Nonadditive hepatic tumor promoting effects by a mixture of two structurally different polychlorinated biphenyls in female rat livers.

This study evaluates and quantifies the interactive hepatic tumor promoting effects of two PCBs, the Ah receptor agonist PCB 126 (3,3',4,4',5-pentachlorobiphenyl) and the constitutive androstane receptor (CAR) agonist PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl). Promotion of altered hepatic foci was evaluated utilizing a medium-term 8-week bioassay for promoters of hepatocarcinogenesis. The assay employs placental glutathione-S-transferase positive (GST-P+) liver cell foci as markers of preneoplasia in female Fischer 344 rats treated with the known initiator diethylnitrosamine followed by partial hepatectomy and by gavage exposure to test chemicals. GST-P+ foci were quantified by histomorphometry and were reported as areas and numbers of GST-P+ foci within the area of liver examined. For PCB 126, the doses were 0.1, 1.0, and 10 microg/kg body weight. For PCB 153, the doses were 10, 100, 1000, 5000, and 10,000 microg/kg body weight. Combined PCB 126 and 153 exposures were 0.1 + 10, 1 + 100, 10 + 1000, 10 + 5000, and 10 + 10,000 microg/kg, respectively. Individual PCB treatment resulted in dose dependent increases in liver and adipose concentrations. Hepatic PCB 153 levels were significantly increased (p < 0.01) after combined exposure. Treatment with PCB 126 or PCB 153 alone resulted in a significant (p < 0.01) dose dependent increase in GST-P+ foci area and number compared with controls. Treatment with the mixture of PCB 126 and 153 resulted in antagonistic GST-P+ focus formation (p < 0.001) for both foci area and number. The less than additive effect was present at all 5 PCB 126/PCB 153 dose combinations, including the low doses of PCB 126 and 153 that did not show significant promotional activity alone.

Gas chromatographic determination of catecholestrogens following isolation by solid-phase extraction.

A sensitive and specific assay for the determination of the catecholestrogens 2-hydroxyestradiol (2-OHE2) and 4-hydroxyestradiol (4-OHE2) using gas chromatography with electron-capture detection (GC-ECD) is described. The formation of 2- and 4-OHE2 was assessed following activation of 17beta-estradiol in the microsomal fraction of female rat livers. The analytes were isolated by solid-phase extraction, derivatized to their heptafluorobutyryl esters with heptafluorobutyric acid anhydride, and subjected to solvent exchange prior to analysis; this resulted in minimal chromatographic interference, long column life, and stable derivatized analytes. Derivatized catechols were separated and confirmed with dual column chromatography (DB-5 and DB-608) and quantitated using GC-ECD. The DB-608 column was preferred for quantitation as it provided better 4-OHE2 resolution from interference. Key validation parameters for the assay include sensitivity, intra- and inter-assay precision, and accuracy. Instrument sensitivity and limits of detection (LOD) and quantitation (LOQ) were determined statistically from fortification data approaching expected limits. For 2-OHE2 and 4-OHE2, respective values for these parameters were; instrument sensitivities of 0.4 and 0.7 pg, LODs of 0.8 and 1.3 ng/mg, and LOQs of 2.6 and 4.3 ng/mg.

Effects of malathion on survival, growth, development, and equilibrium posture of bullfrog tadpoles (Rana catesbeiana).

Bullfrog (Rana catesbeiana) tadpoles were exposed to malathion in water in a 28-d static renewal test. The effects of malathion on survival, growth, development, and loss of equilibrium posture were determined. Survival was significantly decreased at malathion concentrations of 2,500 micrograms/L and higher. Development of tadpoles was delayed significantly by malathion exposure as indicated by a dose-related decrease in developmental stage over time. Development of tadpoles in the 1,000-microgram/L and higher treatment groups was significantly delayed from that observed in the control. The effects of malathion on developmental stage suggest that malathion may decrease thyroid function in tadpoles, as it does in other species. Maintenance of equilibrium posture following agitation of the test containers was significantly impaired in tadpoles in all the malathion treatment groups (500 to 3,000 micrograms/L) relative to the control. Maintenance of equilibrium posture was thus the most sensitive end point measured in this study. Loss of equilibrium posture could increase predation losses and decrease feeding in populations of bullfrog tadpoles in the field. However, concentrations of malathion that produced adverse effects in our study are higher than published, measured concentrations found in wetlands or streams.

