Can Incorrect Analysis of Time-Dependent Exposure Explain Associations between PM2.5 Exposure and Risk of Dementia?

Background: Epidemiological studies have reported positive associations between long-term exposure to particulate matter of 2.5 microns or less in diameter (PM2.5) and risk of Alzheimer's disease and other clinical dementia. Many of these studies have analyzed data using Cox Proportional Hazards (PH) regression, which estimates a hazard ratio (HR) for the treatment (in this case, exposure) effect on the time-to-event outcome while adjusting for influential covariates. PM2.5 levels vary over time. As air quality standards for PM2.5 have become more stringent over time, average outdoor PM2.5 levels have decreased substantially. Objective: Investigate whether a Cox PH analysis that does not properly account for exposure that varies over time could produce a biased HR of similar magnitude to the HRs reported in recent epidemiological studies of PM2.5 and dementia risk. Methods: Simulation analysis. Results: We found that the biased HR can affect statistical analyses that consider exposure levels at event times only, especially if PM2.5 levels decreased consistently over time. Furthermore, the direction of such bias is away from the null and of a magnitude that is consistent with the reported estimates of dementia risk in several epidemiological studies of PM2.5 exposure (HR≈1.2 to 2.0). Conclusions: This bias can be avoided by correctly assigning exposure to study subjects throughout the entire follow-up period. We recommend that investigators provide a detailed description of how time-dependent exposure variables were accounted for in their Cox PH analyses when they report their results.

Is the cholesterol-perfluoroalkyl substance association confounded by dietary fiber intake?: a Bayesian analysis of NHANES data with adjustment for measurement error in fiber intake.

BACKGROUND: Serum concentrations of total cholesterol and related lipid measures have been associated with serum concentrations of per- and polyfluoroalkyl substances (PFAS) in humans, even among those with only background-level exposure to PFAS. Fiber is known to decrease serum cholesterol and a recent report based on National Health and Nutrition Examination Survey (NHANES) showed that PFAS and fiber are inversely associated. We hypothesized that confounding by dietary fiber may account for some of the association between cholesterol and PFAS. METHODS: We implemented a Bayesian correction for measurement error in estimated intake of dietary fiber to evaluate whether fiber confounds the cholesterol-PFAS association. The NHANES measure of diet, two 24-h recalls, allowed calculation of an estimate of the "true" long-term fiber intake for each subject. We fit models to the NHANES data on serum cholesterol and serum concentration of perfluorooctanoic acid (PFOA) and two other PFAS for 7,242 participants in NHANES. RESULTS: The Bayesian model, after adjustment for soluble fiber intake, suggested a decrease in the size of the coefficient for PFOA by 6.4% compared with the fiber-unadjusted model. CONCLUSIONS: The results indicated that the association of serum cholesterol with PFAS was not substantially confounded by fiber intake.

Cross-sectional Study of Workers Employed at a Copper Smelter-Effects of Long-term Exposures to Copper on Lung Function and Chronic Inflammation.

OBJECTIVE: The aim of the study was to assess the effect of exposure to copper-containing dust on lung function and inflammatory endpoints among workers of a German copper plant, effects rarely studied before. METHODS: One hundred four copper-exposed smelter workers and 70 referent workers from the precious metal and lead facilities were included, with different metal exposures in both groups due to the different process materials. Body plethysmography, exhaled nitric oxide (FeNO) measurements, and blood sampling were conducted in all workers. Smoking status and the use of respiratory protective equipment were considered. In a subgroup of 40 nonsmoking volunteers (28 copper-exposed and 12 referents), sputum biomarkers were assessed. RESULTS: Median lung function values of both copper-exposed and the referent groups were within reference ranges of "healthy" individuals, and statistical differences between the groups were mostly not evident. Similarly, differences in blood and sputum biomarkers were too small to be biologically relevant. CONCLUSION: The results suggest the absence of the detectable effects of copper-containing dust exposure on lung function or chronic inflammation within the investigated cohort.

