Air pollution exposure and social responsiveness in childhood: The cincinnati combined childhood cohorts.

Autism Spectrum Disorder (ASD) affects about 1 in 44 children and environmental exposures may contribute to disease onset. Air pollution has been associated with adverse neurobehavioral outcomes, yet little research has examined its association with autistic-like behaviors. Therefore, our objective was to examine the association between exposure to air pollution, including NO2 and PM2.5, during pregnancy and the first year of life to ASD-like behaviors during childhood. Participants (n = 435) enrolled in the Cincinnati Childhood Allergy and Air Pollution Study and the Health Outcomes and Measures of the Environment Study were included in the analysis. Daily exposures to NO2 and PM2.5 at the residential addresses of participants were estimated using validated spatiotemporal models and averaged to obtain prenatal and first year exposure estimates. ASD-like behaviors were assessed via the Social Responsiveness Scale (SRS) questionnaire at age 12. Linear regression models adjusting for confounders were applied to estimate the association between pollutants and SRS scores. After adjusting for covariates, the association between NO2 and PM2.5 and SRS scores remained positive but were no longer statistically significant. Prenatal and first year exposure to NO2 were associated with total SRS T-scores with an estimated 0.4 point increase (95% CI: -0.7, 1.6) per 5.2 ppb increase in NO2 exposure and 0.7 point (95% CI: -0.3, 1.6) per 4.2 ppb increase in NO2 exposure, respectively. For PM2.5, a 2.6 µg/m3 increase in prenatal exposure was associated with a 0.1 point increase (95% CI: -1.1, 1.4) in SRS Total T-scores and a 1.3 µg/m3 increase first year of life was associated with a 1 point increase (95% CI: -0.2, 2.3). In summary, exposure to NO2 and PM2.5 during pregnancy and the first year of life were not significantly associated with higher autistic-like behaviors measured with SRS scores after adjustment of covariates. Additional research is warranted given prior studies suggesting air pollution contributes to ASD.

Residential greenness, asthma, and lung function among children at high risk of allergic sensitization: a prospective cohort study.

BACKGROUND: While benefits of greenness to health have been reported, findings specific to child respiratory health are inconsistent. METHODS: We utilized a prospective birth cohort followed from birth to age 7 years (n = 617). Residential surrounding greenness was quantified via Normalized Difference Vegetation Index (NDVI) within 200, 400, and 800 m distances from geocoded home addresses at birth, age 7 years, and across childhood. Respiratory health outcomes were assessed at age 7 years, including asthma and lung function [percent predicted forced expiratory volume in the first second (%FEV1), percent predicted forced vital capacity (%FVC), and percent predicted ratio of forced expiratory volume in the first second to forced vital capacity (%FEV1/FVC)]. We assessed associations using linear and logistic regression models adjusted for community deprivation, household income, and traffic-related air pollution. We tested for effect measure modification by atopic status. RESULTS: We noted evidence of positive confounding as inverse associations were attenuated upon adjustment in the multivariable models. We found evidence of effect measure modification of NDVI and asthma within 400 m at age 7 years by atopic status (p = 0.04), whereby children sensitized to common allergens were more likely to develop asthma as exposure to greenness increased (OR = 1.3, 95% CI: 0.9, 2.0) versus children not sensitized to common allergens (OR = 0.8, 95% CI: 0.5, 1.2). We found consistently positive associations between NDVI and %FEV1 and %FVC which similarly evidenced positive confounding upon adjustment. In the adjusted regression models, NDVI at 7 years of age was associated with %FEV1 (200 m: ß = 2.1, 95% CI: 0.1, 3.3; 400 m: ß = 1.6, 95% CI: 0.3, 2.9) and %FVC (200 m: ß = 1.8, 95% CI: 0.7, 3.0; 400 m: ß = 1.6, 95% CI: 0.3, 2.8; 800 m: ß = 1.5, 95% CI: 0.1, 2.8). Adjusted results for %FEV1/FVC were non-significant except exposure at birth in the 400 m buffer (ß = 0.81, 95% CI: 0.1, 1.5). We found no evidence of effect measure modification of NDVI by atopic status for objective measures of lung function. CONCLUSION: Sensitivity to allergens may modify the effect of greenness on risk for asthma in children but greenness is likely beneficial for concurrent lung function regardless of allergic status.

