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1.  Impact of neighborhoods and body size on survival after breast cancer diagnosis 
Health & place  2015;36:162-172.
With data from the Neighborhoods and Breast Cancer Study, we examined the associations between body size, social and built environments, and survival following breast cancer diagnosis among 4347 women in the San Francisco Bay Area. Lower neighborhood socioeconomic status and greater neighborhood crowding were associated with higher waist-to-hip ratio (WHR). After mutual adjustment, WHR, but not neighborhood characteristics, was positively associated with overall mortality and marginally with breast cancer-specific mortality. Our findings suggest that WHR is an important modifiable prognostic factor for breast cancer survivors. Future WHR interventions should account for neighborhood characteristics that may influence WHR.
PMCID: PMC4684167  PMID: 26606455
Body size; Waist-to-hip ratio; Breast cancer survival; Neighborhood
2.  Association between Serum Polybrominated Diphenylether Levels and Residential Proximity to Solid Waste Facilities 
Environmental science & technology  2016;50(7):3945-3953.
As consumer products treated with polybrominated diphenyl ethers (PBDEs) reach the end of their life cycle, they often are discarded into solid waste facilities, offering a potential reservoir for exposure. The likelihood of exposures to PBDEs by residents living near those sites rarely has been explored. This study collected blood samples from 923 female participants in the California Teachers Study in 2011–2013 and examined the association between participants’ residential proximity to solid waste facilities with potential release of PBDEs and serum levels of three congeners (BDE-47, BDE-100 and BDE-153). General linear regression analysis was used to examine the association, adjusting for age, race, body mass index, neighborhood socioeconomic status and urban residency. Compared to participants living >10 km from any selected site, those living within 2 km had 45% higher BDE-47 (95% CI: 5–100%) and BDE-100 (95% CI: 0–109%) levels, and those living between 2–10 km had 35% higher BDE-47 (95% CI: 0–82%) and 29% higher BDE-100 (95% CI: −9 to 82%) levels. No associations were found for BDE-153. Living close to some solid waste sites may be related to higher serum BDE-47 and BDE-100 levels. Studies with comprehensive exposure assessments are needed to confirm these initial observations.
Graphical Abstract
PMCID: PMC5102683  PMID: 26906616
3.  Residential Exposure to Estrogen Disrupting Hazardous Air Pollutants and Breast Cancer Risk: the California Teachers Study 
Epidemiology (Cambridge, Mass.)  2015;26(3):365-373.
Some studies show increased breast cancer risk from exposure to xenoestrogens, but few have explored exposures via ambient air, which could impact large populations.
This study explored the association between breast cancer risk and residential exposures to ambient estrogen disruptors among participants in a large cohort study, the California Teachers Study.
Participants consisted of 112,379 women free of breast cancer and living at a California address in 1995/1996. Eleven hazardous air pollutants (HAPs) from the U.S. EPA 2002 list were identified as estrogen disruptors based on published endocrine disrupting chemical lists and literature review. Census-tract estrogen disruptor concentrations modeled by the U.S. EPA in 2002 were assigned to participants’ baseline addresses. Cox proportional hazards models were used to estimate hazard ratios associated with exposure to each estrogen disruptor and a summary measure of nine estrogenic HAPs among all participants and selected subgroups, adjusting for age, race/birthplace, socioeconomic status, and known breast cancer risk factors.
5,361 invasive breast cancer cases were identified between 1995 and 2010. No associations were found between residential exposure to ambient estrogen disruptors and overall breast cancer risk or hormone-responsive-positive breast cancer risk, nor among targeted subgroups of participants (pre/peri-menopausal women, post-menopausal women, never smokers, non-movers, and never-smoking non-movers). However, elevated risks for hormone-responsive-negative tumors were observed for higher exposure to cadmium compounds and possibly inorganic arsenic among never-smoking non-movers.
Long-term low-dose exposure to ambient cadmium compounds or possibly inorganic arsenic may be a risk factor for breast cancer.
