Preterm birth and prenatal maternal occupation: the role of Hispanic ethnicity and nativity in a population-based sample in Los Angeles, California.

OBJECTIVES: We investigated preterm birth (PTB) in relation to maternal occupational exposure and whether effect measures were modified by Hispanic ethnicity and nativity in a population-based sample with high proportion of Hispanics. METHODS: We used a case-control study (n = 2543) nested within a cohort of 58,316 births in Los Angeles County, California, in 2003. We categorized prenatal occupations using the US Census Occupation Codes and Classification System and developed a job exposure matrix. Odds ratios for PTB were estimated using logistic regression. RESULTS: Odds ratios for PTB were increased for all women in health care practitioner and technical occupations, but the 95% confidence intervals included the null value; effects were more pronounced among Hispanics. We estimated elevated odds ratios for foreign-born Hispanic women in building and grounds cleaning and maintenance occupations. Shift work and physically demanding work affected births among US-born but not foreign-born Hispanics. CONCLUSIONS: Hispanic women are at particular risk for PTB related to adverse prenatal occupational exposure. Nativity may moderate these effects on PTB. Maternal occupational exposures likely contribute to ethnic disparities in PTB.

Prenatal air pollution exposure and ultrasound measures of fetal growth in Los Angeles, California.

BACKGROUND: Few previous studies examined the impact of prenatal air pollution exposures on fetal development based on ultrasound measures during pregnancy. METHODS: In a prospective birth cohort of more than 500 women followed during 1993-1996 in Los Angeles, California, we examined how air pollution impacts fetal growth during pregnancy. Exposure to traffic related air pollution was estimated using CALINE4 air dispersion modeling for nitrogen oxides (NOx) and a land use regression (LUR) model for nitrogen monoxide (NO), nitrogen dioxide (NO2) and NOx. Exposures to carbon monoxide (CO), NO2, ozone (O3) and particles <10µm in aerodynamic diameter (PM10) were estimated using government monitoring data. We employed a linear mixed effects model to estimate changes in fetal size at approximately 19, 29 and 37 weeks gestation based on ultrasound. RESULTS: Exposure to traffic-derived air pollution during 29 to 37 weeks was negatively associated with biparietal diameter at 37 weeks gestation. For each interquartile range (IQR) increase in LUR-based estimates of NO, NO2 and NOx, or freeway CALINE4 NOx we estimated a reduction in biparietal diameter of 0.2-0.3mm. For women residing within 5km of a monitoring station, we estimated biparietal diameter reductions of 0.9-1.0mm per IQR increase in CO and NO2. Effect estimates were robust to adjustment for a number of potential confounders. We did not observe consistent patterns for other growth endpoints we examined. CONCLUSIONS: Prenatal exposure to traffic-derived pollution was negatively associated with fetal head size measured as biparietal diameter in late pregnancy.

Effects of residential indoor air quality and household ventilation on preterm birth and term low birth weight in Los Angeles County, California.

OBJECTIVES: The purpose of our study was to examine the effects of indoor residential air quality on preterm birth and term low birth weight (LBW). METHODS: We evaluated 1761 nonsmoking women from a case-control survey of mothers who delivered a baby in 2003 in Los Angeles County, California. In multinomial logistic regression models adjusted for maternal age, education, race/ethnicity, parity and birthplace, we evaluated the effects of living with smokers or using personal or household products that may contain volatile organic compounds and examined the influence of household ventilation. RESULTS: Compared with unexposed mothers, women exposed to secondhand smoke (SHS) at home had increased odds of term LBW (adjusted odds ratio [OR] = 1.36; 95% confidence interval [CI] = 0.85, 2.18) and preterm birth (adjusted OR = 1.27; 95% CI = 0.95, 1.70), although 95% CIs included the null. No increase in risk was observed for SHS-exposed mothers reporting moderate or high window ventilation. Associations were also observed for product usage, but only for women reporting low or no window ventilation. CONCLUSIONS: Residential window ventilation may mitigate the effects of indoor air pollution among pregnant women in Los Angeles County, California.

Epidemiology of rhabdoid tumors of early childhood.