Mortality of workers employed in refractory ceramic fiber manufacturing: An update.

This study evaluates the possible association between refractory ceramic fiber (RCF) exposure and all causes of death. Current and former employees (n = 1,119) hired from 1952 to 1999 at manufacturing facilities in New York (NY) state and Indiana were included. Work histories and quarterly plant-wide sampling from 1987 to 2015 provided cumulative fiber exposure (CFE) estimates. The full cohort was evaluated as well as individuals with lower and higher exposure, <45 and ≥45 fiber-months/cc. The Life-Table-Analysis-System was used for all standardized mortality rates (SMRs). Person-years at risk were accumulated from start of employment until 12/31/2019 or date of death. There was no significant association with all causes, all cancers, or lung cancer in any group. In the higher exposed, there was a significant elevation in both malignancies of the "urinary organs" (SMR = 3.59, 95% confidence interval [CI] 1.44, 7.40) and "bladder or other urinary site" (SMR = 4.04, 95% CI 1.10, 10.36), which persisted in comparison to regional mortality rates from NY state and Niagara County. However, six of the nine workers with urinary cancers were known smokers. In the lower exposed, there was a significant elevation in malignancies of the lymphatic and hematopoietic system (SMR = 2.54, 95% CI 1.27, 4.55) and leukemia (SMR = 4.21, 95% CI 1.69, 8.67). There was one pathologically unconfirmed mesothelioma death. A second employee currently living with a pathologically confirmed mesothelioma was identified, but the SMR was non-significant when both were included in the analyses. The association of these two mesothelioma cases with RCF exposure alone is unclear because of potential past exposure to asbestos.

NAT1 genetic variation increases asthma risk in children with secondhand smoke exposure.

OBJECTIVE: We previously reported that children exposed to secondhand smoke (SHS) that carried variants in the NAT1 gene had over two-fold higher hair cotinine levels. Our objective was to determine if NAT1 polymorphisms confer increased risk for developing asthma in children exposed to SHS. METHODS: White participants in the Cincinnati Childhood Allergy and Air Pollution Study (n = 359) were genotyped for 10 NAT1 variants. Smoke exposure was defined by hair cotinine and parental report. Asthma was objectively assessed by spirometry and methacholine challenge. Findings were replicated in the Genomic Control Cohort (n = 638). RESULTS: Significant associations between 5 NAT1 variants and asthma were observed in the CCAAPS exposed group compared to none in the unexposed group. There was a significant interaction between NAT1 rs13253389 and rs4921581 with smoke exposure (p = 0.02, p = 0.01) and hair cotinine level (p = 0.048, p = 0.042). Children wildtype for rs4921581 had increasing asthma risk with increasing hair cotinine level, whereas those carrying the NAT1 minor allele had an increased risk of asthma regardless of cotinine level. In the GCC, 13 NAT1 variants were associated with asthma in the smoke-exposed group, compared to 0 in the unexposed group, demonstrating gene-level replication. CONCLUSIONS: Variation in the NAT1 gene modifies asthma risk in children exposed to secondhand-smoke. To our knowledge, this is the first report of a gene-environment interaction between NAT1 variants, smoke exposure, cotinine levels, and pediatric asthma. NAT1 genotype may have clinical utility as a biomarker of increased asthma risk in children exposed to smoke.

Residential surrounding greenness and self-reported symptoms of anxiety and depression in adolescents.