PMCID: PMC5101045  PMID: 25760782
4.  Neighborhood influences on recreational physical activity and survival after breast cancer 
Cancer causes & control : CCC  2014;25(10):1295-1308.
Higher levels of physical activity have been associated with improved survival after breast cancer diagnosis. However, no previous studies have considered the influence of the social and built environment on physical activity and survival among breast cancer patients.
Our study included 4,345 women diagnosed with breast cancer (1995–2008) from two population-based studies conducted in the San Francisco Bay Area. We examined questionnaire-based moderate/strenuous recreational physical activity during the 3 years before diagnosis. Neighborhood characteristics were based on data from the 2000 US Census, business listings, parks, farmers’ markets, and Department of Transportation. Survival was evaluated using multivariable Cox proportional hazards models, with follow-up through 2009.
Women residing in neighborhoods with no fast-food restaurants (vs. fewer fast-food restaurants) to other restaurants, high traffic density, and a high percentage of foreign-born residents were less likely to meet physical activity recommendations set by the American Cancer Society. Women who were not recreationally physically active had a 22 % higher risk of death from any cause than women that were the most active. Poorer overall survival was associated with lower neighborhood socioeconomic status (SES) (p trend = 0.02), whereas better breast cancer-specific survival was associated with a lack of parks, especially among women in high-SES neighborhoods.
Certain aspects of the neighborhood have independent associations with recreational physical activity among breast cancer patients and their survival. Considering neighborhood factors may aide in the design of more effective, tailored physical activity programs for breast cancer survivors.
PMCID: PMC4194215  PMID: 25088804
Breast cancer; Built environment; Neighborhood; Physical activity; Socioeconomic status
5.  Light at Night and Breast Cancer Risk Among California Teachers 
Epidemiology (Cambridge, Mass.)  2014;25(5):697-706.
There is convincing evidence that circadian disruption mediated by exposure to light at night promotes mammary carcinogenesis in rodents. The role that light at night plays in human breast cancer etiology remains unknown. We evaluated the relationship between estimates of indoor and outdoor light at night and the risk of breast cancer among members of the California Teachers Study.
Indoor light-at-night estimates were based on questionnaire data regarding sleep habits and use of night time lighting while sleeping. Estimates of outdoor light at night were derived from imagery data obtained from the U.S. Defense Meteorological Satellite Program assigned to geocoded addresses of study participants. Analyses were conducted among 106,731 California Teachers Study members who lived in California, had no prior history of breast cancer, and provided information on lighting while sleeping. 5,095 cases of invasive breast cancer diagnosed 1995–2010 were identified via linkage to the California Cancer Registry. We used age-stratified Cox proportional hazard models to calculate hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for breast cancer risk factors and neighborhood urbanization and socioeconomic class.
An increased risk was found for women living in areas with the highest quintile of outdoor light at night exposure estimates (HR=1.12 [95% CI=1.00 – 1.26], test for trend, P=0.06). While more pronounced among premenopausal women (HR=1.34 [95% CI=1.07 – 1.69], test for trend, P=0.04), the associations did not differ statistically by menopausal status (test for interaction, P=0.34).
Women living in areas with high levels of ambient light at night may be at an increased risk of breast cancer. Future studies that integrate quantitative measurements of indoor and outdoor light at night are warranted.
PMCID: PMC4130422  PMID: 25061924
6.  Associations of Mortality with Long-Term Exposures to Fine and Ultrafine Particles, Species and Sources: Results from the California Teachers Study Cohort 
Environmental Health Perspectives  2015;123(6):549-556.
Although several cohort studies report associations between chronic exposure to fine particles (PM2.5) and mortality, few have studied the effects of chronic exposure to ultrafine (UF) particles. In addition, few studies have estimated the effects of the constituents of either PM2.5 or UF particles.
