Biomedical subjects

David L Ashley

Publications and source records attributed to David L Ashley.

At least 19 recordsLinked to original sources

PubMed2006

Quantification of flavor-related compounds in the unburned contents of bidi and clove cigarettes.

Bidi cigarettes, small hand-rolled cigarettes produced primarily in India, are sold in the United States in a wide variety of candy-like flavors (e.g. dewberry, chocolate, clove) and are popular with adolescents. Many flavored bidis contain high concentrations of compounds such as eugenol, anethole, methyleugenol, pulegone, and estragole; several of these compounds have known toxic or carcinogenic properties. Clove cigarettes, or kreteks, are another highly flavored tobacco product with high levels of eugenol due to clove buds present in the tobacco filler. In this study, compounds in the burnable portion-the filler and wrapper material actually consumed during the smoking of bidis, kreteks, and U.S. cigarettes-were analyzed. Flavor-related compounds were solvent extracted from the burnable portion of each cigarette with methanol. An aliquot of the methanol extract was heated, and the sample headspace was sampled with a solid-phase microextraction fiber and introduced into a gas chromatograph-mass spectrometer for analysis in selected-ion monitoring mode. High levels of eugenol were detected in five clove-flavored bidi brands ranging from 78.6 to 7130 microg/cigarette (microg/cig), whereas diphenyl ether (128-3550 microg/cig) and methyl anthranilate (154-2360 microg/cig) were found in one grape-flavored bidi brand. A nontobacco herbal bidi brand contained the greatest variety of compounds, including anethole (489-665 microg/cig), eugenol (1670-2470 microg/cig), methyleugenol (27.7-36.6 microg/cig), safrole (32.4-34.4 microg/cig), myristicin (170-247 microg/cig), and elemicin (101-109 microg/cig). Filler from kreteks was found to contain high levels of eugenol, anethole, and coumarin. Flavored bidis and clove cigarettes contain a number of compounds that are present at levels far exceeding those reported in U.S. cigarette tobacco. Research is underway to determine the levels of these compounds delivered in smoke. It is not known what effect inhalation of these compounds has on smokers.

Filtration↗

PubMed2006

Quantification of 31 volatile organic compounds in whole blood using solid-phase microextraction and gas chromatography-mass spectrometry.

The prevalence of exposure to volatile organic compounds (VOCs) has raised concern about possible health effects resulting from chronic human exposure. To support studies exploring the relation between VOC exposure and health effects, we developed an automated analytical method using solid-phase microextraction (SPME), capillary gas chromatography (GC), and quadrupole mass spectrometry (MS). This method quantifies trace levels (low parts per trillion) of 14 halogenated alkanes, 5 halogenated alkenes, 10 aromatic compounds, and 2 other VOCs in human blood. Detection limits for the SPME-GC-MS method range from 0.005 to 0.12 microg/L, with linear calibration curves spanning three orders of magnitude. The improved throughput of this method will enable us to expand biomonitoring efforts to assess nonoccupational VOC exposure in large epidemiological studies.

Gas Chromatography-Mass Spectrometry↗

PubMed2006

Determination of 14 polycyclic aromatic hydrocarbons in mainstream smoke from U.S. brand and non-U.S. brand cigarettes.

Tobacco smoke contains thousands of chemical compounds, including many carcinogenic polycyclic aromatic hydrocarbons (PAHs). To determine the concentration ranges of PAHs in tobacco smoke and to understand what factors alter their levels, we quantitatively measured 14 PAHs in mainstream smoke from a transnational U.S. brand (Marlboro) and from locally popular brand cigarettes from 14 countries. We used standardized machine smoking conditions (35-mL puff volume, 60-s puff interval, and 2-s puff duration), extraction of total particulate matter from the Cambridge filters, and gas chromatography/mass spectrometry detection. Deliveries of total PAHs in mainstream smoke of local brands were statistically significantly higher (p < 0.01) than Marlboros in seven countries. In four countries, Marlboro cigarettes had mainstream smoke total PAH levels that were statistically significantly higher (p < 0.01) than local brands. In the remaining three countries, the differences in PAH levels were not statistically significant. Under standard machine smoking conditions, PAH levels were negatively correlated with cigarette filter ventilation levels. We found that several local brands containing primarily flue-cured tobacco filler had relatively high mainstream smoke PAH deliveries, in agreement with findings by previous researchers that flue-cured tobacco typically delivers more PAHs than other tobacco types. We also observed that PAHs were inversely correlated with total carcinogenic tobacco-specific nitrosamines and nitrate content, but these correlations were not statistically significant at the 95% confidence interval. The findings suggest that tobacco blend and nitrate levels may influence PAH deliveries, but other factors may confound this relation.