BACKGROUND: Evidence on the relationship between exposure to greenness and adolescent mental health is limited. The purpose of this study was to examine the association between greenness throughout childhood and mental health at age 12 years. METHODS: We assessed greenness using the satellite-based measure of Normalized Difference Vegetation Index (NDVI) within 200m, 400m, and 800m of home address at birth, age 12 years, and across childhood (averaged for each year from birth to age 12) among the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) cohort. Self-reported symptoms of anxiety and depression were assessed at age 12 years using the Spence Children's Anxiety Scale (SCAS) and Children's Depression Inventory 2 (CDI 2), respectively. Associations were estimated using linear regression, adjusting for covariates including traffic-related air pollution, neurological hazard exposure, blood lead level, household income, and community deprivation. RESULTS: In adjusted models, NDVI was largely not associated with self-reported anxiety and depression symptoms, except for the SCAS separation anxiety subscale at 400m and 800m (0.1 unit increase mean NDVI 400m: ß = -0.97, 95% CI: -1.86, -0.07; 800m: ß = -1.33, 95% CI: -2.32, -0.34). CONCLUSION: While we found no direct relationship between greenness and overall symptoms of anxiety and depression in adolescents upon adjustment for relevant covariates at the 200m distance, greenness may lesson symptoms of separation anxiety within 400m and 800m distance from the home address at age 12 years. Future research should examine mechanisms for these relationships at the community- and individual-level.

Quantitative and semiquantitative estimates of mold exposure in infancy and childhood respiratory health.

BACKGROUND: Previous epidemiologic studies of dampness and mold relied on metrics that did not fully assess exposure-response relationships. Our objective was to examine quantitative metrics of dampness and mold during infancy and respiratory health outcomes during childhood. METHODS: In-home visits were conducted before age 1 for children in the Cincinnati Childhood Allergy and Air Pollution Study. Respiratory outcomes included age 3 wheeze and age 7 asthma and wheeze. The associations between home exposure and respiratory outcomes were evaluated for 779 children using logistic regression adjusting for household income, neighborhood socioeconomic status, and the presence of pests. RESULTS: Children residing in homes with ≥0.29 m2 of moisture damage were significantly more likely to have wheezing at age 3 and persistent wheeze through age 7 (adjusted odds ratio [aOR] = 2.2; 95% confidence interval [CI] = 1.0, 4.3 and aOR = 3.2; CI = 1.3, 7.5, respectively). Additionally, homes having ≥0.19 m2 of mold damage were associated with wheezing at age 3 and early transient wheeze assessed at age 7 (aOR = 2.9; CI = 1.3, 6.4 and aOR = 3.5; CI = 1.5, 8.2, respectively). Mold damage <0.19 m2 and moisture damage <0.29 m2 were not associated with health outcomes. Mold and moisture damage were also not associated with asthma. CONCLUSION: Our data indicate that only the highest categories analyzed for mold (≥0.19 m2) and moisture damage (≥0.29 m2) in homes at age 1 were significantly associated with wheeze at ages 3 and 7; however, data below these levels were too sparse to assess the shape of the relationship or explore potential health-relevant thresholds.

Reduced gray matter volume and cortical thickness associated with traffic-related air pollution in a longitudinally studied pediatric cohort.

Early life exposure to air pollution poses a significant risk to brain development from direct exposure to toxicants or via indirect mechanisms involving the circulatory, pulmonary or gastrointestinal systems. In children, exposure to traffic related air pollution has been associated with adverse effects on cognitive, behavioral and psychomotor development. We aimed to determine whether childhood exposure to traffic related air pollution is associated with regional differences in brain volume and cortical thickness among children enrolled in a longitudinal cohort study of traffic related air pollution and child health. We used magnetic resonance imaging to obtain anatomical brain images from a nested subset of 12 year old participants characterized with either high or low levels of traffic related air pollution exposure during their first year of life. We employed voxel-based morphometry to examine group differences in regional brain volume, and with separate analyses, changes in cortical thickness. Smaller regional gray matter volumes were determined in the left pre- and post-central gyri, the cerebellum, and inferior parietal lobe of participants in the high traffic related air pollution exposure group relative to participants with low exposure. Reduced cortical thickness was observed in participants with high exposure relative to those with low exposure, primarily in sensorimotor regions of the brain including the pre- and post-central gyri and the paracentral lobule, but also within the frontal and limbic regions. These results suggest that significant childhood exposure to traffic related air pollution is associated with structural alterations in brain.