BACKGROUND: Rhabdoid tumors are a rare and aggressive cancer subtype which is usually diagnosed in early childhood. Little is known about their etiology. The purpose of this study was to describe the epidemiology of rhabdoid tumors and examine their relation to perinatal characteristics. METHODS: We identified 44 atypical teratoid/rhabdoid tumors (AT/RT) of the central nervous system (CNS) and 61 rhabdoid sarcomas (renal and extra-renal non-CNS tumors) from California Cancer Registry records of diagnoses 1988-2007 among children <6 years of age. We randomly selected 208,178 controls from California birthrolls. Multivariable logistic regression was used to examine associations between rhabdoid tumors and perinatal characteristics. RESULTS: After adjustment for demographic characteristics, low birthweight (<2,500 g) strongly increased risk for developing both rhabdoid sarcomas (OR = 2.43, 95% CI 1.09, 5.41) and AT/RT (OR = 2.99, 95% CI 1.31, 6.84). Both preterm delivery (<37 weeks gestation, OR = 2.63, 95% CI 1.34, 5.17) and late term delivery (>42 weeks, OR = 3.66, 95% CI 1.54, 8.71) also increased risk of rhabdoid sarcomas. Rhabdoid sarcoma cases (OR = 3.08, 95% CI 1.11, 8.55) and AT/RT cases (OR = 3.16, 95% CI 1.23, 8.13) also were more likely to be multiple births. CONCLUSION: The excess of twin pregnancies may suggest an association with infertility treatments. This is the first population-based epidemiologic study to examine these rare tumors.

Assessing the influence of traffic-related air pollution on risk of term low birth weight on the basis of land-use-based regression models and measures of air toxics.

Few studies have examined associations of birth outcomes with toxic air pollutants (air toxics) in traffic exhaust. This study included 8,181 term low birth weight (LBW) children and 370,922 term normal-weight children born between January 1, 1995, and December 31, 2006, to women residing within 5 miles (8 km) of an air toxics monitoring station in Los Angeles County, California. Additionally, land-use-based regression (LUR)-modeled estimates of levels of nitric oxide, nitrogen dioxide, and nitrogen oxides were used to assess the influence of small-area variations in traffic pollution. The authors examined associations with term LBW (≥37 weeks' completed gestation and birth weight <2,500 g) using logistic regression adjusted for maternal age, race/ethnicity, education, parity, infant gestational age, and gestational age squared. Odds of term LBW increased 2%-5% (95% confidence intervals ranged from 1.00 to 1.09) per interquartile-range increase in LUR-modeled estimates and monitoring-based air toxics exposure estimates in the entire pregnancy, the third trimester, and the last month of pregnancy. Models stratified by monitoring station (to investigate air toxics associations based solely on temporal variations) resulted in 2%-5% increased odds per interquartile-range increase in third-trimester benzene, toluene, ethyl benzene, and xylene exposures, with some confidence intervals containing the null value. This analysis highlights the importance of both spatial and temporal contributions to air pollution in epidemiologic birth outcome studies.

Perinatal characteristics and retinoblastoma.

PURPOSE: The etiology of retinoblastoma remains poorly understood. In the present study, we examined associations between perinatal factors and retinoblastoma risk in California children. METHODS: We identified 609 retinoblastoma cases (420 unilateral, 187 bilateral, and 2 with laterality unknown) from California Cancer Registry records of diagnoses 1988-2007 among children < 6 years of age. We randomly selected 209,051 controls from California birth rolls. The source of most study data was birth certificates. Multivariable logistic regression was used to examine associations between retinoblastoma and perinatal characteristics. RESULTS: Bilateral retinoblastoma was associated with greater paternal age [for fathers over 35, crude odds ratio (OR) = 1.73, 95 % confidence interval (CI) 1.20, 2.47] and with twin births (OR = 1.93, 95 % CI 0.99, 3.79). Among unilateral cases, we observed an increased risk among children of US-born Hispanic mothers (OR = 1.34, 95 % CI 1.01, 1.77) while a decreased risk was observed for infants born to mothers with less than 9 years of education (OR = 0.70, 95 % CI 0.49, 1.00), a group that consisted primarily of mothers born in Mexico. We observed that maternal infection in pregnancy with any STD (OR = 3.59, 95 % CI 1.58, 8.15) was associated with bilateral retinoblastoma. CONCLUSIONS: This study supports the findings of previous investigations reporting associations between parental age, HPV infection, and retinoblastoma.

Use of generalized additive models and cokriging of spatial residuals to improve land-use regression estimates of nitrogen oxides in Southern California.