We used a statewide cohort of > 100,000 women from the California Teachers Study who were followed from 2001 through 2007. Exposure data at the residential level were provided by a chemical transport model that computed pollutant concentrations from > 900 sources in California. Besides particle mass, monthly concentrations of 11 species and 8 sources or primary particles were generated at 4-km grids. We used a Cox proportional hazards model to estimate the association between the pollutants and all-cause, cardiovascular, ischemic heart disease (IHD), and respiratory mortality.
We observed statistically significant (p < 0.05) associations of IHD with PM2.5 mass, nitrate, elemental carbon (EC), copper (Cu), and secondary organics and the sources gas- and diesel-fueled vehicles, meat cooking, and high-sulfur fuel combustion. The hazard ratio estimate of 1.19 (95% CI: 1.08, 1.31) for IHD in association with a 10-μg/m3 increase in PM2.5 is consistent with findings from the American Cancer Society cohort. We also observed significant positive associations between IHD and several UF components including EC, Cu, metals, and mobile sources.
Using an emissions-based model with a 4-km spatial scale, we observed significant positive associations between IHD mortality and both fine and ultrafine particle species and sources. Our results suggest that the exposure model effectively measured local exposures and facilitated the examination of the relative toxicity of particle species.
Ostro B, Hu J, Goldberg D, Reynolds P, Hertz A, Bernstein L, Kleeman MJ. 2015. Associations of mortality with long-term exposures to fine and ultrafine particles, species and sources: results from the California Teachers Study cohort. Environ Health Perspect 123:549–556;
PMCID: PMC4455590  PMID: 25633926
7.  Impact of neighborhood and individual socioeconomic status on survival after breast cancer varies by race/ethnicity: The Neighborhood and Breast Cancer Study 
Research is limited on the independent and joint effects of individual- and neighborhood-level socioeconomic status (SES) on breast cancer survival across different racial/ethnic groups.
We studied individual-level SES, measured by self-reported education, and a composite neighborhood SES (nSES) measure in females (1,068 non-Hispanic whites, 1,670 Hispanics, 993 African-Americans, and 674 Asian-Americans), aged 18–79 years and diagnosed 1995–2008, in the San Francisco Bay Area. We evaluated all-cause and breast cancer-specific survival using stage-stratified Cox proportional hazards models with cluster adjustment for census block groups.
In models adjusting for education and nSES, lower nSES was associated with worse all-cause survival among African-Americans (p-trend=0.03), Hispanics (p-trend=0.01) and Asian-Americans (p-trend=0.01). Education was not associated with all-cause survival. For breast cancer-specific survival, lower nSES was associated with poorer survival only among Asian-Americans (p-trend=0.01). When nSES and education were jointly considered, women with low education and low nSES had 1.4 to 2.7-times worse all-cause survival than women with high education and high nSES across all races/ethnicities. Among African-Americans and Asian-Americans, women with high education and low nSES had 1.6 to 1.9-times worse survival, respectively. For breast cancer-specific survival, joint associations were found only among Asian-Americans with worse survival for those with low nSES regardless of education.
Both neighborhood and individual SES are associated with survival after breast cancer diagnosis, but these relationships vary by race/ethnicity.
A better understanding of the relative contributions and interactions of SES with other factors will inform targeted interventions towards reducing long-standing disparities in breast cancer survival.
PMCID: PMC4018239  PMID: 24618999
breast cancer survival; neighborhood socioeconomic status; education; race/ethnicity
8.  Hazardous air pollutants and breast cancer risk in California teachers: a cohort study 
Environmental Health  2015;14:14.
Studies suggest that higher breast cancer rates in urban areas persist after accounting for the prevalence of known risk factors, leading to speculation that urban environmental exposures, such as air pollution, may play a role in the etiology of breast cancer. Combining modeled ambient air concentrations with data from a large prospective cohort of California women with over 15 years of follow-up, we examined the relationship between breast cancer incidence and modeled concentrations of air pollutants shown to be mammary gland carcinogens (MGCs).