Respiratory follow-up pre- and post-engineering controls or cessation of added diacetyl at four microwave popcorn facilities.

In a 7-year study at 4 microwave popcorn facilities, mixing room employees exposed to diacetyl prior to the introduction of respirators showed significant loss of lung function but did not continue to decline longitudinally faster than other job categories http://bit.ly/2xwWRiw.

Myo-inositol mediates the effects of traffic-related air pollution on generalized anxiety symptoms at age 12 years.

BACKGROUND: Exposure to traffic-related air pollution (TRAP) has been linked to childhood anxiety symptoms. Neuroimaging in patients with anxiety disorders indicate altered neurochemistry. OBJECTIVES: Evaluate the impact of TRAP on brain metabolism and its relation to childhood anxiety symptoms in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS). METHODS: Adolescents (n = 145) underwent magnetic resonance spectroscopy. Brain metabolites, including myo-inositol, N-acetylaspartate, creatine, choline, glutamate, glutamate plus glutamine, and glutathione were measured in the anterior cingulate cortex. Anxiety symptoms were assessed using the Spence Children's Anxiety Scale. TRAP exposure in early-life, averaged over childhood, and during the 12 months prior to imaging was estimated using a validated land use regression model. Associations between TRAP exposure, brain metabolism, and anxiety symptoms were estimated using linear regression and a bootstrapping approach for testing mediation by brain metabolite levels. RESULTS: Recent exposure to high levels of TRAP was associated with significant increases in myo-inositol (ß = 0.26; 95%CI 0.01, 0.51) compared to low TRAP exposure. Recent elevated TRAP exposure (ß = 4.71; 95% CI 0.95, 8.45) and increased myo-inositol levels (ß = 2.98; 95% CI 0.43, 5.52) were also significantly associated with increased generalized anxiety symptoms with 12% of the total effect between TRAP and generalized anxiety symptoms being mediated by myo-inositol levels. CONCLUSIONS: This is the first study of children to utilize neuroimaging to link TRAP exposure, metabolite dysregulation in the brain, and generalized anxiety symptoms among otherwise healthy children. TRAP may elicit atypical excitatory neurotransmission and glial inflammatory responses leading to increased metabolite levels and subsequent anxiety symptoms.

Using high-resolution residential greenspace measures in an urban environment to assess risks of allergy outcomes in children.

Despite reported health benefits of urban greenspace (gs), the epidemiological evidence is less clear for allergic disease. To address a limitation of previous research, we examined the associations of medium- and high-resolution residential gs measures and tree and/or grass canopies with allergic outcomes for children enrolled in the longitudinal cincinnati childhood allergy and air pollution study (ccaaps). We estimated residential gs based on 400 m radial buffers around participant addresses (n = 478) using the normalized differential vegetation index (ndvi) and land cover-derived urban greenspace (ugs) (tree and grass coverage, combined and separate) at 30 m and 1.5-2.5 m resolution, respectively. Associations between outdoor aeroallergen sensitization and allergic rhinitis at age 7 and residential gs measures at different exposure windows were examined using multivariable logistic regression models. A 10% increase in ugs-derived grass coverage was associated with an increased risk of sensitization to grass pollens (adjusted odds ratio [aor]: 1.27; 95% confidence interval = 1.02-1.58). For each 10% increase in ugs-derived tree canopy coverage, nonstatistically significant decreased odds were found for grass pollen sensitization, tree pollen sensitization, and sensitization to either (aor range = 0.87-0.94). Results similar in magnitude to ugs-tree canopy coverage were detected for ndvi and allergic sensitizations. High-resolution (down to 1.5 m) gs measures of grass- and tree-covered areas showed associations in opposite directions for different allergy outcomes. These data suggest that measures strongly correlated with tree canopy (e.g., ndvi) may be insufficient to detect health effects associated with proximity to different types of vegetation or help elucidate mechanisms related to specific gs exposure pathways.