Land-use regression (LUR) models have been developed to estimate spatial distributions of traffic-related pollutants. Several studies have examined spatial autocorrelation among residuals in LUR models, but few utilized spatial residual information in model prediction, or examined the impact of modeling methods, monitoring site selection, or traffic data quality on LUR performance. This study aims to improve spatial models for traffic-related pollutants using generalized additive models (GAM) combined with cokriging of spatial residuals. Specifically, we developed spatial models for nitrogen dioxide (NO(2)) and nitrogen oxides (NO(x)) concentrations in Southern California separately for two seasons (summer and winter) based on over 240 sampling locations. Pollutant concentrations were disaggregated into three components: local means, spatial residuals, and normal random residuals. Local means were modeled by GAM. Spatial residuals were cokriged with global residuals at nearby sampling locations that were spatially auto-correlated. We compared this two-stage approach with four commonly-used spatial models: universal kriging, multiple linear LUR and GAM with and without a spatial smoothing term. Leave-one-out cross validation was conducted for model validation and comparison purposes. The results show that our GAM plus cokriging models predicted summer and winter NO(2) and NO(x) concentration surfaces well, with cross validation R(2) values ranging from 0.88 to 0.92. While local covariates accounted for partial variance of the measured NO(2) and NO(x) concentrations, spatial autocorrelation accounted for about 20% of the variance. Our spatial GAM model improved R(2) considerably compared to the other four approaches. Conclusively, our two-stage model captured summer and winter differences in NO(2) and NO(x) spatial distributions in Southern California well. When sampling location selection cannot be optimized for the intended model and fewer covariates are available as predictors for the model, the two-stage model is more robust compared to multiple linear regression models.

Comparing exposure assessment methods for traffic-related air pollution in an adverse pregnancy outcome study.

BACKGROUND: Previous studies reported adverse impacts of traffic-related air pollution exposure on pregnancy outcomes. Yet, little information exists on how effect estimates are impacted by the different exposure assessment methods employed in these studies. OBJECTIVES: To compare effect estimates for traffic-related air pollution exposure and preeclampsia, preterm birth (gestational age less than 37 weeks), and very preterm birth (gestational age less than 30 weeks) based on four commonly used exposure assessment methods. METHODS: We identified 81,186 singleton births during 1997-2006 at four hospitals in Los Angeles and Orange Counties, California. Exposures were assigned to individual subjects based on residential address at delivery using the nearest ambient monitoring station data [carbon monoxide (CO), nitrogen dioxide (NO(2)), nitric oxide (NO), nitrogen oxides (NO(x)), ozone (O(3)), and particulate matter less than 2.5 (PM(2.5)) or less than 10 (PM(10))µm in aerodynamic diameter], both unadjusted and temporally adjusted land-use regression (LUR) model estimates (NO, NO(2), and NO(x)), CALINE4 line-source air dispersion model estimates (NO(x) and PM(2.5)), and a simple traffic-density measure. We employed unconditional logistic regression to analyze preeclampsia in our birth cohort, while for gestational age-matched risk sets with preterm and very preterm birth we employed conditional logistic regression. RESULTS: We observed elevated risks for preeclampsia, preterm birth, and very preterm birth from maternal exposures to traffic air pollutants measured at ambient stations (CO, NO, NO(2), and NO(x)) and modeled through CALINE4 (NO(x) and PM(2.5)) and LUR (NO(2) and NO(x)). Increased risk of preterm birth and very preterm birth were also positively associated with PM(10) and PM(2.5) air pollution measured at ambient stations. For LUR-modeled NO(2) and NO(x) exposures, elevated risks for all the outcomes were observed in Los Angeles only--the region for which the LUR models were initially developed. Unadjusted LUR models often produced odds ratios somewhat larger in size than temporally adjusted models. The size of effect estimates was smaller for exposures based on simpler traffic density measures than the other exposure assessment methods. CONCLUSION: We generally confirmed that traffic-related air pollution was associated with adverse reproductive outcomes regardless of the exposure assessment method employed, yet the size of the estimated effect depended on how both temporal and spatial variations were incorporated into exposure assessment. The LUR model was not transferable even between two contiguous areas within the same large metropolitan area in Southern California.

Traffic-related air toxics and preterm birth: a population-based case-control study in Los Angeles County, California.