Underground salt and potash workers exposed to nitrogen oxides and diesel exhaust: assessment of specific effect biomarkers.

PURPOSE: Occupational exposure limits (OEL) for nitrogen oxides (NO, NO2) and diesel exhaust (EC-DPM) were reassessed by the German authorities in 2016/2017. We performed a clinical cross-sectional study among salt and potash underground workers exposed to these substances at relatively high levels to examine possible indicators of acute effects on workers' health. METHODS: We measured post- versus pre-shift differences in cardiovascular, inflammatory, immune, and respiratory effect biomarkers and assessed their associations with personal exposures measured during the same shift. We also compared post- versus pre-shift differences in biomarker levels between exposure groups defined based on work site and job type. RESULTS: None of the above-ground workers exceeded the OEL for NO2 and only 5% exceeded the OEL for EC-DPM exposure. Among underground workers, 33% of miners and 7% underground maintenance workers exceeded the OEL for NO2; the OEL for EC-DPM was exceeded by 56% of miners and 17% of maintenance workers. Some effect biomarkers (thrombocytes, neutrophils, MPO, TNF-α, IgE, FeNO) showed statistically significant differences between pre- versus post-shift measurements; however, there were no consistent associations between pre- and post-shift differences and exposure group or personal exposure measurements during the shift. CONCLUSIONS: We did not find evidence of associations between workplace exposure to NO, NO2 or EC-DPM and clinically relevant indicators of acute cardiovascular, inflammatory and immune, or respiratory effects among salt and potash underground workers in Germany.

Household air pollution from wood-burning cookstoves and C-reactive protein among women in rural Honduras.

Household air pollution from solid fuel combustion was estimated to cause 2.31 million deaths worldwide in 2019; cardiovascular disease is a substantial contributor to the global burden. We evaluated the cross-sectional association between household air pollution (24-h gravimetric kitchen and personal particulate matter (PM2.5) and black carbon (BC)) and C-reactive protein (CRP) measured in dried blood spots among 107 women in rural Honduras using wood-burning traditional or Justa (an engineered combustion chamber) stoves. A suite of 6 additional markers of systemic injury and inflammation were considered in secondary analyses. We adjusted for potential confounders and assessed effect modification of several cardiovascular-disease risk factors. The median (25th, 75th percentiles) 24-h-average personal PM2.5 concentration was 115 µg/m3 (65,154 µg/m3) for traditional stove users and 52 µg/m3 (39, 81 µg/m3) for Justa stove users; kitchen PM2.5 and BC had similar patterns. Higher concentrations of PM2.5 and BC were associated with higher levels of CRP (e.g., a 25% increase in personal PM2.5 was associated with a 10.5% increase in CRP [95% CI: 1.2-20.6]). In secondary analyses, results were generally consistent with a null association. Evidence for effect modification between pollutant measures and four different cardiovascular risk factors (e.g., high blood pressure) was inconsistent. These results support the growing evidence linking household air pollution and cardiovascular disease.

A Health Surveillance Study of Workers Employed at a Copper Smelter-Effects of Long-Term Exposure to Copper on Lung Function Using Spirometric Data.

OBJECTIVE: Significantly lower permissible occupational exposure limits for copper dust are being discussed in Europe and other jurisdictions. However, little data are published on exposures in occupational settings and copper-specific effects in humans. Hence, a health surveillance study was performed among workers employed at a copper smelter between 1972 and 2018. METHODS: Possible effects of long-term exposures to dust containing copper on lung function were assessed. Specifically, declines in forced expiratory volume in 1 second (FEV1) were compared between a copper-exposed and control group. Cumulative copper exposures were derived from historical airborne monitoring data. RESULTS: FEV1 declines among exposed and control never smokers were similar to a typical age-dependent decline of 29 mL/y. CONCLUSION: The study findings indicate that cumulative inhalable copper dust exposure averaging 4.61 mg/m3-years over an exposure duration of ∼22 years is not associated with adverse effects on lung function.

