Timothy J. Buckley

Impact of the 2002 Canadian Forest Fires on Particulate Matter Air Quality in Baltimore City

With increasing evidence of adverse health effects associated with particulate matter (PM), the exposure impact of natural sources, such as forest fires, has substantial public health relevance. In addition to the threat to nearby communities, pollutants released from forest fires can travel thousands of kilometers to heavily populated urban areas. There was a dramatic increase in forest fire activity in the province of Quebec, Canada, during July 2002. The transport of PM released from these forest fires was examined using a combination of a moderate-resolution imaging spectroradiometer satellite image, back-trajectories using a hybrid single-particle Lagrangian integrated trajectory, and local light detection and ranging measurements. Time- and size-resolved PM was evaluated at three ambient and four indoor measurement sites using a combination of direct reading instruments (laser, time-of-flight aerosol spectrometer, nephelometer, and an oscillating microbalance). The transport and monitoring results consistently identified a forest fire related PM episode in Baltimore that occurred the first weekend of July 2002 and resulted in as much as a 30-fold increase in ambientfine PM. On the basis of tapered element oscillating microbalance measurements, the 24 h PM25 concentration reached 86 microg/m3 on July 7, 2002, exceeding the 24 h national ambient air quality standard. The episode was primarily comprised of particles less than 2.5 microm in aerodynamic diameter, highlighting the preferential transport of the fraction of PM that is of greatest health concern. Penetration of the ambient episode indoors was efficient (median indoor-to-outdoor ratio 0.91) such that the high ambient levels were similarly experienced indoors. These results are significant in demonstrating the impact of a natural source thousands of kilometers away on ambient levels of and potential exposures to air pollution within an urban center. This research highlights the significance of transboundary air pollution and the need for studies that assess the public health impacts associated with such sources and transport processes.

Home environmental intervention in inner-city asthma: a randomized controlled clinical trial

BACKGROUND Airborne pollutants and indoor allergens increase asthma morbidity in inner-city children; therefore, reducing exposure, if feasible, should improve asthma morbidity. OBJECTIVE To conduct a randomized controlled trial of methods to reduce environmental pollutant and allergen exposure in the homes of asthmatic children living in the inner city. METHODS After the completion of questionnaires, spirometry and allergen skin tests, home inspection, and measurement of home air pollutant and allergen levels, 100 asthmatic children aged 6 to 12 years were randomized to the treatment group (home-based education, cockroach and rodent extermination, mattress and pillow encasings, and high-efficiency particulate air cleaner) or to the control group (treated at the end of the 1-year trial). Outcomes were evaluated by home evaluations at 6 and 12 months, clinic evaluation at 12 months, and multiple telephone interviews. RESULTS In the treatment group, 84% received cockroach extermination and 75% used the air cleaner. Levels of particulate matter 10 microm or smaller declined by up to 39% in the treatment group but increased in the control group (P < .001). Cockroach allergen levels decreased by 51% in the treatment group. Daytime symptoms increased in the control group and decreased in the treatment group (P = .04). Other measures of morbidity, such as spirometry findings, nighttime symptoms, and emergency department use, were not significantly changed. CONCLUSIONS A tailored, multifaceted environmental treatment reduced airborne particulate matter and indoor allergen levels in inner-city homes, which, in turn, had a modest effect on morbidity.

