS) and 24h excretion rates were calculated for each day. The ratio of between-individual variance and the total variance, the intra-class correlation (ICC) was calculated based on natural log-transformed 24h excretion. Correlation coefficients were calculated between excretion rates (mass/24h), and concentrations adjusted for creatinine and SG.Geometric means (GM), and 90-percentiles are presented for each element. The 24h excretion was higher in men than in women for most elements, and the difference was statistically significant for Cr, Cu, Fe, Li, P, Pb, S, Se, U, V, and Zn. However, for Cd and Co, the excretion was higher in women. Variability between days was low for Cd, Co, Hg, Pb, Sn, Se, V, and Zn (ICC 0.75-0.90), highest for Cr (ICC=0.3) and Sb (ICC=0.18), and moderate for the other elements. Spearman's rank correlation coefficients were about 0.8-0.9 for 17 elements, and 0.3-0.7 for Br, Cu, P, S, Se. Excretion of P and S were highly correlated, and also associated with excretion of most of the other elements, especially Cu, Se, V, and Zn. A high correlation was also found between As and Hg, between Mo and W, as well as between Cr, Fe and Mn.These data present normal variability of 24h excretion of a number of elements, and can also be used as updated reference levels for elements with no or limited previous literature available. Information on variability within- and between individuals is important to know when designing studies with urine levels of elements used as exposure biomarker in studies of associations with health outcomes.
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| 8. |
- Börjesson, Jimmy, et al.
(författare)
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In vivo XRF analysis of mercury: the relation between concentrations in the kidney and the urine
- 1995
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 40:3, s. 413-426
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to determine the concentrations of mercury in organs of occupationally exposed workers using in vivo x-ray fluorescence analysis. Twenty mercury exposed workers and twelve occupationally unexposed referents participated in the study. Their mercury levels in kidney, liver and thyroid were measured using a technique based on excitation with partly plane polarized photons. The mercury levels in blood and urine were determined using atomic absorption spectrophotometry. The detection limit for mercury in the kidney was exceeded in nine of the exposed workers, but in none of the referents. The mean kidney mercury concentration (including estimates below the detection limits) was 24 mu g g(-1) in the exposed workers, and 1 mu g g(-1) in the referents. The association between mercury in the kidney and in urine was statistically significant, but it was unclear whether the relation was linear. The measurements on liver (n = 10) and thyroid (n = 8) in the exposed workers showed mercury levels below the detection limit. The study shows that it is now possible to measure the mercury concentrations in kidneys of occupationally exposed persons, using in vivo x-ray fluorescence. The estimated concentrations are in reasonable agreement with the limited human autopsy data, and the results of animal studies.
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| 9. |
- Ellingsen, D. G., et al.
(författare)
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The variability of arsenic in blood and urine of humans
- 2023
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Ingår i: Journal of Trace Elements in Medicine and Biology. - 0946-672X. ; 78
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Tidskriftsartikel (refereegranskat)abstract
- Background: Humans are exposed to inorganic and organic arsenic. The total arsenic (As) concentration in urine is a commonly used biomarker of exposure. However, little is known about variability of As in biological fluids and the diurnal variation of As excretion.Objectives: Main objectives were to assess the variability of As in urine, plasma (P-As), whole blood (B-As), and the blood cell fraction (C-As), and to assess diurnal variation of As excretion. Methods: Six urine samples were collected at fixed times during 24 h on two different days around one week apart among 29 men and 31 women. Blood samples were collected when the morning urine samples were delivered. The intra-class correlation coefficient (ICC) was calculated as the ratio of the between-individuals variance to the total observed variance.Results: Geometric mean (GM) 24 h urinary excretions of As (U-As24 h) were 41 and 39 mu g/24 h on the two days of sampling. Concentrations of B-As, P-As and C-As were highly correlated with U-As24 h and As in first void morning urine. No statistically significant differences were observed for the urinary As excretion rate between the different sampling times. A high ICC was observed for As in the cellular blood fraction (0.803), while ICC for first morning urine corrected for creatine was low (0.316).Conclusions: The study suggests that C-As is the most reliable biomarker for use in exposure assessment of individual exposure. Morning urine samples have low reliability for such use. No apparent diurnal variation was observed in the urinary As excretion rate.
