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McCracken, John Patrick

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McCracken

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John Patrick

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McCracken, John Patrick
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    Longitudinal Relationship between Personal CO and Personal \(PM_{2.5}\) among Women Cooking with Woodfired Cookstoves in Guatemala
    (Public Library of Science, 2013) McCracken, John Patrick; Schwartz, Joel; Diaz, Anaite; Bruce, Nigel; Smith, Kirk R.
    Household air pollution (HAP) due to solid fuel use is a major public health threat in low-income countries. Most health effects are thought to be related to exposure to the fine particulate matter (PM) component of HAP, but it is currently impractical to measure personal exposure to PM in large studies. Carbon monoxide (CO) has been shown in cross-sectional analyses to be a reliable surrogate for particles<2.5 µm in diameter (\(PM_{2.5}\)) in kitchens where wood-burning cookfires are a dominant source, but it is unknown whether a similar \(PM_{2.5}\)-CO relationship exists for personal exposures longitudinally. We repeatedly measured (216 measures, 116 women) 24-hour personal \(PM_{2.5}\) (median [IQR] = 0.11 [0.05, 0.21] mg/\(m^3\)) and CO (median [IQR] = 1.18 [0.50, 2.37] mg/\(m^3\)) among women cooking over open woodfires or chimney woodstoves in Guatemala. Pollution measures were natural-log transformed for analyses. In linear mixed effects models with random subject intercepts, we found that personal CO explained 78% of between-subject variance in personal \(PM_{2.5}\). We did not see a difference in slope by stove type. This work provides evidence that in settings where there is a dominant source of biomass combustion, repeated measures of personal CO can be used as a reliable surrogate for an individual's \(PM_{2.5}\) exposure. This finding has important implications for the feasibility of reliably estimating long-term (months to years) \(PM_{2.5}\) exposure in large-scale epidemiological and intervention studies of HAP.
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    Intervention to Lower Household Wood Smoke Exposure in Guatemala Reduces ST-Segment Depression on Electrocardiograms
    (National Institute of Environmental Health Sciences, 2011) McCracken, John Patrick; Smith, Kirk R.; Stone, Peter; Díaz, Anaité; Arana, Byron; Schwartz, Joel
    Background: A large body of evidence suggests that fine particulate matter (PM) air pollution is a cause of cardiovascular disease, but little is known in particular about the cardiovascular effects of indoor air pollution from household use of solid fuels in developing countries. RESPIRE (Randomized Exposure Study of Pollution Indoors and Respiratory Effects) was a randomized trial of a chimney woodstove that reduces wood smoke exposure. Objectives: We tested the hypotheses that the stove intervention, compared with open fire use, would reduce ST-segment depression and increase heart rate variability (HRV). Methods: We used two complementary study designs: a) between-groups comparisons based on randomized stove assignment, and b) before-and-after comparisons within control subjects who used open fires during the trial and received chimney stoves after the trial. Electrocardiogram sessions that lasted 20 hr were repeated up to three times among 49 intervention and 70 control women 38–84 years of age, and 55 control subjects were also assessed after receiving stoves. HRV and ST-segment values were assessed for each 30-min period. ST-segment depression was defined as an average value below –1.00 mm. Personal fine PM [aerodynamic diameter ≤ 2.5 μm (PM\(_{2.5}\))] exposures were measured for 24 hr before each electrocardiogram. Results: PM\(_{2.5}\) exposure means were 266 and 102 μg/m\(^3\) during the trial period in the control and intervention groups, respectively. During the trial, the stove intervention was associated with an odds ratio of 0.26 (95% confidence interval, 0.08–0.90) for ST-segment depression. We found similar associations with the before-and-after comparison. The intervention was not significantly associated with HRV. Conclusions: The stove intervention was associated with reduced occurrence of nonspecific ST-segment depression, suggesting that household wood smoke exposures affect ventricular repolarization and potentially cardiovascular health.
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    Effects of Particulate Air Pollution on Blood Pressure in a Highly Exposed Population in Beijing, China: A Repeated-Measure Study
    (BioMed Central, 2011) Baccarelli, Andrea; Barretta, Francesco; Dou, Chang; Zhang, Xiao; McCracken, John Patrick; Díaz, Anaité; Bertazzi, Pier Alberto; Schwartz, Joel; Wang, Sheng; Hou, Lifang
    Background: Particulate Matter (PM) exposure is critical in Beijing due to high population density and rapid increase in vehicular traffic. PM effects on blood pressure (BP) have been investigated as a mechanism mediating cardiovascular risks, but results are still inconsistent. The purpose of our study is to determine the effects of ambient and personal PM exposure on BP. Methods: Before the 2008 Olympic Games (June 15-July 27), we examined 60 truck drivers and 60 office workers on two days, 1-2 weeks apart (n = 240). We obtained standardized measures of post-work BP. Exposure assessment included personal \(PM_{2.5}\) and Elemental Carbon (EC, a tracer of traffic particles) measured using portable monitors during work hours; and ambient \(PM_{10}\) averaged over 1-8 days pre-examination. We examined associations of exposures (exposure group, personal \(PM_{2.5}/EC\), ambient \(PM_{10}\)) with BP controlling for multiple covariates. Results: Mean personal \(PM_{2.5}\) was \(94.6 μg/m^3\) (SD = 64.9) in office workers and 126.8 (SD = 68.8) in truck drivers (p-value < 0.001). In all participants combined, a \(10 μg/m^3\) increase in 8-day ambient \(PM_{10}\) was associated with BP increments of 0.98 (95%CI 0.34; 1.61; p-value = 0.003), 0.71 (95%CI 0.18; 1.24; p-value = 0.01), and 0.81 (95%CI 0.31; 1.30; p-value = 0.002) mmHg for systolic, diastolic, and mean BP, respectively. BP was not significantly different between the two groups (p-value > 0.14). Personal \(PM_{2.5}\) and EC during work hours were not associated with increased BP. Conclusions: Our results indicate delayed effects of ambient \(PM_{10}\) on BP. Lack of associations with exposure groups and personal \(PM_{2.5}/EC\) indicates that PM effects are related to background levels of pollution in Beijing, and not specifically to work-related exposure.
