Cornel Lencar

Bio: Cornel Lencar is an academic researcher from University of British Columbia. The author has contributed to research in topics: Population & Cohort study. The author has an hindex of 7, co-authored 14 publications receiving 1311 citations.

A Cohort Study of Traffic-Related Air Pollution Impacts on Birth Outcomes

Abstract: Numerous studies have indicated associations between exposure to ambient air pollution and adverse pregnancy outcomes. Such associations, if determined to be causal, are likely to result in significant public health impacts given the widespread exposure to air pollution and the fact that low birth weight (LBW) or preterm births are subsequently associated with long-term sequelae such as developmental disability and chronic lung disease (Cano et al. 2001; Dik et al. 2004). Determination of a causal relationship between air pollution and adverse pregnancy outcomes would have implications for burden of disease measures and add to the importance of strategies to mitigate the health effects of air pollution exposure. Previous studies have been reviewed in detail. Sram et al. (2005) concluded that evidence is sufficient to support a causal association between ambient concentrations of particulate matter and LBW, but evidence of effects for other pollutants and for other outcomes such as preterm birth is less robust. Maisonet et al. (2004) concluded that studies to date support small effects of air pollution on preterm birth and small for gestational age birth (SGA), but not full-term LBW. In a systematic review, Glinianaia et al. (2004) suggested that evidence of associations with air pollution and fetal growth or pregnancy duration is limited and inconclusive and argued for population-based cohort designs using high-quality individual exposure estimates. These reviews highlight the difficulties in interpreting an evidence base with differences among methods and with important limitations. First, most studies are either time-series studies (Dugandzic et al. 2006; Liu et al. 2003, 2007; Mannes et al. 2005; Sagiv et al. 2005) that relate relatively short-term changes in air pollution concentrations to temporal changes in rates of adverse pregnancy outcomes or, less frequently, cohort analyses that compare outcomes between locations with differing levels of ambient air pollution (Salam et al. 2005) based on interpolated ambient monitoring network data. Between-city comparisons are subject to potential confounding because covariates may be highly correlated with air pollution, whereas time-series studies are problematic to interpret because they relate short-term changes in air pollution that are driven primarily by meteorology to outcomes. They inherently assume that the impact of air pollution on birth outcomes is acute, require knowledge of the relevant periods of pregnancy during which air pollution may have impacts, and are subject to potential confounding by seasonally varying factors. As reviewed by Glinianaia et al. (2004), a number of studies have suggested stronger relationships between birth outcomes and exposure during specific periods of pregnancy based on comparison of statistical effect sizes. However, results across studies have not consistently identified specific periods of exposure that are most closely linked to adverse pregnancy outcomes. Increasingly, air pollution researchers have identified important spatial variability in air pollution concentrations within airsheds (Hoek et al. 2002b; Lewne et al. 2004; Zhang et al. 2004; Zhu et al. 2004). In many situations these contrasts are of greater magnitude than between-city or temporal contrasts (Jerrett et al. 2005). Such spatial contrasts, primarily related to measures of proximity to traffic corridors, have been associated with a number of health impacts including mortality (Hoek et al. 2002a; Maynard et al. 2007; Miller et al. 2007; Nafstad et al. 2004; Roemer and van Wijnen 2001), asthma and respiratory symptoms (Bayer-Oglesby et al. 2006; Brauer et al. 2002, 2007; Gauderman et al. 2005, 2007; McConnell et al. 2006; Ryan et al. 2005; Smargiassi et al. 2006), and otitis media (Brauer et al. 2006). Application of within-airshed spatial contrasts in birth outcome studies are few (Leem et al. 2006; Parker et al. 2005; Ritz and Yu 1999; Ritz et al. 2000; Slama et al. 2007; Wilhelm and Ritz 2003, 2005). These studies, though provocative, have been limited largely to Southern California—a metropolitan area with relatively high levels of ambient air pollution. They relied on interpolated ambient monitoring data or simple road proximity measures rather than high-resolution spatial contrasts in concentrations. We sought to assess the relationship between reproductive outcomes and spatial and temporally varying levels of air pollution in the metropolitan area of Vancouver, British Columbia, Canada, a city with relatively low levels of ambient air pollution. We estimated exposures at the individual level, for a population-based cohort using both monitor-based methods and land use regression models based on proximity to traffic sources, land use, population density, and topographic features. Even in Vancouver, an area with a dense ambient monitoring network, exposure assessment based on regulatory monitoring network data is more suited to characterizing temporal variability. Land use regression models, even those with temporal components, as in this analysis, focus on high-resolution spatial variability in air pollutant concentrations. The literature describing associations between air pollution and birth outcomes has focused on clinically defined outcomes of LBW and preterm birth, defined in a variety of ways, which complicates comparisons. The underlying biological processes—fetal growth restriction and inadequate gestational length—are incompletely understood and imperfectly represented in routinely available perinatal measurements available in vital statistic records. We elected to focus on SGA births as a primary outcome measure, because birth weight as a function of gestational age has a direct effect on perinatal morbidity and mortality (Pollack and Divon 1992). LBW may result from complex and multiple pathways of fetal growth restriction attributed to maternal, fetal, or placental factors. Three broad categories of biological factors have been suggested to play a role in inadequate fetal gestation: abnormality of the biological clock, abnormal implantation, and infection and inflammation (Mattison et al. 2003). The current theories provide multiple sites at which environmental factors may influence biological factors to modulate fetal growth and induce preterm birth. However, specific toxicologic mechanisms including relevant timing during gestational development are not known. We explored each of these processes, fetal growth restriction and inadequate gestational length, separately, and explored the influences of exposure timing in early and late pregnancy.