The study population of 112,378 California Teachers Study participants included 5,676 women diagnosed with invasive breast cancer. Modeled annual average ambient air concentrations of 24 MGCs from the U.S. Environmental Protection Agency were linked to participants’ addresses. Cox proportional hazards models were used to estimate hazard rate ratios and 95% confidence intervals associated with residential MGC levels. MGCs were examined individually and as a combined summary variable for all participants, in selected subsets, and by tumor hormone responsiveness.
Initial models yielded some evidence for increased risk for several compounds, including acrylamide, carbon tetrachloride, chloroprene, 4,4'-methylene bis(2-chloroaniline), propylene oxide, and vinyl chloride, but after adjustment for multiple comparisons, only results for propylene oxide and vinyl chloride remained statistically significant. In subset analyses, estrogen-receptor positive or progesterone-receptor positive (ER+/PR+) tumors were associated with higher ambient levels of acrylamide, benzidine, carbon tetrachloride, ethylidene dichloride, and vinyl chloride, while ER-/PR- tumors were associated with higher ambient levels of benzene. Interesting results for different compounds were observed within certain subsets of the population.
While our initial models yielded several elevated risk estimates, after adjusting for multiple comparisons and breast cancer risk factors, most hazard ratios were no longer statistically significant. Our subset analyses, however, suggest that elevated risk may be associated with some compounds for certain subgroups of interest. A summary variable for all 24 MGCs did not offer any advantage over the models for individual compounds. Results must be interpreted cautiously, as estimated exposure was limited to modeled annual average ambient air concentrations, and could not account for other sources or routes other than inhalation.
Electronic supplementary material
The online version of this article (doi:10.1186/1476-069X-14-14) contains supplementary material, which is available to authorized users.
PMCID: PMC4417287  PMID: 25636809
Breast cancer; Hazardous air pollutant; Air pollution; National-scale Air Toxics Assessment; Estrogen receptor; Progesterone receptor; Ethylidene dichloride; Vinyl chloride; Benzene; Carbon tetrachloride
9.  A cross-sectional analysis of light at night, neighborhood sociodemographics and urinary 6-sulfatoxymelatonin concentrations: implications for the conduct of health studies 
There is accumulating evidence that circadian disruption, mediated by alterations in melatonin levels, may play an etiologic role in a wide variety of diseases. The degree to which light-at-night (LAN) and other factors can alter melatonin levels is not well-documented. Our primary objective was to evaluate the degree to which estimates of outdoor environmental LAN predict 6-sulftoxymelatonin (aMT6s), the primary urinary metabolite of melatonin. We also evaluated other potential behavioral, sociodemographic, and anthropomorphic predictors of aMT6s.
Study participants consisted of 303 members of the California Teachers Study who provided a 24-hour urine specimen and completed a self-administered questionnaire in 2000. Urinary aMT6s was measured using the Bühlmann ELISA. Outdoor LAN levels were estimated from satellite imagery data obtained from the U.S. Defense Meteorological Satellite Program’s (DMSP) Operational Linescan System and assigned to study participants’ geocoded residential address. Information on other potential predictors of aMT6s was derived from self-administered surveys. Neighborhood socioeconomic status (SES) was based on U.S. Census block group data.
Lower aMT6s levels were significantly associated with older age, shorter nights, and residential locations in lower SES neighborhoods. Outdoor sources of LAN estimated using low-dynamic range DMSP data had insufficient variability across urban neighborhoods to evaluate. While high-dynamic range DMSP offered much better variability, it was not significantly associated with urinary aMT6s.
Future health studies should utilize the high-dynamic range DMSP data and should consider other potential sources of circadian disruption associated with living in lower SES neighborhoods.
PMCID: PMC3766028  PMID: 24127816
Circadian disruption; Light at night; Melatonin; aMT6s; Socioeconomic status; Women
10.  Determinants and Within-Person Variability of Urinary Cadmium Concentrations among Women in Northern California 
Environmental Health Perspectives  2013;121(6):643-649.
Background: Cadmium (Cd) is a toxic metal associated with increased morbidity and mortality. Urinary Cd (U-Cd) concentration is considered a biomarker of long-term exposure.