1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene and polychlorinated biphenyls and breast cancer: combined analysis of five U.S. studies.

BACKGROUND: Environmental exposure to organochlorines has been examined as a potential risk factor for breast cancer. In 1993, five large U.S. studies of women located mainly in the northeastern United States were funded to evaluate the association of levels of 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) and polychlorinated biphenyls (PCBs) in blood plasma or serum with breast cancer risk. We present a combined analysis of these results to increase precision and to maximize statistical power to detect effect modification by other breast cancer risk factors. METHODS: We reanalyzed the data from these five studies, consisting of 1400 case patients with breast cancer and 1642 control subjects, by use of a standardized approach to control for confounding and assess effect modification. We calculated pooled odds ratios (ORs) and 95% confidence intervals (CIs) by use of the random-effects model. All statistical tests were two-sided. RESULTS: When we compared women in the fifth quintile of lipid-adjusted values with those in the first quintile, the multivariate pooled OR for breast cancer associated with PCBs was 0.94 (95% CI = 0.73 to 1.21), and that associated with DDE was 0.99 (95% CI = 0.77 to 1.27). Although in the original studies there were suggestions of elevated breast cancer risk associated with PCBs in certain groups of women stratified by parity and lactation, these observations were not evident in the pooled analysis. No statistically significant associations were observed in any other stratified analyses, except for an increased risk with higher levels of PCBs among women in the middle tertile of body mass index (25-29.9 kg/m(2)); however, the risk was statistically nonsignificantly decreased among heavier women. CONCLUSIONS: Combined evidence does not support an association of breast cancer risk with plasma/serum concentrations of PCBs or DDE. Exposure to these compounds, as measured in adult women, is unlikely to explain the high rates of breast cancer experienced in the northeastern United States.

Joint effects of nine polychlorinated biphenyl (PCB) congeners on breast cancer risk.

BACKGROUND: Polychlorinated biphenyls (PCB) have been a major environmental health concern because of their wide distribution and persistence in the environment. Estimating joint effects of all congeners in a single analysis is complicated by correlation among exposure levels, and the resulting collinearity makes the results difficult to interpret. METHODS: Patients with breast-related surgery at Yale-New Haven Hospital were interviewed using a standardized questionnaire, and breast adipose tissue samples were analysed for nine PCB congeners (74, 118, 138, 153, 156, 170, 180, 183, 187). The study recruited 490 women (304 cases and 186 controls) between 1994 and 1997. Logistic ridge regression was used to analyse the instability caused by collinearity. RESULTS: Although total PCB did not appear to be associated with breast cancer risk, significant differences in effect were observed among the nine congeners. Logistic ridge regression demonstrated a protective effect on breast cancer risk for a potentially anti-oestrogenic and dioxin-like congener, 156, while two phenobarbital, CYP1A and CYP2B inducers had an adverse effect, 180 and 183. This analysis also suggested that a protective effect for another phenobarbital congener, 153, was largely explained by instability caused by collinearity. CONCLUSIONS: These results indicate that studies of PCB congeners and health require an in-depth statistical analysis in order to better understand the complex issues related to their collinearity.

Field evaluation of a portable photoionization detector for assessing exposure to solvent mixtures.

