Timothy Buckley - Academia.edu (original) (raw)

Papers by Timothy Buckley

Journal of Exposure Science and Environmental Epidemiology, Sep 23, 2020

PLOS ONE, Sep 18, 2013

Background: Criteria pollutants have been associated with exacerbation of children's asthma, but ... more Background: Criteria pollutants have been associated with exacerbation of children's asthma, but the role of air toxics in relation to asthma is less clear. Our objective was to evaluate whether exposure to outdoor air toxics in early childhood increased asthma risk or severity. Methods: Air toxics exposure was estimated using the 2002 National Air toxics Assessment (NATA) and linked to longitudinal data (n=6950) from a representative sample of US children born in 2001 and followed through kindergarten-age in the Early Child Longitudinal Study-Birth Cohort (ECLS-B). Results: Overall, 17.7% of 5.5 year-olds had ever been told by a healthcare professional they had asthma, and 6.8% had been hospitalized or visited an emergency room for an asthma attack. Higher rates of asthma were observed among boys (20.1%), low-income (24.8%), and non-Hispanic black children (30.0%) (p≤0.05). Air toxics exposure was greater for minority race/ethnicity (p<0.0001), low income (p<0.0001), non-rural area (p<0.001). Across all analyses, greater air toxics exposure, as represented by total NATA respiratory hazard index, or when limited to respiratory hazard index from onroad mobile sources or diesel PM, was not associated with a greater prevalence of asthma or hospitalizations (p trend >0.05). In adjusted logistic regression models, children exposed to the highest respiratory hazard index were not more likely to have asthma compared to those exposed to the lowest respiratory hazard index of total, onroad sources, or diesel PM. Conclusions: Early childhood exposure to outdoor air toxics in a national sample has not previously been studied relative to children's asthma. Within the constraints of the study, we found no evidence that early childhood exposure to outdoor air toxics increased risk for asthma. As has been previously reported, it is evident that there are environmental justice and disparity concerns for exposure to air toxics and asthma prevalence in US children.

Environment International, 1997

... Environment International Volume 23, Issue 5, 1997, Pages 705-732 Environmental Aspects of th... more ... Environment International Volume 23, Issue 5, 1997, Pages 705-732 Environmental Aspects of the Lower Rio Grande Valley. ... Environmental and biomarker measurements in nine homes in the Lower Rio Grande Valley: Multimedia results for Pesticides, metals, PAHs, and VOCs. ...

Environmental Health Perspectives, Apr 1, 2004

The absence of human exposure information constitutes a critical source of uncertainty for risk-b... more The absence of human exposure information constitutes a critical source of uncertainty for risk-based regulatory decision making. Risk assessments are used by the U.S. Environmental Protection Agency (U.S. EPA) to estimate the likelihood that exposure to a given pollutant will produce an adverse health effect and to determine what regulatory actions are necessary to protect public health. In the absence of human exposure data, policy makers, risk assessors, regulators, researchers, and public health officials often must rely on estimates or surrogates of human exposure levels, such as proximity to a hazardous waste site or regional ambient air quality data. Such estimates may be derived from models that predict levels of environmental contamination in the air. These approaches are limited in identifying health risks because they rely on assumptions about actual exposures experienced by people, thus introducing uncertainty in their risk estimates and ensuing policies. Although monitoring

Environmental health perspectives, Sep 18, 2022

Risk Analysis, Dec 16, 2020

The use of consumer products presents a potential for chemical exposures to humans. Toxicity test... more The use of consumer products presents a potential for chemical exposures to humans. Toxicity testing and exposure models are routinely employed to estimate risks from their use; however, a key challenge is the sparseness of information concerning who uses products and which products are used contemporaneously. Our goal was to demonstrate a method to infer use patterns by way of purchase data. We examined purchase patterns for three types of personal care products (cosmetics, hair care, and skin care) and two household care products (household cleaners and laundry supplies) using data from 60,000 households collected over a one‐year period in 2012. The market basket analysis methodology frequent itemset mining (FIM) was used to identify co‐occurring sets of product purchases for all households and demographic groups based on income, education, race/ethnicity, and family composition. Our methodology captured robust co‐occurrence patterns for personal and household products, globally and for different demographic groups. FIM identified cosmetic co‐occurrence patterns captured in prior surveys of cosmetic use, as well as a trend of increased diversity of cosmetic purchases as children mature to teenage years. We propose that consumer product purchase data can be mined to inform person‐oriented use patterns for high‐throughput chemical screening applications, for aggregate and combined chemical risk evaluations.

