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PubMed1979

Exposure and accumulation of cadmium in populations from Japan, the United States, and Sweden.

Studies were carried out in Japan, United States, and Sweden regarding comparability of analytical methods for cadmium, daily intake of cadmium via food, daily amount of cadmium in feces, concentrations of cadmium in different tissues and the body burden of cadmium, urinary excretion of cadmium and cadmium concentrations in blood. It was found that the cadmium intake via food among adults is about 35 mug/day in Japan (Tokyo) and about 17 mug/day in the U.S. (Dallas) and Sweden (Stockholm). It varies with age in a way similar to calorie intake. Body burden increases rapidly with age. The half-time of cadmium is longer in muscles than in liver or kidneys. In the cross-sectional population samples studied (smokers and nonsmokers mixed) the average cadmium body burden at age 45 was about 21 mg in Japan, 9 mg in the U.S., and 6 mg in Sweden. Among nonsmokers in the U.S. and Sweden the body burden at age 45 was about 5-6 mg. The difference in average body burden for smokers and nonsmokers is explained by differences in smoking habits. Cadmium excretion in urine was closely correlated with body burden and about 0.005-0.01% of body burden is excreted daily in urine. Cadmium concentration in the blood was a good indicator of average recent intake over a 3-month period. Neither blood cadmium nor urine cadmium changed immediately after an increase of exposure level.

Adolescent↗
PubMed1986

Enhanced withdrawal from chickens of hexachlorobenzene (HCB) and pentachlorophenol (PCP) by colestipol, mineral oil, and/or restricted feeding.

Young chickens fed hexachlorobenzene (HCB) or pentachlorophenol (PCP) for 14 d at 10 ppm in the diet contained body burdens of 573 or 362 micrograms, respectively. These diets were withdrawn (d 0) and replaced for 21 d with diets containing 5% mineral oil (MO), or 5% colestipol (CO), a bile-acid-binding resin, or the chickens were restricted in feed intake to 50% of controls (50-RF), fed MO plus 50-RF, or CO plus 50-RF. Without any treatment during withdrawal, body burdens were reduced to 63% and 70% of the d 0 values for HCB and PCP, respectively. MO, CO, or 50-RF reduced body burdens of HCB to 37% of d 0 burdens, but the combination treatments with 50-RF reduced body burdens to 19% of d 0 values. PCP was at 35% of the d 0 burdens from 50-RF, while all other treatments had reduced body burdens to nondetectable amounts of less than 0.7 micrograms/bird by d 21 of withdrawal. Body fat was not reduced by mineral oil, but was reduced to some extent by CO, and was markedly reduced by 50-RF. 50-RF always reduced body burdens of PCP or HCB alone or in combination with MO or CO. These data are discussed in relationship to the nonbiliary excretion of xenobiotics.

Adipose Tissue↗
PubMed1995

Modeling of the toxicokinetics of polychlorinated dibenzo-p-dioxins and dibenzofurans in mammalians, including humans. II. Kinetics of absorption and disposition of PCDDs/PCDFs.

In the present study, a physiologically based model which describes the absorption and disposition kinetics of PCDDs/PCDFs (globally called PCDXs) in mammalian species, including humans, is developed. The model integrates the distribution model developed in the first article of this series, which described the fractional distribution of total PCDXs between liver and adipose tissues as a function of overall body concentration (G. Carrier, R. C. Brunet, and J. Brodeur, 1995, Toxicol. Appl. Pharmacol. 131, 253-266). In particular it is shown that the liver fraction of the total body burden decreases as overall body concentration decreases. Since elimination is principally through the liver, this leads to lower global elimination rates and longer half-lives of PCDXs. Absorption and disposition kinetics of PCDXs are captured using nonlinear differential equations with anatomically and biochemically relevant input parameters which are readily available. These are solved to predict the fate of PCDXs in liver, adipose tissues, and the body as a whole, as a function of time. Model simulations are in agreement with published data on absorption and disposition kinetics of these substances in rats and in humans. The kinetic profiles are similar for rats and humans, but the varying half-lives differ considerably in both species: weeks with rats, years with humans. For a given body burden, the adipose tissue concentrations vary in an inversely proportional manner to the mass of the adipose tissues; this observation has considerable relevance for interpretation of clinical data for humans. The interest of the proposed model rests upon the fact that it is generalized and broadly applicable: it allows the study of the kinetics of PCDXs for any pattern of exposure from background to highly toxic levels, taking into account variations in time of anatomical and biochemical parameters.

