Relationships between environmental organochlorine contaminant residues, plasma corticosterone concentrations, and intermediary metabolic enzyme activities in Great Lakes herring gull embryos.
Experiments were conducted to survey and detect differences in plasma corticosterone concentrations and intermediary metabolic enzyme activities in herring gull (Larus argentatus) embryos environmentally exposed to organochlorine contaminants in ovo. Unincubated fertile herring gull eggs were collected from an Atlantic coast control site and various Great Lakes sites in 1997 and artificially incubated in the laboratory. Liver and/or kidney tissues from approximately half of the late-stage embryos were analyzed for the activities of various intermediary metabolic enzymes known to be regulated, at least in part, by corticosteroids. Basal plasma corticosterone concentrations were determined for the remaining embryos. Yolk sacs were collected from each embryo and a subset was analyzed for organochlorine contaminants. Regression analysis of individual yolk sac organochlorine residue concentrations, or 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs), with individual basal plasma corticosterone concentrations indicated statistically significant inverse relationships for polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs), total polychlorinated biphenyls (PCBs), non-ortho PCBs, and TEQs. Similarly, inverse relationships were observed for the activities of two intermediary metabolic enzymes (phosphoenolpyruvate carboxykinase and malic enzyme) when regressed against PCDDs/PCDFs. Overall, these data suggest that current levels of organochlorine contamination may be affecting the hypothalamo-pituitary-adrenal axis and associated intermediary metabolic pathways in environmentally exposed herring gull embryos in the Great Lakes. (+info)
Biomarkers for exposure to ambient air pollution--comparison of carcinogen-DNA adduct levels with other exposure markers and markers for oxidative stress.
Human exposure to genotoxic compounds present in ambient air has been studied using selected biomarkers in nonsmoking Danish bus drivers and postal workers. A large interindividual variation in biomarker levels was observed. Significantly higher levels of bulky carcinogen-DNA adducts (75.42 adducts/10(8) nucleotides) and of 2-amino-apidic semialdehyde (AAS) in plasma proteins (56.7 pmol/mg protein) were observed in bus drivers working in the central part of Copenhagen, Denmark. In contrast, significantly higher levels of AAS in hemoglobin (55.8 pmol/mg protein), malondialdehyde in plasma (0. 96 nmol/ml plasma), and polycyclic aromatic hydrocarbon (PAH)-albumin adduct (3.38 fmol/ microg albumin) were observed in the suburban group. The biomarker levels in postal workers were similar to the levels in suburban bus drivers. In the combined group of bus drivers and postal workers, negative correlations were observed between bulky carcinogen-DNA adduct and PAH-albumin levels (p = 0.005), and between DNA adduct and [gamma]-glutamyl semialdehyde (GGS) in hemoglobin (p = 0.11). Highly significant correlations were found between PAH-albumin adducts and AAS in plasma (p = 0.001) and GGS in hemoglobin (p = 0.001). Significant correlations were also observed between urinary 8-oxo-7, 8-dihydro-2'-deoxyguanosine and AAS in plasma (p = 0.001) and PAH-albumin adducts (p = 0.002). The influence of the glutatione S-transferase (GST) M1 deletion on the correlation between the biomarkers was studied in the combined group. A significant negative correlation was only observed between bulky carcinogen-DNA adducts and PAH-albumin adducts (p = 0.02) and between DNA adduct and urinary mutagenic activity (p = 0.02) in the GSTM1 null group, but not in the workers who were homozygotes or heterozygotes for GSTM1. Our results indicate that some of the selected biomarkers can be used to distinguish between high and low exposure to environmental genotoxins. (+info)
Lead and hypertension in a sample of middle-aged women.
OBJECTIVES: The role of lead exposure as a risk factor for hypertension is less well defined among women than among men. This case-control study assessed the relation of blood and bone lead concentrations to hypertension in women. METHODS: Cases and controls were a subsample of women from the Nurses' Health Study. Hypertension was defined as a physician diagnosis of hypertension between 1988 and 1994 or measured systolic blood pressure > or = 140 mm Hg or diastolic blood pressure > or = 90 mm Hg. RESULTS: Mean (SD) blood lead concentration was 0.15 (0.11) mumol/L; mean tibia and patella lead concentrations by K-x-ray fluorescence were 13.3 (9.0) and 17.3 (11.1) micrograms/g, respectively. After adjustment for potentially confounding factors, an increase from the 10th to the 90th percentile of patella lead values (25 micrograms/g) was associated with approximately 2-fold (95% confidence interval = 1.1, 3.2) increased risk of hypertension. There was no association between hypertension and either blood or tibia lead concentrations. CONCLUSIONS: These findings support a potentially important role for low-level lead exposure as a risk factor for hypertension among non-occupationally exposed women. (+info)
Impact of diet on lead in blood and urine in female adults and relevance to mobilization of lead from bone stores.