Identification of two early life eczema and non-eczema phenotypes with high risk for asthma development.

BACKGROUND: The "atopic march" has been considered a linear progression starting with eczema and culminating with development of asthma. Not all asthma cases, however, are preceded by eczema, and not all children with eczema go on to develop asthma. OBJECTIVE: The aim of this study was to explore the impact of allergic sensitization patterns on the association between early eczema and later childhood asthma. Given the numerous reported associations of the ciliary gene KIF3A with the atopic march, we also examined the impact of KIF3A risk allele rs12186803 on our analyses. METHODS: We studied 505 participants in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), a prospective birth cohort, with longitudinal eczema and asthma outcomes as well as prospective data regarding timing of sensitization to foods and aeroallergens. KIF3A genotypes were available on all children. RESULTS: Two high-risk groups were identified: one with and one without early eczema. The high-risk group with early eczema was more likely to be sensitized to food allergens, while the group without early eczema was more likely to be polysensitized to aeroallergens. The KIF3A rs12186803 risk allele interacted with food sensitization to increase asthma risk in children with eczema (P = 0.02). In children without eczema, asthma was associated with the interaction between rs12186803 and aeroallergen sensitization (P = 0.007). CONCLUSIONS & CLINICAL RELEVANCE: KIF3A interacted differentially with sensitization pattern to increase the risk of asthma in two high-risk groups of children with and without early eczema. Given the reported role of KIF3A in epithelial cell functioning, the results add evidence to the hypothesis that an impaired epithelial barrier is a key aspect in the development of allergic disease.

lifetime exposure to traffic-related air pollution and symptoms of depression and anxiety at age 12 years.

BACKGROUND: While air pollution has been associated with depression and anxiety in adults, its impact on childhood mental health is understudied. OBJECTIVE: We examined lifetime exposure to traffic-related air pollution (TRAP) and symptoms of depression and anxiety at age 12 years in the Cincinnati Childhood Allergy and Air Pollution Study cohort. METHODS: We estimated exposure to elemental carbon attributable to traffic (ECAT), a surrogate of diesel exhaust, at birth, age 12 years, and average exposure throughout childhood, using a validated land use regression model. We assessed depression and anxiety at age 12 years by parent report with the Behavior Assessment System for Children-2, and by child report with the Child Depression Inventory-2 (CDI-2) and the Spence Children's Anxiety Scale (SCAS). Associations between TRAP at birth, age 12 years, and childhood average and mental health outcomes were estimated using linear regression models adjusting for covariates including parent depression, secondhand smoke exposure, race, household income, and others. RESULTS: Exposure to ECAT was not significantly associated with parent-reported depression or anxiety. However, exposure to ECAT at birth was associated with increased child-reported depression and anxiety. Each 0.25 µg/m3 increase in ECAT was associated with a 3.5 point increase (95% CI 1.6-5.5) in CDI-2 scores and 2.3 point increase (95% CI 0.8-3.9) in SCAS total anxiety scores. We observed similar associations between average childhood ECAT exposures but not for concurrent exposures at age 12. CONCLUSIONS: TRAP exposure during early life and across childhood was significantly associated with self-reported depression and anxiety symptoms in children. The negative impact of air pollution on mental health previously reported among adults may also be present during childhood.

A Pediatric Asthma Risk Score to better predict asthma development in young children.