Estimating the Population Health Impact of Recently Introduced Modified Risk Tobacco Products: A Comparison of Different Approaches.

INTRODUCTION: Various approaches have been used to estimate the population health impact of introducing a Modified Risk Tobacco Product (MRTP). AIMS AND METHODS: We aimed to compare and contrast aspects of models considering effects on mortality that were known to experts attending a meeting on models in 2018. RESULTS: Thirteen models are described, some focussing on e-cigarettes, others more general. Most models are cohort-based, comparing results with or without MRTP introduction. They typically start with a population with known smoking habits and then use transition probabilities either to update smoking habits in the "null scenario" or joint smoking and MRTP habits in an "alternative scenario". The models vary in the tobacco groups and transition probabilities considered. Based on aspects of the tobacco history developed, the models compare mortality risks, and sometimes life-years lost and health costs, between scenarios. Estimating effects on population health depends on frequency of use of the MRTP and smoking, and the extent to which the products expose users to harmful constituents. Strengths and weaknesses of the approaches are summarized. CONCLUSIONS: Despite methodological differences, most modellers have assumed the increase in risk of mortality from MRTP use, relative to that from cigarette smoking, to be very low and have concluded that MRTP introduction is likely to have a beneficial impact. Further model development, supplemented by preliminary results from well-designed epidemiological studies, should enable more precise prediction of the anticipated effects of MRTP introduction. IMPLICATIONS: There is a need to estimate the population health impact of introducing modified risk nicotine-containing products for smokers unwilling or unable to quit. This paper reviews a variety of modeling methodologies proposed to do this, and discusses the implications of the different approaches. It should assist modelers in refining and improving their models, and help toward providing authorities with more reliable estimates.

C-reactive protein from dried blood spots: Application to household air pollution field studies.

Household air pollution (HAP) is estimated to be an important risk factor for cardiovascular disease, but little clinical evidence exists and collecting biomarkers of disease risk is difficult in low-resource settings. Among 54 Nicaraguan women with woodburning cookstoves, we evaluated cross-sectional associations between 48-hour measures of HAP (eg, fine particulate matter, PM2.5 ) and C-reactive protein (CRP) via dried blood spots; secondary analyses included seven additional biomarkers of systemic injury and inflammation. We conducted sub-studies to calculate the intraclass correlation coefficient (ICC) in biomarkers collected over four consecutive days in Nicaragua and to assess the validity of measuring biomarkers in dried blood by calculating the correlation with paired venous-drawn samples in Colorado. Measures of HAP were associated with CRP (eg, a 25% increase in indoor PM2.5 was associated with a 7.4% increase in CRP [95% confidence interval: 0.7, 14.5]). Most of the variability in CRP concentrations over the 4-day period was between-person (ICC: 0.88), and CRP concentrations were highly correlated between paired dried blood and venous-drawn serum (Spearman ρ = .96). Results for secondary biomarkers were primarily consistent with null associations, and the sub-study ICCs and correlations were lower. Assessing CRP via dried blood spots provides a feasible approach to elucidate the association between HAP and cardiovascular disease risk.

Exposure to household air pollution from biomass cookstoves and self-reported symptoms among women in rural Honduras.

Household air pollution from combustion of solid fuels is an important risk factor for morbidity and mortality, causing an estimated 2.6 million premature deaths globally in 2016. Self-reported health symptoms are a meaningful measure of quality of life, however, few studies have evaluated symptoms and quantitative measures of exposure to household air pollution. We assessed the cross-sectional association of self-reported symptoms and exposures to household air pollution among women in rural Honduras using stove type (traditional [n = 76]; cleaner-burning Justa [n = 74]) and 24-hour average personal and kitchen fine particulate matter (PM2.5) concentrations. The odds of prevalent symptoms were higher among women using traditional stoves vs Justa stoves (e.g. headache: odds ratio = 2.23; 95% confidence interval = 1.13-4.39). Associations between symptoms and measured PM2.5 were generally consistent with the null. These results add to the evidence suggesting reduced exposures and better health-related quality of life among women using cleaner-burning biomass stoves.