Absorption↗
PubMed1999

Retention level of Cs-137 and K-40 in some users of an Egyptian nuclear research center.

Body burden activities of Cs-137 and K-40 of about 120 humans, of composite sex, were measured using Inshas whole body counter facilities. The contained body burden activity in such distribution is found to be 3.5-10 Bq l-1 for Cs-137 and 3.39 x 10(-3) kg l-1 as well as 3.69 x 10(-3) kg l-1 for K-40 respectively for females and males. It was found, that the amount of Cs Kg l-1 K increases significantly with increase of either the body volumes and/or the total body potassium. It seemed reasonably to conjecture that, from the results of this study, the retention time of Cs-137 in body is closely connected to the amount of K-40. The discrimination factor related to the body burden content of Cs-137 to K-40 is also experimentally predicted. Moreover, the burden activities of Cs-137 and K-40 over a period of two years are scanned monthly. The results show a slight continuous increase in body burden activity of both elements. The net daily intakes of Cs-137 and K-40 are calculated using a formula developed from ICRP. The calculated results for K-40 show a variation ranging from 30 to 40 Bq per day for females and from 45 to 55 B per day for males. While for Cs-137 show a slight variation ranged from 5.2 to 6.8 Bq per day for a composite sex. The authors emphasise the importance of the periodic measurement of human population since both the consumed food chain and the environmental enclosure contained both radio elements. Accumulation of the daily ingested activity of Cs-137 and K-40, and of food eaten, showed that the predicted body burden retained activity is relatively higher by a range of 5-25% for Cs-137 and 3-15% for K-40 when compared with that detected by the whole body counter over the 24-month scanning course.

Adult↗
PubMed2005

Lead bioaccumulation in earthworms, Lumbricus terrestris, from exposure to lead compounds of differing solubility.

This study examined the relative effects of soluble and less soluble Pb compounds on Pb accumulation by Lumbricus terrestris. The earthworms were exposed to composted cattle manure contaminated with a range of concentrations of either soluble lead acetate trihydrate (PbAc) (14.5, 72.2, 137, 257, and 603 microg/g) or less soluble lead carbonate (Pb(CO(3))(2)) (5.09, 171, 575, and 710 microg/g). Relative Pb bioaccumulation rates in earthworms from the PbAc and Pb(CO(3))(2) lead carbonate trials were compared over time (0, 20, 40, and 60 days). The two molecular forms of Pb were heavily adsorbed onto the organic matter. Relative soluble Pb concentrations in the manure pore water were very low, at 0.049% and 0.022% of total Pb for PbAc and Pb(CO(3))(2), respectively. There was a significant uptake of lead by earthworms from both the readily soluble and less soluble forms of Pb. Regression surfaces relating organic matter total Pb concentration to exposure time and Pb body burden were compared. For the PbAc trial, the following equation was fitted: Body burden=2.3429+0.0014 x--0.0632 y+0.0008 xy (R(2)=0.8494, p<0.0001). For the Pb(CO(3))(2) trial, the equation was: Body burden=-2.0760--0.0067 x-0.2297 y-0.0038 y(2)+0.0003 xy (R(2)=0.5686, p<0.0001) (for x=organic matter Pb concentration in microg/g and y=time in days). The Pb bioaccumulation resulting from the PbAc exposure was significantly higher than that from Pb(CO(3))(2). Body burdens of earthworms exposed to PbAc were linearly related to exposure time and total Pb concentration. Worms exposed to Pb(CO(3))(2) had non-linear Pb accumulation over time that suggested a decrease in Pb bioavailability with increasing exposure time. The results indicate that L. terrestris feeding on detritus in the upper soil levels can mobilize and accumulate Pb from the principal transformation products of metallic Pb, as at shooting ranges and lead smelter sites.