BACKGROUND: Numerous studies have associated air pollutant exposures with adverse birth outcomes, but there is still relatively little information to attribute effects to specific emission sources or air toxics. We used three exposure data sources to examine risks of preterm birth in Los Angeles women when exposed to high levels of traffic-related air pollutants--including specific toxics--during pregnancy. METHODS: We identified births during 6/1/04-3/31/06 to women residing within five miles of a Southern California Air Quality Management District (SCAQMD) Multiple Air Toxics Exposure Study (MATES III) monitoring station. We identified preterm cases and, using a risk set approach, matched cases to controls based on gestational age at birth. Pregnancy period exposure averages were estimated for a number of air toxics including polycyclic aromatic hydrocarbons (PAHs), source-specific PM2.5 (fine particulates with aerodynamic diameter less than 2.5 µm) based on a Chemical Mass Balance model, criteria air pollutants based on government monitoring data, and land use regression (LUR) estimates of nitric oxide (NO), nitrogen dioxide (NO2) and nitrogen oxides (NOx). Associations between these metrics and odds of preterm birth were estimated using conditional logistic regression. RESULTS: Odds of preterm birth increased 6-21% per inter-quartile range increase in entire pregnancy exposures to organic carbon (OC), elemental carbon (EC), benzene, and diesel, biomass burning and ammonium nitrate PM2.5, and 30% per inter-quartile increase in PAHs; these pollutants were positively correlated and clustered together in a factor analysis. Associations with LUR exposure metrics were weaker (3-4% per inter-quartile range increase). CONCLUSIONS: These latest analyses provide additional evidence of traffic-related air pollution's impact on preterm birth for women living in Southern California and indicate PAHs as a pollutant of concern that should be a focus of future studies. Other PAH sources besides traffic were also associated with higher odds of preterm birth, as was ammonium nitrate PM2.5, the latter suggesting potential importance of secondary pollutants. Future studies should focus on accurate modeling of both local and regional spatial and temporal distributions, and incorporation of source information.

Paternal support and preterm birth, and the moderation of effects of chronic stress: a study in Los Angeles county mothers.

Maternal psychosocial stress is an important risk factor for preterm birth, but support interventions have largely been unsuccessful. The objective of this study is to assess how support during pregnancy influences preterm birth risk and possibly ameliorates the effects of chronic stress, life event stress, or pregnancy anxiety in pregnant women. We examined 1,027 singleton preterm births and 1,282 full-term normal weight controls from a population-based retrospective case-control study of Los Angeles County, California women giving birth in 2003, a mostly Latina population (both US-born and immigrant). We used logistic regression to assess whether support from the baby's father during pregnancy influences birth outcomes and effects of chronic stress, pregnancy anxiety, and life event stress. Adjusted odds of preterm birth decreased with better support (OR 0.73 [95%CI 0.52, 1.01]). Chronic stress (OR 1.46 [95%CI 1.11, 1.92]), low confidence of a normal birth (OR 1.57 [95% CI 1.17, 2.12]), and fearing for the baby's health (OR 1.67 [95%CI 1.30, 2.14]) increased preterm birth risk, but life events showed no association. Our data also suggested that paternal support may modify the effect of chronic stress on the risk of preterm birth, such that among mothers lacking support, those with moderate-to-high stress were at increased odds of delivering preterm (OR 2.15 [95%CI 0.92, 5.03]), but women with greater support had no increased risk with moderate-to-high chronic stress (OR 1.13 [95%CI 0.94, 1.35]). Paternal support may moderate the effects of chronic stress on the risk of preterm delivery.

Predicting traffic-related air pollution in Los Angeles using a distance decay regression selection strategy.

Land use regression (LUR) has emerged as an effective means of estimating exposure to air pollution in epidemiological studies. We created the first LUR models of nitric oxide (NO), nitrogen dioxide (NO2) and nitrogen oxides (NOX) for the complex megalopolis of Los Angeles (LA), California. Two-hundred and one sampling sites (the largest sampling design to date for LUR estimation) for two seasons were selected using a location-allocation algorithm that maximized the potential variability in measured pollutant concentrations and represented populations in the health study. Traffic volumes, truck routes and road networks, land use data, satellite-derived vegetation greenness and soil brightness, and truck route slope gradients were used for predicting NOX concentrations. A novel model selection strategy known as "ADDRESS" (A Distance Decay REgression Selection Strategy) was used to select optimized buffer distances for potential predictor variables and maximize model performance. Final regression models explained 81%, 86% and 85% of the variance in measured NO, NO2 and NOX concentrations, respectively. Cross-validation analyses suggested a prediction accuracy of 87-91%. Remote sensing-derived variables were significantly correlated with NOX concentrations, suggesting these data are useful surrogates for modeling traffic-related pollution when certain land use data are unavailable. Our study also demonstrated that reactive pollutants such as NO and NO2 could have high spatial extents of influence (e.g., > 5000 m from expressway) and high background concentrations in certain geographic areas. This paper represents the first attempt to model traffic-related air pollutants at a fine scale within such a complex and large urban region.