BACKGROUND: Asthma phenotypes are currently not amenable to primary prevention or early intervention because their natural history cannot be reliably predicted. Clinicians remain reliant on poorly predictive asthma outcome tools because of a lack of better alternatives. OBJECTIVE: We sought to develop a quantitative personalized tool to predict asthma development in young children. METHODS: Data from the Cincinnati Childhood Allergy and Air Pollution Study (n = 762) birth cohort were used to identify factors that predicted asthma development. The Pediatric Asthma Risk Score (PARS) was constructed by integrating demographic and clinical data. The sensitivity and specificity of PARS were compared with those of the Asthma Predictive Index (API) and replicated in the Isle of Wight birth cohort. RESULTS: PARS reliably predicted asthma development in the Cincinnati Childhood Allergy and Air Pollution Study (sensitivity = 0.68, specificity = 0.77). Although both the PARS and API predicted asthma in high-risk children, the PARS had improved ability to predict asthma in children with mild-to-moderate asthma risk. In addition to parental asthma, eczema, and wheezing apart from colds, variables that predicted asthma in the PARS included early wheezing (odds ratio [OR], 2.88; 95% CI, 1.52-5.37), sensitization to 2 or more food allergens and/or aeroallergens (OR, 2.44; 95% CI, 1.49-4.05), and African American race (OR, 2.04; 95% CI, 1.19-3.47). The PARS was replicated in the Isle of Wight birth cohort (sensitivity = 0.67, specificity = 0.79), demonstrating that it is a robust, valid, and generalizable asthma predictive tool. CONCLUSIONS: The PARS performed better than the API in children with mild-to-moderate asthma. This is significant because these children are the most common and most difficult to predict and might be the most amenable to prevention strategies.

Residential Greenspace Association with Childhood Behavioral Outcomes.

OBJECTIVE: To assess the relationship between greenspace exposure and childhood internalizing and externalizing behaviors. STUDY DESIGN: We analyzed data from the Cincinnati Childhood Allergy and Air Pollution Study, an ongoing prospective birth cohort. Greenspace exposure was estimated based on children's addresses using normalized difference vegetation index (NDVI) images. Neurobehavioral outcomes were assessed using the Behavioral Assessment System for Children, Second Edition. Regression models adjusted for neighborhood deprivation, maternal education, race, and sex assessed the risk for problematic internalizing and externalizing behaviors at residential greenspace buffers of 200, 400, and 800 m. RESULTS: There were 562 and 313 children in our age 7- and 12-year analyses, respectively. At age 7 years, a 0.1-unit increase in NDVI was associated with decreased conduct scores (ß = -1.10, 95% CI [-2.14, -0.06], 200 m). At age 12 years, a 0.1-unit increase in NDVI was associated with a decrease in anxiety scores (ß = -1.83, 95% CI [-3.44, -0.22], 800 m), decreased depression scores (ß = -1.36, 95% CI [-2.61, -0.12], 200 m), and decreased somatization scores (ß = -1.83, 95% CI [-3.22, -0.44], 200 m). CONCLUSIONS: This study provides evidence that increased exposure to residential greenspace is associated with reduced youth's problematic internal and external behaviors, measured by Behavioral Assessment System for Children, Second Edition, at ages 7 and 12 years. Improved understanding of this mechanism could allow for implementation of neighborhood-level approaches for reducing the risk for childhood behavioral problems.

A 30-year mortality and respiratory morbidity study of refractory ceramic fiber workers.

AIM: Report mortality (n = 1119), cancer incidence (n = 1207) and radiographic (n = 1451) findings from a 30-year investigation of current and former refractory ceramic fiber (RCF) workers. METHODS: Cause of death, health and work histories, radiographs and spirometry were collected. Mortality and cancer incidence were analyzed. Logistic regression analysis investigated the associations of latency and cumulative fiber exposure (CFE) on radiographic changes. RESULTS: The mortality study showed no increase in standardized mortality rates (SMR) for lung cancer, but urinary cancers were significantly elevated in the higher exposed group (SMR = 3.62, 95% CI: 1.33-7.88) and leukemia in the total cohort (SMR = 2.51, 95% CI: 1.08-4.94). One death attributed to mesothelioma was identified (SMR = 2.86, 95% CI: 0.07-15.93) in a worker reporting some asbestos exposure. The overall rate of pleural changes was 6.1%, attaining 21.4% in the highest CFE category for all subjects (adjusted odds ratio (aOR) = 6.9, 95% CI: 3.6-13.4), and 13.0% for those with no reported asbestos exposure (OR= 9.1, 95% CI: 2.5-33.6). Prevalence for recent hires (≥1985) was similar to the background. Interstitial changes were not elevated. Localized pleural thickening was associated with small decreases in spirometry results. CONCLUSION: Increases in leukemia and urinary cancer but not lung cancer mortality were found. One death attributed to mesothelioma was observed in a worker with self-reported asbestos exposure and a work history where occupational asbestos exposure may have occurred, rendering uncertainties in assigning causation. Radiographic analyses indicated RCF exposure alone is associated with increased pleural but not interstitial changes. Reductions in RCF exposure should continue. The mortality study is ongoing.