To evaluate a portable photoionization detector for assessing personal exposure to solvent mixtures, a set of 26 side-by-side, time-weighted average (TWA) personal breathing zone samples were collected during various construction painting tasks by two different sampling methods: (1) standard charcoal sorbent tubes analyzed by gas chromatography (CST/GC), and (2) a direct-reading photoionization detector coupled with an extended data-logger (PID). The TWA concentrations of the hydrocarbons detected by CST/GC analysis were summed for comparison with the TWA concentration obtained from the direct-reading PID. Based on linear regression between the log TWA concentrations of the two sampling methods, the data were highly correlated (r2 = 0.95). Since the solvents had effects that may be considered additive, threshold limit values (TLVs) for mixtures were developed using American Conference of Governmental Industrial Hygienists formulas to evaluate solvent exposure. The logs of the TLV mixture data from the sampling methods were highly correlated (r2 = 0.94). Based on the linear regression analyses, the response of the portable PID was highly correlated to the CST/GC results for hydrocarbon mixtures encountered during various painting tasks. Due to the short duration of tasks, highly fluctuating exposures, and complexity of the mixtures, the PID may provide the most cost-effective, detailed exposure assessment for solvent mixtures.

Lack of promotional effects of groundwater contaminant mixtures on the induction of preneoplastic foci in rat liver.

F344 rats were exposed to drinking water mixtures of seven of the most common groundwater contaminants associated with hazardous waste sites [arsenic, benzene, chloroform, chromium, lead, phenol, and trichloroethylene (TCE)] as the full mixture or submixtures of the organic and/or inorganic chemicals. The lowest concentrations (1x) of the individual chemicals were environmentally realistic and below what would be expected to induce significant short-term toxicity. This study was intended to determine if previously reported increases in localized hepatocellular proliferation in response to these chemicals might be correlated with increased risk for hepatocarcinogenesis. Rats were exposed via a drinking water solution to the full seven- chemical mixture (at 1x and 10x concentrations), submixtures of the organic or inorganic chemicals (at 10x concentrations), a mixture of TCE, lead, and chloroform (TLC submixture at 10x and 100x concentrations), or deionized water as a control. The rats were evaluated for promotion of placental glutathione-S-transferase (GST-P) positive preneoplastic liver cell foci after diethylnitrosamine (DEN) initiation and partial hepatectomy. Focus formation, cell proliferation, and apoptosis were evaluated after exposure to DEN or saline controls, the chemical mixtures or deionized water controls, or combinations of these treatments. The total number and area of GST-P positive foci in DEN-treated rats exposed to the full seven-chemical mixture was increased as compared with the DEN-water controls, but this was statistically significant only for total focus area in the 1x dose group. In DEN-treated rats, the inorganic or TLC submixtures resulted in a significant reduction in number and area of GST-P positive foci. Focus area also was decreased in the organic submixture-treated group, but not significantly. Hepatocellular proliferation was not significantly changed in the chemical mixture saline groups as compared with the mixture water controls. After DEN treatment, however, cell proliferation was significantly decreased after the 10x seven-chemical and organic mixture treatments and the 100x TLC mixture treatment. Different groups showed either increased or decreased apoptotic rates which did not correlate well with proliferation rates or focus formation. Mixtures of these seven chemicals, therefore, did not appear to act as promoters of hepatic foci at environmentally relevant concentrations, and some mixture combinations appeared to decrease promotional activity.

Comparison of organochlorine pesticide and polychlorinated biphenyl residues in human breast adipose tissue and serum.

The presence of organochlorine pesticides, such as p,p'-DDT[2,2-bis(p-chlorophenyl)-1,1,1-trichloroethanel, and of polychlorinated biphenyls (PCBs) in human serum and adipose tissue has been reported in many studies over the last four decades. Recently, debate has heightened concerning the link of these compounds to breast cancer. To clarify and resolve this issue, accurate analytical residue data must be obtained. Separation of the organochlorine pesticides from the PCBs in breast tissue is critical to obtaining valid residue data. Based on methods refined in the Analytical Laboratory at Colorado State University, accurate residue levels were established for nine individual PCB congeners and eight organochlorine pesticides. The breast adipose tissue method used was a modification of the Mills et al. and de Faubert Maunder et al. methods. The serum method employed was a modification of the Burse et al. method. Both breast adipose tissue and serum from 36 women were analyzed, and correlations of the residues from the two substrates were evaluated. Serum concentrations of p,p'-DDE, the primary metabolite of p,p'-DDT, were correlated (alpha = .05) with the concentrations of p,p'-DDE in human breast adipose tissue (r = .808). Serum concentrations of the PCB congener BZ 153 were also significantly correlated to the human breast adipose tissue concentrations of BZ 153 (r = .377). No significant relationship was found between serum concentrations and tissue residues for 15 of the 17 compounds analyzed. This lack of correlation between breast adipose tissue and serum, as well as an absence of the compound residues in serum, emphasized that adipose tissue should be analyzed in addition to serum to fully understand the relationship of the organochlorine compounds to breast cancer.