Animals↗
PubMed2002

Infant exposure to dioxin-like compounds in breast milk.

We used a one-compartment, first-order pharmacokinetic model to predict the infant body burden of dioxin-like compounds that results from breast-feeding. Validation testing of the model showed a good match between predictions and measurements of dioxin toxic equivalents (TEQs) in breast-fed infants, and the exercise highlighted the importance of the assumption of the rate of dissipation of TEQs in the infant. We evaluated five nursing scenarios: no nursing (i.e., formula only), and nursing for 6 weeks, 6 months, 1 year, and 2 years. We assumed that an infant weighs 3.3 kg at birth and is exposed to a total of 800 pg TEQ/day by consumption of breast milk, leading to an estimated body weight-based dose of 242 pg TEQ/kg-day, which drops to 18 pg TEQ/kg-day after 1 year. This decline is due to declines in dioxin concentration in mother's milk and infant body weight increases. This range is significantly higher, on a body-weight basis, than adult TEQ exposure, which has been estimated to average about 1 pg TEQ/kg-day. For the nursing scenarios of >or= 6 months, we predict that body burdens (expressed as a body lipid concentration) peak at around 9 weeks at 44 ppt TEQ lipid. We predict that the body burden of the formula-fed infants will remain below 10 ppt TEQ lipid during the first year. These results compare to the current adult average body burden of 25 ppt TEQ lipid. We also found that an infant who had been breast-fed for 1 year had an accumulated dose 6 times higher than a 1-year-old infant who had not been breast-fed. For a 70-year lifetime, individuals who had been breast-fed had an accumulated dose 3-18% higher than individuals who had not been breast-fed.

Adult↗
PubMed2001

MTBE inhaled alone and in combination with gasoline vapor: uptake, distribution, metabolism, and excretion in rats.

The purpose of these studies was to extend previous evaluation of methyl tert-butyl ether (MTBE)* tissue distribution, metabolism, and excretion in rats to include concentrations more relevant to human exposure (4 and 40 ppm) and to determine the effects of coinhalation of the volatile fraction of unleaded gasoline on the tissue distribution, metabolism, and excretion of MTBE. Groups of male F344 rats were exposed nose-only for 4 hours to 4, 40, or 400 ppm 14C-MTBE or to 20 or 200 ppm of the light fraction of unleaded gasoline (LFG) containing 4 or 40 ppm 14C-MTBE, respectively. To evaluate the effects of repeated inhalation of LFG on MTBE tissue distribution, metabolism, and excretion, rats were exposed for 4 hours on each of 7 consecutive days to 20 or 200 ppm LFG with MTBE (4 or 40 ppm) followed on the eighth day by a similar exposure to LFG containing 14C-MTBE. Subgroups of rats were evaluated for respiratory parameters, initial body burdens, rates and routes of excretion, and tissue distribution and elimination. The concentrations of MTBE and its chief metabolite, tert-butyl alcohol (TBA), were measured in blood and kidney immediately after exposure, and the major urinary metabolites-2-hydroxyisobutyric acid (IBA) and 2-methyl-1,2-propanediol (2MePD)-were measured in urine. Inhalation of MTBE alone or as a component of LFG had no concentration-dependent effect on respiratory minute volume. The initial body burdens of MTBE equivalents achieved after 4 hours of exposure to MTBE did not increase linearly with exposure concentration. MTBE equivalents rapidly distributed to all tissues examined, with the largest percentages distributed to liver. The observed initial body burden did not increase linearly between 4 and 400 ppm. At 400 ppm, elimination half-times of MTBE equivalents from liver increased and from lung, kidney, and testes decreased compared with the two smaller doses. Furthermore, at 400 ppm the elimination half-time for volatile organic compounds (VOCs) in breath was significantly shorter and the percentage of the initial body burden of MTBE equivalents eliminated as VOCs in breath increased significantly. These changes probably reflect a saturation of blood with MTBE at 400 ppm and strongly suggest that the uptake and fate of MTBE are notably different at exposure concentrations above and below 400 ppm. Single and repeated coexposure to 20 and 200 ppm LFG with MTBE had opposite effects on the total body burden of MTBE equivalents present at the end of exposures compared with those achieved after 4 and 40 ppm MTBE exposures: 20 ppm LFG increased and 200 ppm LFG significantly decreased the burdens of MTBE equivalents present. The effects of coexposure to LFG on blood levels of MTBE equivalents paralleled the effects on body burden. These differences in overall uptake of MTBE equivalents cannot be attributed to alterations of minute volume. The reason for the increase in overall uptake after 20-ppm LFG exposure is not clear. Decreased MTBE absorption (uptake) after single and repeated coexposure to 200 ppm LFG may be due to a decrease in solubility of MTBE in blood caused by inhalation of other hydrocarbons. Investigations on the blood/air partition coefficient of MTBE in the absence and presence of LFG would be needed to confirm this hypothesis. Single and repeated coexposure to either 20 or 200 ppm LFG significantly decreased the percentage of the initial body burden from MTBE equivalents in tissues, including liver, kidney, and testes, immediately and 72 hours after