Socioeconomic and Racial Disparities in Cancer Risk from Air Toxics in Maryland

We linked risk estimates from the U.S. Environmental Protection Agency’s National Air Toxics Assessment (NATA) to racial and socioeconomic characteristics of census tracts in Maryland (2000 Census) to evaluate disparities in estimated cancer risk from exposure to air toxics by emission source category. In Maryland, the average estimated cancer risk across census tracts was highest from on-road sources (50% of total risk from nonbackground sources), followed by nonroad (25%), area (23%), and major sources (< 1%). Census tracts in the highest quartile defined by the fraction of African-American residents were three times more likely to be high risk (> 90th percentile of risk) than those in the lowest quartile (95% confidence interval, 2.0–5.0). Conversely, risk decreased as the proportion of whites increased (p < 0.001). Census tracts in the lowest quartile of socioeconomic position, as measured by various indicators, were 10–100 times more likely to be high risk than those in the highest quartile. We observed substantial risk disparities for on-road, area, and nonroad sources by socioeconomic measure and on-road and area sources by race. There was considerably less evidence of risk disparities from major source emissions. We found a statistically significant interaction between race and income, suggesting a stronger relationship between race and risk at lower incomes. This research demonstrates the utility of NATA for assessing regional environmental justice, identifies an environmental justice concern in Maryland, and suggests that on-road sources may be appropriate targets for policies intended to reduce the disproportionate environmental health burden among economically disadvantaged and minority populations.

Household mouse allergen exposure and asthma morbidity in inner-city preschool children

BACKGROUND Inner-city children experience disproportionate asthma morbidity, and suspected reasons include indoor environmental exposures. OBJECTIVE To determine if mouse allergen exposure is a risk factor for asthma morbidity. METHODS Preschool children with asthma were recruited from inner-city Baltimore, MD. Skin testing was performed and blood was collected at the baseline visit for quantification of mouse allergen specific IgE. A questionnaire evaluated symptoms, medication, and health care use at baseline, 3 months, and 6 months. A trained technician collected dust samples from the childs home for analysis of Mus m 1 at baseline, 3 months, and 6 months. Outcomes were compared between mouse-sensitized, highly exposed children and all other children. RESULTS A total of 127 children had complete data for mouse sensitization status and bedroom settled dust mouse allergen levels at baseline. The mean age of the children was 4.4 years, 92% were African American, and 26% were sensitized to mouse. Mouse-sensitized children exposed to higher levels of Mus m 1 (>0.5 microg/g) had 50% more days of symptoms (incidence rate ratio [IRR], 1.5; 95% confidence interval [CI], 1.1-2.1) and 80% more days of beta-agonist use than other children (IRR, 1.8; 95% CI, 1.3-2.5). Children in the sensitized and highly exposed group were also more likely to have an unscheduled physician visit (odds ratio [OR], 3.1; 95% CI, 1.6-6.3), emergency department visit (OR, 2.1; 95% CI, 1.1-4.1), and hospitalization (OR, 36.6; 95% CI, 4.1-327.3) than other children. These associations between mouse allergen exposure and asthma symptoms and morbidity remained statistically significant after adjusting for potential confounders, including atopy and cockroach sensitization and exposure. CONCLUSIONS In mouse-sensitized inner-city children, exposure to mouse allergen may be an important cause of asthma morbidity.

Airborne Multidrug-Resistant Bacteria Isolated from a Concentrated Swine Feeding Operation

The use of nontherapeutic levels of antibiotics in swine production can select for antibiotic resistance in commensal and pathogenic bacteria in swine. As a result, retail pork products, as well as surface and groundwaters contaminated with swine waste, have been shown to be sources of human exposure to antibiotic-resistant bacteria. However, it is unclear whether the air within swine operations also serves as a source of exposure to antibiotic-resistant bacterial pathogens. To investigate this issue, we sampled the air within a concentrated swine feeding operation with an all-glass impinger. Samples were analyzed using a method for the isolation of Enterococcus. A total of 137 presumptive Enterococcus isolates were identified to species level using standard biochemical tests and analyzed for resistance to erythromycin, clindamycin, virginiamycin, tetracycline, and vancomycin using the agar dilution method. Thirty-four percent of the isolates were confirmed as Enterococcus, 32% were identified as coagulase-negative staphylococci, and 33% were identified as viridans group streptococci. Regardless of bacterial species, 98% of the isolates expressed high-level resistance to at least two antibiotics commonly used in swine production. None of the isolates were resistant to vancomycin, an antibiotic that has never been approved for use in livestock in the United States. In conclusion, high-level multidrug-resistant Enterococcus, coagulase-negative staphylococci, and viridans group streptococci were detected in the air of a concentrated swine feeding operation. These findings suggest that the inhalation of air from these facilities may serve as an exposure pathway for the transfer of multidrug-resistant bacterial pathogens from swine to humans.