We measured high precision lead isotope ratios and lead concentrations in blood, urine, and environmental samples to assess the significance of diet as a contributing factor to blood and urine lead levels in a cohort of 23 migrant women and 5 Australian-born women. We evaluated possible correlations between levels of dietary lead intake and changes observed in blood and urine lead levels and isotopic composition during pregnancy and postpartum. Mean blood lead concentrations for both groups were approximately 3 microg/dl. The concentration of lead in the diet was 5.8 +/- 3 microg Pb/kg [geometric mean (GM) 5.2] and mean daily dietary intake was 8.5 microg/kg/day (GM 7.4), with a range of 2-39 microg/kg/day. Analysis of 6-day duplicate dietary samples for individual subjects commonly showed major spikes in lead concentration and isotopic composition that were not reflected by associated changes in either blood lead concentration or isotopic composition. Changes in blood lead levels and isotopic composition observed during and after pregnancy could not be solely explained by dietary lead. These data are consistent with earlier conclusions that, in cases where levels of environmental lead exposure and dietary lead intake are low, skeletal contribution is the dominant contributor to blood lead, especially during pregnancy and postpartum. (+info)
Juvenile hypothyroidism among two populations exposed to radioiodine.
We found an epidemic of juvenile hypothyroidism among a population of self-defined "downwinders" living near the Hanford nuclear facility located in southeast Washington State. The episode followed massive releases of 131I. Self-reported data on 60 cases of juvenile hypothyroidism (<20 years of age) among a group of 801 Hanford downwinders are presented, as well as data concerning the thyroid status of approximately 160,000 children exposed to radioiodine before 10 years of age as a result of the 26 April 1986 Chernobyl explosion in the former Soviet Union. These children were residents of five regions near Chernobyl. They were examined by standardized screening protocols over a period of 5 years from 1991 to 1996. They are a well-defined group of 10 samples. Fifty-six cases of hypothyroidism were found among boys and 92 among girls. Body burdens of 137Cs have been correlated with hypothyroidism prevalence rates. On the other hand, the group of juvenile (<20 years of age) Hanford downwinders is not a representative sample. Most of the 77 cases of juvenile hypothyroidism in the Hanford group were diagnosed from 1945 to 1970. However, the ratio of reported cases to the county population under 20 years of age is roughly correlated with officially estimated mean levels of cumulative thyroid 131I uptake in these counties, providing evidence that juvenile hypothyroidism was associated with radioiodine exposures. Because even subtle hypothyroidism may be of clinical significance in childhood and can be treated, it may be useful to screen for the condition in populations exposed to radioiodine fallout. Although radiation exposure is associated with hypothyroidism, its excess among fallout-exposed children has not been previously quantified. (+info)
Estimation of the dermal absorption of m-xylene vapor in humans using breath sampling and physiologically based pharmacokinetic analysis.
A physiologically-based pharmacokinetic model, containing a skin compartment, was derived and used to simulate experimentally determined exposure to m-xylene, using human volunteers exposed under controlled conditions. Biological monitoring was conducted by sampling, in exhaled alveolar air and blood, m-xylene and urinary methyl hippuric acid concentrations. The dermal absorption of m-xylene vapor was successfully and conveniently studied using a breath sampling technique, and the contribution to m-xylene body burden from the dermal route of exposure was estimated to be 1.8%. The model was used to investigate the protection afforded by an air-fed, half-face mask. By iteratively changing the dermal exposure concentration, it was possible to predict the ambient concentration that was required to deliver the observed urinary excretion of methylhippuric acid, during and following inhalation exposure to 50 ppm m-xylene vapor. This latter extrapolation demonstrates how physiologically-based pharmacokinetic modeling can be applied in a practical and occupationally relevant way, and permitted a further step not possible with biological monitoring alone. The ability of the model to extrapolate an ambient exposure concentration was dependent upon human metabolism data, thereby demonstrating the mechanistic toxicological basis of model output. The methyl hydroxylation of m-xylene is catalyzed by the hepatic mixed function oxidase enzyme, cytochrome P450 2E1 and is active in the occupationally relevant, (<100 ppm) exposure range of m-xylene. The use of a scaled-up in vitro maximum rate of metabolism (Vmaxc) in the model also demonstrates the increasingly valuable potential utility of biokinetic data determined using alternative, non-animal methods in human chemical-risk assessment. (+info)
Evaluation of diabetes mellitus, serum glucose, and thyroid function among United States workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin.