Air Pollutants↗
PubMed1981

Effects of age and body lead burden on CNS function in young children. I. slow cortical potentials.

The effects of body Pb burden on slow cortical potentials were studied in 63 children aged 13-75 months. Slow wave (SW) voltage during sensory conditioning varied as a linear function of blood lead (PbB) level. The slope of this function, moreover, changed systematically with age. For children under 5 years of age, SW voltage tended to be positive at low PbBs and to be negative above 30 micrograms/dl. For children over 5 years of age, SW voltage tended to be negative at low PbBs and to be less negative (or positive) above 30 micrograms/dl. These results provide evidence of altered CNS function at the lowest Pb effect level ever reported.

Aging↗
PubMed2004

Levels of PCB 126 and PCB 153 in plasma and tissues in goats exposed during gestation and lactation.

The aim of the present study was to gain knowledge about the disposition of the PCB congeners 126 and 153 in a goat model where pregnant does were given oral doses of PCB from day 60 of gestation until delivery. The goat kids were thus exposed to PCB during gestation and lactation. The doses of PCB 153 and PCB 126 were 98 and 49 ng/kg body wt/day, respectively. PCB levels were measured in plasma from the does at day 90 of gestation and at delivery, and in plasma from the kids at birth and four weeks post partum. Concentrations of PCB were analysed in brain, liver and fat tissue from the does six weeks after delivery and in liver and fat tissue from the kids at nine months of age. The ratio of estimated body burden to ingested dose in the does, was 0.95 +/- 0.07 for PCB 153 and 0.41 +/- 0.03 for PCB 126. Approximately 9% of PCB 153 and 6% of PCB 126 was transferred from the mothers to their kids during gestation and lactation. Prenatal exposure contributed to a much lower fraction of the body burden than postnatal PCB intake via milk, due to the fact that almost 100% of the PCB 153 transferred from the does to kids was transferred via milk, and the PCB 126 intake via milk was threefold higher than the calculated body burden. The hepatic PCB 126 concentration in both does and kids was significantly higher than the concentration in fat, in contrast to PCB 153, where the highest concentrations were found in fat. A significant difference in body burden between the does at delivery, the newborn kids, and the kids at four weeks of age, did not influence the plasma concentration of PCB 153 on a fat weight basis, which showed no difference with sampling time. Our results suggest that PCB 126 and PCB 153 have different pharmacokinetic properties. The higher levels of PCB 126 in liver tissue compared to fat tissue confirm the concept of hepatic sequestration. The similar blood concentration of PCB 153 in the does at delivery and their newborn kids despite the considerable difference in body burden, suggests a high degree of placental transfer. This supports previous observations that low molecular weight, lipid-soluble, non-polar chemicals reach the fetus to the greatest possible extent. For PCB 153, the body burden may provide the appropriate dose metric at steady state, but may give a minor underestimation of PCB 126 at low environmental exposure levels due to hepatic sequestration.