Methodological issues in studies of air pollution and reproductive health.

In the past decade there have been an increasing number of scientific studies describing possible effects of air pollution on perinatal health. These papers have mostly focused on commonly monitored air pollutants, primarily ozone (O(3)), particulate matter (PM), sulfur dioxide (SO(2)), carbon monoxide (CO), and nitrogen dioxide (NO(2)), and various indices of perinatal health, including fetal growth, pregnancy duration, and infant mortality. While most published studies have found some marker of air pollution related to some types of perinatal outcomes, variability exists in the nature of the pollutants and outcomes associated. Synthesis of the findings has been difficult for various reasons, including differences in study design and analysis. A workshop was held in September 2007 to discuss methodological differences in the published studies as a basis for understanding differences in study findings and to identify priorities for future research, including novel approaches for existing data. Four broad topic areas were considered: confounding and effect modification, spatial and temporal exposure variations, vulnerable windows of exposure, and multiple pollutants. Here we present a synopsis of the methodological issues and challenges in each area and make recommendations for future study. Two key recommendations include: (1) parallel analyses of existing data sets using a standardized methodological approach to disentangle true differences in associations from methodological differences among studies; and (2) identification of animal studies to inform important mechanistic research gaps. This work is of critical public health importance because of widespread exposure and because perinatal outcomes are important markers of future child and adult health.

Outdoor air pollution, family and neighborhood environment, and asthma in LA FANS children.

We examined associations between outdoor air pollution and childhood asthma, using measures of SES, neighborhood quality, and social support from the Los Angeles Family and Neighborhood Survey (LA FANS). We linked residential census tracts for 3114 children to government air monitoring stations and estimated average pollutant concentrations for the year before interview. CO and NO(2) levels increased and O(3) levels decreased as neighborhood quality decreased, yet correlations were low. Pollutant levels were not correlated with neighborhood support. Even after adjustment for social environment characteristics, LA FANS children living in high O(3), PM(10), and CO areas appeared to have worse asthma morbidity.

Environmental public health tracking of childhood asthma using California health interview survey, traffic, and outdoor air pollution data.

BACKGROUND: Despite extensive evidence that air pollution affects childhood asthma, state-level and national-level tracking of asthma outcomes in relation to air pollution is limited. OBJECTIVES: Our goals were to evaluate the feasibility of linking the 2001 California Health Interview Survey (CHIS), air monitoring, and traffic data; estimate associations between traffic density (TD) or outdoor air pollutant concentrations and childhood asthma morbidity; and evaluate the usefulness of such databases, linkages, and analyses to Environmental Public Health Tracking (EPHT). METHODS: We estimated TD within 500 feet of residential cross-streets of respondents and annual average pollutant concentrations based on monitoring station measurements. We used logistic regression to examine associations with reported asthma symptoms and emergency department (ED) visits/hospitalizations. RESULTS: Assignment of TD and air pollution exposures for cross-streets was successful for 82% of children with asthma in Los Angeles and San Diego, California, Counties. Children with asthma living in high ozone areas and areas with high concentrations of particulate matter < 10 microm in aerodynamic diameter experienced symptoms more frequently, and those living close to heavy traffic reported more ED visits/hospitalizations. The advantages of the CHIS for asthma EPHT include a large and representative sample, biennial data collection, and ascertainment of important socio-demographic and residential address information. Disadvantages are its cross-sectional design, reliance on parental reports of diagnoses and symptoms, and lack of information on some potential confounders. CONCLUSIONS: Despite limitations, the CHIS provides a useful framework for examining air pollution and childhood asthma morbidity in support of EPHT, especially because later surveys address some noted gaps. We plan to employ CHIS 2003 and 2005 data and novel exposure assessment methods to re-examine the questions raised here.