Infection Control and Hospital Epidemiology, Sep 1, 2002

Atmospheric Environment. Part B. Urban Atmosphere, 1990

Concentrations of airborne continuous fine particulate matter or (PM 2.5), black carbon (BC), and... more Concentrations of airborne continuous fine particulate matter or (PM 2.5), black carbon (BC), and ultrafine particles (UFP) were continuously measured over 5 days in winter and summer both indoors and outdoors at residences for forty-eight adults in 2005 and forty-seven asthmatic children in 2006. During 2006, personal concentrations of PM 2.5 were also measured continuously. All 4 continuous instruments employed performed well both in laboratory and field conditions. Mean outdoor concentrations of PM 2.5 , BC, and UFP were significantly higher than either indoor or personal concentrations. Air exchange rates were low (median value only 0.2/h), there was widespread use of central forced air and high-quality furnace filters. Outdoor concentrations of all particle-related pollutants showed overnight decreases followed by increases during the morning rush hours. Afternoon concentrations increased for UFP and decreased for BC, with PM 2.5 staying about the same. Between 5:00 pm and 7:00 pm, indoor UFP and PM 2.5 concentrations exceeded their mean daily values by 160% and 60%, respectively, suggesting that cooking is an extremely important source for these two pollutants. However, BC values did not increase at these hours. The highest indoor-outdoor ratios were observed for UFP suggesting that indoor sources were relatively more important for UFP than for other particle components. BC measurements in Windsor agreed moderately well (R 2 = 41%) with an independent measure of elemental carbon (EC) in Detroit. This large residential air pollution study has provided data making it possible to identify short-term variations and possible sources that can influence the relationships between pollutants and environments.

Journal of Applied Microbiology, Aug 16, 2011

Multiple cross displacement amplification with gold nanoparticles-based lateral flow biosensor co... more Multiple cross displacement amplification with gold nanoparticles-based lateral flow biosensor could be used for detection of Pseudomonas aeruginosa, which would save much time compared with the clinical traditional method.

Epidemiology, Sep 1, 2005

Scandinavian Journal of Work, Environment & Health, Jun 1, 2006

Objectives Workers' behavior is identified as an important determinant of dermal exposure and is ... more Objectives Workers' behavior is identified as an important determinant of dermal exposure and is influenced by knowledge, attitudes, and risk perceptions. Because behavior may be a significant predictor of exposure, its assessment provides a means for examining exposure and designing strategies and incentives that encourage worker protective behavior. Currently, there are no psychosocial instruments examining worker knowledge, attitudes, and perceptions with respect to dermal hazards. Accordingly, a questionnaire was developed and tested to provide an instrument for measuring worker knowledge, attitudes, and perceptions. Methods The questionnaire was developed on the basis of a literature review and expert consultation. Scales were constructed based on standard methods. Two worker focus groups were used to evaluate worker understanding and content validity of the KAP (knowledge, attitudes, perceptions) questionnaire. The resulting 115item questionnaire that included scales for knowledge (N=13), attitudes (N=27), perceptions (N=15), behavior (N=8), behavioral intentions (N=15), barriers (N=13), and facilitators (N=5) was tested on 89 workers from 19 facilities. Results The concepts identified in the focus groups included worker perception of higher risk due to a poor fit and replacement frequency for personal protective equipment and cross-contamination by workers moving into work zones. Field testing of the questionnaire (N=89) yielded Cronbach's alpha reliability scores ranging from 0.87 for the self-efficacy personal protective equipment scale to 0.92 for the overall belief scale, indicating high internal reliability. Conclusions Although further testing and refinement is needed, this survey instrument provides an initial and conceptually unique means for evaluating behavioral determinants of worker dermal exposure.

Environmental Health Perspectives, Jun 1, 1998

An improved understanding of the contribution made by environmental exposures to disease burden i... more An improved understanding of the contribution made by environmental exposures to disease burden in children is essential, given current increasing rates of childhood illnesses such asthma and cancer. Children must be routinely included in environmental research. Exposure assessment, both external (e.g., air, water) and internal dose (e.g., biomarkers), is an integral component of such research. Biomarker measurement has some advantages that are unique in children. These include assessment of potentially increased absorption because of behaviors that differ from adults (i.e., hand-to-mouth activity); metabolite measurement, which can help identify age-related susceptibility differences; and improved assessment of dermal exposure, an important exposure route in children. Environmental exposure assessment in children will require adaption of techniques that are currently applied in adult studies as well as development of tools and validation of strategies that are unique for children. Designs that focus on parent-child study units provide adult comparison data and allow the parent to assist with more complex study designs. Use of equipment that is sized appropriately for children, such as small air pumps and badge monitors, is also important. When biomarkers are used, biologic specimens that can be obtained noninvasively are preferable. Although the current need is primarily for small focused studies to address specific questions and optimize research tools, the future will require establishment of large prospective cohorts. Urban children are an important study cohort because of relatively high morbidity observed in the urban environment. Finally, examples of completed or possible future studies utilizing these techniques are discussed for specific exposures such as benzene, environmental tobacco smoke, aflatoxin, volatile organic compounds, and polycyclic aromatic hydrocarbons.