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| 10. |
- Eriksson, Janna, 1992, et al.
(författare)
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Urinary iodine excretion and optimal time point for sampling when estimating 24-h urinary iodine
- 2023
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Ingår i: British Journal of Nutrition. - : Cambridge University Press (CUP). - 0007-1145 .- 1475-2662. ; 130:8, s. 1289-97
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Tidskriftsartikel (refereegranskat)abstract
- Iodine deficiency may cause thyroid dysfunction. The iodine intake in a population is measured by urinary iodine concentration (UIC) in spot samples or 24-h urinary iodine excretion (24UIE). 24UIE is considered the gold standard and may be estimated using an equation including UIC, urinary creatinine concentration, sex and age (e24UIE). The aims of this study were to evaluate the preferable timing of UIC when using this equation and assess the variability of UIE. Sixty healthy non-smoking women (n 31) and men (n 29) were included in Gothenburg, Sweden. Twelve urine samples were collected at six fixed times on two separate days. Variability was calculated for UIC, 24UIE, e24UIE, iodine excretion per hour (iHr) and UIC adjusted for creatinine and specific gravity. Median 24UIE was 156 mu g/24 h and the median UIC (all spot samples) was 104 mu g/l. UIC (P < 0 center dot 001), 24UIE (P = 0 center dot 001) and e24UIE (P < 0 center dot 001) were significantly higher in men. e24UIE was relatively similar to 24UIE. However, when e24UIE was calculated from UIC in the first void, it was about 15 % lower than 24UIE (P < 0 center dot 001). iHr was lowest in the morning and highest in the afternoon. Median iHr was higher in men (7 center dot 4 v. 5 center dot 3 mu g/h, P < 0 center dot 001). The variability of UIE was higher within individuals than between individuals. This study suggests that most time points for estimation of individual 24UIE are appropriate, but they should preferably not be collected in the first void.
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| 11. |
- Fransson, M. N., et al.
(författare)
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Physiologically-Based Toxicokinetic Model for Cadmium Using Markov-Chain Monte Carlo Analysis of Concentrations in Blood, Urine, and Kidney Cortex from Living Kidney Donors
- 2014
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Ingår i: Toxicological Sciences. - : Oxford University Press (OUP). - 1096-6080 .- 1096-0929. ; 141:2, s. 365-376
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Tidskriftsartikel (refereegranskat)abstract
- The health effects of low-level chronic exposure to cadmium are increasingly recognized. To improve the risk assessment, it is essential to know the relation between cadmium intake, body burden, and biomarker levels of cadmium. We combined a physiologically-based toxicokinetic (PBTK) model for cadmium with a data set from healthy kidney donors to re-estimate the model parameters and to test the effects of gender and serum ferritin on systemic uptake. Cadmium levels in whole blood, blood plasma, kidney cortex, and urinary excretion from 82 men and women were used to calculate posterior distributions for model parameters using Markov-chain Monte Carlo analysis. For never-and ever-smokers combined, the daily systemic uptake was estimated at 0.0063 mu g cadmium/kg body weight in men, with 35% increased uptake in women and a daily uptake of 1.2 mu g for each pack-year per calendar year of smoking. The rate of urinary excretion from cadmium accumulated in the kidney was estimated at 0.000042 day(-1), corresponding to a half-life of 45 years in the kidneys. We have provided an improved model of cadmium kinetics. As the new parameter estimates derive from a single study with measurements in several compartments in each individual, these new estimates are likely to be more accurate than the previous ones where the data used originated from unrelated data sets. The estimated urinary excretion of cadmium accumulated in the kidneys was much lower than previous estimates, neglecting this finding may result in a marked under-prediction of the true kidney burden.
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| 12. |
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| 13. |
- Hemmingsen, J. G., et al.