Animals↗
PubMed1987

Mortality among plutonium and other radiation workers at a plutonium weapons facility.

Mortality among 5,413 white males who were employed for at least two years at a plutonium weapons facility was investigated to measure risks from exposures to low levels of plutonium and external radiation. When compared with US death rates, fewer deaths than expected were found for all causes of death, all cancers, and lung cancer. No bone cancer was observed. An excess of brain tumors was found for the cohort in general. Elevated rate ratios for all causes of death and all lymphopoietic neoplasms were found when employees with plutonium body burdens greater than or equal to 2 nCi were compared with those with body burdens less than 2 nCi, while accounting for age, calendar period, and induction time. Increased rate ratios were also found for esophageal, stomach, colon, and prostate cancers, and for lymphosarcomas and reticulum cell sarcomas. No elevated rate ratios were noted for bone and liver cancers. When employees with cumulative exposures greater than or equal to 1 rem were compared with those with exposures less than 1 rem, elevated rate ratios were found for myeloid leukemia, lymphosarcoma and reticulum cell sarcoma, liver neoplasms, and unspecified brain tumors. No overall dose-response relationships were found for plutonium or external radiation exposures. Standardized rate ratios increased, however, as plutonium body burden levels increased for all causes, all cancers, and digestive cancers at five years induction time. Standardized rate ratios also increased as external radiation exposure categories increased for all lymphopoietic cancers and unspecified brain tumors for a two-year induction period. With the exception of analyses of combined categories of death, and perhaps of lung cancer, confidence limits were wide, indicating limited precision. Nevertheless, these findings suggest that increased risks for several types of cancers cannot be ruled out at this time for individuals with plutonium body burdens of greater than or equal to 2 nCi. Plutonium-burdened individuals should continue to be studied in future years.

Air Pollutants, Radioactive↗
PubMed2002

Coupling toxicokinetics and pharmacodynamics for predicting survival of abalone (Haliotis diversicolor supertexta) exposed to waterborne zinc.

We developed a mortality model, by coupling an acute toxicity model and a pharmacodynamic model, to predict survival of abalone (Haliotis diversicolor supertexta) exposed to waterborne zinc (Zn). We conducted a laboratory 14-day exposure experiment to obtain biokinetic parameters of depuration rate constant (k(2)) and bioconcentration factor (BCF). A one-compartment uptake-depuration model was used to fit the exposure data to estimate BCF and k(2) values. The acute toxicity model was developed based on the receptor theory and was verified with LC(50)(t) data obtained from a 7-day acute toxicity test. A highly significant correlation (r(2) = 0.98) was found between predictions and LC(50)(t) data for the acute toxicity model, indicating a successful description of 7-day LC(50)(t) data of Zn in abalone. The predicted time course of lethal body burden of Zn in abalone was compared with measured data, showing that the average percent error was 14.04 +/- 3.02%. A refined pharmacodynamic model was expressed as the Hill equation, which in terms of waterborne Zn and LC(50)(t) data was used to fit observed mortality percentages to determine the Hill coefficient (r(2) = 0.98). The proposed mortality model in terms of whole body burden and lethal body burden at site of action was then employed to predict the time-varying mortality of abalone exposed to various Zn concentrations in pond water. Our results demonstrate that 96-h LC(50) and incipient LC(50) for H. diversicolor supertexta exposed to Zn are 1.1 and 1.05 mg L(-1), respectively. Our predictions also demonstrate that equilibrium lethal body burden at site of action is about 198 microg g(-1), whereas the mortalities never reach 50% when H. diversicolor supertexta exposed to Zn is < or = 1 mg L(-1).

Animals↗
PubMed1992

The assessment of episodic metal pollution. I. Uses and limitations of tissue contaminant analysis in rainbow trout (Oncorhynchus mykiss) after short waterborne exposure to cadmium or copper.