Diet, Secondhand Smoke, and Glycated Hemoglobin (HbA1c) Levels among Singapore Chinese Adults.

The combination of poor diet and exposure to secondhand smoke may increase hemoglobin A1c (HbA1c) levels, but few studies have explored this interaction. We explored an interaction among 574 never-smoking adults from the Singapore Chinese Health Study. At baseline (age 59 ± 8 years), intakes of omega-3 polyunsaturated fatty acids, vitamin C, vitamin E and fiber were estimated using a modified food frequency questionnaire. At follow-up (age 64 ± 9 years), HbA1c and cotinine were measured. A product term between cotinine (above or below the median value) and each nutrient (high or low intake) was included in separate linear regression models with HbA1c as the outcome. HbA1c among those with high cotinine and low omega-3 polyunsaturated fatty acids intakes were higher than would be expected due to the individual effects alone (p-for-interaction = 0.05). Among those with lower intakes of omega-3 polyunsaturated fatty acids, high cotinine levels were associated with 0.54% higher HbA1c levels (95% confidence interval [CI]: 0.02, 1.06). Conversely, among those with higher intakes of omega-3 polyunsaturated fatty acids, HbA1c differ not differ by exposure (-0.09%; 95% CI: -0.45, 0.30). No evidence of interaction was observed for other nutrients. Diets high in omega-3 polyunsaturated fatty acids may ameliorate secondhand smoke-induced increases in HbA1c.

Exposure to household air pollution from biomass cookstoves and blood pressure among women in rural Honduras: A cross-sectional study.

Growing evidence links household air pollution exposure from biomass cookstoves with elevated blood pressure. We assessed cross-sectional associations of 24-hour mean concentrations of personal and kitchen fine particulate matter (PM2.5 ), black carbon (BC), and stove type with blood pressure, adjusting for confounders, among 147 women using traditional or cleaner-burning Justa stoves in Honduras. We investigated effect modification by age and body mass index. Traditional stove users had mean (standard deviation) personal and kitchen 24-hour PM2.5 concentrations of 126 µg/m3 (77) and 360 µg/m3 (374), while Justa stove users' exposures were 66 µg/m3 (38) and 137 µg/m3 (194), respectively. BC concentrations were similarly lower among Justa stove users. Adjusted mean systolic blood pressure was 2.5 mm Hg higher (95% CI, 0.7-4.3) per unit increase in natural log-transformed kitchen PM2.5 concentration; results were stronger among women of 40 years or older (5.2 mm Hg increase, 95% CI, 2.3-8.1). Adjusted odds of borderline high and high blood pressure (categorized) were also elevated (odds ratio = 1.5, 95% CI, 1.0-2.3). Some results included null values and are suggestive. Results suggest that reduced household air pollution, even when concentrations exceed air quality guidelines, may help lower cardiovascular disease risk, particularly among older subgroups.

Household air pollution from biomass-burning cookstoves and metabolic syndrome, blood lipid concentrations, and waist circumference in Honduran women: A cross-sectional study.