Air Pollutants↗

PubMed2006

Changes in breath trihalomethane levels resulting from household water-use activities.

Common household water-use activities such as showering, bathing, drinking, and washing clothes or dishes are potentially important contributors to individual exposure to trihalomethanes (THMs), the major class of disinfection by-products of water treated with chlorine. Previous studies have focused on showering or bathing activities. In this study, we selected 12 common water-use activities and determined which may lead to the greatest THM exposures and result in the greatest increase in the internal dose. Seven subjects performed the various water-use activities in two residences served by water utilities with relatively high and moderate total THM levels. To maintain a consistent exposure environment, the activities, exposure times, air exchange rates, water flows, water temperatures, and extraneous THM emissions to the indoor air were carefully controlled. Water, indoor air, blood, and exhaled-breath samples were collected during each exposure session for each activity, in accordance with a strict, well-defined protocol. Although showering (for 10 min) and bathing (for 14 min), as well as machine washing of clothes and opening mechanical dishwashers at the end of the cycle, resulted in substantial increases in indoor air chloroform concentrations, only showering and bathing caused significant increases in the breath chloroform levels. In the case of bromodichloromethane (BDCM), only bathing yielded a significantly higher air level in relation to the preexposure concentration. For chloroform from showering, strong correlations were observed for indoor air and exhaled breath, blood and exhaled breath, indoor air and blood, and tap water and blood. Only water and breath, and blood and breath were significantly associated for chloroform from bathing. For BDCM, significant correlations were obtained for blood and air, and blood and water from showering. Neither dibromochloromethane nor bromoform gave measurable breath concentrations for any of the activities investigated because of their much lower tap-water concentrations. Future studies will address the effects that changes in these common water-use activities may have on exposure.

Adult↗

PubMed2006

Using biologic markers in blood to assess exposure to multiple environmental chemicals for inner-city children 3-6 years of age.

We assessed concurrent exposure to a mixture of > 50 environmental chemicals by measuring the chemicals or their metabolites in the blood of 43 ethnically diverse children (3-6 years of age) from a socioeconomically disadvantaged neighborhood in Minneapolis. Over a 2-year period, additional samples were collected every 6-12 months from as many children as possible. We analyzed blood samples for 11 volatile organic compounds (VOCs), 2 heavy metals (lead and mercury, 11 organochlorine (OC) pesticides or related compounds, and 30 polychlorinated biphenyl (PCB) congeners. The evidence suggests that numerous VOCs originated from common sources, as did many PCBs. Longitudinal measurements indicate that between-child variance was greater than within-child variance for two VOCs (benzene, toluene), for both heavy metals (Pb, Hg), for all detectable OC pesticides, and for 15 of the measured PCB congeners (74, 99, 101, 118, 138-158, 146, 153, 156, 170, 178, 180, 187, 189, 194, 195). Despite the relatively small sample size, highest measured blood levels of 1,4-dichlorobenzene, styrene, m-/p-xylene, Pb, Hg, heptachlor epoxide, oxychlordane, dichlorodiphenyldichloroethene (p,p -DDE), trans-nonachlor, and PCB congeners 74, 99, 105, 118, 138, 146, 153, 156, 170, and 180 were comparable with or higher than 95th percentile measurements of older children and adults from national surveys. Results demonstrate that cumulative exposures to multiple environmental carcinogens and neurotoxins can be comparatively high for children from a poor inner-city neighborhood.

Biomarkers↗

PubMed2005

From the mouse to the mass spectrometer: detection and differentiation of the endoproteinase activities of botulinum neurotoxins A-G by mass spectrometry.