OBJECTIVE: Some studies suggest that exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may affect glucose metabolism and thyroid function. To further assess the relation between exposure to TCDD and endocrine function, data from the largest morbidity study of industrial workers exposed to TCDD were examined. METHODS: A cross sectional study of workers employed > 15 years earlier in the manufacture of 2,4,5-trichlorophenol or one of its derivatives at two United States chemical plants was conducted. The referent group consisted of people with no occupational exposure to phenoxy herbicides and were recruited from the neighbourhoods where the workers lived. RESULTS: A total of 281 workers and 260 unexposed referents participated. The mean current serum lipid adjusted TCDD concentration among workers was 220 pg/g lipid, and among referents was 7 pg/g lipid (p < 0.05). The half life extrapolated TCDD concentrations (the estimated TCDD concentration when occupational exposure to TCDD stopped) among workers averaged 1900 pg/g lipid (range: not detected--30,000 pg/g lipid). Overall, the prevalence of diabetes mellitus was not significantly different between the workers and referents. Also, there was not a significant positive trend between prevalence of diabetes and increasing serum TCDD concentration. However, diabetes was found in six of 10 (60%) workers with current serum TCDD concentrations > 1500 pg/g lipid. After excluding subjects being treated for diabetes, workers in the group with the highest half life extrapolated TCDD concentrations had a significantly increased adjusted mean serum glucose concentration compared with referents (p = 0.03). Workers were also found to have a significantly higher adjusted mean free thyroxine index compared with referents (p = 0.02), especially among workers in the group with the highest half life extrapolated TCDD concentrations. However, no evidence was found that workers exposed to TCDD were at increased risk of thyroid disease. CONCLUSIONS: These findings provide modest evidence that exposure to TCDD may affect thyroid function and glucose metabolism. (+info)
Follow up of workers previously exposed to silver solder containing cadmium.
OBJECTIVES: To study longitudinal biological monitoring data on urinary and blood cadmium collected in a small cohort of nine workers who had been brazing for several years with solders containing cadmium. METHODS: Cadmium was measured by neutron activation analysis in livers and kidneys, and estimates of renal function were carried out in 1983 and 1995. During the intervening period exposure to cadmium was dramatically reduced by local exhaust ventilation control and substitution of the solder containing cadmium. RESULTS: From urinary protein measurements there was evidence within the group of increasing renal tubular damage over the 12 year period, even though exposure to cadmium was dramatically reduced over this period and almost eliminated by 1995. There was no evidence from serum creatinine of decreasing glomerular filtration rate, and the renal tubular handling of calcium, phosphate, or urate had not worsened significantly. Blood and urinary cadmium concentrations reduced significantly over the 12 year period but were still substantial in 1995. Blood cadmium concentrations tended to reflect cadmium body burden in 1995 when exposure had been low for several years, and decreased most significantly during 1983-90. By contrast urinary cadmium concentrations only decreased significantly from about 1990 onwards. Urinary cadmium was not significantly correlated with liver or kidney cadmium concentration in either 1983 or 1995. This may be due to the level of tubular dysfunction in the cohort. Calculated cumulative excretion of cadmium over the 12 year period was substantially greater than the loss of cadmium measured in livers and kidneys and the derived loss in body burden. Reasons for this are discussed. It is possible that in cohorts, where renal damage is apparent, urinary concentrations reflect a substantial component of current exposure rather than stored body losses. CONCLUSIONS: The data reinforce the concept that blood cadmium concentrations may not always reflect recent exposure, but may reflect body burden derived from historical exposure depending on the degree of current exposure; and that the decline in urinary and blood cadmium measurements after removal from, or reduction in, exposure will be slow and depend on the historical body burden. (+info)