Rainbow trout were exposed to 8 h episodes of either Cd (0.1 or 0.2 mg/L) or Cu (0.1 or 0.6 mg/L) at pH 7. Gill, liver, mucus, blood, skin, muscle, and body remainder were examined for metal content during and after exposure. Accumulation of Cd occurred mostly in the gill, liver, mucus, and muscle, with the gill supporting 21-36% of the body burden. Copper appeared primarily in the gill, liver and mucus, with the gill supporting 4-40% of the body burden. After exposure, rapid clearance of toxicant from the gill and mucus occurred within 16 h, while contamination in the liver increased, resulting in the liver supporting 11-14% or 58-61% of the Cd or Cu body burdens respectively 24 h after exposure. The time of sampling after exposure as well as choice of organs and control data are important aspects of post-exposure analysis. In the absence of control data, exposure status may be derived from the ratio of contaminants in the gill/liver and the distribution of the body burden.

Animals↗
PubMed2002

Impact of physiologically based pharmacokinetic modeling on benchmark dose calculations for TCDD-induced biochemical responses.

In risk assessment, noncancer risk is currently estimated using a no observed adverse effect level (NOAEL) from an experimental dose-response study, divided by uncertainty factors, to estimate a presumably safe level of human exposure. A benchmark dose approach, in which an effective dose (ED) resulting in a specified percentage increase over background for effects is estimated by empirical modeling, has been proposed as a replacement for the NOAEL methodology. The aim of this analysis is to compare methods for estimation of body burden resulting in a 1 or 10% maximum increase over background (BB(01) or BB(10)) for biochemical responses following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in female Sprague-Dawley rats. In one method, an ED resulting in a prespecified increase in response over background was estimated using average daily doses and an empirical Hill model. The ED was then converted to an equivalent body burden by a simple kinetic model assuming steady-state conditions, half-life of TCDD in the rat, and 100% absorption of TCDD. Alternatively, a mechanistic physiologically based pharmacokinetic (PBPK) model of TCDD in the rat was used to predict body burdens for administered doses. These PBPK-modeled body burdens were then used directly by the Hill model to calculate a BB(01) or BB(10). In general, the body burden values derived from EDs were within five-fold of BB(01) or BB(10) calculated from the PBPK model. BB(01) and BB(10) values from both methods were within two orders of magnitude of current human general population exposure to all dioxin-like compounds.

Animals↗
PubMed1999

Chelation therapy for patients with elevated body lead burden and progressive renal insufficiency. A randomized, controlled trial.

BACKGROUND: Nephropathy is known to occur in persons exposed to high levels of lead, but the question of whether long-term exposure to low levels of environmental lead is associated with impaired renal function remains controversial. OBJECTIVE: To examine whether chelation therapy slows the progression of renal insufficiency in patients with mildly elevated body lead burden. DESIGN: Randomized, controlled trial. SETTING: Academic medical center in Taiwan. PATIENTS: 32 patients with chronic renal insufficiency (serum creatinine level > 132.6 micromol/L [1.5 mg/dL] and < 353.8 micromol/L [4.0 mg/dL]), mildly elevated body lead burden (> 0.72 micromol [150 microg] of lead per 72-hour urine collection and < 2.90 micromol [600 microg] of lead per 72-hour urine collection [EDTA mobilization tests]), and no history of heavy lead exposure. INTERVENTION: The treatment group received 2 months of chelation therapy; the control group received no therapy. MEASUREMENTS: The reciprocal of serum creatinine (1/Cr) was used as an index of progressive renal insufficiency. RESULTS: Rates of progression of renal insufficiency were similar in the treatment group and the control group during a 12-month baseline observation period (1/Cr, 0.000054 L/micromol per month compared with 0.000046 L/micromol per month; P > 0.2). After the 2-month treatment period, improvement in renal function was greater in the treatment group than in the control group. In the 12 months after the treatment period, renal insufficiency progressed more slowly in the treatment group than in the control group (1/Cr, 0.000033 +/- 0.00038 L/micromol per month compared with 0.000045 +/- 0.000038 L/micromol per month; P = 0.0030). CONCLUSION: Chelation therapy seems to slow the progression of renal insufficiency in patients with mildly elevated body lead burden. This implies that long-term exposure to low levels of environmental lead may be associated with impaired renal function in patients with chronic renal disease.