We have developed an assay (Endopep-MS) that detects the specific endoproteinase activities of all seven BoNT types by mass spectrometry (MS). Each BoNT type cleaves a unique site on proteins involved in neuronal transmission. Target peptide substrates based on these proteins identify a BoNT type by its enzymatic action on the substrate and the production of two peptide products, which are then detected by matrix-assisted laser desorption/ionization time-of-flight MS or liquid chromatography electrospray ionization MS/MS. We showed the ability to detect all seven toxin types in a multiplexed assay format. The detection limits achieved range from 0.039 to 0.625 mouse LD(50)/mL for toxin types A, B, E, and F in a buffer system. The Endopep-MS assay is the first to differentiate all seven BoNT types, is sensitive, specific, and has the potential to quantify toxin activity.

Amino Acid Sequence↗

PubMed2005

Determination of carcinogenic tobacco-specific nitrosamines in mainstream smoke from U.S.-brand and non-U.S.-brand cigarettes from 14 countries.

Tobacco-specific nitrosamines (TSNAs) comprise one of the major classes of carcinogenic compounds in mainstream cigarette smoke. As part of collaborative efforts between the World Health Organization and the U.S. Centers for Disease Control and Prevention (CDC) to reduce tobacco use and resulting disease, the CDC examined carcinogenic TSNA levels from cigarettes obtained from selected countries around the world. Using a modern, high-throughput liquid chromatography/mass spectrometry/mass spectrometry method under stringent quality control protocols, we determined the carcinogenic TSNA levels in mainstream smoke from a globally marketed brand, Marlboro, and from local top-selling cigarette brands from 14 countries. The levels of carcinogenic TSNAs in mainstream smoke collected using a 35-ml puff volume, 60-s puff interval, and 2-s puff duration correlated well (R=0.79, p<.0001) with previously reported levels in the corresponding tobacco filler. Marlboro cigarettes purchased in 10 countries had significantly higher carcinogenic TSNA levels in mainstream smoke than did local-brand cigarettes from the same country. In only one country, Brazil, were the carcinogenic TSNA levels in mainstream smoke from Marlboro cigarettes significantly lower than in the locally popular brand. However, carcinogenic TSNA levels in mainstream smoke from Brazilian Marlboro cigarettes were usually lower than those in mainstream smoke from the Marlboros purchased in the other 13 countries, suggesting a reason for the difference. The wide range of mainstream smoke carcinogenic TSNA levels measured in the present study (8.7-312 ng/cigarette) suggest that manufacturers can lower the carcinogenic TSNA levels and that, for similar filter ventilation, carcinogenic TSNA levels in the tobacco filler of a cigarette are a useful indicator of the corresponding levels in mainstream smoke.

Carcinogens↗

PubMed2005

Measurement of trihalomethanes and methyl tert-butyl ether in whole blood using gas chromatography with high-resolution mass spectrometry.

The prevalence of disinfection by-products in drinking water supplies has raised concerns about possible adverse health effects from chronic exposure to these compounds. To support studies exploring the relation between exposure to trihalomethanes (THMs) and adverse health effects, an automated analytical method was developed using capillary gas chromatography (GC) and high-resolution mass spectrometry (MS) with selected ion mass detection and isotope-dilution techniques. This method quantified trace levels of THMs (including chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and methyl tert-butyl ether (MTBE) in human blood. Analyte responses were adequate for measuring background levels after extraction of these volatile organic compounds with either purge-and-trap extraction or headspace solid-phase microextraction (SPME). The SPME method was chosen because of its ease of use and higher throughput. Detection limits for the SPME GC-MS method ranged from 0.3 to 2.4 ng/L, with linear ranges of three orders of magnitude. This method proved adequate for measuring the THMs and MTBE in most blood samples tested from a diverse U.S. reference population.

Environmental Monitoring↗

PubMed2005

Influence of tap water quality and household water use activities on indoor air and internal dose levels of trihalomethanes.