Exposure assessment models for elemental components of particulate matter in an urban environment: A comparison of regression and random forest approaches.

Exposure assessment for elemental components of particulate matter (PM) using land use modeling is a complex problem due to the high spatial and temporal variations in pollutant concentrations at the local scale. Land use regression (LUR) models may fail to capture complex interactions and non-linear relationships between pollutant concentrations and land use variables. The increasing availability of big spatial data and machine learning methods present an opportunity for improvement in PM exposure assessment models. In this manuscript, our objective was to develop a novel land use random forest (LURF) model and compare its accuracy and precision to a LUR model for elemental components of PM in the urban city of Cincinnati, Ohio. PM smaller than 2.5 µm (PM2.5) and eleven elemental components were measured at 24 sampling stations from the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS). Over 50 different predictors associated with transportation, physical features, community socioeconomic characteristics, greenspace, land cover, and emission point sources were used to construct LUR and LURF models. Cross validation was used to quantify and compare model performance. LURF and LUR models were created for aluminum (Al), copper (Cu), iron (Fe), potassium (K), manganese (Mn), nickel (Ni), lead (Pb), sulfur (S), silicon (Si), vanadium (V), zinc (Zn), and total PM2.5 in the CCAAPS study area. LURF utilized a more diverse and greater number of predictors than LUR and LURF models for Al, K, Mn, Pb, Si, Zn, TRAP, and PM2.5 all showed a decrease in fractional predictive error of at least 5% compared to their LUR models. LURF models for Al, Cu, Fe, K, Mn, Pb, Si, Zn, TRAP, and PM2.5 all had a cross validated fractional predictive error less than 30%. Furthermore, LUR models showed a differential exposure assessment bias and had a higher prediction error variance. Random forest and other machine learning methods may provide more accurate exposure assessment.

Childhood exposure to Libby amphibole asbestos and respiratory health in young adults.

OBJECTIVES: Vermiculite ore containing Libby amphibole asbestos (LAA) was mined in Libby, MT, from the 1920s-1990. Recreational and residential areas in Libby were contaminated with LAA. This objective of this study was to characterize childhood exposure to LAA and investigate its association with respiratory health during young adulthood. METHODS: Young adults who resided in Libby prior to age 18 completed a health and activity questionnaire, pulmonary function testing, chest x-ray and HRCT scan. LAA exposure was estimated based on participant report of engaging in activities with potential LAA exposure. Quantitative LAA estimates for activities were derived from sampling data and literature reports. RESULTS: A total of 312 participants (mean age 25.1 years) were enrolled and reported respiratory symptoms in the past 12 months including pleuritic chest pain (23%), regular cough (17%), shortness of breath (18%), and wheezing or whistling in the chest (18%). Cumulative LAA exposure was significantly associated with shortness of breath (aOR = 1.12, 95% CI 1.01-1.25 per doubling of exposure). Engaging in recreational activities near Rainy Creek Road (near the former mine site) and the number of instances heating vermiculite ore to make it expand or pop were also significantly associated with respiratory symptoms. LAA exposure was not associated with pulmonary function or pleural or interstitial changes on either chest x-ray or HRCT. CONCLUSIONS: Pleural or interstitial changes on x-ray or HRCT were not observed among this cohort of young adults. However, childhood exposure to LAA was significantly associated with respiratory symptoms during young adulthood. Pleuritic chest pain, in particular, has been identified as an early symptom associated with LAA exposure and therefore warrants continued follow-up given findings of progressive disease in other LAA exposed populations.