Objectives: Our objectives were to evaluate the within-person correlation among repeat samples and to identify predictors of U-Cd concentrations.
Methods: U-Cd concentrations (micrograms per liter) were measured in 24-hr urine samples collected from 296 women enrolled in the California Teachers Study in 2000 and a second 24-hr sample collected 3–9 months later from 141 of the participants. Lifestyle and sociodemographic characteristics were obtained via questionnaires. The Total Diet Study database was used to quantify dietary cadmium intake based on a food frequency questionnaire. We estimated environmental cadmium emissions near participants’ residences using a geographic information system.
Results: The geometric mean U-Cd concentration was 0.27 µg/L and the range was 0.1–3.6 µg/L. The intraclass correlation among repeat samples from an individual was 0.50. The use of a single 24-hr urine specimen to characterize Cd exposure in a case–control study would result in an observed odds ratio of 1.4 for a true odds ratio of 2.0. U-Cd concentration increased with creatinine, age, and lifetime pack-years of smoking among ever smokers or lifetime intensity-years of passive smoking among nonsmokers, whereas it decreased with greater alcohol consumption and number of previous pregnancies. These factors explained 42–44% of the variability in U-Cd concentrations.
Conclusion: U-Cd levels varied with several individual characteristics, and a single measurement of U-Cd in a 24-hr sample did not accurately reflect medium- to long-term body burden.
PMCID: PMC3672909  PMID: 23552363
cadmium; biomarkers; diet; exposure science; GIS
11.  Long-Term Exposure to Air Pollution and Cardiorespiratory Disease in the California Teachers Study Cohort 
Rationale: Several studies have linked long-term exposure to particulate air pollution with increased cardiopulmonary mortality; only two have also examined incident circulatory disease.
Objectives: To examine associations of individualized long-term exposures to particulate and gaseous air pollution with incident myocardial infarction and stroke, as well as all-cause and cause-specific mortality.
Methods: We estimated long-term residential air pollution exposure for more than 100,000 participants in the California Teachers Study, a prospective cohort of female public school professionals. We linked geocoded residential addresses with inverse distance-weighted monthly pollutant surfaces for two measures of particulate matter and for several gaseous pollutants. We examined associations between exposure to these pollutants and risks of incident myocardial infarction and stroke, and of all-cause and cause-specific mortality, using Cox proportional hazards models.
Measurements and Main Results: We found elevated hazard ratios linking long-term exposure to particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5), scaled to an increment of 10 μg/m3 with mortality from ischemic heart disease (IHD) (1.20; 95% confidence interval [CI], 1.02–1.41) and, particularly among postmenopausal women, incident stroke (1.19; 95% CI, 1.02–1.38). Long-term exposure to particulate matter less than 10 μm in aerodynamic diameter (PM10) was associated with elevated risks for IHD mortality (1.06; 95% CI, 0.99–1.14) and incident stroke (1.06; 95% CI, 1.00–1.13), while exposure to nitrogen oxides was associated with elevated risks for IHD and all cardiovascular mortality.
Conclusions: This study provides evidence linking long-term exposure to PM2.5 and PM10 with increased risks of incident stroke as well as IHD mortality; exposure to nitrogen oxides was also related to death from cardiovascular diseases.
PMCID: PMC3208653  PMID: 21700913
particulate matter; cardiovascular diseases; air pollutants; epidemiology
12.  Determinants of Agricultural Pesticide Concentrations in Carpet Dust 
Environmental Health Perspectives  2011;119(7):970-976.
Background: Residential proximity to agricultural pesticide applications has been used as a surrogate for exposure in epidemiologic studies, although little is known about the relationship with levels of pesticides in homes.
Objective: We identified determinants of concentrations of agricultural pesticides in dust.