Individual exposure to trihalomethanes (THMs) in tap water can occur through ingestion, inhalation, or dermal exposure. Studies indicate that activities associated with inhaled or dermal exposure routes result in a greater increase in blood THM concentration than does ingestion. We measured blood and exhaled air concentrations of THM as biomarkers of exposure to participants conducting 14 common household water use activities, including ingestion of hot and cold tap water beverages, showering, clothes washing, hand washing, bathing, dish washing, and indirect shower exposure. We conducted our study at a single residence in each of two water utility service areas, one with relatively high and the other low total THM in the residence tap water. To maintain a consistent exposure environment for seven participants, we controlled water use activities, exposure time, air exchange, water flow and temperature, and nonstudy THM sources to the indoor air. We collected reference samples for water supply and air (pre-water use activity), as well as tap water and ambient air samples. We collected blood samples before and after each activity and exhaled breath samples at baseline and post-activity. All hot water use activities yielded a 2-fold increase in blood or breath THM concentrations for at least one individual. The greatest observed increase in blood and exhaled breath THM concentration in any participant was due to showering (direct and indirect), bathing, and hand dishwashing. Average increase in blood THM concentration ranged from 57 to 358 pg/mL due to these activities. More research is needed to determine whether acute and frequent exposures to THM at these concentrations have public health implications. Further research is also needed in designing epidemiologic studies that minimize data collection burden yet maximize accuracy in classification of dermal and inhalation THM exposure during hot water use activities.

Air Pollutants↗

PubMed2005

Children's exposure to volatile organic compounds as determined by longitudinal measurements in blood.

Blood concentrations of 11 volatile organic compounds (VOCs) were measured up to four times over 2 years in a probability sample of more than 150 children from two poor, minority neighborhoods in Minneapolis, Minnesota. Blood levels of benzene, carbon tetrachloride, trichloroethene, and m-/p-xylene were comparable with those measured in selected adults from the Third National Health and Nutrition Examination Survey (NHANES III), whereas concentrations of ethylbenzene, tetrachloroethylene, toluene, 1,1,1-trichloroethane, and o-xylene were two or more times lower in the children. Blood levels of styrene were more than twice as high, and for about 10% of the children 1,4-dichlorobenzene levels were greater than or equal to 10 times higher compared with NHANES III subjects. We observed strong statistical associations between numerous pairwise combinations of individual VOCs in blood (e.g., benzene and m-/p-xylene, m-/p-xylene and o-xylene, 1,1,1-trichloroethane and m-/p-xylene, and 1,1,1-trichloroethane and trichloroethene). Between-child variability was higher than within-child variability for 1,4-dichlorobenzene and tetrachloroethylene. Between- and within-child variability were approximately the same for ethylbenzene and 1,1,1-trichloroethane, and between-child was lower than within-child variability for the other seven compounds. Two-day, integrated personal air measurements explained almost 79% of the variance in blood levels for 1,4-dichlorobenzene and approximately 20% for tetrachloroethylene, toluene, m-/p-xylene, and o-xylene. Personal air measurements explained much less of the variance (between 0.5 and 8%) for trichloroethene, styrene, benzene, and ethylbenzene. We observed no significant statistical associations between total urinary cotinine (a biomarker for exposure to environmental tobacco smoke) and blood VOC concentrations. For siblings living in the same household, we found strong statistical associations between measured blood VOC concentrations.

Air Pollutants↗

PubMed2005

Botulinum neurotoxin detection and differentiation by mass spectrometry.

Botulinum neurotoxins (BoNTs) are proteases that cleave specific cellular proteins essential for neurotransmitter release. Seven BoNT serotypes (A-G) exist; 4 usually cause human botulism (A, B, E, and F). We developed a rapid, mass spectrometry-based method (Endopep-MS) to detect and differentiate active BoNTs A, B, E, and F. This method uses the highly specific protease activity of the toxins with target peptides specific for each toxin serotype. The product peptides derived from the endopeptidase activities of BoNTs are detected by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry. In buffer, this method can detect toxin equivalents of as little as 0.01 mouse lethal dose (MLD)50 and concentrations as low as 0.62 MLD50/mL. A high-performance liquid chromatography-tandem mass spectrometry method for quantifying active toxin, where the amount of toxin can be correlated to the amount of product peptides, is also described.

Amino Acid Sequence↗

PubMed2004

Solid-phase microextraction-based approach to determine free-base nicotine in trapped mainstream cigarette smoke total particulate matter.