Effect of Early Life Exposure to Air Pollution on Development of Childhood Asthma

Abstract: BackgroundThere is increasing recognition of the importance of early environmental exposures in the development of childhood asthma. Outdoor air pollution is a recognized asthma trigger, but it is ...

Descriptive epidemiological features of bronchiolitis in a population-based cohort.

Abstract: OBJECTIVE. The goal was to investigate the epidemiological features of incident bronchiolitis by using a population-based infant cohort. METHODS. Outpatient and inpatient health records were used to identify incident bronchiolitis cases among 93 058 singleton infants born in the Georgia Air Basin between 1999 and 2002. Additional health-related databases were linked to provide data on sociodemographic variables, maternal characteristics, and birth outcome measures. RESULTS. From 1999 to 2002, bronchiolitis accounted for 12 474 incident health care encounters (inpatient or outpatient contacts) during the first year of life (134.2 cases per 1000 person-years). A total of 1588 hospitalized bronchiolitis cases were identified (17.1 cases per 1000 person-years). Adjusted Cox proportional-hazard analyses for both case definitions indicated an increased risk of incident bronchiolitis in the first year of life (follow-up period: 2–12 months) for boys, infants of First Nations status, infants with older siblings, and infants living in neighborhoods with smaller proportions of maternal postsecondary education. The risk also was elevated for infants born to young mothers ( CONCLUSIONS. This population-based study of the epidemiological features of bronchiolitis provides evidence for intervening with high-risk infants and their families. Clinical and public health interventions are recommended for the modifiable risk factors of maternal breastfeeding and smoking and for modification of vulnerable environments where possible (eg, limiting exposure to other young children), during high-risk periods such as the first few months of life or the winter season.

Influence of Ambient Air Pollutant Sources on Clinical Encounters for Infant Bronchiolitis

Abstract: Rationale: Data regarding the influence of ambient air pollution on infant bronchiolitis are few.Objectives: We evaluated the impact of several air pollutants and their sources on infant bronchiolitis.Methods: Infants in the Georgia Air Basin of British Columbia with an inpatient or outpatient clinical encounter for bronchiolitis (n = 11,675) were matched on day of birth to as many as 10 control subjects. Exposure to particulate matter with a diameter of 2.5 μm or less (PM2.5), PM10, NO2/NO, SO2, CO, and O3 were assessed on the basis of a regional monitoring network. Traffic exposure was assessed using regionally developed land use regression (LUR) models of NO2, NO, PM2.5, and black carbon as well as proximity to highways. Exposure to wood smoke and industrial emissions was also evaluated. Risk estimates were derived using conditional logistic regression and adjusted for infant sex and First Nations (Canadian government term for recognized aboriginal groups) status and for maternal education, age, income...

Review of evidence on health aspects of air pollution – REVIHAAP Project. Technical Report. World Health Organization Regional Office for Europe 2013

Abstract: This document presents answers to 24 questions relevant to reviewing European policies on air pollution and to addressing health aspects of these policies. The answers were developed by a large group of scientists engaged in the WHO project “Review of evidence on health aspects of air pollution – REVIHAAP”. The experts reviewed and discussed the newly accumulated scientific evidence on the adverse effects on health of air pollution, formulating science-based answers to the 24 questions. Extensive rationales for the answers, including the list of key references, are provided. The review concludes that a considerable amount of new scientific information on the adverse effects on health of particulate matter, ozone and nitrogen dioxide, observed at levels commonly present in Europe, has been published in recent years. This new evidence supports the scientific conclusions of the WHO air quality guidelines, last updated in 2005, and indicates that the effects in some cases occur at air pollution concentrations lower than those serving to establish these guidelines. It also provides scientific arguments for taking decisive actions to improve air quality and reduce the burden of disease associated with air pollution in Europe. This publication arises from the project REVIHAAP and has been co-funded by the European Union.

Critical Review of Health Impacts of Wildfire Smoke Exposure

Abstract: Background:Wildfire activity is predicted to increase in many parts of the world due to changes in temperature and precipitation patterns from global climate change. Wildfire smoke contains numerou...

Health effects of particulate air pollution: A review of epidemiological evidence.

Abstract: ACS,American Cancer Society;AD,Alzheimer’s disease;AMI,acute myocardial infarction;APHEA,air pollution and health effects—a European approach;APHENA,air pollution and health: a European and North A...