Quality assurance/quality control procedures for chlorinated hydrocarbons in human breast adipose tissue.

Extensive literature exists supporting the accumulation of organochlorine pesticides such as DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane], and polychlorinated biphenyls (PCBs) in human adipose tissue. Debate has surfaced concerning the link between these environmental contaminants and human breast cancer. Accurate residue analysis and proper analytical procedures are critical in determining the extent to which these compounds play a role in human breast cancer. Further, adequate quality assessment/quality control (QA/QC) is critical for reliable residue analysis. The purpose of this research was twofold: (1) to find an appropriate surrogate for human breast adipose tissue for spiking purposes, as human samples are difficult to obtain, and (2) to develop a human breast adipose tissue pool that yields adequate reproducibility with low coefficients of variation (CVs) for each compound of interest. Using a previously validated method developed in the Analytical Laboratory at Colorado State University, rendered ovine adipose tissue was found to be a suitable spiking material, as it was free of interfering compounds and behaved in a manner similar to human breast adipose tissue throughout the analytical method. Further, this analytical method was used to produce data on three control pool preparations: (A) blended human breast adipose tissue (n = 26), (B) blended and partially rendered human breast adipose tissue (n = 12), and (C) fully blended and rendered human breast adipose tissue (n = 15). The CVs between control pools vary up to 20% for a single compound. The most reproducible preparation procedure requires full blending and rendering.

1995 STP Young Investigator Award recipient. Increased rate of apoptosis correlates with hepatocellular proliferation in Fischer-344 rats following long-term exposure to a mixture of groundwater contaminants.

Apoptosis was evaluated in the livers of Fischer-344 rats following observations of increased hepatocellular proliferation from exposures, at low parts per million (ppm) levels, to a drinking water mixture of 7 groundwater contaminants during a 6-mo time-course study. The 7 chemicals used are among the most frequently detected contaminants associated with hazardous waste sites: arsenic, benzene, chloroform, chromium, lead, phenol, and trichloroethylene. Significant increases in 5-bromo-2'-deoxyuridine hepatocellular labeling were present in a unique pattern surrounding large hepatic veins (0.5-2.0 mm). This did not appear to be a regenerative response due to cytotoxicity, as assessed by the absence of increased plasma enzyme activity and the absence of hepatocellular lesions. Immunohistochemical staining for apoptosis, using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method showed patterns of labeling in treated animals that directly correlated to areas of increased hepatocyte proliferation. Apoptotic activity was maximum at the 1-mo exposure time point, whereas proliferating hepatocytes reached a maximum rate at the 10-day time point. This may have been triggered as a compensatory response to the increased cell proliferation or as a protective response to remove cells with altered DNA due to chemical mixture exposure. The principal findings of this paper are that (a) apoptosis directly correlated with changes in cell proliferation: (b) observed effects were produced by repeated exposures to a relatively low-level chemical mixture; and (c) the TUNEL method detected apoptotic cells at very early and late stages, potentially increasing the observable time period for apoptosis.

A gas-liquid system for enzyme kinetic studies of volatile organic chemicals. Determination of enzyme kinetic constants and partition coefficients of trichloroethylene.