Characterizing nicotine delivery from tobacco products is important in the understanding of their addictive potential. Most previous studies report total nicotine and have not differentiated between nicotine in its protonated or free-base form. Rather than simply determining total nicotine, the method described in this paper determines the amount of free-base nicotine associated with trapped mainstream smoke particulate matter generated using a standardized smoking machine protocol. This method quantitatively determines volatile free-base nicotine associated with the particulate phase portion of mainstream cigarette smoke using solid-phase microextraction combined with gas chromatography-mass spectrometry. The headspace above total particulate matter from mainstream cigarette smoke trapped on a Cambridge filter pad (CFP) was analyzed for free-base nicotine in 26 cigarette brands. The selected cigarette brands were chosen to cover a wide range of tar and nicotine deliveries as measured under Federal Trade Commission machine smoking conditions. In the CFP's headspace the free-base nicotine levels ranged from 0.01 to 0.08 mg/cigarette. The measured ranges of free-base nicotine were remarkably similar over the different tar and nicotine delivery categories of full-flavored, light, and ultralight cigarette brands.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

BCNU as second line therapy for recurrent high-grade glioma previously treated with Temozolomide.

BCNU has an established role in the treatment of high-grade gliomas and has previously been used as first line therapy for recurrent disease. More recently, Temozolomide has taken its place as first line therapy for recurrent high-grade glioma. Thus, BCNU has become our standard second line therapy following disease progression after Temozolomide therapy. This study retrospectively analysed the activity and toxicity associated with BCNU as second line therapy. Twenty four patients with recurrent high-grade gliomas were treated with BCNU having previously received Temozolomide. Patients received BCNU intravenously at 130-200 mg/m2 every 6 weeks. The median number of treatment cycles was two (range 1-8). Of the 24 patients, one patient (4%) achieved a partial response and six (25%) achieved a minor response or stable disease. BCNU was generally well tolerated. In conclusion, BCNU has limited activity as second line chemotherapy following the use of Temozolomide. Novel strategies are required in this patient group.

Adult↗

PubMed2004

Measurement of trihalomethanes and methyl tertiary-butyl ether in tap water using solid-phase microextraction GC-MS.

The prevalence of water disinfection byproducts in drinking water supplies has raised concerns about possible health effects from chronic exposure to these compounds. To support studies exploring the relation between exposure to trihalomethanes (THMs) and health effects, we have developed an automated analytical method using headspace solid-phase microextraction coupled with capillary gas chromatography and mass spectrometry. This method quantitates trace levels of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and methyl tertiary-butyl ether in tap water. Detection limits of less than 100 ng/L for all analytes and linear ranges of three orders of magnitude are adequate for measuring the THMs in tap water samples tested from across the United States. THMs are stable for extended periods in tap water samples after quenching of residual chlorine and buffering to pH 6.5, thus enabling larger epidemiologic field studies with simplified sample collection protocols.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

The recommended role of exposure biomarkers for the surveillance of environmental and occupational chemical exposures in military deployments: policy considerations.

A lack of individual exposure information limited the evaluation of exposure-outcome relationships after the Gulf War. Exposure concerns during Operation Enduring Freedom and Iraqi Freedom deployments have increased interest in individual environmental and occupational chemical exposure assessment. Currently, deployment assessments are conducted using intermittent ambient air monitoring, occasional focused evaluations based on these results, and postdeployment questionnaire documentation of exposure and/or health concerns. Although this strategy is an improvement over previous practice, it has limitations, including a reliance on evidence of an acute problem, to initiate in-depth health evaluation. Exposure biomarkers may have the potential to overcome some of the limitations of current environmental and occupational exposure assessment tools. This article examines current exposure assessment methods, reviews emerging technologies, and recommends a phased approach to introducing exposure biomarkers into a comprehensive occupational and environmental health surveillance program.

Biomarkers↗

PubMed2003

Assessment of tobacco-specific nitrosamines in the tobacco and mainstream smoke of Bidi cigarettes.

Bidi cigarettes, or bidis, are a tobacco product that originated in India and have been gaining popularity in the USA during the past few years, particularly with adolescents. As with conventional cigarettes, tobacco and smoke from bidis contain chemical constituents including carcinogenic chemicals such as the tobacco-specific nitrosamines (TSNAs). To help better assess the potential public health risk associated with bidi cigarettes, we developed modern high throughput methods to accurately quantify TSNA levels in tobacco and mainstream cigarette smoke particulate. We determined the TSNA levels in the tobacco filler and mainstream smoke from 14 bidi cigarette brands. In the bidi tobacco filler, the 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) levels ranged from 0.09 to 0.85 microg/g, while N'-nitrosonornicotine (NNN) levels ranged from 0.15 to 1.44 microg/g. These amounts are comparable with those in typical American blended cigarettes. The levels of NNK in mainstream smoke from bidis ranged from 2.13 to 25.9 ng/cigarette, and NNN levels ranged from 8.56 to 62.3 ng/cigarette. The wide variation in the TSNA levels most probably reflects the hand-rolled nature of the bidi cigarettes, resulting in a product with less homogenous tobacco amount and a wider variation in overall cigarette construction quality. TSNA levels of bidis were comparable with those of conventional cigarettes, and bidis should not be considered a lower-risk alternative tobacco product. Our analytical findings concur with the previous biologic and biochemical evidence supporting epidemiologic studies linking bidi use with various cancers, especially oral cavity and lung cancers.