BACKGROUND: Household air pollution from cooking with solid fuels affects nearly 3 billion people worldwide and is responsible for an estimated 2.5 million premature deaths and 77 million disability-adjusted life years annually. Investigating the effect of household air pollution on indicators of cardiometabolic disease, such as metabolic syndrome, can help clarify the pathways between this widespread exposure and cardiovascular diseases, which are increasing in low- and middle-income countries. METHODS: Our cross-sectional study of 150 women in rural Honduras (76 with traditional stoves and 74 with cleaner-burning Justa stoves) explored the effect of household air pollution exposure on cardiovascular disease risk factors. Household air pollution was measured by stove type and 24-h average kitchen and personal fine particulate matter [PM2.5] mass and black carbon concentrations. Health endpoints included non-fasting total cholesterol, high-density lipoprotein, calculated low-density lipoprotein, triglycerides, waist circumference to indicate abdominal obesity, and presence of metabolic syndrome (defined by current modified international guidelines: waist circumference ≥ 80 cm plus any two of the following: triglycerides > 200 mg/dL, HDL < 50 mg/dL, systolic blood pressure ≥ 130 mmHg, diastolic blood pressure ≥ 85 mmHg, or glycated hemoglobin > 5.6%). RESULTS: Forty percent of women met the criteria for metabolic syndrome. The prevalence ratio [PR] for metabolic syndrome (versus normal) per interquartile range increase in kitchen PM2.5 and kitchen black carbon was 1.16 (95% confidence interval [CI]: 1.01-1.34) per 312 µg/m3 increase in PM2.5, and 1.07 (95% CI: 1.03-1.12) per 73 µg/m3 increase in black carbon. There is suggestive evidence of a stronger effect in women ≥ 40 years of age compared to women < 40 (p-value for interaction = 0.12 for personal PM2.5). There was no evidence of associations between all other exposure metrics and health endpoints. CONCLUSIONS: The prevalence of metabolic syndrome among our study population was high compared to global estimates. We observed a suggestive effect between metabolic syndrome and exposure to household air pollution. These results for metabolic syndrome may be driven by specific syndrome components, such as blood pressure. Longitudinal research with repeated health and exposure measures is needed to better understand the link between household air pollution and indicators of cardiometabolic disease risk.

Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women.

Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justa stoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO).

Assessing the Likelihood and Magnitude of a Population Health Benefit Following the Market Introduction of a Modified-Risk Tobacco Product: Enhancements to the Dynamic Population Modeler, DPM(+1).

Researchers and those responsible for evaluating and implementing policies intended to reduce population harm must assess the potential for both intended and unintended consequences associated with those policies. Such assessments should be based on the combined dimensions of magnitude, and thus likelihood, of shifts in exposure patterns needed to produce a population benefit or harm, and magnitude of the expected population benefit or harm. In response to this assessment need, we provide a conceptual description of the dynamic population modeler, DPM(+1), as well as illustrative analyses that estimate the effects on all-cause mortality, life expectancy, and quality of life-adjusted life expectancy if exposure patterns in the population shift from a higher risk product (e.g., cigarettes) to a lower, or modified, risk tobacco product (MRTP) in specified ways. Estimates from these analyses indicate that, within a single birth cohort, switching completely from cigarette smoking to MRTP use is more likely to lead to a population-level survival benefit than initiating tobacco use with an MRTP instead of cigarettes. This is because tobacco initiation rarely occurs beyond young adulthood, whereas continuing smokers exist in all subsequent age categories, leading to a greater cumulative effect. In addition, complete switching to MRTP use among a small proportion of smokers in each age category offsets the survival deficit caused by unintended shifts in exposure patterns, such as MRTP initiation among never tobacco users followed by transitioning to cigarette smoking and/or cigarette smokers switching to MRTP use instead of quitting.

Associations between thoracic radiographic changes and severity of pulmonary arterial hypertension diagnosed in 60 dogs via Doppler echocardiography: A retrospective study.