Home indoor pollutant exposures among inner-city children with and without asthma

Background Evidence for environmental causes of asthma is limited, especially among African Americans. To look for systematic differences in early life domestic exposures between inner-city preschool children with and without asthma, we performed a study of home indoor air pollutants and allergens. Methods Children 2–6 years of age were enrolled in a cohort study in East Baltimore, Maryland. From the child’s bedroom, air was monitored for 3 days for particulate matter ≤ 2.5 and ≤ 10 μm in aerodynamic diameter (PM2.5, PM10), nitrogen dioxide, and ozone. Median baseline values were compared for children with (n = 150) and without (n = 150) asthma. Housing characteristics related to indoor air pollution were assessed by caregiver report and home inspection. In addition, indoor allergen levels were measured in settled dust. Results Children were 58% male, 91% African American, and 88% with public health insurance. Housing characteristics related to pollutant exposure and bedroom air pollutant concentrations did not differ significantly between asthmatic and control subjects [median: PM2.5, 28.7 vs. 28.5 μg/m3; PM10, 43.6 vs. 41.4 μg/m3; NO2, 21.6 vs. 20.9 ppb; O3, 1.4 vs. 1.8 ppb; all p > 0.05]. Settled dust allergen levels (cat, dust mite, cockroach, dog, and mouse) were also similar in bedrooms of asthmatic and control children. Conclusions Exposures to common home indoor pollutants and allergens are similar for inner-city preschool children with and without asthma. Although these exposures may exacerbate existing asthma, this study does not support a causative role of these factors for risk of developing childhood asthma.

Air pollution exposure assessment for epidemiologic studies of pregnant women and children: lessons learned from the Centers for Children's Environmental Health and Disease Prevention Research

The National Children’s Study is considering a wide spectrum of airborne pollutants that are hypothesized to potentially influence pregnancy outcomes, neurodevelopment, asthma, atopy, immune development, obesity, and pubertal development. In this article we summarize six applicable exposure assessment lessons learned from the Centers for Children’s Environmental Health and Disease Prevention Research that may enhance the National Children’s Study: a) Selecting individual study subjects with a wide range of pollution exposure profiles maximizes spatial-scale exposure contrasts for key pollutants of study interest. b) In studies with large sample sizes, long duration, and diverse outcomes and exposures, exposure assessment efforts should rely on modeling to provide estimates for the entire cohort, supported by subject-derived questionnaire data. c) Assessment of some exposures of interest requires individual measurements of exposures using snapshots of personal and microenvironmental exposures over short periods and/or in selected microenvironments. d) Understanding issues of spatial–temporal correlations of air pollutants, the surrogacy of specific pollutants for components of the complex mixture, and the exposure misclassification inherent in exposure estimates is critical in analysis and interpretation. e) “Usual” temporal, spatial, and physical patterns of activity can be used as modifiers of the exposure/outcome relationships. f) Biomarkers of exposure are useful for evaluation of specific exposures that have multiple routes of exposure. If these lessons are applied, the National Children’s Study offers a unique opportunity to assess the adverse effects of air pollution on interrelated health outcomes during the critical early life period.

The contribution of traffic to indoor concentrations of polycyclic aromatic hydrocarbons