A gas-liquid system was developed for enzyme kinetic study with volatile organic chemicals (VOCs) by modification of the gas uptake method for the in vivo physiologically based pharmacokinetic experiment. This gas-liquid system, designed in our laboratory, is composed of: 1) a diffusion chamber for adjusting initial vapor concentration by mixing ambient air and the VOCs; 2) a condenser for maintaining the liquid level in the incubation chamber; 3) a stainless-steel metal bellows pump for recirculating vapor in this system; 4) a gas chromatograph equipped with an autosampler and a flame ionization detector; and 5) a computer for controlling automation and data processing. Trichloroethylene (TCE) was used as a model chemical, and enzyme kinetics were studied by measuring the depletion of TCE in the gas phase of the system. TCE-at initial concentrations of 56, 620, and 1240 ppm-was incubated with rat liver microsomes and a NADPH regenerating system in a 100-ml round-bottom flask. Based on parallel enzyme assays using p-nitrophenol as a substrate, cytochrome P450IIE1, activity remained stable up to 3 hr under the incubation conditions (37 degrees C and pH 7.4) whereas addition of glutathione into the incubation mixture did not affect TCE metabolism. Kinetic constants were analyzed using a two-compartment pharmacokinetic model and the computer software SimuSolv. Statistical optimization using the maximum-likelihood method produced apparent in vitro Vmax and KM values of 0.55 nmol/mg protein/min and 0.9 microM, respectively. In addition, this newly developed methodology has a number of advantages over those reported in the literature, including the potential utility of determining tissue partition coefficients of VOCs for physiologically based pharmacokinetic modeling. We conclude that this gas-liquid system is suitable for determination of kinetic constants near realistic environmental concentrations of VOCs including TCE.

Exploration of an interaction threshold for the joint toxicity of trichloroethylene and 1,1-dichloroethylene: utilization of a PBPK model.

Physiologically based pharmacokinetic (PBPK) modeling and gas uptake experiments were utilized to verify the competitive inhibition mechanism of interaction between trichloroethylene (TCE) and 1,1-dichloroethylene (DCE) and to investigate the presence of an interaction threshold between the two chemicals. Initially, gas uptake experiments were conducted on Fischer 344 rats where the initial concentrations of both DCE and TCE were 2000:0, 0:2000, 2000:2000, 1000:0, 1000:1000, and 500:500 ppm, respectively. When the different modes of inhibition interactions (competitive, uncompetitive and noncompetitive) were employed in the PBPK model, the model description of the competitive inhibition provided the best description of the declining concentrations in the gas uptake chamber. Furthermore, to predict the range at which the interaction threshold would be found, the PBPK model included a mathematical description of the percentage of enzyme sites occupied by either chemical in the presence or the absence of the other. By comparing the percentage of occupied sites by one chemical, in the presence of the other, to those sites occupied in the absence of the latter, the PBPK model predicted a range of concentrations (100 ppm or less) of either chemical where the competitive inhibition interaction would not be observed. Consequently, gas uptake experiments were designed where the initial concentration was selected at 2000 ppm for one chemical while the other chemical was set at 100 in one experiment and 50 ppm in another. Under these conditions, the best stimulation to the concentration depletion curves in the gas uptake system of the chemical in the higher concentration was obtained when the PBPK model was run under the assumption of no-interaction. This substantiated the model predictions of the presence of observable interaction only at concentrations higher than 100 ppm.

The application of physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling for exploring risk assessment approaches of chemical mixtures.