Environmental Science & Technology, Oct 29, 2010

Carpets are both sinks and sources for exposure to chemicals, allergens, and microbes and consequ... more Carpets are both sinks and sources for exposure to chemicals, allergens, and microbes and consequently influence health, including asthma, allergies, and infectious diseases. Asthmatics, children, and the immune-compromised are particularly vulnerable to health risks resulting from exposure to carpet contaminants. To address this risk, a commercial upright vacuum cleaner with an ultraviolet germicidal lamp (λ)253.7 nm, UVC) has been developed for residential and commercial uses. However, its effectiveness in reducing microbial load on realworld carpets has not been previously demonstrated. Accordingly, the purpose of the current study was to evaluate the effectiveness of a UVC-equipped vacuum in reducing the carpet surface-bound microbial load. This was accomplished by comparing the carpet microbial surface load from pre-to posttreatment of 9 ft 2 in-use carpet sections under three treatment scenarios: 1) UVC alone (UV), 2) the beater-bar plus vacuum (BB+Vac), or 3) a combination of all three (COMB). Each treatment was two minutes in duration. Microbial surface loads were measured by pressing contact plates containing Sabourauds Dextrose agar onto the carpet surface. In-use carpets from three locations were tested in place. The treatment effect was evaluated at two levels. First, we considered the mean reduction in CFU from pre-to post-treatment for each 9 ft 2 carpet grid (n) 4 for each treatment). The second level considered each 1 ft 2 section using a paired analysis (n) 40 to 49 for each treatment). A total of 125 pre/post-sample pairs were collected across the three treatments. Results showed that all three treatments were associated with a reduction in carpet microbial load (p < 0.0001). The COMB yielded the largest reduction of 13 CFU/plate (87% reduction) and was approximately the sum of the individual effects of either UVC (6.6 CFU/plate, 60% reduction, p) 0.009) or BB+Vac (7.3 CFU/plate, 78% reduction, p < 0.0001). We therefore conclude that a UVC-equipped vacuum approximately doubles the unit's effectiveness in reducing surface-bound microbial load, thereby holding promise as a means for decreasing indoor infectious disease risk.

Forensic Science International, Dec 1, 2001

Anecdotal reports suggest that high environmental or occupational exposures to the fuel oxygenate... more Anecdotal reports suggest that high environmental or occupational exposures to the fuel oxygenate methyl tert-butyl ether (MTBE) may result in breath concentrations that are suf®ciently elevated to cause a false positive on commercial breathalcohol analyzers. We evaluated this possibility in vitro by establishing a response curve for simulated breath containing MTBE in ethanol. Two types of breath-alcohol analyzers were evaluated. One analyzer's principle of operation involves in situ wet chemistry (oxidation of ethanol in a potassium dichromate solution) and absorption of visible light. The second instrument uses a combination of infrared absorption and an electrochemical sensor. Both types of instruments are currently used, although the former method represents older technology while the latter method represents newer technology. The percent blood alcohol response curve was evaluated over a breath concentration range thought to be relevant to highlevel environmental or occupational exposure (0±361 mg/l). Results indicate that MTBE positively biases the response of the older technology Breathalyzer TM when evaluated as a single constituent or in combination with ethanol. We conclude that a false positive is possible on this instrument if the MTBE exposure is very high, recent with respect to testing, and occurs in combination with ethanol consumption. The interference can be identi®ed on the older technology instrument by a time dependent post-reading increase in the instrument response that does not occur for ethanol alone. In contrast, the newer technology instrument using infrared and electrochemical detectors did not respond to MTBE at lower levels (0±36 mg/l), and at higher levels (>72 mg/l) the instrument indicated an``interference'' or``error''. For this instrument, a false positive does not occur even at high MTBE levels in the presence of ethanol.