A photoelectric aerosol sensor (PAS) was used to measure real-time indoor concentrations of polycyclic aromatic hydrocarbons (PAHs) at three residences. Semi-quantitative measurements of total indoor particle-bound PAH and temperature were collected continuously every minute for approximately 2 weeks at each location. The purpose of this study was to examine the effect of traffic on indoor concentrations of PAHs. This was accomplished by collecting indoor measurements at an urban, semi-urban, and suburban residential location with varying levels of, and proximity to, traffic. Since the homes were occupied, the effects of cooking, the dominant indoor source, were also examined among the three nonsmoking households. The results indicate that traffic was the main outdoor source of PAH concentrations measured indoors for all locations. In fact, a significant ( p<0.001) traffic-related trend in weekday PAH concentration was detected with a geometric mean concentration at the urban location (31 ng/m 3) nearly two times that at the semi-urban location (19 ng/m 3) and over three times larger than the suburban location (8.0 ng/m 3), once adjusted for indoor sources. Hourly average concentration profiles also revealed weekday rush hour peaks of PAHs at all locations. No pronounced peaks and significantly lower concentrations (10, 10, and 4.9 ng/m 3) were seen during the weekends for all locations i.e., the urban, semi-urban and suburban locations, respectively. Indoor sources including frying/sautéing, broiling, and candle-burning were characterized by peak concentration, duration of PAH elevation, and potential dose. This analysis suggests that cooking, and especially frying/sautéing, may be an important source of indoor PAH concentrations.

Real-Time Indoor and Outdoor Measurements of Black Carbon in an Occupied House: An Examination of Sources

Abstract Black carbon (BC) was measured every 5 min for two years (May 1998–May 2000) inside and immediately outside a northern Virginia house (suburban Washington, DC) occupied by two nonsmokers. Two aethalometers, which measure BC by optical transmission through a quartz fiber tape, were employed indoors and outdoors. Meteorological parameters were obtained on an hourly basis from nearby Dulles airport. Indoor activities were recorded to identify indoor sources such as combustion activities, which occurred 9% of the time during the first year and 4% of the time during the second year. At times without indoor sources, indoor/outdoor BC ratios averaged 0.53 in the first year and 0.35 in the second year. The main outdoor source of BC was the general regional background, contributing 83–84% of the total during each of the two years. Morning rush hour traffic contributed 8–9% of the total BC. An evening peak in the fall and winter, thought to include contributions from wood burning, was responsible for ~8% of the annual average BC concentration. The main indoor sources of BC were cooking and candle burning, contributing 16 and 31%, respectively, of the annual average indoor concentrations in the two years. Relative humidity (RH) affected the outdoor aethalometer in both years. An artifact associated with the tape advance was noted for the aethalometer, but a correction factor was developed that reduced the associated error by a factor of 2.

Antibiotic Administration Routes Significantly Influence the Levels of Antibiotic Resistance in Gut Microbiota

ABSTRACT This study examined the impact of oral exposure to antibiotic-resistant bacteria and antibiotic administration methods on antibiotic resistance (AR) gene pools and the profile of resistant bacteria in host gastrointestinal (GI) tracts using C57BL/6J mice with natural gut microbiota. Mice inoculated with a mixture of tet(M)-carrying Enterococcus spp. or blaCMY-2-carrying Escherichia coli were treated with different doses of tetracycline hydrochloride (Tet) or ampicillin sodium (Amp) and delivered via either feed or intravenous (i.v.) injection. Quantitative PCR assessment of mouse fecal samples revealed that (i) AR gene pools were below the detection limit in mice without prior inoculation of AR gene carriers regardless of subsequent exposure to corresponding antibiotics; (ii) oral exposure to high doses of Tet and Amp in mice inoculated with AR gene carriers led to rapid enrichment of corresponding AR gene pools in feces; (iii) significantly less or delayed development of AR in the GI tract of the AR carrier-inoculated mice was observed when the same doses of antibiotics were administered via i.v. injection rather than oral administration; and (iv) antibiotic dosage, and maybe the excretion route, affected AR in the GI tract. The shift of dominant AR bacterial populations in the gut microbiota was consistent with the dynamics of AR gene pools. The emergence of endogenous resistant bacteria in the gut microbiota corresponding to drug exposure was also observed. Together, these data suggest that oral administration of antibiotics has a prominent effect on AR amplification and development in gut microbiota, which may be minimized by alternative drug administration approaches, as illustrated by i.v. injection in this study and proper drug selection.