When dealing with health impacts of environmental or occupational exposure such as groundwater contamination from or remediation effort associated with hazardous waste sites, we are obviously not facing individual, single chemicals. Thus, we are immediately confronted with the following questions: (1) Is single chemical risk assessment approach applicable to the multiple chemicals in hazardous waste sites? (2) How do we handle risk assessment of chemical mixtures? Although there were pioneering and commendable efforts from the USEPA to formulate guidelines for risk assessment of chemical mixtures, these guidelines were principally based on additivity concept. As new scientific advances are made, improvement and refinement of risk assessment methodology will be anticipated. At Colorado State University (CSU), our research effort is devoted to the challenges and potential applications of physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling in the risk assessment of chemical mixtures. With the ultimate goal of Predictive Toxicology, 3 specific research projects are described: (1) PBPK/PD modeling of toxicologic interactions between trichloroethylene (TCE) and 1,1-dichloroethylene (1,1-DCE) and the investigation and defining of an 'Interaction Threshold'; (2) PBPK/PD modeling of toxicologic interactions between Kepone and carbon tetrachloride (CCl4) and the coupling of Monte Carlo simulation for the prediction of acute toxicity; (3) PBPK modeling of the inhibition of pharmacokinetics and enzyme kinetics of TCE caused by low-level, repeated dosing of a chemical mixture of 7 groundwater contaminants. Since this paper is meant to be a commentary and the emphasis is on approaches for dealing with chemical mixtures, detailed presentation of data is avoided. These examples illustrate partially our ongoing research activities and the related ideas with respect to possible novel risk assessment applications to chemical mixtures.

Canine exposure to herbicide-treated lawns and urinary excretion of 2,4-dichlorophenoxyacetic acid.

A recent study by Hayes et al. (J. Natl. Cancer. Inst., 83: 1226-1231, 1991) found an increased risk of malignant lymphoma associated with exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) in pet dogs. We conducted a study to determine the extent to which dogs absorb and excrete 2,4-D in urine after contact with treated lawns under natural conditions. Among 44 dogs potentially exposed to 2,4-D-treated lawns an average of 10.9 days after application, 2,4-D concentrations greater than or equal to 10.0 micrograms/l were found in 33 dogs (75%) and concentrations of > or = 50 micrograms/l were found in 17 (39%). Among 15 dogs with no known exposure to a 2,4-D-treated lawn in the previous 42 days, 4 (27%) had evidence of 2,4-D in urine, 1 at a concentration of > or = 50 micrograms/l. The odds ratio for the association between exposure to a 2,4-D-treated lawn and the detection of > or = 50 micrograms/l 2,4-D in urine was 8.8 (95% confidence interval, 1.4-56.2). Dogs exposed to lawns treated within 7 days before urine collection were more than 50 times as likely to have 2,4-D at concentrations > or = 50 micrograms/l than dogs with exposure to a lawn treated more than 1 week previously (odds ratio = 56.0; 95% confidence interval, 10.0-312.2). The highest mean concentration of 2,4-D in urine (21.3 mg/l) was found in dogs sampled within 2 days after application of the herbicide.(ABSTRACT TRUNCATED AT 250 WORDS)

Two-stage evaluation of exposure to mercury and biomarkers of neurotoxicity at a hazardous waste site.

Communities surrounding the Rocky Mountain Arsenal (RMA), a Superfund site in Colorado, were studied in order to determine whether exposures to mercury were greater among persons who resided there than among residents of a comparison area 12-15 miles distant. From a census-based stratified random sample, 469 persons were interviewed and urine samples were obtained for biomonitoring. Mercury was detected in urine from 32 (6.8%) of the 469 persons sample at a detection limit of 5 ppb. Trace levels of mercury (detectable, but nonquantifiable) were found in 80 (17.1%) of the persons sampled. Neither the frequency of detection, the arithmetic mean, nor the geometric mean value for urine mercury was found to be statistically different when persons living near the site were compared to persons from the more distant comparison area. The risk of mercury exposure associated with demographic variables, residence, occupation, hobbies, dietary habits, water supply, housing, and activity patterns was evaluated. In the second stage of the evaluation, the Neurobehavioral Core Test Battery (NCTB) is being used to assess individual functional deficits and nervous system disorders associated with exposure to mercury and other neurotoxic chemicals.

Risk factors for exposure to arsenic at a hazardous waste site.