Meeting report: atmospheric pollution and human reproduction.

BACKGROUND: There is a growing body of epidemiologic literature reporting associations between atmospheric pollutants and reproductive outcomes, particularly birth weight and gestational duration. OBJECTIVES: The objectives of our international workshop were to discuss the current evidence, to identify the strengths and weaknesses of published epidemiologic studies, and to suggest future directions for research. DISCUSSION: Participants identified promising exposure assessment tools, including exposure models with fine spatial and temporal resolution that take into account time-activity patterns. More knowledge on factors correlated with exposure to air pollution, such as other environmental pollutants with similar temporal variations, and assessment of nutritional factors possibly influencing birth outcomes would help evaluate importance of residual confounding. Participants proposed a list of points to report in future publications on this topic to facilitate research syntheses. Nested case-control studies analyzed using two-phase statistical techniques and development of cohorts with extensive information on pregnancy behaviors and biological samples are promising study designs. Issues related to the identification of critical exposure windows and potential biological mechanisms through which air pollutants may lead to intrauterine growth restriction and premature birth were reviewed. CONCLUSIONS: To make progress, this research field needs input from toxicology, exposure assessment, and clinical research, especially to aid in the identification and exposure assessment of feto-toxic agents in ambient air, in the development of early markers of adverse reproductive outcomes, and of relevant biological pathways. In particular, additional research using animal models would help better delineate the biological mechanisms underpinning the associations reported in human studies.

Local variations in CO and particulate air pollution and adverse birth outcomes in Los Angeles County, California, USA.

We extended our previous analyses of term low birth weight (LBW) and preterm birth to 1994-2000, a period of declining air pollution levels in the South Coast Air Basin. We speculated that the effects we observed previously for carbon monoxide, particulate matter < 10 microm in aerodynamic diameter (PM10), and traffic density were attributable to toxins sorbed to primary exhaust particles. Focusing on CO, PM10, and particulate matter < 2.5 microm in aerodynamic diameter (PM2.5), we examined whether varying residential distances from monitoring stations affected risk estimates, because effect attenuation may result from local pollutant heterogeneity inadequately captured by ambient stations. We geocoded home locations, calculated the distance to the nearest air monitors, estimated exposure levels by pregnancy period, and performed logistic regression analyses for subjects living within 1-4 mi of a station. For women residing within a 1-mi distance, we observed a 27% increase in risk for high (> or = 75th percentile) first-trimester CO exposures and preterm birth and a 36% increase for high third-trimester pregnancy CO exposures and term LBW. For particles, we observed similar size effects during early and late pregnancy for both term LBW and preterm birth. In contrast, smaller or no effects were observed beyond a 1-mi distance of a residence from a station. Associations between CO and PM10 averaged over the whole pregnancy and term LBW were generally smaller than effects for early and late pregnancy. These new results for 1994-2000 generally confirm our previous observations for the period 1989-1993, again linking CO and particle exposures to term LBW and preterm birth. In addition, they confirm our suspicions about having to address local heterogeneity for these pollutants in Los Angeles.

Residential proximity to traffic and adverse birth outcomes in Los Angeles county, California, 1994-1996.

We reported previously that increases in ambient air pollution in the Los Angeles basin increased the risk of low weight and premature birth. However, ambient concentrations measured at monitoring stations may not take into account differential exposure to pollutants found in elevated concentrations near heavy-traffic roadways. Therefore, we used an epidemiologic case-control study design to examine whether residential proximity to heavy-traffic roadways influenced the occurrence of low birth weight (LBW) and/or preterm birth in Los Angeles County between 1994 and 1996. We mapped subject home locations at birth and estimated exposure to traffic-related air pollution using a distance-weighted traffic density (DWTD) measure. This measure takes into account residential proximity to and level of traffic on roadways surrounding homes. We calculated odds ratios (ORs) and risk ratios (RRs) for being LBW and/or preterm per quintile of DWTD. The clearest exposure-response pattern was observed for preterm birth, with an RR of 1.08 [95% confidence interval (CI), 1.01-1.15] for infants in the highest DWTD quintile. Although higher risks were observed for LBW infants, exposure-response relations were less consistent. Examining the influence of season, we found elevated risks primarily for women whose third trimester fell during fall/winter months (OR(term LBW) = 1.39; 95% CI, 1.16-1.67; OR(preterm and LBW) = 1.24; 95% CI = 1.03-1.48; RR(all preterm) = 1.15; 95% CI, 1.05-1.26), and exposure-response relations were stronger for all outcomes. This result is consistent with elevated pollution in proximity to sources during more stagnant air conditions present in winter months. Our previous research and these latest results suggest exposure to traffic-related pollutants may be important.