(författare)
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Controlled exposure to particulate matter from urban street air is associated with decreased vasodilation and heart rate variability in overweight and older adults
- 2015
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Ingår i: Particle and Fibre Toxicology. - : Springer Science and Business Media LLC. - 1743-8977. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Exposure to particulate matter (PM) is generally associated with elevated risk of cardiovascular morbidity and mortality. Elderly and obese subjects may be particularly susceptible, although short-term effects are poorly described. Methods: Sixty healthy subjects 25 males, 35 females, age 55 to 83 years, body mass index > 25 kg/m(2)) were included in a cross-over study with 5 hours of exposure to particle or sham filtered air from a busy street using an exposure-chamber. The sham-versus particle-filtered air had average particle number concentrations of similar to 23.000 versus similar to 1800/cm(3) and PM2.5 levels of 24 versus 3 mu g/m(3), respectively. The PM contained similar fractions of elemental and black carbon (similar to 20-25%) in both exposure scenarios. Reactive hyperemia and nitroglycerin-induced vasodilation in finger arteries and heart rate variability (HRV) measured within 1h after exposure were primary outcomes. Potential explanatory mechanistic variables included markers of oxidative stress (ascorbate/dehydroascorbate, nitric oxide-production cofactor tetrahydrobiopterin and its oxidation product dihydrobiopterin) and inflammation markers (C-reactive protein and leukocyte differential counts). Results: Nitroglycerin-induced vasodilation was reduced by 12% [95% confidence interval: -22%; -1.0%] following PM exposure, whereas hyperemia-induced vasodilation was reduced by 5% [95% confidence interval: -11.6%; 1.6%]. Moreover, HRV measurements showed that the high and low frequency domains were significantly decreased and increased, respectively. Redox and inflammatory status did not change significantly based on the above measures. Conclusions: This study indicates that exposure to real-life levels of PM from urban street air impairs the vasomotor function and HRV in overweight middle-aged and elderly adults, although this could not be explained by changes in inflammation, oxidative stress or nitric oxide-cofactors.
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| 14. |
- Molin, M, et al.
(författare)
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Mobilized mercury in subjects with varying exposure to elemental mercury vapour.
- 1991
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Ingår i: International Archives of Occupational and Environmental Health. - 0340-0131 .- 1432-1246. ; 63:3, s. 187-92
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Tidskriftsartikel (refereegranskat)abstract
- In a mercury mobilization test, 0.3 g of the complexing agent sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) was given orally to 10 workers with moderate occupational exposure to elemental mercury vapour, to 8 dentists with slight exposure, to 18 matched controls, and to 5 referents without amalgam fillings. In the workers, DMPS caused an increase in 24-h urinary mercury excretion by a factor of 10; in the dentists, 5.9; in the controls, 5.3; and in the amalgam-free referents, 3.8. Of the mercury excreted during 24 h, 59% appeared during the first 6 h. Close, albeit non-linear, associations were found between mobilized mercury and the premobilization mercury levels in plasma and urine, but not with the duration of occupational exposure or the rough estimate of the integrated function of blood levels vs time. The present data indicate that mercury mobilized after a single DMPS dose in close connection with exposure is mainly an index of recent exposure and is not significantly affected by slow body pools or long-term exposure.
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| 15. |
- Murgia, Nicola, et al.
(författare)
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8-ISOPROSTANE IN EXHALED BREATH CONDENSATE AFTER EXPERIMENTAL EXPOSURE TO WOOD SMOKE IN HUMANS
- 2016
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Ingår i: Journal of Biological Regulators and Homeostatic Agents. - 0393-974X. ; 30:1, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- Wood smoke, a well-known indoor and outdoor air pollutant, may cause adverse health effects through oxidative stress. In this study 8-isoprostane, a biomarker of oxidative stress, was measured in exhaled breath condensate (EBC) and urine before and after experimental exposure to wood smoke. The results were compared with measurements of other biomarkers of oxidative stress and inflammation. Thirteen subjects were exposed first to clean air and then, after 1 week, to wood smoke in an exposure chamber during 4-hour sessions. Exhaled breath condensate, exhaled nitric oxide, blood and urine were sampled before and at various intervals after exposure to wood smoke and clean air. Exhaled breath condensate was examined for 8-isoprostane and malondialdehyde (MDA), while exhaled air was examined for nitric oxide, serum for Clara cell protein (CC16) and urine for 8-isoprostane. 8-isoprostane in EBC did not increase after wood smoke exposure and its net change immediately after exposure was inversely correlated with net changes in MDA (r(s)= -0.57, p= 0.041) and serum CC16 (S-CC16) (r(p)= -0.64, p= 0.020) immediately after the exposure. No correlation was found between 8-isoprostane in urine and 8-isoprostane in EBC. In this study controlled wood smoke exposure in healthy subjects did not increase 8-isoprostane in EBC.