Communities surrounding the Rocky Mountain Arsenal (RMA), a Superfund site in Colorado, were studied in order to determine whether exposures to arsenic were greater among persons who resided there than among residents of a comparison area. A census was conducted in areas adjacent to the RMA and in a comparison area 12-15 miles distant. From a stratified random sample, 469 persons were interviewed and urine samples obtained. Arsenic was detected in urine from 43 (9.2%) of the 469 persons sampled at a detection limit of 10 ppb. Trace levels of arsenic (detectable, but non-quantifiable) were found in 184 (39.2%) of those persons sampled. Neither the frequency of detection, the arithmetic mean nor the geometric mean values for urine arsenic was found to be statistically different when persons living near the site were compared to persons from the more distant comparison area. Therefore, the data were pooled across the study areas to evaluate risk factors for exposure to arsenic in this population-based sample. Multivariate logistic regression analyses were conducted to evaluate the risk of arsenic exposure associated with variables included in the interviews while controlling for confounding. Pathways for exposure to arsenic were evaluated through analysis of residence history, occupation, hobbies, dietary habits, water supply, housing and activity patterns. Children of Hispanic origin or non-white race, children who drank less than three glasses of water daily, and children who spent more time outdoors had an increased risk of having > or = 10 ppb of arsenic in their urine. Among adults, younger persons, especially those less than 40 years of age, persons of Hispanic origin or nonwhite race, and those employed in occupations where arsenic is likely to be found had an increased risk of having > or = 10 ppb of urine arsenic. Consumption of red wine or fish during the week prior to sampling was associated with trace levels of arsenic in urine.

Investigation of solid-phase ozonolysis reactions for use in a personal sampling method for ozone.

Three ozonolysis reactions were tested in the solid phase for reproducibility and quantitative yield of an aldehyde reaction product. The three starting olefins were t-stilbene, 4,4'-dimethoxystilbene and 1,2-di-(4-pyridyl) ethylene which, when reacted with ozone, gave benzaldehyde, p-anisaldehyde and pyridine-4-aldehyde, respectively. The starting olefins were coated on a variety of solid substrates, exposed to known ozone concentrations and then analyzed for the corresponding aldehyde with a gas chromatograph equipped with a flame-ionization detector. The best combination found for all three reactions was with the starting olefin coated on 30/60 mesh Florisil. Consistent yield was obtained for the methoxystilbene reaction within one batch of sorbent; very reproducible results were obtained within four replicate samples for the pyridyl ethylene reaction. No consistency was obtained, however, with any of the reactions between batches of sorbents and between different sets of samples. Several problems were identified which led to the inconsistent results. The t-stilbene and pyridyl ethylene sorbents oxidized over time while stored to form high aldehyde blanks. All three aldehydes, once formed on the sorbent, were volatilized off the sorbent bed as a result of airflow through the bed. Several different solid sorbents were tried unsuccessfully as traps for the purged aldehydes. Finally, lower flow rates resulted in the finding that significant amounts of the aldehydes also were being formed by oxygen in the air sample. Since oxygen was a strong positive interferent, these reactions were considered unacceptable as indicators of ozone.

National study of chlorinated hydrocarbon insecticide residues in human milk, USA. I. Geographic distribution of dieldrin, heptachlor, heptachlor epoxide, chlordane, oxychlordane, and mirex.

Human milk samples obtained from 1436 women residing in the United States were analyzed by gas-liquid chromatography for the chlorinated hydrocarbon insecticides--dieldrin, chlordane, heptachlor, heptachlor epoxide, oxychlordane and Mirex. Dieldrin was found above the detection limit (1.0 ppb) in over 80% of all the samples collected. Chlordane was not found in any of the 1436 milk samples but its metabolite, oxychlordane, was found above the detection limit in 74% of the samples. Although heptachlor was recovered in less than 2% of the samples, its metabolite, heptachlor epoxide, was found above the detection limit in 63% of the samples. It was of considerable interest that Mirex was not positively identified in any of the samples. The proportion of samples with values above the detection limit for dieldrin, heptachlor epoxide and oxychlordane varied significantly among the five geographic regions with the southeastern United States having the highest mean residue level for each of these three contaminants. For the United States the mean fat adjusted residue levels of those samples above the detection limit were 164.2 ppb for dieldrin, 91.4 ppb for heptachlor epoxide, and 95.8 ppb for oxychlordane.