Methods: We collected samples of carpet dust and mapped crops within 1,250 m of 89 residences in California. We measured concentrations of seven pesticides used extensively in agriculture (carbaryl, chlorpyrifos, chlorthal-dimethyl, diazinon, iprodione, phosmet, and simazine). We estimated use of agricultural pesticides near residences from a statewide database alone and by linking the database with crop maps. We calculated the density of pesticide use within 500 and 1,250 m of residences for 180, 365, and 730 days before collection of dust and evaluated relationships between agricultural pesticide use estimates and pesticide concentrations in carpet dust.
Results: For five of the seven pesticides evaluated, residences with use of agricultural pesticides within 1,250 m during the previous 365 days had significantly higher concentrations of pesticides than did residences with no nearby use. The highest correlation with concentrations of pesticides was generally for use reported within 1,250 m of the residence and 730 days before sample collection. Regression models that also accounted for occupational and home use of pesticides explained only a modest amount of the variability in pesticide concentrations (4–28%).
Conclusions: Agricultural pesticide use near residences was a significant determinant of concentrations of pesticides in carpet dust for five of seven pesticides evaluated.
PMCID: PMC3222988  PMID: 21330232
agriculture; dust; exposure; GIS; pesticides
14.  Factors Associated with Residential Mobility in Children with Leukemia: Implications for Assigning Exposures 
Annals of epidemiology  2009;19(11):834-840.
In epidemiologic studies, neighborhood characteristics are often assigned to individuals based on a single residence despite the fact that people frequently move and, for most cancer outcomes, the relevant time-window of exposure is not known. The authors evaluated residential mobility patterns for a population-based series of childhood leukemia cases enrolled in the Northern California Childhood Leukemia Study.
Complete residential history from one year prior to birth to date of diagnosis was obtained for 380 cases diagnosed between 1995 and 2002. All residences were assigned U.S. Census block group designations using a geographic information system.
Overall, two-thirds (65.8%) of children had moved between birth and diagnosis, and a third (34.5%) moved during the first year of life. Approximately 25% of the mothers had moved during the year before the child's birth. Multivariable analysis indicated greater residential mobility to be associated with older age of the child at diagnosis, younger age of the mother at child's birth, and lower household income. Among those who had moved, residential urban/rural status for birth and diagnosis residences changed for about 20% of subjects, and neighborhood SES for 35%.
These results suggest that neighborhood attribute estimates in health studies should account for patterns of residential mobility. Estimates based on a single residential location at a single point in time may lead to different inferences.
PMCID: PMC2761989  PMID: 19364662
Childhood leukemia; Epidemiology; Exposure classification; Residential mobility; Socioeconomic status
15.  Residential Proximity to Agricultural Pesticide Applications and Childhood Acute Lymphoblastic Leukemia 
Environmental research  2009;109(7):891-899.
Ambient exposure from residential proximity to applications of agricultural pesticides may contribute to the risk of childhood acute lymphoblastic leukemia (ALL). Using residential histories collected from the families of 213 ALL cases and 268 matched controls enrolled in the Northern California Childhood Leukemia Study, the authors assessed residential proximity within a half-mile (804.5 meters) of pesticide applications by linking address histories with reports of agricultural pesticide use. Proximity was ascertained during different time windows of exposure, including the first year of life and the child’s lifetime through the date of diagnosis for cases or reference for controls. Agricultural pesticides were categorized a priori into groups based on similarities in toxicological effects, physicochemical properties, and target pests or uses. The effects of moderate and high exposure for each group of pesticides were estimated using conditional logistic regression. Elevated ALL risk was associated with lifetime moderate exposure, but not high exposure, to certain physicochemical categories of pesticides, including organophosphates, cholorinated phenols, and triazines, and with pesticides classified as insecticides or fumigants. A similar pattern was also observed for several toxicological groups of pesticides. These findings suggest future directions for the identification of specific pesticides that may play a role in the etiology of childhood leukemia.
PMCID: PMC2748130  PMID: 19700145
Agricultural pesticides; cancer; childhood leukemia; environmental exposure; geographic information systems
16.  Long-Term Exposure to Constituents of Fine Particulate Air Pollution and Mortality: Results from the California Teachers Study 
Environmental Health Perspectives  2009;118(3):363-369.