Adult↗
PubMed1989

A model for scaling the results of U excretion rate studies in beagle dogs to man.

A biokinetic model was used to simulate retention and excretion of two forms of U: ammonium diuranate (ADU), a relatively soluble form, and U3O8, a relatively insoluble form. These two U forms represent those most likely to be encountered in the U milling industry. The simulation model was compared with results from a study of aerosols of commercial refined U ore inhaled by laboratory animals. Beagle dogs were exposed by inhalation to ADU aerosols to achieve a median initial body burden of 0.058 mg U kg-1 body weight (within a range of 0.016 to 0.64 mg U kg-1), or to U3O8 aerosols to achieve a median retained body burden of 0.28 mg U kg-1 (0.030-0.81 mg U kg-1). The simulation model accurately described the accumulation of nephrotoxic concentrations of U in kidneys of animals exposed to ADU. Very small fractions of the initial body burden of U3O8 were translocated to kidney, and these fractions were overestimated by the model. The model showed general agreement with results of other laboratory animal studies and with available information from human exposures to ADU, UF6, or U3O8.

Administration, Inhalation↗
PubMed1989

Enhanced withdrawal of polychlorinated biphenyls: a comparison of colestipol, mineral oil, propylene glycol, and petroleum jelly with or without restricted feeding.

Meat type chickens were fed a commercial mixture of polychlorinated biphenyl (PCB), Aroclor 1254, at 10 ppm for 14 days, then treated for 21 days to hasten the withdrawal of PCB with either mineral oil (MO), petroleum jelly (PJ), propylene glycol (PG), or colestipol (CO) at 5% of the diet, or at 10% of the diet when restricted to 50% of control intake (50% FR). Whole carcass analyses for PCB revealed that MO + 50% FR reduced PCB to 1.91 mg/bird, or 32% of the body burden (5.96 mg) in nontreated chickens previously fed PCB, whereas those restricted in feed intake by 50% (50% FR) had almost no change (6.44 mg/bird) in body burdens. The PJ, PG, and CO in combination with 50% FR reduced body burdens of PCB to 47, 57, and 77%, respectively, of the control value. When treated with MO, PJ, PG, or CO alone (no 50% FR), chickens had body burdens reduced to only 67 to 90% of control, depending on th compound. Thus, feed restriction was necessary for the MO and PJ to have their greatest effect. Carcass lipid values and body weight gains were markedly reduced by the feed restriction. The CO reduced carcass lipid in nonrestricted chickens by 30%.

Animal Feed↗
PubMed1999

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.

Adult↗
PubMed2001

Short-Term dermal absorption and penetration of chemicals from aqueous solutions: theory and experiment.

Dermal penetration of organic chemical-contaminated water from showering and bathing scenarios is a concern of regulatory agencies that have been tasked with determining safe exposure levels. During household showering and bathing, nearly the entire surface area of the body is exposed for short periods of time (5-15 minutes). The primary means of predicting body burden during brief exposures is to estimate total chemical penetrated from the steady-state penetration rate using a skin permeability coefficient. A variety of approaches has been recommended to estimate "body burden." The purpose of this investigation was to collect experimental data from short-term exposures to an organic chemical (dibromomethane [DBM]) in aqueous solution so that methods for estimating body burden could be compared. Rat skins were exposed in vitro to saturated aqueous solutions of DBM for 20 minutes and the amount of chemical in the receptor solution and the skin was analyzed. The total DBM mass in the receptor solution and the skin was taken to represent an in vivo body burden. These results were compared with the estimates of penetration from steady-state calculations, square root of time calculations, and a biologically based mathematical model. Results indicated that the amount of chemical in the skin and its fate during short exposures is important. The square root of time approach predicted total amount of chemical absorbed and penetrated better than did the steady-state approach. The biologically based mathematical model accurately predicted total body burden and could be used to distinguish between the amount of chemical in the skin and the amount of chemical that penetrated through the skin, which would be useful for understanding local toxicity.

Absorption↗