Environmental Science & Technology, Feb 1, 2007

The present study was conducted to optimize methods for measurement of volatile organic compounds... more The present study was conducted to optimize methods for measurement of volatile organic compounds (VOCs) by use of headspace solid-phase microextraction (HS-SPME) and to provide a preliminary assessment of levels in human milk. MTBE (methyl tert-butyl ether), chloroform, benzene, and toluene were measured from two sources of milk: a North Carolina milk bank (n) 5) and multiple samples from three women within nonsmoking households in inner-city Baltimore, MD (n) 8). In Baltimore, indoor air VOC concentrations in the respective households were also measured by active sampling and thermal desorption gas chromatography/mass spectrometry in selective ion monitoring (GC/MS/SIM) over each of the 3 days of milk collection. By application of these optimized methods, we observed median VOC concentrations in Baltimore human milk of 0.09, 0.55, 0.12, and 0.46 ng/mL for MTBE, chloroform, benzene, and toluene, respectively. For benzene, toluene, and MTBE, milk levels trended with observed indoor air concentrations. On the basis of measured concentrations in air and milk, infant average daily dose by inhalation exceeded ingestion rates by 25-135-fold. Thus, VOC exposure from breast milk is vastly exceeded by that from indoor air in nonsmoking households. Accordingly, strategies to mitigate infant VOC exposure should focus on the indoor air inhalation pathway of exposure.

International Journal of Environmental Science and Technology, Nov 3, 2021

Background:Per- and polyfluoroalkyl substances have been documented at all spatial scales with co... more Background:Per- and polyfluoroalkyl substances have been documented at all spatial scales with concerns of adverse ecological and human health effects. Human exposures and relative pathway contributions depend on the specific population, their exposure scenarios, and pathways of local sources.Objectives:Provide a narrative overview of (1) current per- and polyfluoroalkyl substances knowledge for sources, concentrations, and exposures; (2) critical per- and polyfluoroalkyl substances exposure information gaps and needs, and (3) United States Environmental Protection Agency’s strategies and action plans in collaboration with other federal, industrial, and academic partners.Methods:A literature review was conducted for per- and polyfluoroalkyl substances (primarily perfluorooctane sulfonate and perfluorooctanoic acid) compounds in blood, water, soil, house dust, indoor and outdoor air, consumer products, food, and fish, as well as per- and polyfluoroalkyl substances exposure modeling.Results:Large variability exists in measured per- and polyfluoroalkyl substances environmental concentrations and human exposures. Literature indicated that ingestion of food (“background”), drinking water (“contaminated” scenarios), and house dust (for children) are main pathways for perfluorooctane sulfonate and perfluorooctanoic acid.Discussion:Needs for addressing critical data gaps are identified. More information is available on long-chain per- and polyfluoroalkyl substances than for replacement and emerging compounds. A large-scale research effort by the United States Environmental Protection Agency and other federal agencies is underway for a better understanding of per- and polyfluoroalkyl substances exposures.

Toxicology Mechanisms and Methods, 2007

Water contamination of public drinking and recreational waters with volatile organic compounds (V... more Water contamination of public drinking and recreational waters with volatile organic compounds (VOCs) is widespread, resulting in human exposure through multiple routes. Although dermal absorption is of considerable importance, there is great uncertainty in the dermal permeability coefficient (K P) for many VOCs due to the methods by which they are derived. We present a human in vivo experimental approach for the measurement of VOC dermal uptake from water contaminated at environmentally relevant concentrations and for determination of K P. Dermal permeability was estimated from 11 adult subjects following immersion of their hand and forearm into a sealed 4.8-L Plexiglas cylinder containing 100 µg/L each of chloroform, 1,1,1-trichloroethane (111-TCA), and toluene and 400 µg/L of methyl tertiary butyl ether (MTBE) in water. Uptake was determined by measuring the decrease in VOC water concentration during the exposure. A control glass arm accounted for nondermal losses. The concentration of VOCs was determined by solid-phase microextraction (SPME) and analysis with gas chromatography/mass spectrometry. For the eight male and three female adult subjects, on average there was a dermal uptake-attributed 13.5%, 14.9%, 20.8%, and 7.3% decrease in the concentration after 1 h exposure for chloroform, 111-TCA, toluene, and MTBE, respectively. The resulting mean K P (standard deviation) was estimated to be 0.166 (0.108), 0.167 (0.107), 0.250 (0.064), and 0.109 (0.157) cm/h for the respective analytes. The experimental K P values presented here exceed the previously published model-estimated K P values by factors ranging from 6 to 57, suggesting that the published modelestimated K P values may underestimate actual VOC dermal absorption from water.