Doppler echocardiography is a noninvasive method for estimating and grading pulmonary arterial hypertension. No current literature associates significance of radiographic findings with severity of pulmonary arterial hypertension. We hypothesized that the number and conspicuity of radiographic findings suggestive of pulmonary arterial hypertension would be greater based on the severity of pulmonary arterial hypertension. Dogs with pulmonary arterial hypertension and normal control dogs were included in this retrospective, case control study. Three radiologists blinded to echocardiographic results scored thoracic radiographs for right ventricular and main pulmonary artery enlargement and pulmonary lobar artery enlargement, tortuosity, and blunting by multiple methods. Presence or absence of each finding was scored in an additive fashion and averaged for each grade of pulmonary arterial hypertension severity. Seventy-one dogs (60 dogs with pulmonary arterial hypertension and 11 control dogs) of which some had multiple studies were included: 20 mild, 21 moderate, 25 severe, and 11 absent pulmonary arterial hypertension. The following radiographic findings were significantly associated with increasing pulmonary arterial hypertension severity: right ventricular enlargement by "reverse D" and "3/5-2/5 cardiac ratio" methods, main pulmonary artery enlargement, and caudal lobar artery enlargement by the "3rd rib" method. Mean scores for severe pulmonary arterial hypertension and normal dogs were significantly different (P-value < 0.0001). Mean scores between different pulmonary arterial hypertension grades increased with severity but were not statistically significant. Individually and in combination, radiographic findings performed poorly in differentiating severity of pulmonary arterial hypertension. Findings indicated that thoracic radiographs should be utilized in conjunction with Doppler echocardiography in a complete diagnostic work-up for dogs with suspected pulmonary arterial hypertension.

Interactions Between Diet and Exposure to Secondhand Smoke on Glycated Hemoglobin Levels Among US Children: Results From NHANES 2007-2012.

INTRODUCTION: Antioxidant-rich diets may lessen the adverse metabolic responses triggered by exposure to secondhand smoke (SHS), but no studies have investigated these potential interactions. OBJECTIVE: To examine the interaction between diet and exposure to SHS on glycated hemoglobin (HbA1c) levels among 2551 children, ages 12-19 years, who participated in the 2007-2012 National Health and Nutrition Examination Survey (NHANES). METHODS: Exposure to SHS was assessed by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), cotinine, and self-report. Weighted linear regression models evaluated the cross-sectional association between exposure to SHS and HbA1c levels. Additive interaction was assessed by introducing product terms (with SHS) of individual nutrients (dietary fiber, eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA], vitamin C, and vitamin E) to separate models. RESULTS: Over half of the children had NNAL or cotinine levels above the limit of detection (56% and 71%, respectively). The median HbA1c level was 5.2% (95% confidence interval: 5.17%, 5.23%). The interaction results suggest that the effects of exposure to SHS and certain dietary nutrients (EPA, DHA, vitamin C) on HbA1c levels may not be independent. For example, although there was only a slight difference in adjusted mean HbA1c levels across NNAL categories among children with high EPA intakes, the adjusted mean HbA1c level was 0.09% higher for high NNAL as compared to low NNAL among children with low EPA intakes. CONCLUSIONS: Further research is needed to inform public health strategies for limiting increases in HbA1c levels among children. Messages may need to focus both on reducing exposure to SHS and improving diets to obtain the maximum benefit. IMPLICATIONS: Our results suggest that the effects of exposure to SHS and diet on HbA1c levels may not be independent. For example, although there was little effect of exposure to SHS on HbA1c levels among children with high EPA intakes, high exposure to SHS was associated with an increase in HbA1c levels among children with low EPA intakes. Further research is necessary; however, based on these joint effects, strategies for limiting increases in HbA1c levels that focus both on reducing exposure to SHS and improving diets may achieve the largest public health benefits.

REPEATABILITY AND RELIABILITY OF GLOMERULAR FILTRATION RATE DETERMINATION VIA GAMMA CAMERA UPTAKE OF TC-99M-DTPA IN CATS WITH CHRONIC KIDNEY DISEASE.