Several studies have reported associations between long-term exposure to ambient fine particulate matter (PM) and cardiovascular mortality. However, the health impacts of long-term exposure to specific constituents of PM2.5 (PM with aerodynamic diameter ≤ 2.5 μm) have not been explored.
We used data from the California Teachers Study, a prospective cohort of active and former female public school professionals. We developed estimates of long-term exposures to PM2.5 and several of its constituents, including elemental carbon, organic carbon (OC), sulfates, nitrates, iron, potassium, silicon, and zinc. Monthly averages of exposure were created using pollution data from June 2002 through July 2007. We included participants whose residential addresses were within 8 and 30 km of a monitor collecting PM2.5 constituent data. Hazard ratios (HRs) were estimated for long-term exposure for mortality from all nontraumatic causes, cardiopulmonary disease, ischemic heart disease (IHD), and pulmonary disease.
Approximately 45,000 women with 2,600 deaths lived within 30 km of a monitor. We observed associations of all-cause, cardiopulmonary, and IHD mortality with PM2.5 mass and each of its measured constituents, and between pulmonary mortality and several constituents. For example, for cardiopulmonary mortality, HRs for interquartile ranges of PM2.5, OC, and sulfates were 1.55 [95% confidence interval (CI), 1.43–1.69], 1.80 (95% CI, 1.68–1.93), and 1.79 (95% CI, 1.58–2.03), respectively. Subsequent analyses indicated that, of the constituents analyzed, OC and sulfates had the strongest associations with all four outcomes.
Long-term exposures to PM2.5 and several of its constituents were associated with increased risks of all-cause and cardiopulmonary mortality in this cohort. Constituents derived from combustion of fossil fuel (including diesel), as well as those of crustal origin, were associated with some of the greatest risks. These results provide additional evidence that reduction of ambient PM2.5 may provide significant public health benefits.
PMCID: PMC2854764  PMID: 20064787
cardiopulmonary mortality; chronic exposure; cohort study; elemental carbon; fine particles; organic carbon; PM2.5; species; sulfates
17.  Residential Traffic Density and Childhood Leukemia Risk 
Exposures to carcinogenic compounds from vehicle exhaust may increase childhood leukemia risk, and the timing of this exposure may be important.
We examined the association between traffic density and childhood leukemia risk for three time periods: birth, time of diagnosis, and lifetime average, based on complete residential history in a case-control study. Cases were rapidly ascertained from participating hospitals in northern and central California between 1995 and 2002. Controls were selected from birth records, individually matched on age, sex, race, and Hispanic ethnicity. Traffic density was calculated by estimating total vehicle miles traveled per square mile within a 500-foot (152 meter) radius area around each address. We used conditional logistic regression analyses to account for matching factors and to adjust for household income.
We included 310 cases of acute lymphocytic leukemias (ALL) and 396 controls in our analysis. The odds ratio for ALL and residential traffic density above the 75th percentile, compared with subjects with zero traffic density, was 1.17 [95% confidence interval (95% CI), 0.76–1.81) for residence at diagnosis and 1.11 (95% CI, 0.70–1.78) for the residence at birth. For average lifetime traffic density, the odds ratio was 1.24 (95% CI, 0.74–2.08) for the highest exposure category.
Living in areas of high traffic density during any of the exposure time periods was not associated with increased risk of childhood ALL in this study.
PMCID: PMC2706505  PMID: 18768496
18.  Residential Proximity to Agricultural Pesticide Use and Incidence of Breast Cancer in California, 1988–1997 
Environmental Health Perspectives  2005;113(8):993-1000.