Prenatal exposure to air toxics and risk of Wilms' tumor in 0- to 5-year-old children.

OBJECTIVE: To study prenatal air toxic exposure and Wilms' tumor in children. METHODS: We identified 337 Wilms' tumor cases among children younger than 6 years (1988 to 2008) from the California Cancer Registry, randomly selected 96,514 controls from California birth rolls in 20:1 ratio matched to all cancer cases, then linked birth addresses to air monitors within 15 miles to assess exposures. Multiple logistic regressions were applied to estimate effects. RESULTS: Children prenatally exposed to formaldehyde, polycyclic aromatic hydrocarbons, perchloroethylene, or acetaldehyde in the third trimester had an increased odds of Wilms' tumor per interquartile increase in concentration (odds ratio [95% confidence interval]: 1.28 [1.12 to 1.45], 1.10 [0.99 to 1.22], 1.09 [1.00 to 1.18], 1.25 [1.07 to 1.45], respectively). CONCLUSIONS: We found positive associations for four air toxics. This is the first study of this kind. Future studies are needed to confirm our findings.

Maternal occupation and term low birth weight in a predominantly latina population in los angeles, california.

OBJECTIVES: Focusing on Latinas, we investigated whether maternal occupations during pregnancy increase term low birth weight (TLBW) (less than 2500 g; 37 weeks or more). METHODS: In a case-control study (n = 1498) nested within a 2003 birth cohort (n = 58,316) in Los Angeles County, California (65% Latina), we assessed the influence of maternal occupation on TLBW, using Occupational Codes based on the 2000 US Census Occupational Classification System. RESULTS: Odds ratios (ORs) for TLBW were increased among women working during pregnancy in "transportation and material moving operations" (adjusted OR = 3.28; 95% confidence interval = 1.00 to 10.73), "food preparation and serving occupations" (adjusted OR = 3.03, 95% confidence interval = 1.21 to 7.62), or "production occupations" (adjusted OR = 2.63, 95% confidence interval = 1.01 to 6.82) compared with "office occupations;" 73% to 93% of women working in these higher-risk jobs were immigrant Latinas. CONCLUSIONS: Working conditions in various jobs held mainly by first-generation immigrant Latinas increase risks for TLBW and need to be addressed to develop strategies to reduce TLBW.

Ambient air pollution and autism in Los Angeles county, California.

BACKGROUND: The prevalence of autistic disorder (AD), a serious developmental condition, has risen dramatically over the past two decades, but high-quality population-based research addressing etiology is limited. OBJECTIVES: We studied the influence of exposures to traffic-related air pollution during pregnancy on the development of autism using data from air monitoring stations and a land use regression (LUR) model to estimate exposures. METHODS: Children of mothers who gave birth in Los Angeles, California, who were diagnosed with a primary AD diagnosis at 3-5 years of age during 1998-2009 were identified through the California Department of Developmental Services and linked to 1995-2006 California birth certificates. For 7,603 children with autism and 10 controls per case matched by sex, birth year, and minimum gestational age, birth addresses were mapped and linked to the nearest air monitoring station and a LUR model. We used conditional logistic regression, adjusting for maternal and perinatal characteristics including indicators of SES. RESULTS: Per interquartile range (IQR) increase, we estimated a 12-15% relative increase in odds of autism for ozone [odds ratio (OR) = 1.12, 95% CI: 1.06, 1.19; per 11.54-ppb increase] and particulate matter ≤ 2.5 µm (OR = 1.15; 95% CI: 1.06, 1.24; per 4.68-µg/m3 increase) when mutually adjusting for both pollutants. Furthermore, we estimated 3-9% relative increases in odds per IQR increase for LUR-based nitric oxide and nitrogen dioxide exposure estimates. LUR-based associations were strongest for children of mothers with less than a high school education. CONCLUSION: Measured and estimated exposures from ambient pollutant monitors and LUR model suggest associations between autism and prenatal air pollution exposure, mostly related to traffic sources.