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    Diversity of the Gut Microbiota and Eczema in Early Life
    (BioMed Central, 2008) Forno, Erick; Onderdonk, Andrew; McCracken, John Patrick; Litonjua, Augusto A.; Laskey, Daniel; Delaney, Mary; DuBois, Andrea M; Gold, Diane; Ryan, Louise; Weiss, Scott; Celedón, Juan C
    Background: A modest number of prospective studies of the composition of the intestinal microbiota and eczema in early life have yielded conflicting results. Objective: To examine the relationship between the bacterial diversity of the gut and the development of eczema in early life by methods other than stool culture. Methods: Fecal samples were collected from 21 infants at 1 and 4 months of life. Nine infants were diagnosed with eczema by the age of 6 months (cases) and 12 infants were not (controls). After conducting denaturating gradient gel electrophoresis (DGGE) of stool samples, we compared the microbial diversity of cases and controls using the number of electrophoretic bands and the Shannon index of diversity (H') as indicators. Results: Control subjects had significantly greater fecal microbial diversity than children with eczema at ages 1 (mean H' for controls = 0.75 vs. 0.53 for cases, P = 0.01) and 4 months (mean H' for controls = 0.92 vs. 0.59 for cases, P = 0.02). The increase in diversity from 1 to 4 months of age was significant in controls (P = 0.04) but not in children who developed eczema by 6 months of age (P = 0.32). Conclusion: Our findings suggest that reduced microbial diversity is associated with the development of eczema in early life.
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    Annual Ambient Black Carbon Associated with Shorter Telomeres in Elderly Men: Veterans Affairs Normative Aging Study
    (National Institute of Environmental Health Sciences, 2010) Hoxha, Mirjam; Dioni, Laura; McCracken, John Patrick; Baccarelli, Andrea; Melly, Steven; Coull, Brent; Suh MacIntosh, Helen H.; Vokonas, Pantel; Schwartz, Joel
    Background: Telomere length reflects biological age and is inversely associated with risk of cardiovascular disease (CVD). Ambient air pollution is associated with CVD, but its effect on telomere length is unknown. Objective: We investigated whether ambient black carbon (BC), a marker for traffic-related particles, is associated with telomere length in the Normative Aging Study (NAS). Methods: Among 165 never-smoking men from the NAS, leukocyte telomere length (LTL) was measured repeatedly approximately every 3 years from 1999 through 2006 using quantitative real-time polymerase chain reaction (qRT-PCR). BC concentration at their residences during the year before each LTL measurement was estimated based on a spatiotemporal model calibrated with BC measurements from 82 locations within the study area. Results: The median [interquartile range (IQR)] annual moving-average BC concentration was 0.32 (0.20–0.45) μg/m3. LTL, expressed as population-standardized ratio of telomere repeat to single-copy gene copy numbers, had a geometric mean (geometric SD) of 1.25 (1.42). We used linear mixed-effects models including random subject intercepts and adjusted for several potential confounders. We used inverse probability of response weighting to adjust for potential selection bias due to loss to follow-up. An IQR increase in annual BC (0.25 μg/m3) was associated with a 7.6% decrease (95% confidence interval, −12.8 to −2.1) in LTL. We found evidence of effect modification, with a stronger association among subjects ≥ 75 years of age compared with younger participants (p = 0.050) and statin medications appearing protective of the effects of BC on LTL (p = 0.050). Conclusions: Telomere attrition, linked to biological aging, may be associated with long-term exposures to airborne particles, particularly those rich in BC, which are primarily related to automobile traffic.
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    Chimney Stove Intervention to Reduce Long-term Wood Smoke Exposure Lowers Blood Pressure among Guatemalan Women
    (National Institute of Environmental Health Sciences, 2007) McCracken, John Patrick; Smith, Kirk R.; Díaz, Anaité; Mittleman, Murray; Schwartz, Joel
    Background and Objective: RESPIRE, a randomized trial of an improved cookstove, was conducted in Guatemala to assess health effects of long-term reductions in wood smoke exposure. Given the evidence that ambient particles increase blood pressure, we hypothesized that the intervention would lower blood pressure. Methods: Two study designs were used: a) between-group comparisons based on randomized stove assignment, and b) before-and-after comparisons within subjects before and after they received improved stoves. From 2003 to 2005, we measured personal fine particle (particulate matter with aerodynamic diameter < 2.5 μm; PM2.5) exposures and systolic (SBP) and diastolic blood pressure (DBP) among women > 38 years of age from the chimney woodstove intervention group (49 subjects) and traditional open wood fire control group (71 subjects). Measures were repeated up to three occasions. Results: Daily average PM2.5 exposures were 264 and 102 μg/m3 in the control and intervention groups, respectively. After adjusting for age, body mass index, an asset index, smoking, secondhand tobacco smoke, apparent temperature, season, day of week, time of day, and a random subject intercept, the improved stove intervention was associated with 3.7 mm Hg lower SBP [95% confidence interval (CI), −8.1 to 0.6] and 3.0 mm Hg lower DBP (95% CI, −5.7 to −0.4) compared with controls. In the second study design, among 55 control subjects measured both before and after receiving chimney stoves, similar associations were observed. Conclusion: The between-group comparisons provide evidence, particularly for DBP, that the chimney stove reduces blood pressure, and the before-and-after comparisons are consistent with this evidence.