California is the largest agricultural state in the United States and home to some of the world’s highest breast cancer rates. The objective of our study was to evaluate whether California breast cancer rates were elevated in areas with recent high agricultural pesticide use. We identified population-based invasive breast cancer cases from the California Cancer Registry for 1988–1997. We used California’s pesticide use reporting data to select pesticides for analysis based on use volume, carcinogenic potential, and exposure potential. Using 1990 and 2000 U.S. Census data, we derived age- and race-specific population counts for the time period of interest. We used a geographic information system to aggregate cases, population counts, and pesticide use data for all block groups in the state. To evaluate whether breast cancer rates were related to recent agricultural pesticide use, we computed rate ratios and 95% confidence intervals using Poisson regression models, adjusting for age, race/ethnicity, and neighborhood socioeconomic status and urbanization. This ecologic (aggregative) analysis included 176,302 invasive breast cancer cases and 70,968,598 person-years of observation. The rate ratios did not significantly differ from 1 for any of the selected pesticide categories or individual agents. The results from this study provide no evidence that California women living in areas of recent, high agricultural pesticide use experience higher rates of breast cancer.
PMCID: PMC1280339  PMID: 16079069
breast neoplasms; geographic information system; incidence; pesticides
19.  Childhood cancer incidence rates and hazardous air pollutants in California: an exploratory analysis. 
Environmental Health Perspectives  2003;111(4):663-668.
Hazardous air pollutants (HAPs) are compounds shown to cause cancer or other adverse health effects. We analyzed population-based childhood cancer incidence rates in California (USA) from 1988 to 1994, by HAP exposure scores, for all California census tracts. For each census tract, we calculated exposure scores by combining cancer potency factors with outdoor HAP concentrations modeled by the U.S. Environmental Protection Agency. We evaluated the relationship between childhood cancer rates and exposure scores for 25 potentially carcinogenic HAPs emitted from mobile, area, and point sources and from all sources combined. Our study period saw 7,143 newly diagnosed cancer cases in California; of these, 6,989 (97.8%) could be assigned to census tracts and included in our analysis. Using Poisson regression, we estimated rate ratios (RRs) adjusted for age, race/ethnicity, and sex. We found little evidence for elevated cancer RRs for all sites or for gliomas among children living in high-ranking combined-source exposure areas. We found elevated RRs and a significant trend with increasing exposure level for childhood leukemia in tracts ranked highest for exposure to the combined group of 25 HAPs (RR = 1.21; 95% confidence interval, 1.03, 1.42) and in tracts ranked highest for point-source HAP exposure (RR = 1.32; 95% confidence interval, 1.11, 1.57). Our findings suggest an association between increased childhood leukemia rates and high HAP exposure, but studies involving more comprehensive exposure assessment and individual-level exposure data will be important for elucidating this relationship.
PMCID: PMC1241461  PMID: 12676632
20.  Childhood cancer and agricultural pesticide use: an ecologic study in California. 
Environmental Health Perspectives  2002;110(3):319-324.
We analyzed population-based childhood cancer incidence rates throughout California in relation to agricultural pesticide use. During 1988-1994, a total of 7,143 cases of invasive cancer were diagnosed among children under 15 years of age in California. Building on the availability of high-quality population-based cancer incidence information from the California Cancer Registry, population data from the U.S. Census, and uniquely comprehensive agricultural pesticide use information from California's Department of Pesticide Regulation, we used a geographic information system to assign summary population, exposure, and outcome attributes at the block group level. We used Poisson regression to estimate rate ratios (RRs) by pesticide use density adjusted for race/ethnicity, age, and sex for all types of childhood cancer combined and separately for the leukemias and central nervous system cancers. We generally found no association between pesticide use density and childhood cancer incidence rates. The RR for all cancers was 0.95 [95% confidence interval (CI), 0.80-1.13] for block groups in the 90th percentile and above for use of pesticides classified as probable carcinogens, compared to the block groups with use of < 1 lb/mi(2). The RRs were similar for leukemia and central nervous system cancers. Childhood leukemia rates were significantly elevated (RR = 1.48; 95% CI, 1.03-2.13) in block groups with the highest use of propargite, although we saw no dose-response trend with increasing exposure categories. Results were unchanged by further adjustment for socioeconomic status and urbanization.
PMCID: PMC1240773  PMID: 11882484

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