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| 16. |
- Nilsson Sommar, Johan, et al.
(författare)
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Long-term exposure to particulate air pollution and black carbon in relation to natural and cause-specific mortality: a multicohort study in Sweden
- 2021
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Ingår i: Bmj Open. - : BMJ. - 2044-6055. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To estimate concentration-response relationships for particulate matter (PM) and black carbon (BC) in relation to mortality in cohorts from three Swedish cities with comparatively low pollutant levels. Setting Cohorts from Gothenburg, Stockholm and Umea, Sweden. Design High-resolution dispersion models were used to estimate annual mean concentrations of PM with aerodynamic diameter <= 10 mu m (PM10) and <= 2.5 mu m (PM2.5), and BC, at individual addresses during each year of follow-up, 1990-2011. Moving averages were calculated for the time windows 1-5 years (lag1-5) and 6-10 years (lag6-10) preceding the outcome. Cause-specific mortality data were obtained from the national cause of death registry. Cohort-specific HRs were estimated using Cox regression models and then meta-analysed including a random effect of cohort. Participants During the study period, 7 340 cases of natural mortality, 2 755 cases of cardiovascular disease (CVD) mortality and 817 cases of respiratory and lung cancer mortality were observed among in total 68 679 individuals and 689 813 person-years of follow-up. Results Both PM10 (range: 6.3-41.9 mu g/m(3)) and BC (range: 0.2-6.8 mu g/m(3)) were associated with natural mortality showing 17% (95% CI 6% to 31%) and 9% (95% CI 0% to 18%) increased risks per 10 mu g/m(3) and 1 mu g/m(3) of lag1-5 exposure, respectively. For PM2.5 (range: 4.0-22.4 mu g/m(3)), the estimated increase was 13% per 5 mu g/m(3), but less precise (95% CI -9% to 40%). Estimates for CVD mortality appeared higher for both PM10 and PM2.5. No association was observed with respiratory mortality. Conclusion The results support an effect of long-term air pollution on natural mortality and mortality in CVD with high relative risks also at low exposure levels. These findings are relevant for future decisions concerning air quality policies.
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| 17. |
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| 18. |
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| 19. |
- Sällsten, Gerd, 1952, et al.
(författare)
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Variability of lead in urine and blood in healthy individuals
- 2022
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Ingår i: Environmental Research. - : Elsevier BV. - 0013-9351. ; 212
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lead is a non-essential toxic trace element. Lead in blood (BPb) is the most common biomarker of lead exposure but lead in urine (UPb) has also been used. There is, however, limited data on the variability of UPb in the general population and the association with BPb. Objectives: Our aims were to assess variability of lead in repeated blood and urine samples. The diurnal variation of UPb was also examined as well as associations with BPb. Methods: We established an openly available biobank including 60 healthy non-smoking individuals, 29 men and 31 women, 21–64 years of age (median 31 years), with repeated sampling of blood and urine. Timed urine samples were collected at six fixed time points in two 24 h periods, about one week apart, and adjusted for creatinine and specific gravity (SG). BPb and UPb were analyzed by inductively coupled plasma mass spectrometry. The within- and between-individual variabilities and intra-class correlation coefficients (ICCs; ratios of the between-individual to total observed variances) were calculated using mixed-effects models. Results: The ICCs for UPb samples were mostly above 0.5, when adjusted for creatinine or SG, and higher for overnight samples compared with daytime samples. The highest ICCs were obtained for BPb (ICC = 0.97) and for urine samples corrected for dilution by SG or creatinine. The ICC was 0.66 for overnight samples adjusted for creatinine. High correlations with BPb were found for 24 h UPb (rs = 0.77) and overnight samples, e.g. rs = 0.74 when adjusted for SG. There was diurnal variation of UPb with lowest excretion rate in overnight samples. There was also a significant association between the Pb excretion rate and urinary flow rate. Conclusions: In addition to BPb, UPb adjusted for creatinine or SG seems to be a useful biomarker for exposure assessment in epidemiological studies.
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