Measurement of glomerular filtration rate (GFR) via gamma camera uptake of 99mTc-diethylenetriaminepentaacetic acid is a standard method for quantifying renal function. Aims of this retrospective, observer agreement study were to determine intra- and interobserver variation in GFR values for cats with chronic kidney disease and to determine whether renal insufficiency classification changed between observers. Guideline cut-points were established for the difference in repeated GFRs to differentiate changes caused by therapeutic effect vs. inherent variation. Included cats had a diagnosis of chronic kidney disease and had undergone GFR examinations between the years of 2010 and 2013. Twenty-nine GFR studies were sampled. Each study was read twice, 6 months apart, by two veterinary radiologists and one radiology resident. Modified Bland-Altman plots were used to investigate differences between readings 1 and 2 by observer and between pairs of observers by reading. Reliability of clinical classification was assessed through comparisons between readings and observers. Measurements were not systematically different between readings for the experienced observers but were higher in reading 1 than reading 2 for the inexperienced observer. Measurements were not systematically different between the experienced observers in reading 1 or between any two observers in reading 2. Reliability for GFR measurements was high among experienced observers; variations in GFR measurements rarely led to differences in clinical classification. Results suggested that, for experienced observers, changes in GFR values following treatment in cats with chronic kidney disease between -0.4 and 0.4 mL/min/kg may be due to inherent variability rather than treatment effect.

Interactions Between Diet and Exposure to Secondhand Smoke on Metabolic Syndrome Among Children: NHANES 2007-2010.

CONTEXT: Metabolic syndrome is likely influenced by a complex interaction between exposure to secondhand smoke (SHS) and diet, but no studies have evaluated this relationship. OBJECTIVE: This study aimed to investigate the interaction between diet and exposure to SHS on metabolic syndrome among 12-19 year olds. DESIGN AND PARTICIPANTS: We used weighted logistic regression, adjusting for potential confounders, to examine interaction of these risk factors on the prevalence of metabolic syndrome among 12-19 year olds participating in the National Health and Nutrition Examination Survey (2007-2010). Interaction was assessed by introducing product terms between SHS (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, cotinine, and self-report) and the individual nutrients (dietary fiber, eicosapentaenoic acid, docosahexaenoic acid, vitamin C, and vitamin E) and nutrient patterns in separate models; the relative excess risk due to interaction was used to evaluate interaction on the additive scale. RESULTS: The joint effect between high exposure to SHS and low levels of certain nutrients (vitamin E and omega-3 polyunsaturated fatty acids) on metabolic syndrome risk was greater than would be expected from the effects of the individual exposures alone (for example, relative excess risk due to interaction for SHS and vitamin E = 7.5; 95% confidence interval, 2.5-17.8). CONCLUSIONS: Prevention strategies for metabolic syndrome aimed at reducing SHS exposures and improving diet quality may exceed the expected benefits based on targeting these risk factors separately.

The Fort Collins Commuter Study: Impact of route type and transport mode on personal exposure to multiple air pollutants.

Traffic-related air pollution is associated with increased mortality and morbidity, yet few studies have examined strategies to reduce individual exposure while commuting. The present study aimed to quantify how choice of mode and route type affects personal exposure to air pollutants during commuting. We analyzed within-person difference in exposures to multiple air pollutants (black carbon (BC), carbon monoxide (CO), ultrafine particle number concentration (PNC), and fine particulate matter (PM2.5)) during commutes between the home and workplace for 45 participants. Participants completed 8 days of commuting by car and bicycle on direct and alternative (reduced traffic) routes. Mean within-person exposures to BC, PM2.5, and PNC were higher when commuting by cycling than when driving, but mean CO exposure was lower when cycling. Exposures to CO and BC were reduced when commuting along alternative routes. When cumulative exposure was considered, the benefits from cycling were attenuated, in the case of CO, or exacerbated, in the case of particulate exposures, owing to the increased duration of the commute. Although choice of route can reduce mean exposure, the effect of route length and duration often offsets these reductions when cumulative exposure is considered. Furthermore, increased ventilation rate when cycling may result in a more harmful dose than inhalation at a lower ventilation rate.