Nitrosamines↗

PubMed2003

Simultaneous determination of five tobacco-specific nitrosamines in mainstream cigarette smoke by isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry.

Tobacco-specific nitrosamines (TSNAs) have been previously implicated as a source of carcinogenicity in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risk. We have developed and validated a specific and sensitive method to simultaneously measure five TSNAs in the particulate phase of mainstream tobacco smoke. Cigarette smoke particulate, produced using standardized machine smoking protocols, was collected on a Cambridge filter pad. The particulate matter was extracted using methylene chloride, back extracted into aqueous solution, further purified by solid-phase extraction, and analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry using isotopically labeled analogues as internal standards. Limits of detection for this method ranged from 0.05 to 1.23 ng/mL using an injection volume of 20 microL. A linear calibration range spanning 2.5-2500 ng/mL was adequate to measure TSNA levels in cigarette smoke. The method achieved excellent reproducibility and accuracy. The identity of each TSNA was established by chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of two product/precursor ion pairs. This new method provides higher sensitivity, specificity, and throughput than earlier methods for TSNA determination.

Calibration↗

PubMed2003

Effect of perchloroethylene, smoking, and race on oxidative DNA damage in female dry cleaners.

Perchloroethylene (PERC) is used widely as an industrial dry cleaning solvent and metal degreaser. PERC is an animal carcinogen that produces increased incidence of renal adenomas, adenocarcinomas, mononuclear cell leukemia, and hepatocellular tumors. Oxidative DNA damage and lipid peroxidation were assessed in 38 women with (dry cleaners) or without (launderers) occupational exposure to PERC. PERC exposure was assessed by collecting breathing zone samples on two consecutive days of a typical work week. PERC levels were measured in blood drawn on the morning of the second day of breathing zone sample collection in dry cleaners and before a typical workday in launderers. Blood PERC levels were two orders of magnitude higher in dry cleaners compared to launderers. A significant correlation was noted between time weighted average (TWA) PERC and blood PERC in dry cleaners (r=0.7355, P<0.002). 8-Hydroxydeoxyguanosine (8-OHdG), ng/mg deoxyguanosine (dG) in leukocyte nuclear DNA was used as an index of steady-state oxidative DNA damage. Urinary 8-OHdG, microg/g creatinine was used as an index of oxidative DNA damage repair. Urinary 8-epi-prostaglandin F(2alpha) (8-epi-PGF), ng/g creatinine was used as an index of lipid peroxidation. The mean+/-S.D. leukocyte 8-OHdG in launderers was 16.0+/-7.3 and was significantly greater than the 8.1+/-3.6 value for dry cleaners. Urinary 8-OHdG and 8-epi-PGF were not significantly different between dry cleaners and launderers. Unadjusted Pearson correlation analysis of log transformed PERC exposure indices and biomarkers of oxidative stress indicated a significant association in launderers between blood PERC and day 1 urinary 8-OHdG (r=0.4661, P<0.044). No significant associations between exposure indices and biomarkers were evident in linear models adjusted for age, body mass index, race, smoking (urinary cotinine, mg/g creatinine) and blood levels of the antioxidants Vitamin E and beta-carotene. The mean+/-S.D. leukocyte 8-OHdG value in control white women was 17.8+/-7.4 and was significantly greater than the 11.8+/-5.9 in control black women. No significant differences by race were evident for the other biomarkers. Smoking status was not significantly associated with any of the oxidative damage indices. Results indicate a reduction in oxidative DNA damage in PERC exposed dry cleaners relative to launderers, but PERC could not clearly be defined as the source of the effect.

8-Hydroxy-2'-Deoxyguanosine↗